JPH0357691B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to an improvement in a ground fault line selection relay used for protection against single-phase ground faults in parallel multi-line electric wires.

(b) Conventional technology When a high-resistance grounded parallel two-circuit transmission line (hereinafter referred to as a protected transmission line) is installed on the same tower as another transmission line (hereinafter referred to as an induced transmission line), in other words, a multi-circuit In the case of an overhead power transmission line, a large zero-phase circulating current flows between two circuits of the protected power transmission line due to induction by the current of the induced power transmission line. A general ground fault line selection relay uses the zero-sequence difference current between protected parallel transmission lines (hereinafter simply referred to as zero-sequence difference current) as the calculation amount to identify a ground fault line. If the current is large, this effect makes normal protection impossible.

As a countermeasure against this problem, a ground fault line selection relay is used that identifies a line in which a ground fault has occurred by using the change in zero-sequence difference current from the value before the fault at the time of a one-phase ground fault fault. As a result, even when the zero-phase circulating current is large, it is possible to protect the protected power transmission line from a one-phase ground fault. However, if a change occurs in the operating status of the induced power transmission line at the same time as an accident is detected on the protected power transmission line or after the accident is detected, a change in circulating current occurs due to this change, making normal protection impossible.

That is, the zero-sequence difference current is twice the value of the above-mentioned zero-sequence circulating current during normal operation, but when an internal fault occurs in the protected power transmission line, the zero-sequence difference current becomes the same as the fault. The phase relationship between the zero-sequence difference current for the fault and the zero-sequence voltage is reversed depending on which line of the parallel power transmission line has the fault. A relay that uses the change in the zero-sequence difference current memorizes the constant zero-sequence difference current, and when a ground fault is detected due to the occurrence of zero-sequence voltage, the relay uses the current zero-sequence difference current and the stored zero-sequence difference. The fault difference current is obtained by calculating the difference in current, and the ground fault fault line is identified based on the phase relationship between this and the zero-sequence voltage.

However, if the induced power transmission line is a directly grounded system and the fault current is large due to a ground fault, the induced voltage will be large, and the zero-sequence voltage induced in the protected power transmission line will often exceed the fault detection level. In this case, the circulating current also changes at the same time by a value corresponding to the fault current. A relay using the above-mentioned change malfunctions due to the change in the zero-sequence difference current due to this change. Furthermore, even if the induced voltage is not so large, if a one-phase ground fault occurs in the protected transmission line at the same time, the ground fault will be detected based on the resulting zero-phase voltage. The zero-sequence difference current at this time is the sum of the variation in the circulating current and the fault difference current, and the fault line is often mistakenly selected depending on the variation in the circulating current. The above-mentioned malfunctions can be prevented by, for example, setting the relay to a time-limited operation and waiting until the fault on the induced power transmission line has been cut off. However, the circulating current when one line of the induced power transmission line is stopped due to a shingle break has a value different from the circulating current before the accident, and this change is expressed as the change in the zero-sequence difference current. be exposed. There is also a risk of malfunction due to this variation.

(c) Purpose The present invention has been made in view of the above facts, and its purpose is to compensate for the change in circulating current due to a change in the situation of the induced transmission line, out of the change in differential current, and to reduce the circulating current. To provide a ground fault line selection relay which reduces the influence of changes and does not malfunction even when it is highly sensitive.

(d) Structure and operation FIG. 1 is a diagram showing the structure of an embodiment of the present invention. In the figure, 1 is a bus bar, and a, b, and c indicate phase symbols. 2 and 3 are parallel power transmission lines to be protected, which are connected to the bus 1 via bow breakers 4 and 5. 6 and 7 are current transformers provided on the power transmission lines 2 and 3, and 8 is a voltage transformer. 9 is an input converter, 10 is a sample and hold circuit, 11 is a multiplexer, 12 is an AD converter, and 13 is a computer, which includes a CPU and a memory input/output device. Transmission lines 2 and 3 by current transformers 6 and 7
Obtain the current corresponding to the current of , and by the connections shown,
Differential current i _as of each phase a, b, c of both transmission lines 2 and 3,
i _bs and I _cs and 3×(zero-sequence difference current) 3i _ps are obtained.
Further, voltages v _a , v b , v _c and v _p corresponding to the a, _b , c phase voltages and zero-phase voltage of the terminals of the power transmission lines 2 and 3 are obtained through the bus 1 by the instrument transformer 8 . These currents and voltages are applied to the input converter 9 and converted into voltages with values suitable for the sample and hold circuit 10 at the next stage. The input converter 9 is provided with a filter, and only the fundamental wave component of each voltage and current is obtained as an output. The sample and hold circuit samples and holds the input value at the same time and at a constant cycle (eg, 1/12 cycle of one cycle of voltage or current). This hold value is sequentially supplied to the AD converter 12 by the multiplexer 11 and converted into a digital value. The computer 13 follows a predetermined program, performs necessary calculations using the output of the AD converter 12, and instructs the sinter breaker 4 or 5 to sever when the input data meets a predetermined condition.

An example of the calculation flow performed by the computer 13 is shown in FIG. First, when a start command is received in step S1, short circuit fault detection is performed in step S2. When a short circuit accident is detected, the process moves to other calculations (usually short circuit protection calculations). If no short circuit fault is detected, the process moves to step S3, where ground fault detection is performed. If no ground fault is detected, the process advances to step S4 and the values of necessary quantities described later are stored. After this storage, the process returns to the beginning and is repeated until a short circuit or ground fault is detected to update the stored value.
If a ground fault is detected in step S3, the step
Proceed to S5.

In step S5, ground fault phase selection is performed. That is, in the order of steps S5-1, S5-2 and S5-3, phase a, b and c ground faults are selected, and a,
Judgment 5Ya, 5 when b or c phase ground fault is detected
Yb or 5Yc is obtained. If no ground fault in any phase is detected, a determination of 5N is obtained and the process moves to another calculation (normal ground fault back-up protection calculation). Judgment 5 at step S5
When Ya, 5Yb or 5Yc is obtained, the process proceeds to step S6, and steps S6-1, S6-2 or S6-3 are performed, respectively, depending on which judgment is obtained, that is, which phase of the ground fault. Then, using the voltage, current, and the memory amount of step S4, the calculation amount e _{ea is}
Find e _eb or e _ec . Once this is determined, a line selection calculation is performed in step S7. Step S7
First, fault detection calculations for power transmission lines 2 and 3 are performed in the order of steps S7-1 and S7-2. If any accident is detected, judge 7Y1 or 7Y2 respectively.
is obtained and the sheath cutter 4 or 5 is sheared. If no accident is detected, a determination of 5N is obtained, and the process moves on to other calculations (usually ground fault backup protection calculations).

The short circuit detection in step S2 and the ground fault detection in step S3 described above are means that are also used in known ground fault line selection relays, and various means are known. In other words, in the short circuit detection in step S2, each phase voltage v _a
A known method is to determine that a short circuit has occurred when any of -v _b , v _b -v _c and v _{c -va} falls below a certain value or drops by a certain amount or more. The ground fault detection in step S3 is normally determined to be a ground fault fault if the zero-phase voltage v _p is greater than a certain value. Furthermore, various means are known for the ground fault phase selection means in step S5, but for example, if the zero-phase voltage v _p is
When within a certain phase range for v _b -v _c , v _c -v _a and v _a -v _b , there are cases where it is determined that there is an a-, b-, or c-phase ground fault, respectively. Since these are all well-known techniques, detailed explanations will be omitted.

In step S4, the following calculation is performed and its value is stored.

i _psM ×v _bcM , i _psM ×v _caM , i _psM ×v _abM , K _1b i _bcM K _1ca (i _csM + i _asM ) × v _caM , K _1b i _bsM ×v _abM …(1) However, i _psM , i _bsM , i _csM , i _asM are zero phase and b phase c, respectively.
The stored values of the phase and a phase difference currents i _ps , i _bs , i _cs and i _as , v _bcM , v _caM and v _abM are the bc, ca and ab phase voltages v _b −v _c , v _c − respectively The stored values K _1b and k _1ca of v _a and v _a −v _b are constants. Furthermore, all of the above equations are cross products, and the symbol (x) below indicates the relationship in equation (2).

A×B=｜AB｜sin(θ _A −θ _B ) …(2) However, A and B are vector quantities, and |AB｜ is AB
The absolute values of the products θ _A and θ _B are the angles of the vector quantities A and B, respectively.

Note that it takes some time after the occurrence of the accident to detect a short circuit or ground fault in step S2 or S3. Therefore, the calculation in step S4 is performed using the value at the time of the accident from the time the accident occurs until the accident is detected. It is not desirable for this value to be used as a memorized value, so when updating the memorized value, if a change is observed in the memorized value, the old value is retained for a while, and if no accident is detected within a certain period of time, it is memorized. Make sure to update the value.

FIG. 3 is a diagram showing the above flow performed in step S4. First, when no ground fault is detected and a determination N is obtained in step S3 of FIG. 2, the value of equation (1) is calculated in step S4-1. Next, in step S4-2, the calculated value in step S4-1 and the stored value in step S4-4 are compared, and it is detected that there is a significant difference. If there is no difference, the process returns to step S1 in FIG. 2, and if there is a difference, the process moves to step S4-3, where it is detected that the difference has continued for a certain period of time. If the predetermined time has not been reached, the process returns to step S1, and this process is repeated until it is determined that the predetermined time has continued. If it is determined that it will continue for a certain period of time, proceed to step S4.
-4, the calculated value of step S4-1 is stored.
Note that the above-mentioned fixed time is a slightly longer time than the short circuit and ground fault detection time in steps S2 and S3.
As a result, even if there is a slight delay in detecting a short circuit or ground fault, the value before the fault is stored.

In step S6, the amount of calculation e _ea expressed by the following formula in steps S6-1, S6-2, or S6-3 is calculated, respectively.
Calculate the value of e _eb or e _ec .

e _ea = e _da −e _ha e _eb = e _db −e _hb e _ec = e _dc −e _hc …(3) However, e _da , e _db and e _dc are the detected amounts, e _ha , e _hb and e _hc is the amount of compensation, and both are expressed by the following equations.

e _da = i _ps ×v _bc −i _psM ×v _bcM d _db = i _ps ×v _cb −i _psM ×v _caM e _dc = i _ps ×v _ab −i _psM ×v _abM …(4) e _ha =K _1b i _bs ×v _bc −K _1b i _bsM ×V _bcM e _ha =K _1b i _bs ×v _bc −K _1b i _bsM ×V _bcM e _hb =K _1ca (i _cs +i _as )×v _ca −K _1ca ( i _csM + i _asM )×V _c
aM e _hc = K _1b i _bs ×v _ab −k _1b i _bsM ×v _abM …(5) However, v _bc , v _ca and v _ab are the phase-to-phase voltages v _b −v _c , v _c
−v _a and v _a −v _b .

The detected amount in equation (4) above is the zero-sequence difference current i _ps
and the voltage in quadrature with respect to the fault phase ₍ hereinafter simply referred to as _quadrature voltage ₎ . (referred to as accident change). Further, the compensation amount in equation (5) is the fault change of the cross product of the differential current i _bs of one phase in the healthy phase or the composite value i _cs + i _as of the differential current of two healthy phases and the orthogonal voltage.

In step S7, steps S7-1 and S7-
2 performs the calculation of equation (6) or equation (7), respectively.

e _ea ＞K _2a ｜V _bc ｜, e _eb ＞K _2b ｜V _ca ｜ or e _ec ＞K _2c ｜v _ab ｜ …(6) −e _ea ＞K _2a ｜v _bc ｜, −e _eb ＞K _2b ｜v _ca ｜ or −e _ec > K _2c ｜v _ab ｜ …(7) However, ｜v _bc ｜ is the magnitude of the voltage v _bc (effective value, average value, peak value, etc.), and from now on, the same symbol will be used. Indicates size. Furthermore, K _2a , K _2b and K _2c are each positive constants.

In equations (6) and (7), one of the values of the calculation amount e _ea , e _eb , or e _ec is calculated in step S6 according to the result of phase selection in step S5, so the calculation for the calculated calculation amount is Only do the following. If the formula (6) is satisfied, the determination 7Y2 is obtained, and if the formula (7) is satisfied, the determination 7Y1 is obtained.

Next, the operation of the present invention will be explained using the drawings. FIG. 4 is a thread diagram for explaining a multi-circuit parallel power transmission line. In the figure, 1L and 2L are induction power transmission lines, 3
L and 4L are protected transmission lines, T is a transformer, R is a neutral point grounding resistor, A, B, C, and D are busbars,
Transmission lines 1L to 4L will be installed on the same tower between EF and EF. The neutral point of transformer T is directly grounded in an inductive system (a system connected to an inductive transmission line without going through a transformer), and in a protected system (a system connected to a protected transmission line without going through a transformer). It is grounded via a neutral point grounding resistor R. The line selection relay protects protected transmission lines 3L and 4L.

FIG. 5 is a diagram showing an example of the arrangement of electric wires in the parallel section. a1, b1, c1, a2, b2, c2, a
3, b3, c3, a4, b4, and c4 are electric wires of phases a, b, and c of power transmission lines 1L, 2L, 3L, and 4L, respectively. This arrangement is for the protected power transmission line 3L.
and 4L are sequential arrays (line symmetrical with respect to the tower), so even if current flows only to protected transmission lines 3L and 4L, unless there is an internal fault (short circuit or ground fault of 3L, 4L), the transmission Electric wires 3L and 4
The current of L is equal in each phase, and the difference current between the same phases of both power transmission lines (hereinafter simply referred to as difference current) is zero.

The electric wire arrangement of the induction power transmission lines 1L and 2L is reversed. If both transmission lines 3L and 4L are operated, and only transmission line 1L (or 2L) is operated and a load current flows through it, the induction caused by this will cause transmission line 3L (or 4L) to
L), and due to this difference, a circulating current i _th circulating between power transmission lines 3L and 4L flows through each phase of a, b, and c as shown in FIG. This induction is a power transmission line 3L
and 4L and induction power transmission line 1L (or 2L)
The closer to , the larger the circulating current is, and the magnitude of the circulating current is largest in the a phase and smallest in the c phase. In addition, the effect of the c-phase (or a-phase) current near the transmission lines 3L and 4L of the induced transmission line 1L (or 2L) is large, and the circulating current of the transmission lines 3L and 4L is a,
For each phase of b and c, c of the transmission line 1L (or 2L)
The phase difference between the current and the phase (or a-phase) current is small.
Further, the circulating current when the load current flows through both the power transmission lines 1L and 2L is a superposition of the circulating current when the load current flows independently through each of the power transmission lines 1L and 2L. In addition, 1L or 2L of power transmission line
The circulating current when a phase-to-ground fault occurs is significantly larger than that during normal operation, and the phase difference with the ground-fault phase current is small, because the ground-fault fault current flows as the main induced current.

From the above relationship, the circulating currents i _ath , i _bth and
The phase difference of i _cth is relatively small, and its zero-phase component, i.e., zero-phase circulating current i _pth (=(i _ath + i _bth + i _cth /3)) is relatively large. When calculated for various states of the induced power transmission line, the following values are obtained.However, since each difference current appears twice the value of the circulating current, it is shown as twice the value.

[Condition 1] When 1L of the induction power transmission line is stopped and 2L is in normal operation, the current of 2L is the state of equation (8): I' _A = 2000 0° [A] I' _B = 2000 120° [A], I' _C = 2000 120゜[A] …(8) However, I _A ′, I _B ′ and I _C ′ are a of transmission line 2L,
b and c are the currents of each phase. Also, □゜ indicates εj□°, □゜ indicates ε−j□°, and the same applies hereinafter.

2i _ath =98.8 4゜ [A] 2i _bth =44.4 12゜ [A] 2i _cth =26.4 15゜ [A] 2i _pth =56.4 8゜ [A] ...(9) [Condition 2] Inductive power transmission line 1L and Both 2L are operating normally.
Each current is in the state of equation (10) I _A = I _A ′=1000 0° [A] I _B = I _B ′=1000 240° [A] I _C = I _C ′=1000 120° [A] … (10) However, I _A , I _B and I _C are a of 1L transmission line, respectively.
b and c are the currents of each phase.

2i _ath = 94.4 25゜ [A] 2i _bth = 42.8 27゜ [A] 2i _cth = 25.6 27゜ [A] 2i _pth = 54.2 26゜ [A] …(11) Ratio of circulating current of each phase and zero phase does not change even if the current value in equation (8) or (10) changes while the three phases are in equilibrium. Circulating currents also result from induced power line faults. An example of this calculation is shown below.

[Condition 3] Induction power transmission line 1L and 2L no-load operation, 1L
C- _phase 1- _phase ground fault condition where the current _{I A} ′ is 7000 [A] at point F of _pth = 285 143゜ [A] ...(12) For example, suppose the following change occurs.

[Change 1] It is assumed that a ground fault occurs in the induction power transmission line 1L under the normal operating state of condition 2, and the fault current of condition 3 is superimposed in this accident. It is also assumed that at this time, a one-phase ground fault is also detected on the protected power transmission line. At this time, the fault change in the circulating current of the protected power transmission line is equal to the value of equation (12), and the relationship between each phase and the combined value is as follows.

△i _ath : △i _bth : △i _cth : △i _ath +△i _cth : △i _pth 1.66 1゜: 0.81 0゜: 0.53 1゜: 21.9 0゜: 1 0゜ ...(13) However, △i _ath , Δi _bth , Δi _cth and Δi _pth are accidental changes in a, b, c and zero-sequence circulating currents i _ath , i _bth , i _cth and i _pth , respectively.

[Change 2] Assume that the power transmission line 1L is suddenly disconnected from the above state, and the state becomes the condition 1. The fault change in the circulating current at this time is equal to the difference between the values of equations (9) and (11), and is the following value:

2△i _ath =98.8 4゜〔A〕−94.4 25°
[A] = 35.5 70゜ [A] 2△i _ath = 98.8 4゜ [A] −94.4 25°
[A] = 35.5 70゜ [A] 2△i _bth = 44.4 12゜ [A] - 42.8 27゜ [A] = 11.5 63
゜〔A〕 2△i _ath =98.8 4゜〔A〕−94.4 25°
[A] = 35.5 70゜ [A] 2△i _bth = 44.4 12゜ [A] - 42.8 27゜ [A] = 11.5 63
゜〔A〕 2△i _cth =26.4 15゜〔A〕−25.6 27゜〔A〕＝5.3 61゜〔A〕 2△i _ath ＝98.8 4゜〜〔A〕−94.4 25°
[A] = 35.5 70゜ [A] 2△i _bth = 44.4 12゜ [A] - 42.8 27゜ [A] = 11.5 63
゜ [A] 2 △ I _CTH = 26.4 15 ゜ [a] -25.6 27 ゜ [a] = 5.3 61 ゜ [a] 2 △ I _PTH = 56.4 8 ゜ [a] -54.2 26 ゜ [A] = 17.5 6゜[A] 2(△i _ath + △i _cth ) = 40.8 69゜[A]...(14) The following ratio can be obtained from equation (14).

△i _ath : △i _bth : △i _cth : △i _ath + △i _cth : △i _pth = 2.03 4゜: 0.66 3゜: 0.30 5゜: 2.33 3゜: 1 0
゜ ...(15) Comparing the ratios of equations (13) and (15), the difference in phase is slight, and the difference in absolute value is not that large either. The present invention uses such a relationship.

The difference current between each phase and zero phase is expressed by the following equation.

i _as = i _af +2i _ath i _bs = i _bf +2i _bth i _cs = i _cf +2i _cth i _ps = i _pf +2i _pth ...(16) However, i _af , i _bf , i _cf and i _pf are a and b, respectively. , c, and the zero-phase fault difference current, and i _pf is expressed by the following equation.

i _pf = 1/3 (i _af + i _bf + i _cf ) ...(17) In equations (16) and (17), the fault differential currents i _af , i _bf and i _cf are calculated when there is an internal fault in the protected transmission line. It only flows during the accident phase. It is zero in the healthy phase, and in the case of an external accident, it is also zero in the accident phase. Therefore, the zero phase difference current i _pf is equal to 1/3 of the fault phase difference current in the case of an internal fault, and is zero in other cases.

The phenomenon that occurs when a one-phase ground fault occurs in the protected system is a.
This will be explained using a phase-to-ground fault as an example. In the case of a one-phase ground fault in a resistance grounding system, the fault current is small, so the difference in voltage between the fault point and the relay installation point is small, so the voltage will be explained in terms of the fault point voltage. As is well known, the symmetrical voltage and current at the fault point is expressed by the following equation.

I _a1F = I _a2F = I _a0F 1/Z ₁ +Z ₂ +Z ₀ +3R _G・E _a1F …(19) However, V _a1F , V _a2F , and V _a0F are the positive, negative, and zero values at the accident point, respectively. The phase voltage, E _a1F is the positive sequence voltage before the fault at the fault point, I _a1F , I _a2F and
I _a0F are the positive, reverse, and zero-sequence currents at the fault point, all of which are based on the a-phase. Also, R _G
is the fault point resistance, Z ₁ , Z ₂ and Z ₀ are positive at the fault point,
Reverse and zero-sequence drive point impedance. _Z1 ,
Z ₂ and Z ₀ have the following relationship.

Z ₁ = Z ₂ ≪Z ₀ …(20) From equations (18) and (20), the right-angle voltage at the fault point
V _bcF is as follows.

V _bcF = a ² V _a1F + aV _2aF − (aV _a1F + a ² V _a2F = (a ² − a) (V _a1F − V _a2F = (a ² − a) E _a1F
...(21) However, a=1 120°.

Equation (21) shows that the voltage V _bcF is √3 times the voltage E _a1F and
E is 90° behind _a1F , thus indicating no change from the pre-accident value. Therefore, the relay voltage v _bc does not change before and after the ground fault occurs. In addition, the voltage v _bc is almost in phase with V _bcF , and is smaller than the voltage E _a1F .
It is delayed by 90°.

Also, from equation (19), the fault phase current I _aF at the fault point is given by the following equation.

I _aF = I _a1F + I _a2F + I _a0F ≒3/Z ₀ +3R _G E _a1F …(22) In equation (22), Z ₀ is an impedance with a small reactance component and a large resistance component, and R _G is a resistance, so the current I _aF is approximately in phase with voltage E _a1F . In the case of an internal fault, this current flows into the faulty transmission line through its terminals. This produces a fault differential current i _af . If the direction of the difference current is shown in Figure 1, the current
i _af is the current I _aF or the voltage E _a1F in the case of an accident on transmission line 2
It is in the same phase as the transmission line 3, and in the case of an accident on the transmission line 3, it is in the opposite phase. From the above relationship, the fault differential current i _af is the quadrature voltage
In the case of an accident on transmission line 2, it is approximately 90° ahead of v _bc , and in the case of an accident on transmission line 3, it is delayed by approximately 90°.

The above description has been made regarding the a-phase ground fault, but the relative relationship between the phases is the same in the case of a b-phase or c-phase ground fault, and the relative relationship of the fault differential current of the fault phase to the quadrature voltage remains the same.

As described above, since the quadrature voltage does not change before and after the occurrence of a one-phase ground fault, the following relationship holds between the quadrature voltages in equations (4) and (5).

v _bc = v _bcM , V _ca = v _caM , v _ab = v _abM … (23) If e _da in equation (4) is transformed using this relationship, e _da = (i _ps − i _psM ) × v _bc … (24) The relationship between the currents i _ps and i _psM in equations (16) and (17) and the healthy phase fault difference currents i _bf and i _cf are zero, and the fault difference current is zero at the value i _psM before fault detection. Transforming _{equation ( 24 )} using _{the fact} that It is a circulating current.

As described above, each detected amount in equation (4) is expressed by the following equation.

However, △i _pth = i _pth − i _pthM , which is the fault change in the zero-sequence circulating current.

Furthermore, since the healthy phase difference current does not include the fault difference current, each compensation amount in equation (5) is expressed by the following equation in the same way as above.

e _ha =2K _1b △i _bth ×v _bc e _hb =2K _1ca (△i _cth +△i _ath ) ×v _ca e _hc =2K _1b △i _bth ×v _ab …(27) However, △i _bth , △ i _cth and Δi _ath are fault changes in the b, c, and a phase circulating currents, respectively. From equations (26) and (27), the amount of calculation in equation (3) is as follows.

However, e _ea ′, e _eb ′, and e _ec ′ are compensation errors, and are expressed by the following equation.

e _ea ′＝(2△i _pth −2K _1b △i _bth )×v
_bc e _eb ′={2△i _pth −2K _1ca (△i _cth +△i _ath )}×v _ca e _ec ′=(2△i _pth −2K _1b △i _bth ×v _ab …(29) Next The response at the time of accident detection in this embodiment will be explained.
If a one-phase ground fault occurs in the protected system and there is no change in the condition of the induced transmission line, the circulating current will not change, so △i _pth , △i _ath , △i _bth and △i in equation (29) _cth
are all zero. Therefore, the amount of calculation is only the cross product of the fault differential current and quadrature voltage of the fault phase, as shown in equation (30).

If the fault is an external fault, the fault difference current i _af , i _bf
Alternatively, since i _cf is zero, the calculation amount e _ea , e _eb , or e _ec is also zero, and both equations (6) and (7) do not hold, and the relay does not operate. In the case of an internal fault, in the case of the fault on transmission line 2 in Figure 1, the fault differential current (e.g. i _af ) of the fault phase is approximately equal to the quadrature voltage (e.g. v _bc ) as described above.
Since the lead is 90°, the amount of calculation in equation (30) is e _e (e _ea , e _eb
and e _ec (used for calculation) is positive, and if the size satisfies equation (6), it will work and the step will work.
Judgment SY1 is obtained in S7, and the breaker 4 is cut off. In the case of an accident on power transmission line 3, the phase relationship is opposite to the above, so the calculation amount _e is negative, and if the magnitude satisfies equation (7), it will operate, and judgment 7Y2 will be obtained.
to refuse.

Taking the a-phase as an example, the operating conditions when applying _e in equation (30) to equations (6) and (7) are as follows.

1/3i _af ×v _bc ＞K _2a ｜v _bc ｜ …(31) −1/3i _af ×V _bc ＞K _2a ｜v _bc ｜ …(32) Equation (31) is 1/3 of the fault phase difference current, i.e. This shows that 1/3i _af operates when the leading reactive component (component in phase with the 90° lead of v _bc ) with respect to the quadrature voltage v _bc is greater than a certain value K _2a , and equation (32) is reversed. indicates that it operates when the delayed reactive component is greater than or equal to a certain value K _2a . This operating value does not change as the magnitude of the quadrature voltage V _bc changes. In this way, the fact that the operating value is not affected by the magnitude of the voltage used as a medium for line selection (hereinafter referred to as polarity voltage) is considered to be a superior characteristic compared to the prior art.

If the situation of the induced transmission line changes at the same time as the fault is detected, the compensation error in equation (29) e _e ′ (e _ea ′e _eb ′
e _ec ′ used in the calculation). If there is no internal accident, the calculation amount e _e will be equal to the compensation error amount e _e ′, so the operating value must be set to a value that will not malfunction due to this compensation error amount. Equation (29) is expressed as follows.

e _ea ′=i _ea ′×v _bc e _eb ′=i _eb ′×v _ca e _ec ′=i _ec ′×v _ab …(33) However, i _ea ′, i _eb ′, and i _ec ′ are compensation errors It is a current and is expressed by the following formula.

i _ea ′=i _ec ′=2△i _pth −2K _1b △i _bth i _eb ′=2△i _pth −2K _1ca (△i _cth +△i _ath ) …(34) Constants K _1b and K _1ca are circular It is selected so that the compensation error current i _e ' (whichever of i _ea ', i _eb ', and i _ec ' is used for calculation) does not become large with respect to various changes in current. Based on the relationship between equations (13) and (15) in changes 1 and 2 above, each constant is set to the value of equation (35), for example.

K _1b = 1.4 0゜ K _1ca = 0.44 0゜ ...(35) The magnitude of the compensation error current in this case is calculated as follows from the value of equation (12) (equal to the change of change 1) and the value of equation (14). The value is .

[Change 1] |i _ea ′|=|i _ec ′|=40[A] |i _eb ′|=11[A] …(36) [Change 2] |i _ea ′|=|i _ec ′|= 1.67 [A] |i _eb ′|=1.0 [A] …(37) If the constants K _2a , K _2b and K _2c in equations (6) and (7) are made larger than this value, this compensation error current i No matter what phase _e ′ is, equations (6) and (7) hold due to the compensation error e _e ′, and no malfunction occurs. Therefore, when targeting change 1, for example, set the values of K _2a and K _2c to 56A, the value of K _2b to 15 [A],
For example, when targeting change 2, K _2a and K _2c
can be set to 2.2AK _2b to 1.4 [A]. Change 1
If a large fault current flows through the induction line, as in the case of , the induction transmission line will be cut off quickly, so change 1 can be eliminated by using measures such as time-limited operation to prevent the line from breaking during this time. You can select the operating value using Conventional equipment responds to changes in circulating current, so if change 1 is the target, the operating value (K _2a , K _2b and K _2c values) cannot be lower than 285A, and change 2 is the target. If so, set the operating value
Since the current cannot be lowered to 17.5 A or less, the sensitivity can be significantly improved in the above embodiment.

(e) Modification of voltage and current used for calculation (e1) General In the above embodiment, the zero-sequence difference current i _ps is used as the detection current i _d , and the healthy phase difference current i _bs or the composite current of the healthy two-phase difference current i _cs +i _as is the compensation current i _h , and the quadrature voltage v _bc , v _ca or v _ab is the polar voltage v _p , the cross product i _d ×v _p of the detection current i _d and the polar voltage v _p , and the compensation current i _h and the polarity. A ground fault line is detected using the change in the value after the fault detection (fault change) with respect to the value before the fault detection of each of the outer product i _h ×v _p of the voltage v _p .

Detection current i _d , compensation current i _h , polarity voltage v _p
Using the equations (3), (4), and (5) of the above embodiment, the calculation amount, detection amount, and compensation amount are expressed as follows.

e _e ＝e _d −e _h e _d ＝i _d −v _p −i _dM ×v _pM e _h ＝i _h ×v _p −i _hM ×v _pM …(38) i _da ＝i _db ＝i _dc ＝i _ps i _ha = i _hc = K _1b i _bs i _ob = K _1ca (i _ca + i _as ) v _pa = v _bc , v _pb = v _ca , v _pc = v _ab …(39) However, e _e , e _d , e _h , i _d , i _h and v _p respectively indicate the same symbol with a subscript a, b or c added, and are used in the calculation, i _da , i _db , i _dc , i _ha ,
i _hb , i _hc , v _pa , v _pb and v _pc are a, b or c respectively
Detection current i _d , compensation current i _h and polarity voltage v _p used in phase-to-earth fault are shown. Moreover, i _hM , i _dM and v _pM are the stored values of i _d , i _h and v _p, respectively.

Furthermore, according to the above expressions, equations (6) and (7) are expressed by the following equations (40) and (41), respectively.

e _e ＞K ₂ ｜v _p ｜ …(40) −e _e ＞K ₂ ｜v _p ｜ …(41) However, K ₂ indicates the one used in the calculation among K _2a , K _2b and K _2c .

(38) and (39), the detection current i _d and the compensation current are
i _h and polarity voltage v _p can be modified in various ways within the following conditions.

(i) Detection current i _d : Current obtained from the fault phase difference current or a composite current of the same phase difference current including the fault phase difference current. (ii) Compensation current i _h : Current obtained from the same phase difference current or its composite current, which is the fault phase difference current. The current component is sufficiently smaller than the detected current i _d (iii) Polarity voltage v _p : Voltage that changes only slightly before and after the occurrence of a one-phase ground fault in the protected system, that is, the voltage v for which equation (42) holds true. _p = v _pM (42) That is, under the conditions of equation (42), equation (38) is transformed as follows.

e _d = (i _d − i _dM )×v _p e _h = (i _h −i _hM )×v _p …(43) Since the currents i _d and i _h are both the same phase difference current or their combined current, Each is expressed by the following formula.

i _d −i _dM = i _df +2△i _dth i _h −i _hM = i _hf +2△i _hth (44) However, i _df and i _hf are the fault current portions of the currents i _d and i _h , respectively.

△i _dth and △i _hth are the fault changes in the circulating currents of i _d and i _h , respectively.

From these relationships, the amount of calculation _e in equation (38) is (28)
And as in the case of equation (29), it is expressed as follows.

e _e = (i _df −i _hf )×v _p −e _e ′ …(45) e _e ′=2(△i _dth −△i _hth )×v _p …(46) In general, compensation is Fault current i _hf to current i _h
In other words, the healthy phase difference current or the composite current of the healthy two-phase difference current is defined as the compensation current i _h . As a result, i _hf in equation (45) becomes zero. However, this is not always necessary, and if i _hf is sufficiently smaller than i _df , the fault current i _hf can be included in the compensation current i _h . Furthermore, for the compensation error component e _e ' in equation (46), the detection current _{i d and} compensation current i _h are selected so that the compensation error current i e ' in equation (47) is sufficiently small.

i _e ′=2(Δi _dth −Δi _hth ) (47) (e2) Modification of detection current i _d Equation (48) shows a modification of the detection current i _d .

i _da = i _dc = i _cs + i _as i _db = i _bs …(48) Compensation current i _h and polarity voltage for this example
The case where v _p is expressed as (39) will be explained. The compensation error current in this case is expressed by the following equation from the relationship between i _h in equation (39) and equations (47) and (48).

i _ea ′=i _ec ′=2(△i _cth +△i _ath −
K _1b △i _bth ) i _eb ′=2 {△i _bth −K _1ca (△i _cth + △i _ath )} (49) In equation (49), let each constant be the following value, for example.

k _1b = 3.1 0゜ K _1ca = 0.32 0゜ ...(50) In this case, the magnitude of the compensation error current when there is a fault change in the circulating current is calculated from the values of equations (12) and (14) as follows. The value is .

[Change 1]; |i _ea ′|=|i _ec ′|=96[A], |i _eb ′|=32[A] …(51) [Change 2]; |i _ea ′|=|i _ec ′｜=6.5 [A], |i _eb ′｜=2.0 [A] …(52) On the other hand, since the fault differential current flows only in the fault phase, the detection current i _d in equation (48) and equation (39) The fault current component of the compensation current i _h is expressed by the following equation.

i _dfa = i _af , i _dfb = i _bf , i _dfc = i _cf … (53) i _hfa = i _hfb = i _hfc = 0 … (54) However, i _dfa , i _dfb , i _dfc , i _hfa , i _hfb and i _hfc are each
These are the fault currents of i _da , i _db , i _dc , i _ha , i _ob and i _hc .

The value of the fault current in equation (53) is three times the value when the zero-sequence difference current i _ps is used as the detection current, like the detection current i _d in equation (39). In other words, when there is no fault change in the circulating current and the compensation error current i _e ' in equation (49) is zero, the calculation amount e _e in equation (45) becomes equation (55), and under the same conditions, (30) This is three times the amount of calculation in the equation.

e _e = i _f ×v _p (56) where i _f indicates the fault differential current of the fault phase, that is, i _af , i _bf or i _cf for the a, b or c phase ground fault.

An example in which the detection current i _d is expressed as (48) is (56)
Correctly detect the faulty line according to equation (45) or (46) depending on the amount of calculation in equation.

In addition, the compensation error current i _e ′ is maximum 96 [A] for one change,
Variation 2 has a maximum of 6.5A and the operating value can be reduced to this value. This is sufficiently smaller than the operating value of the conventional device, which is a minimum of 285 [A] for change 1 and a minimum of 17.5 [A] for change 2. Moreover, as mentioned above, the value of the fault differential current is three times that of the conventional device, so the sensitivity is extremely high.

Next, as a second modified example of the detection current i _d , one using the negative phase differential current based on the fault phase is shown in equation (56).

i _da = i _a2s , i _db = i _b2s , i _dc = i _c2s (56) However, i _a2s , i _b2s and i _c2s are the negative phase differential currents based on the a, b, or c phase, respectively. It is expressed by the following formula.

However, a=1 120°.

When each detected current is divided into a fault current component and a circulating current component, the fault difference current flows only in the fault phase, so the following equation is obtained.

However, i _a2th , i _b2th , and i _c2th are each negative phase circulating currents based on the fault phase and are expressed by the following equations.

i _a2th = 1/3 (i _ath + a ² i _bth + ai _cth ) i _b2th = ai _ath i _c2th = a ² i _ath (59) In this example, the circulating current of equation (58) 2i _a2th ,
The current obtained by compensating the fault change of 2i _b2th or 2i _c2th with the fault change of compensation current i _h is the compensation error current i _e ′
Then, the fault line is identified by the fault current 1/3i _af , 1/3i _bf , or 1/3i _cf in formula (58). The fault current component is the same as that of the conventional device, and when no fault variation occurs in the circulating current, the sensitivity is the same as that of the conventional device.

When the compensation current i _h is expressed by equation (39), the compensation error current i _e ' is expressed by the following equation.

i _ea ′=2(△i _a2th −K _1b △i _bth ) i _eb ′=2{△i _b2th −K _1ca (△i _cth +△i _ath )} i _ec ′=2(△i _c2th −K _1b a ² _bth ) ...(60) However, △i _a2th , △i _b2th and △i _c2th are the fault changes in the negative sequence circulating currents i _a2th , i _b2th and i _c2th based on the fault phase, respectively, and are expressed by the following equations: .

△i _a2th = 1/3 (△i _ath + a ² △i _bth + a△i _cth ) △i _b2th = a△i _a2th △i _c2th = a ² △i _a2th … (61) 2△ of change 1 and change 2 When the value of i _a2th is calculated from equations (12) and (14), the following value is obtained.

[Change 1]; 2△i _a2th = 97.3 155゜[A]...(62) [Change 2]; 2△i _a2th = 9.0 60゜[A]...(63) In equation (60), each constant is changed to, for example, be the value of

K _1b = 0.6 7゜, K _1ca = 0.19 130゜ ...(64) In this case, the magnitude of the compensation error current at change 1 and change 2 is expressed as (12), (14), (62) and (63). The following value is obtained from the formula.

[Change 1] |i _ca ′|= |i _ec ′|=43.7[A] |i _eb ′|=2.2[A] …(65) [Change 2] |i _ea ′|= |i _ec ′|= 2.2 [A] |i _eb ′|=1.26 [A] …(66) As shown above, the compensation error current i _e ′ is maximum at change 1.
43.7A, 2.2A with change 2, and the operating value can be reduced to the minimum value. Moreover, since the fault current component in the detection current is the same as that of the conventional device, protection can be achieved with extremely high sensitivity.

The above examples are just a few examples of the detection current i _d , and various types of fault phase difference currents or composite currents of the same phase difference current including the fault phase difference current can be used as the detection current i _d . For example, for a phase or c phase ground fault, a
The phase difference current i _as or the c phase difference current i _cs can be used, and the b phase difference current i _bs and another same phase difference current can be combined and used for the b phase ground fault. Also 2
For example, when combining two identical phase difference currents, (48)
It is also possible to compose not only i _cs + i _as as in the formula, but also in a form such as i _cs +K ₃ i _as (where K ₃ is a complex constant). Also, the composite current of the three same phase difference currents is the above-mentioned zero-sequence difference current i _ps and anti-phase difference current i _a2s ,
In addition to i _b2s and i _c2s , various types such as positive phase difference current can be used.

(e3) Modification of compensation current i _h Various types of compensation current i _h can be used in addition to i _h in equation (39). That is, all the compensation currents can be obtained from the differential current of one phase among the healthy phases, and one example thereof is shown in equation (67).

i _ha = K _1b i _bs i _hb = K _1c i _cs , i _hc = K _1a i _as ...(67) However, K _1c and K _1a are constants.

In this embodiment, a case will be explained in which the detected current i _d is set as the zero-sequence difference current i _ps as shown in equation (39).
In this case, the compensation error current i _e ' is given by the following equation from the relationship of equation (47).

i _ea ′=2(△i _pth −K _1b △i _bth ) i _eb ′=2(△i _pth −K _1c △i _cth ) i _ec ′=2(△i _pth −K _1a △i _ath ) …( 68) The current i _ea ′ in equation (68) is the same as i _ea ′ in equation (34). Changes 1 and 2 with each constant as the value of equation (69)
When the magnitude of the compensation error current i _e ' in the case of is calculated from equations (12) and (14), the values are obtained from equations (70) and (71).

k _1b = 1.4 0°, K _1c = 2.6 0°, K _1a = 0.55 0° …(69) [Change 1] | i _ea ′ | = 40 [A], | _eb ′ | = 105 [A], | i _ec ′=25 [A] …(70) [Change 2]｜i _ea ′｜=1.67 [A], | _eb ′｜=4.0 [A]
, ｜i _ec ′=2.4 [A] …(71) The maximum values of equations (70) and (71) are 105A and 4.0A, which allows the operating values to be sufficiently small compared to conventional devices. . In addition, in equation (67), if the compensation current i _hb is the a-phase difference current i _as instead of the c-phase current i _cs , the compensation error current i _eb ′ becomes equal to i _ec ′,
Furthermore, highly sensitive protection becomes possible.

The compensation current can also be obtained from various composite currents of the difference currents of the healthy two phases. Examples (72)
As shown in the formula.

i _ha = K _1bc (i _bs + i _cs 60°) i _hb = K _1ca (i _cs + i _as 60°) i _hc = K _1ab (i _as +i _bs 60°) …(72) However, K _1bc , K _1ca and K _1ab is a constant.

Regarding this embodiment, a case will be described in which the detected current i _d is set to a zero-sequence difference current i _ps as shown in equation (39). In this case, the compensation error current i _e ' is given by the following equation from the relationship of equation (47).

i _ea ′=2{△i _pth −K _1bc (△i _bth +
△i _cth 60°)｝ i _eb ′=2{△i _pth −K _1ca (△i _cth +△i _ath 60°)} i _eb ′=2{△i _pth −K _1ca (△i _cth +△i _ath 60゜)｝ i _ec ′=2 {△i _pth −K _1ab (△i _ath +△i _cth 60゜)}
...(73) When the current values of the second term on the right side of equation (73) in change 1 and change 2 are determined, equations (74) and (75) are obtained, respectively.

[Change 1] 2 (△i _bth + △i _cth 60°) = 330A 166°2 (△i _cth + △i _ath 60°) = 566A 189°2 (△i _ath + △i _bth 60°) = 610A 161°…(74) [Change 2] 2 (△i _bth + △i _cth 60°) = 14.8A 44°2 (△i _cth + △i _ath 60°) = 39.2A 16°2 (△i _ath + △i _bth 60゜) = 41.2A 55゜…(75) Let the value of each constant in formula (73) be formula (76), and change 1
The magnitude of the compensation error current i _e ' in the case of 2 and 2 is determined by the values of equations (77) and (78).

K _1bc = 1.0 22°, K _1ca = 0.47 48°, K _1ab = 0.45 15°
…(76) [Change 1] |i _ea ′|=45A, |i _eb ′|=21A, |i _ec ′
｜
=18A...(77) [Change 2] |i _ea ′|=2.7A, |i _eb ′|=11A, |i _ec ′
|=1.6A (78) The values of equations (77) and (78) allow significantly higher sensitivity than conventional devices.

In each of the above embodiments of the compensation current i _h , the compensation current is obtained from the composite current of the same phase difference current of two healthy phases or the same phase difference current of one phase among the healthy phases. Therefore, these compensation currents i _h do not include the fault phase difference current component, and the fault current component i _hf is zero. Therefore, if the compensation current i _h is varied within the above range, the compensation error e _e ' in equation (45) will be different, but the other term (i _df −
i _hf ) × v _p is not affected. The compensation error e _e ′ is
Since the compensation error current i _e ' has different values as described above, the values are different, but in each case, sufficiently high sensitivity can be obtained compared to the conventional device. In addition, in the above explanation, only the case where the detection current i _d is the zero-sequence difference current i _ps was explained, but (48)
The same effect can be obtained for other detection currents such as equation (56).

However, the compensation current i _h is not limited to the above, and can be obtained from a composite current of the same phase difference current including the fault phase difference current. In this case, since the fault current i _hf is included in the compensation current, it is necessary to make the fault phase difference current component in the compensation current i _h sufficiently smaller than the fault phase difference current component in the detection current i _h , but it is fully applicable. . As an example of this, where the detection current is the negative phase difference current of equation (56), the compensation current i _h is shown in equation (79).

i _ha = K _1o i _ps i _hb = aK _1o i _ps i _hc = a ² K _1o i _ps (79) However, K _1o is a constant whose absolute value is sufficiently smaller than 1.

The compensation error current i _e ' in this case is expressed as follows.

i _ea ′=2(△i _a2th −K _1o △i _pth ) i _eb ′=2(△i _b2th −aK _1o △i _pth ) i _ec ′=2(△i _c2th −a ² K _1o △i _pth ) …(80) Let the constant K _1o be the value of equation (81), and change 1 and 2
Calculating the magnitude of the compensation error current i _e ' in the case of , results in equations (82) and (83).

K _1o =0.43 9゜ …(81) [Change 1] |i _ea ′|= |i _eb ′|= |i _ec ′|=15.8A
…(82) [Change 2]｜i _ea ′｜=｜i _eb ′｜=｜i _ec ′｜=17.5A
...(83) The detected current i _d in equation (56) includes the fault current (58)
The zero-sequence difference current i _ps included as shown in the equation and used for the compensation current i _h includes 1/3 of the fault phase difference current component, and the fault difference current component is a, b, or c phase ground fault. are respectively 1/3i _af , 1/3i _bf or 1/3i _cf , so
The current i _df −i _hf (the fault current used for the calculation amount e _e , hereinafter referred to as the fault calculation current and represented by the symbol i _ef ) of the first term on the right side of equation (45) is calculated as follows.

However, i _efa , i _efb and i _efc are the calculation amounts e _ea , e _eb
and the fault calculation current i _ef used for e _ec .

If we rearrange equation (84) using the constant K _1o as the value of equation (81), we get equation (85).

In this way, the fault calculation current i _ef is different for each phase,
The i _efa of the a phase is reduced to 0.58 times the value 1/3i _af when the compensation current i _h does not include the fault current i _hf . in this case,
For the operating value determined by the value of equation (82) or (83), the value of the fault calculation current i _ef is 0.58 times the normal case, and the fault calculation current is 1/1 of the normal case. Considering 3i _af , the magnitude of the compensation error current i _e ′ is essentially 1/0.58 times the value of equations (82) and (83),
That is, change 1 is 27.3 [A] and change 2 is 3.02 [A]. However, even with this value, protection with sufficiently high sensitivity compared to conventional devices is possible.

As described above, the compensation current i _h can be obtained from the same phase difference current or a composite current thereof, as long as the fault phase difference current component is sufficiently smaller than the fault phase difference current component of the detected current i _d .

(e4) Modification of polarity voltage v _p The polarity voltage v _p is not limited to the example of equation (39), but is a voltage that changes only slightly before and after the occurrence of a one-phase ground fault in the protected system, that is, equation (42) holds true. Various modifications can be made as long as the voltage is the same.

For the voltage in equation (39), the relationship in equation (42) holds only under the condition of Z ₂ = Z ₁ without the condition of Z ₂ ≪ Z ₀ in equation (20), but if Z ₂ ≪ Z ₀ If the conditions are met, the relationship in equation (42) holds true at various voltages. That is, when Z ₂ << _{Z 0} , the voltage at the time of the a-phase 1-phase ground fault in equation (18) is transformed as follows.

Therefore, the following relationship occurs at the accident point.

V _aF −V _a0F ＝V _a1F ＋V _a2F ≒E _a1F V _bF −V _a0F ＝a ² _V a1F ＋V _a2F ≒E _a1F V _cF −V _a0F ＝aV _a1F ＋V _a2F ≒aE _a1F V _caF ＝aV _a1F ＋a ² V _a2F −V _a1F −V _a2F ≒(a−1)E _a1F V _abF =V _a1F −a ² V _a1F −aV _a2F ≒(1−a ² )E _a1F …(87) However, V _aF , V _bF , V _cF , V _caF and V _abF are the a, b and c phases, the ca phase and the ca phase at the fault point, respectively.
This is the voltage between the a and b phases.

In addition, the voltage V _a1F in equation (36) and all the voltages in equation (87) show slight changes before and after the accident. A voltage with a small change before and after the fault at the fault point has a small change in voltage at other points, so a similar voltage at the relay installation point can be used as the polarity voltage. When the calculation of the detected quantity e _d and the compensation quantity e _h used for the detected quantity e _e is the cross product calculation of equation (38), an example of the polarity voltage v _p that can be used under the condition of Z ₂ ≪ Z ₀ is as follows. It is something.

v _pa = v _a1 90°, (v _a − v _p ) 90°,
(v _b −v _p 30°, (v _c −v _p ) 150°, v _ca 120° or v _ab 120°v _pb = v _b1 90°, (v _b −v _p ) 90°, (v _c − v _p 30°, (v _a −v _p ) 150°, v _ab 120° or v _bc 120°v _pc = v _c1 90°, (v _c −v _p ) 90°, (v _a −v _p 30° , v _pc = v _c1 90°, (v _c − v _p ) 90°, (v _a − _{v p} 30°, (v _b − v _p ) 150° v _bc 120° or v _ca 120°…(
88) As explained from the relationship in equations (86) and (87), each of the above polar voltages is in phase with the polar voltage v _p in equation (39), and can be used in exactly the same way.
Since the zero-phase voltage v _p is the same regardless of the reference phase, the reference phase symbol is omitted from the illustration.

The polarity voltage v _p is also not necessarily limited to that obtained from the grid voltage as described above. That is, the voltage of an oscillator that generates a sinusoidal AC voltage whose frequency is controlled to be synchronized with the system frequency does not change before and after the accident, so it can be used. Also, the polarity voltage v _p
Instead, if the current does not change before and after the accident occurs, the polar current i _p can be obtained by adding a voltage that can be used as the polar voltage v _p to a constant impedance, and the frequency is synchronized with the grid frequency. A controlled sinusoidal alternating current can be generated from the oscillator current.

(f) Modification of calculation contents In the above explanation, all calculations were performed to calculate the cross product as shown in equation (38). However, this is not limited to the cross product, and can be performed using various functions.
These will be explained below. Equation (89) is a modified example of calculation of the detection amount e _d and the compensation amount e _h .

e _d ＝i _d・v _p −i _dM・v _pM e _h ＝i _h・v _p −i _hM・v _pM …(89) However, all of the above equations are inner products, and below the symbol (・) is used to express inner products. show.

Equation (89) uses an inner product instead of an outer product. In this case, by relatively advancing the phase relationship of the polarity voltage _{v p with} respect to the detection current i _d and the compensation current i h by 90°, the same result as when using the outer product can be obtained. Therefore, for example, the polarity voltage v _p in equation (39) or equation (88) needs to be advanced by 90°. In this case, for example, if the voltage v _a1 or v _a −v _p is used as the polarity voltage v _pa , there is no need to delay the phase by 90° as in equation (88), and the calculation is simplified.

Equation (90) is a second modified example of calculation of the detection amount e _d and the compensation amount e _h .

Equation (90) uses the operation as a quotient. In this case, in order to make the judgment result in step S7 similar to the example using the calculation of equation (89) and the judgment of equations (40) and (41), the polarity voltage v _p must be set as (39).
Alternatively, the equation (88) is advanced by 90 degrees, and the determinations in steps S7-1 and S7-2 are made into equations (91) and (92), respectively.

e Effective component of _e ＞K ₂ / | v _p | …(91) −e Effective component of _e ＞K ₂ /|v _p | …(92) Also, each term of the operation in equation (90) can be expressed as a simple quotient. If we use the effective part of the quotient instead, we can obtain similar results by simply determining the value _{of e} as in equations (93) and (94).

e _e > K ₂ / | v _p | … (93) −e _e K ₂ / | v _p | … (94) Also, if each term in the operation of equation (90) is the invalid part of the quotient, (39) Or the polarity voltage v _p of equation (88) and (93)
Similar results can be obtained using the determination of equation (94).

Equation (95) shows a further modified embodiment of the calculation of the detection amount e _d and the compensation amount e _h .

e _d ＝i _d ×v _p −｜K ₄ i _d・v _p ｜−(i _dM ×v _pM −｜K ₄ i _dM・v _pM ｜) e _h ＝i _h ×v _p −｜K ₄ i _h・v _p |−(i _hM ×v _pM − |K ₄ i _hM・v _pM |) (95) However, K ₄ is a constant.

This will be explained. If we rearrange the amount of calculation e _e using equation (95), we get the following from the relationship e _e = e _d − e _h in equation (38).

e _e = (i _d −i _h )×v _p − |K ₄ (i _d −i _h ) ・v _p |−{(i _dM −i _hM ×v _pM −|K ₄ (i _dM −i _hM )・v _pM ｜｝ …(96) If v _p = v _pM in equation (96), the following is obtained.

e _e = i _e ×v _p − | K ₄ i _e・v _p | (97) However, i _e is the calculated current and is expressed by the following equation.

i _e = (i _d − i _dM ) − (i _h − i _hM ) …(98) The operation characteristics when the calculation amount e _e of equation (97) is determined by equation (40) are expressed as the operation of the calculation current i _e 6th in terms of range
Let it be the polygonal line A in the figure. In other words, the in-phase or anti-phase component of current i _e with respect to voltage v _p is zero, and |K ₄ i _e・
When the value of v _p | is zero, it operates when the leading reactive component of current i _e is K ₂ , but as |K ₄ i _e・v _p | increases, the leading reactive component of current i _e increases. Otherwise, it will not work and will have the characteristics of A. Such a polygonal line characteristic is often used in ordinary ground fault line selection relays.

On the other hand, for the calculation of equation (38), the operating range is shown by the straight line RO in FIG. In other words, when the calculation amount e _e in equation (38) is expressed by the detection current i _d and the polarity voltage v _p , e _e = (i _d − i _h ) × v _p − (i _dM − i _hM ) × v _pM … ( 99) In equation (94), set V _p = v _pM , and calculate current i _e in equation (98).
Expressed as: e _e =i _e ×v _p (100), and when judged using equation (40), it operates when the leading reactive component of the calculation current j _e with respect to the polarity voltage v _p is larger than a constant value K ₂ . Such a linear characteristic is a characteristic generally used in ordinary ground fault line selection relays.

In the above explanation, as shown in equations (38), (89), (90), and (96), the cross product of the detected current i _d and the polarity voltage v _p is calculated in steps S4 and S6.
After separately calculating a function such as an inner product or quotient and a similar function of compensation current i _h and polarity voltage v _p , the difference in each accident change is calculated to calculate the detected amount e _d and the compensation amount e _h
The calculation amount e _e is calculated from the difference e _d −e _h between the two. However, it is not necessary to use only such means, and the same calculation contents can be implemented with various modifications.

An example of this is shown in equations (96) and (99). That is, in equation (96), the storage amount e _M of the following equation is stored in step S4.

e _M = (i _dM − i _hM ) × v _pM … (101) In this case, before detecting the fault, first calculate the difference i _dM − i _hM between the detected current and the compensation current, and then calculate this difference current and polarity voltage v Calculate and store the cross product of _pM . Step S6
After fault detection, first calculate the difference i _d −i _h between the detected current and the compensation current, and then calculate this difference current and polarity voltage v _p
After calculating the cross product of , calculate the difference from the storage amount e _M and set it as the calculation amount e _e .

In equation (96), the memory amount e _M is expressed by the following equation.

e _M = (i _dM −i _hM )×v _pM − |K ₃ (i _dM −i _hM )・V _pM
(102) Also in this case, the difference current i _dM −i _hM is first calculated, then the outer product and inner product are calculated, and then the storage amount e _M is calculated.

As described above, in each of the above embodiments, the values of the functions of the detection current, compensation current, and polarity voltage (or polarity current) are stored before an accident is detected, and the values of the detection current, compensation current, and polarity are stored after the accident is detected. The amount of change in the value of the voltage (or polarity current) function with respect to the stored value is determined, and a ground fault line is detected based on this amount of change.

(g) Storage of sample values Although each of the above embodiments stores the values of the functions of the detection current, compensation current, and polarity voltage (or polarity current), the present invention does not necessarily store the values of the functions. It can be carried out without memorization.
In this case, the sample value of the current is stored in step S4. In this case, the calculation amount e _e is expressed, for example, by the following equation using the calculation current i _e of equation (98).

e _e = i _e ×v _p … (103) The fault change portions i _d −i _dM and i _h −i _hM of the detection current and compensation current in equation (98) are the respective sample values after the fault detection and the fault detection It is calculated from the difference between the respective sample values stored before and an integral multiple of the period of each current. A calculation report e _e is obtained by the cross product of the calculation current i _e and the polarity voltage v _p thus calculated, and a faulty line is detected.

The calculated current i _e calculated as above can be used in the same way as a normal ground fault line selection relay, and the polarity voltage v _p (or polarity current) changes before and after the occurrence of a one-phase ground fault fault. need not be small. Therefore, voltages other than equations (39) and (38) can also be used as the polarity voltage v _p . A typical example of this is the zero-sequence voltage v _p .

Zero-sequence voltage V _apF at the fault point when a-phase 1-phase ground fault occurs
is equation (86), and since both Z ₀ and R _G are impedances with a small reactance component and a large resistance component, they are almost in opposite phase to the voltage E _a1F . Therefore, for the quadrature voltage V _bcF in equation (21), the voltage
V _apF lags by almost 90°. In a one-phase ground fault in a resistance grounding system, the fault current is small, so the difference in voltage between the fault point and the relay installation point is small, and the relationship in which the zero-phase voltage v _p lags the quadrature voltage v _bc by approximately 90° is as follows. It won't collapse. This relationship holds true even in accidents involving other phases,
The voltage v _p 90° obtained by advancing the zero-sequence voltage by 90° can be used to calculate the calculation amount e _e in equation (103), similarly to the polarity voltage v _p in equation (39). Also, when using the voltage −v _p with a different sign of the zero-sequence voltage as the polarity voltage v _p ,
The calculation amount e _e can be obtained by calculating the inner product as shown in the following equation.

e _e = i _e ×V _p (104) The calculation method for determining the calculation current i _e is not limited to the above embodiment, and can be implemented in various modifications. That is, even if the sample value of the storage current i _M of equation (105) is stored and the calculated current i _e is calculated by the calculation of equation (106), exactly the same result can be obtained.

i _M = i _dM −i _hM … (105) i _e = i _d −i _h −i _M … (106) In addition, when calculating the fault change in compensation current (i _h −i _hM ), for example, Compensation current i _h in equation (39)
In the case of , the sample values are memorized without multiplying each phase difference current and their combined current i _bs and i _cs + i _as by the constants K _1b and K _1ca , and after calculating each fault change, the result is exactly the same even if multiplied by the constant. The result is obtained.

The embodiments described above are only a few examples of means for directly calculating the calculated current i _e using current sample values and detecting a faulty line based on the relationship between this and the polarity voltage, and various modifications can be made. It is something.

As described above, the present invention identifies a fault line based on the relationship between the difference between the fault change amount of the detected current and the fault change amount of the compensation current and the polarity voltage (also polarity current), and stores the above-mentioned function. is considered to be one way to do so.

(h) Modification of fault line detection means (Step 7) The fault line detection means in Step 7 is not necessarily limited to the means of formulas (40), (41), (93), and (94). There is nothing that can be done. All of these means are considered to be the most ideal, as their sensitivity is unaffected by the magnitude of the polarity voltage _vp . However, in both the polarity voltages v _p of equations (39) and (88), there is a slight change in the case of a one-phase ground fault accident compared to that during normal operation. Therefore, the change in size is almost the same as the change during constant operation, and the range of variation is, for example, about ±10%. Therefore, even if the term of voltage v _p is omitted and the judgment conditions in steps S7-1 and S7-2 are set to equations (107) and (108), respectively, the change in sensitivity is small and there is almost no problem in practical use. It won't happen.

e _e >K ₂ (107) −e _e >K ₂ (108) In this way, the judgment conditions in step S7 can be changed in various ways.

(i) Addition of suppression effect All of the above embodiments can achieve significantly higher sensitivity than conventional devices. but,
When the target is change 1, the magnitude of the compensation error current i _e ' is, for example, a maximum of 40 A in equation (36), and in this case, the operating value cannot be made smaller than this value. The present invention provides a measure that enables high-sensitivity protection in a normal internal accident or an internal accident as in change 2, without malfunctioning due to an external accident even in the case of change 1.

This countermeasure is to use the current obtained from the same phase difference current or the composite current of the same phase difference current as the suppression current,
The suppression effect is performed depending on the magnitude of the fault change in the suppression current or its function. The condition for the suppression current is that its magnitude is approximately proportional to the magnitude of the compensation error current i _e '.

The configuration of the present invention is exactly the same as that shown in FIG. The calculation flow is shown in FIG. In FIG. 7, the same parts as in FIG. 5 are indicated by the same symbols. The difference between Fig. 7 and Fig. 5 is that step S6 is replaced by step S6.
This is because S8 is used. In steps S8-1, S8-2, and S8-3 of step S8, in addition to the calculation amounts e _ea , e _eb , and e _ec , the suppression amount | e _ra
|, |e _rb | and |e _rc | are calculated. The calculation amount e _e and the suppression amount | _er (the one used for the calculation among | _era |, | _erb |, and | _erc |) are used for the determination in step S7.

An example of the amount of suppression | _er | is shown in equation (109). The term voltage |v _p | is used to remove the effect of the magnitude of voltage v _p when the calculation amount e _e is expressed as the product of voltage v _p and calculation current i _e , and this effect is If there is no problem, it can be set as a fixed constant.

｜e _r ｜=｜i _r −i _rM ｜｜v _p ｜ …(109) However, i _r is the suppression current used for calculation, and i _rM is the memorized value of i _r before the accident. It is.

|i _r −i _rM | in equation (109) indicates the magnitude of the fault change i _r −i _rM in the suppression current i _r . i _r −i _rM is calculated from the difference between the sample value after the accident is detected and the sample value before the accident is detected.

The determination conditions in steps S7-1 and S7-2 are, for example, equations (110) and (111), respectively.

e _e ＞M _x [K ₂ ｜v _p ｜, ｜e _r 〕 …(110) e _e ＞M _x 〔K ₂ ｜v _p ｜, ｜e _r 〕 …(111) However, X _x 〔K ₂ ｜ v _p |, |e _r |] is K ₂ |v _p |
is the maximum value of |e _r |, and the maximum value is indicated by a similar symbol below. A specific example of the suppression current i _r is shown in equation (112).

i _ra = i _rc = K _5b i _bs i _rb = K _5ca (i _cs + i _as …(112) where i _ra , i _rb and i _rc are the suppression amounts used for the suppression amounts e _ra , e _rb and e _rc , respectively. Current i _r , K _5b and K _5ca
is a constant.

The suppression current in equation (112) does not include the fault phase difference current, so it is only the fault change in the circulating current, and is expressed as the following equation.

i _ra −i _raM = i _rc −i _rcM = 2K _5b △i _bth i _rb −i _rbM = 2K _5ca (△i _cth + △i _ath ) …(113) The constants K _5b and K _5ca in equation (113) Let K ₂ in equations (110) and (111) be the value of equation (114).

K _5b = 0.2, K _5ca = 0.03, K ₂ = 1A...(114) The magnitude of the fault change in the suppression current in this case is (12)
When calculated from equation (14), equations (115) and (116) are obtained.

[Change 1] |△i _ra |= |△i _rc |=46.4 [A] |△i _rb |=18.7 [A] …(115) [Change 2] |△i _ra |= |△i _rc |= 2.3 [A] |△i _rb |=1.2 [A] …(116) However, △i _ra , △i _rb and △i _rc are the accident changes of i _ra , i _ra and i _rc , respectively, and the following equation It is expressed as

△i _ra = i _ra −i _raM △i _rb = i _rb −i _rbM △i _rc = i _rc −i _rcM …(117) |△i _r | (△i _r is △
The values of i _ra , △i _rb and △i _rc used in the calculation are larger than the magnitude of the compensation error current |i _e ′| in equations (36) and (37), respectively, in the same phase. Therefore, the calculation amount e _e using this suppression amount is expressed by equations (3) to (5), that is, equations (38) and (39), and the judgment conditions are expressed by equations (110) and (111). For example, there will be no malfunction due to compensation error current due to an external accident.

If there is no change in the condition of the induced transmission line due to a normal internal accident, the accidental change in circulating current is zero, so
The amount of suppression | e _r is also zero, and the operating value is K ₂ in equation (114)
It becomes 1A, which is equal to the value of . In addition, if the situation of the induced power transmission line changes, the sensitivity will be the worst in change 1.
The sensitivity will be 46.4A, but if the fault in the induced power transmission line is eventually severed and the situation changes to change 2, the sensitivity will recover to 2.3A at worst. As described above, by using the suppression amount |e _{r |} corresponding to the magnitude of the fault change in the suppression current i _r obtained from _the same phase difference current | While preventing malfunctions when the faulty change in current is extremely large, highly sensitive protection can be provided when the faulty change in circulating current is small.

(j) Modified example of calculation of suppression amount In the above embodiment, the suppression current i _r is stored as its sample value, the fault change in suppression current △i _r = i _r −i _rM is calculated, and from this the suppression amount | e _r | is obtained. When such a sample value storage type is used in combination with the calculation amount e _e obtained by sample value storage, there is an advantage that the stored values can be shared. On the other hand, if the amount of calculation can be obtained by storing the function, it is preferable for the same reason that the amount of suppression can also be obtained by storing the function.

This method will be described below. Equation (118) shows an example of means for obtaining the suppression amount | _er | by function storage.

｜e _r ｜=√( _r × _p − _rM × _pM ) ²
( _r・_p − _rM・_pM ) ² … (118) In other words, find the fault change of the outer product and inner product of the suppression current i _r and the polarity voltage v _p , and calculate the square root of the sum of the squares of each as the suppression amount | e _r | That is. In equation (118), if v _p = v _pM , |e _r |=√{( _r − _rM × _p } ² + {( _r −
_rM )・_p } ² = |i _r −i _rM | | v _p |...(119), and the amount of suppression is equal to equation (109).

Equation (120) shows a second embodiment of the means for obtaining the suppression amount | _er | by function storage.

｜e _r ｜=M _x 〔｜i _r ×v _p −i _rM ×v _pM ｜, ｜i _r
・v _p −i _rM・v _pM ｜, ｜i _r ×v _p −i _rM ×v _pM ｜＋｜i _r
・v _p −i _rM・vi _pM ｜/√2〕…(120) In other words, the absolute value of the fault change of the outer product and inner product of the suppression current i _r and the polarity voltage v _p and (the sum of the respective absolute values)/ Let the maximum value of √2 be the suppression amount | _er |. FIG. 8 is a vector diagram explaining equation (120). Assume that the voltage v _p (=v _pM ) and the current i _rM are the vectors shown. Now, when the first term |i _r ×v _p −i _rM ×v _pM | of equation (120) is equal to a constant value K ₆ , the locus of the current i _r becomes straight lines A and B.
Further, when the second term |i _r ·v _p −i _rM ·v _pM | is equal to the constant value K ₆ , the locus becomes straight lines C and D. Also, the third term (|i _r ×v _p −i _rM ×v _pM |+i _r ×v _p −i _rM・v _pM
When |)/√2 is equal to the constant value K ₆ , the locus becomes a square E. Therefore, the locus of the current i _r when the maximum value of each of these terms is equal to the constant value K ₆ lies on the regular octagon shown by the solid line. For this reason, the amount of suppression | e _r
The magnitude of the accidental change in the current i _r when | is equal to a constant value K ₆ | i _r −i _M | is the distance between the head of the vector of the current i _rM and the solid line regular octagon. This distance is i _r −i _M
between K ₆ and K ₈ /cos22.5°, depending on the phase angle of
Varies between _K6 and _1.08K6 . Therefore |i _r −i _rM
When ||v _p | is equal and the phase angle changes, the amount of suppression | _er | changes between 1 and 1/1.08. This error corresponds to an error of approximately ±4% when the center value is considered to be 1/1.04. In other words, the amount of suppression |e _r | in equation (120) is approximately 4
It realizes |i _r −i _rM |v _p | with an error of %, and can be used almost in the same way as the suppression amounts in equations (109) and (118). (118) and (120)
The amount of suppression in the equation is suitable for those in which the amount of calculation is calculated by the product of the polarity voltages V _p , as in equations (38), (89), and (95).

Equation (121) shows a third embodiment of the means for obtaining the suppression amount | _er | by function storage.

｜e _r ｜=｜i _r ／v _p −i _rM ／v _pM ｜ … (121) This means that the magnitude of the fault change in the quotient of the suppression current i _r with respect to the polarity voltage v _p is expressed as the suppression amount | e _r ｜ This is suitable for calculating the amount of calculation in the form of a quotient for the voltage v _p , as in equation (90). In equation (121), v _p
= v _pM , |e _r |=|i _r −i _rM /v _p | ...(122) For the calculation amount e e using equation (90), the calculation amount _e is different from that of other embodiments. Similarly, the compensation error current
It is used so that the magnitude of the fault change in the suppression current |i _r −i _rM | is larger than the magnitude of i _e ′.
In this case, steps S7-1 and S7
-2 determination conditions are, for example, equations (123) and (124), respectively.

e _e ＞M _x [K ₂ /｜v _p ｜, |e _r ｜] …(123) −e _e ＞X _x [K ₂ /｜v _p , |e _r ｜] …(124) As above , the suppression amount |e _r | related to the magnitude of the fault change in the suppression current |i _r −i _rM | is calculated using the fault change in the function of the suppression current i _r and the polarity voltage v _p (or polarity current). Obtainable.

(k) Modification of suppression current Equation (112) is only one example of suppression current i _r . The current that can be used as the suppression current is that the component i _rf of the fault difference current among the currents obtained from the same phase difference current or the composite current of the same phase difference current is the calculated current
This is sufficiently smaller than the fault difference current component i _ef of i _e . If this component i _rf becomes a large proportion of the component i _ef , the suppression effect due to the fault differential current will be added, and the sensitivity will decrease accordingly, which is not preferable.

From the above points, the current obtained from the healthy phase difference current and its composite current does not contain the fault phase difference current component, and therefore does not contain the fault difference current component, and is therefore most suitable for the suppression current. Examples of the suppression current i _r under such conditions are shown in equations (125) and (126).

i _ra = K _5b i _bs , i _rb = i _rc = K _5a i _as …(125) i _ra = K _5bc (i _bs + i _cs 60°) i _rb = K _5ca (i _cs + i _as 60°) i _rc =K _5ab (i _bs + i _cs 60°) ...(126) However, K _5a , K _5b , K _5bc , K _5ca and K _5ab are constants.

These fault changes in the suppressing current i _r can be used as suppressing currents because the fault changes in the circulating current are large, and when the compensation error current i _e ' is large, they increase almost proportionally.

Furthermore, when the current terms of the suppression current i _r and the compensation current i _h are made equal, there is an advantage that the stored values of sample values or function values can be shared by both. However, it is not necessary to make the two equal, and various combinations of the respective current terms exhibit approximately the same effect. For the sake of simplicity, description of numerical examples will be omitted.

Even if the suppression current i _r also has a fault phase difference current component, it can be applied as long as the fault phase difference current component is sufficiently smaller than the fault phase difference current component of the detection current i _d . An example is shown in equation (127).

i _ra = i _rb = i _rc = K _5o i _ps (127) However, K _5o is a constant whose absolute value is sufficiently smaller than 1.

A case will be described in which this suppression current is applied to the calculation amount of equations (38) and (39).
The fault change in the suppression current i _r in equation (127) is expressed as equation (128) from equation (16).

△i _ra = △i _rb = △i _rc = K _5o (i _pf + 2△i _pth … (128) Since i _pf = 0 in an external fault, the suppression current i _r is 2△
i is equal to _pth . Under these conditions, when the value of K _5o is set to equation (129) and the magnitude of the suppressing current for changes 1 and 2 is calculated, equations (130) and (131) are obtained, respectively.

K _5o =0.2 …(129) [Change 1] |△i _ra |=|△i _rb |=|△i _rc |=57A
…(130) [Change 2] ｜△i _ra ｜=｜△i _rb ｜=｜△i _rc ｜=3.5A
...(131) The values of equations (130) and (131) are larger than the compensation error current values of equations (36) and (37), respectively, and no malfunction will occur due to external faults. Moreover, the value of equation (131) is 3.5A, which is a sufficiently small value.

In the case of an internal fault, K _5o i _pf = 0.2i _pf is added to the suppression current. The sensitivity decreases by this amount, but the zero-sequence fault difference current i _pf flows in the calculation current i _e , and this value is 0.2i _pf.
, so the sensitivity is (130) or (131)
Although it is slightly lower than the value of the formula, it is sufficiently sensitive and can protect. Although such a slight decrease in sensitivity is not desirable, it is sufficient to withstand use.

As described above, the suppression current i _r can be obtained from various same phase difference currents or a composite current of the same phase difference currents.

(l) Variations in how to use the suppression amount Equations (110), (111), (123) and (124) are
These are merely some examples of determination conditions using the suppression amount | _er |. The determination condition using the suppression amount | _er | can be modified in various ways, examples of which are shown below.

e _e ＞K ₂ ｜v _p ｜+｜e _r ｜ …(132) −e _e ＞K ₂ ｜v _p ｜+｜e _r ｜ …(133) Equations (132) and (133) are In formula (111), the maximum values of K ₂ |v _p | and e _r | are used on the right side, whereas the sum of the two is used.
In this case as well, it does not work unless e _e or -e _e is large with respect to | _er |, and has the same effect as the embodiments of equations (110) and (111).

Also, instead of comparing the calculation amount e _e and the suppression amount |e _r | as in equations (110) and (111), for example,
The magnitude of the calculation current i _e |i _e | and the magnitude of the fault change in the suppression current i _r |i _r −i _rM | are compared as shown in equation (134), and a fault line can be detected under this condition. You can also do it.

｜i _e ｜＞｜i _r −i _rM ｜ (134) That is, in equation (110), the amount of suppression | e _r | is, for example, equation (109), and the amount of calculation e _e is, for example, equation (104). , the magnitude of the fault change in the suppression current i _r | i _r −i _rM |
is the magnitude of the compensation error current i _{e ′} out of the calculation current i _e |
i _e ′| is set to be larger than i e ′ to prevent malfunctions caused by the compensation error current i _e ′. Therefore, it is not necessary to perform this action using functions such as equations (104) and (109), and even direct comparison as shown in equation (134) will prevent malfunctions due to the compensation error current i _e '. In addition, it is possible to achieve the purpose of highly sensitive protection when the accidental change in circulating current is small.

When formula (134) is used, a faulty line is detected using determination conditions such as formulas (40) and (41) that do not use suppressing current, provided that formula (134) holds true.

As described above, the suppression of the present invention includes all means for producing a suppression effect by the fault change amount i _r −i _rM of the suppression current i _r . In addition to this suppression, it is of course possible to add other suppression effects depending on the values of other voltages and currents, such as zero-sequence voltage and normal phase-difference current during an accident.

(m) Addition of suppression effect when compensation current i _h is not used.

The above suppressing effect is effective in improving sensitivity even when the compensation current i _h is not used for the calculation amount e _e . This method has already been applied for, but in the present invention, by using the fault variation of the function of the suppression current, the suppression effect corresponding to the magnitude of the fault variation of the suppression current i _r can be obtained without storing sample values. I can make you do it.

e _e = e _d …(135) In this case, the amount of calculation e _e is expressed by equation (135),
The detected amount e _d is expressed by equations (38) and (39).
In addition, the suppression amount | _er | is calculated by equation (118) using the suppression current i _r of equation (112),
The determination conditions are shown by equations (110) and (111). In this case, the fault change in the detected current i _d (= _ips ) is directly affected by the fault change in the circulating current, and the magnitude is 285 A for change 1 and 17.5 A for change 2. Also, equation (112) and (110)
If the constants K _5b , K _5ca and K ₅ in the equations are taken as the values in equation (136), then the magnitude of the fault change in the suppression current is given by equations (137) and (138).

K _5b = 2, K _5ca = 0.6, K ₂ = 1 [A] …(136) [Change 1] |△i _ra |= |△i _rc |=374 [A], |△i _rb |=464 A] …(137) [Change 2] |△i _ra |= |△i _rc |=24.4 [A], |△i _rb |=23.0 [A] …(138) In this way, the fault change in the suppression current size |
i _r | is larger than the fault change in the circulating current of the detected current i _d , and malfunctions will not occur due to changes in the circulating current. Further, in the state of [Change 2], the sensitivity is 24.4A.If there is no change in the circulating current, the sensitivity is 1A, which is significantly higher than the sensitivity of 285 [A], which can prevent malfunctions in the conventional device under Change 1.

Such increased sensitivity is due to (48) and (56)
One uses the detection amount e _d as the calculation amount e _e using other detection currents such as the equation (125) and one that uses the suppression amount e _r using other suppression currents such as equations (126).
, those that use other calculation principles such as equations (89) and (90) to calculate the detected amount e _d , and those that use other calculation principles such as equations (120) and (121) to calculate the suppression amount |e _r | Similar effects are shown for various combinations of methods using the same calculation principle.

As described above, the fault change in the function of the suppression current and polarity voltage (or polarity current) is applied to the ground fault line selection relay that identifies the fault line based on the relationship between the fault change in the detected current and the polarity voltage (or polarity current). Sensitivity can be improved by determining the amount of suppression related to the magnitude of the fault change in the suppression current and adding a suppression effect based on this.

(n) Application to transmission lines with 6 circuits The above explanations are all for transmission lines with 4 circuits, and new problems arise when applied to transmission lines with 6 circuits. This will be explained below. FIG. 9 is a diagram showing an example of the wire arrangement of a six-circuit parallel transmission line, and the same parts as in FIG. 5 are indicated by the same symbols. a5, b5, c5, a6, b6 and c6 are a, b, c of power transmission lines 5L and 6L, respectively
These are the electric wires for each phase. In the wire arrangement shown in the figure, parallel power transmission lines 3L and 4L are largely guided by parallel power transmission lines 1L and 2L and 5L and 6L. On the other hand, parallel transmission lines 1L and 2L and 5L and 6L
receives a large amount of induction from the nearby parallel power transmission lines 3L and 4L, and the induction from other sources is relatively small. Therefore, the power transmission lines 3L and 4L, which receive a large amount of induction from the two parallel power transmission lines, will be described as protected power transmission lines, and the others will be described as induced induction transmission lines.

Power transmission line 3 guided by transmission lines 1L and 2L
There is a relationship between the changes in the circulating currents of L and 4L as shown in equations (13) and (15), and the relationship shown in equation (139) holds approximately for various state changes of the induced transmission line. .

△i _ath ≒R _1a △I, △i _bth ≒R _1b △I, △i _cth ≒R _1c △I, △i _pth ≒R _1o △I … (139) However, R _1a , R _1b , R _1c and R _1o is a constant, and ΔI is a fault change in the induced current (which does not indicate a specific current but provides a reference for circulating current) I in the power transmission lines 1L and 2L.

On the other hand, the accidental change in circulating current due to induction from the power transmission lines 5L and 6L is expressed by an approximate expression (140).

△i _ath ≒R _2a △I′, △i _bth ≒R _2b △I′, △i _cth = R _2c △I′, △i _pth = R _2o △I′ …(140) However, R _2a , R _2b , R _2c and R _2o are constants, and △I′ is the induced current in transmission lines 5L and 6L.
This is the accident change in I′.

The fault change in the circulating current of each phase is the superposition of equations (139) and (140), and is given by the following equation:

_{A … ( _ _ _ _ _ _ _ _ _} 141) In this formula, the relationship between each constant is R _1a > R _1b > R _1c and R _2a < R _2b < R _2c from the relationship with the distance to the induced power transmission line.
The relationship between the fault changes in each circulating current differs depending on the relationship between the magnitudes of the fault changes ΔI and ΔI′ in the induced current.

For this reason, for example, the detection current i _d is expressed as (39),
Even if compensation is performed such that compensation current i _h is expressed as equation (67), appropriate compensation cannot be obtained, and even if suppression is performed such that suppression current i _r is expressed as equation (125), appropriate compensation cannot be obtained. It cannot be suppressed. An embodiment that can perform appropriate compensation and suppression in such a case will be described below.

i _da = i _db = i _dc = i _ps …(142) i _ia = K _6a i _ha , i _rb = K _6b i _hb , i _rc = K _6c i _hc …(144) However, K _6a , K _6b and K _6c are constants, and Y _a ,
Y _b and Y _c are expressed by the following formulas.

In the above equation (143), each compensation current i _ha , i _hb and
Two equations are shown for each of i _hc ;
For example, for current i _ha , |i _bs /i _cs |>K ₆ ...(146) However, K ₆ is a positive constant.

When , an equation using the current i _bs is used, and when equation (146) does not hold, an equation using the current i _cs is used. This is to avoid the fact that when one of i _bs and i _cs is extremely small, errors will become large if a small current is used. current i _hb and
Similarly, for i _hc , the formula used for calculation is selected according to the ratio of the magnitudes of the current terms in each formula.

The operation of the above embodiment will be explained using an a-phase ground fault as an example. From the expressions of △i _bth and △i _cth in equation (141), So, solving this equation gives △I/△I′=R _2b △i _cth −R _2c △i _bth ／R _1c △i _bth −R _1b
△i _cth …(148). For a-phase 1-phase ground fault, △i _bs = 2△i _bth ,
Since △i _cs =2△i _cth , the ratio Y _a in equation (145) is equal to △I/△I'. Therefore, △ in equation (141)
i _bth , △i _cth and △i _pth are as follows.

△i _bth = (R _1b Y _a +R _2b △I′ △i _cth = (R _1c Y _a +R _2c △I′ △i _pth = (R _1o Y _a +R _2o △I′ …(149) Therefore, The fault change △i _ha in the compensation current i _ha in equation (143) is calculated from the relationship between △i _bs = 2△i _bth and △i _cs = 2△i _cth and from equation (149), the current i _bs or i _cs In _{any of} the _{equations using} 2△i _pth caused by the change is compensated. Also,
The suppression current i _r is a current proportional to the compensation current i _h to prevent malfunctions due to compensation error current.

As described above, by determining the coefficient to be used for the compensation current i _h or the suppression current i _r from the relationship of the fault change in the difference current between two healthy phases, it is possible to easily apply it to a 6-circuit parallel transmission line. . The above embodiment is merely an example of such a means, and various modifications may be made, such as making the current terms of the compensation current i _h and the suppression current i _r a current synthesized from the difference current of two healthy phases. It can be used in many ways.

(o) Overall effect As described above, in the present invention, the circulating current component in the fault variation of the detection current is compensated by the fault variation of the compensation current, or the means of suppressing it by the fault variation of the suppression current. With both, it is possible to obtain significantly higher sensitivity than the conventional method which uses only the fault change amount of the detection current. Furthermore, the present invention can be easily applied to a power transmission line with six circuits, by means of which a coefficient for calculating one or both of the compensation current and the suppression current is calculated using the relationship between the difference currents of two healthy phases.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of the present invention, FIG. 2 is a flow diagram showing the calculation flow of the invention, and FIG. 3 is a flow diagram showing the calculation flow of step S4 in FIG.
Fig. 4 is a system diagram showing a multi-circuit parallel transmission line, Fig. 5 is a layout diagram showing the wire arrangement of a four-circuit parallel transmission line, Fig. 6 is a characteristic diagram showing an example of the characteristics of the present invention, and Fig. 7 is a system diagram showing a multi-circuit parallel transmission line. Figure 8 is a flowchart showing the calculation flow of another embodiment of the present invention, Figure 8 is a block diagram explaining the response of one embodiment of the invention, and Figure 9 shows the wire arrangement of a 6-circuit parallel transmission line. It is a layout diagram. 4...Shipping breaker, 9...Input converter, 10...Sample hold circuit, 11...Multiplexer, 12...
AD converter, 13...calculator.

Claims (1)

[Scope of Claims] 1. A ground fault circuit for detecting a single-phase ground fault line with a current obtained by compensating the fault change in the detected current obtained from a parallel three-phase power transmission line with multiple circuits installed by the fault change in the compensation current. The fault line selection relay is such that the detection current is a current obtained from the fault phase difference current of the parallel transmission line (or a composite current of the same phase difference current including the fault phase difference current), and the compensation current is obtained from the same phase difference current (of the fault phase difference current) of the parallel transmission line. or a composite current of the same phase difference current), and makes the fault phase difference current component in the compensation current smaller than the fault phase difference current in the detection current. 2. The compensation current according to claim 1, wherein the compensation current is a current proportional to the same phase difference current from which a fault phase is removed or a composite current of the same phase difference current from which a plurality of fault phases are removed. Fault line selection relay. 3 The detection current is the negative phase portion of the same phase difference current of each of the three phases, and the compensation current is the zero phase portion of the same phase difference current of each of the three phases multiplied by a coefficient whose absolute value is less than 1. Claim 1 characterized in that
Ground fault line selection relay as described in section. 4. Ground fault line selection according to claim 1, characterized in that the value of the fault change in the function of the detection current, the compensation current (or the current used for these) and the polarity voltage (or the polarity current) is used. relay. 5. A one-phase ground fault line is detected using a current obtained by compensating the fault change in the detected current obtained from the parallel three-phase transmission line with multiple circuits by the fault change in the compensation current, and the detected current is The compensation current is a current obtained from the same phase difference current (or a composite current of the same phase difference current) of the parallel transmission line. In addition, in a ground fault line selection relay where the fault phase difference current component in the compensation current is smaller than the fault phase difference current in the detection current, the current obtained from the same phase difference current (or composite current of the same phase difference current) of the parallel transmission line is suppressed. A ground fault line selection relay characterized in that it performs a suppressing action based on a fault change in the suppressing current, and makes a fault phase difference current component in the suppressing current smaller than a fault phase difference current component in the detection current. 6. Claim 5, characterized in that the compensation current and the suppression current are currents that are proportional to the same phase difference current from which a fault phase has been removed or to a composite current of the same phase difference current from which a plurality of fault phases have been removed. Ground fault line selection relay as described. 7 The detection current is the negative phase portion of the same phase difference current of each of the three phases, and the compensation current and suppression current are the zero phase portion of the same phase difference current of each of the three phases multiplied by a coefficient whose absolute value is less than 1. 6. The ground fault line selection relay according to claim 5, wherein the ground fault line selection relay is characterized in that: 8. The method according to claim 5, characterized in that the value of the accidental change in the function of the detection current, compensation current, suppression current (or current used for these) and polarity voltage (or polarity current) is used. Fault line selection relay. 9 In a ground fault line selection relay that detects a ground fault fault line using a detection current obtained from a fault phase difference current (or a composite current of the same phase difference current including the fault phase difference current) of a parallel three-phase transmission line with multiple circuits installed, the above-mentioned A suppression effect that uses the same phase difference current (or composite current of the same phase difference current) of parallel transmission lines as the suppression current, and uses the fault change of the function of this suppression current (or the current used for this) and polarity voltage (or polarity current). What is claimed is: 1. A ground fault line selection relay characterized in that the fault phase difference current component in the suppression current is made smaller than the fault phase difference current component in the detection current.