JPS61251414A - Detection for disconnection of electric circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a method for detecting a disconnection of one wire in a power line supplying power to a three-phase load in a substation with reliability and accuracy. This relates to a detection method.

[Conventional technology]

JP-A-58-53770 discloses a method for detecting a disconnection of one line in three phases A, B, and C on the power supply side of a substation. In other words, when the line current of each phase changes due to a wire disconnection or load opening in a distribution line that supplies power to a three-phase load, for example, for phase input, the vector change in the line current of the two phases and the B phase and C phase The absolute value of the ratio of the vector change of the phase line current to the vector difference is determined, and the absolute values of the remaining two phases, namely, the B phase and the C phase, are determined in the same manner as above. A wire breakage is detected using the fact that the sum of the three absolute values obtained in this way or the absolute value of each of them has a different relationship when one wire is broken and when the load is released.
It is something that

FIG. 4 is a diagram showing a line to which a load L1 and a load power are connected to a substation T1, and shows a line current I in the substation.
. is the vector sum of the line current 1 of the load L1 whose load state or the line state connected only to that load does not change, and the line current I2 of the load L2 whose load state or line state changes.

The line impedance between the substation and each load is ignored as it is smaller than the impedance of each load. Roughly each line voltage is 12
It is assumed that there is a phase difference of 0' and that the phase difference between each line voltage and each line current at point P shown in FIG. 4 does not change even if the line condition of load L2 changes. Therefore, the change in line current at the substation Δ10
is affected only by the change Δ■ due to a change in the line condition of the load L2, and the change Jlo of the load L1 is Jlo=0. Therefore, in the following explanation, the load L1 will not be considered. Therefore, changes in the state of the line of load L2 can be shown by the equivalent circuits shown in FIGS. 5(A) to 5(D). However, Fig. 5 (A) is an equivalent circuit when one line of the human phase is disconnected, CB) in the same figure is an equivalent circuit when the load is opened for a single phase of the BC phase, and (C) of the same figure is an equivalent circuit when the load is opened for the single phase of the AB and CA phases. This is an equivalent circuit when a negative load is released, and (L) in the same figure is an equivalent circuit when a three-phase load is released.

In FIGS. 5(A) to (D), A in the steady state
Each line current of phase, B phase and C phase is ■3・Ib and Ic
The line voltages are Vab, Vbc and Vca, the currents of the loads connected between the lines are lab, Ibc and Ica, and their absolute values are Iab, Ibc.
and ica, and the power factor angles of each load are α, β, and r, each line current is.

Ia= Iab-1ca= 1abeJ''-1caeJ
'-a...-(111b == Ibc-Ia
b = 1bceJβ-a"-1abe1" ・(2
11c = Ica - Ibc = 1caeJ' -a
-1bceJβ-a2-(31・4. However, a: eJ7', a2 = a37
It is g.

Here, when the human line is disconnected as shown in Figure 5 (/'), the currents in each line after the disconnection are I'a, I'b, and I'c, and the load currents are Ia'b, Ib. 'c and Ic'a, I'a = Q I'c = -I'b, and the changes in each line current ΔIa, ΔIb and ΔIC
is as follows.

Δla = I'a −Ia = −(1abeJ″
-1caeJ'-a) -(41 From equations (5) and (6), ΔIb iab ・(d−T) −==・eJ≠=I ... (7) ΔI
c zca From equations (4) and (7), ΔIa=-(iabeJ"-1caeJ'-a),
iab ・ --OtoriCa (7e J'' -ej r-ly ICλ = -ic a (dan-jr-ejr, ΔIc ica knee-(ΔIbeJγ-ΔIceJr-ly-f8
1ΔIc If the equation (8) is transformed, and the absolute value of the right side is taken, a quadratic equation becomes an equation for determining the disconnection index S Ta of the A phase.

Similarly, the formulas for determining the disconnection index at the time of B-phase and C-phase disconnection are as follows.

Next, using the αω formula to the opening formula, the values of the wire breakage indexes STa, STb, and STc at the time of one wire breakage and when switching various loads are determined with reference to FIGS. 6 to 10.

Figures 6 (A) to CD) show when the human phase single wire is disconnected, when the BC phase single phase load is open, and when AB/C
It is a vector diagram of the line current in the substation when the A-phase V negative load is released and the 3-phase load is released, and the line currents 1a, Ib, and Ic of the two-person phase, B phase, and C phase fluctuate, and I′ respectively. It shows the changes ΔIa, JIb and JIc in these vector values when a, I'b and I'c are reached. Figure 7(A).

FIG. 8(A), FIG. 9(A) and FIG. 10(A).

FIG. 6 is a vector diagram showing vector value changes ΔIa, Δ1bJ5, and JIc in FIG. 6(A) to <,0), respectively. Note that the change in line current of each phase ΔIa,
The vectors indicating JIb and JIc are the ratio of their respective absolute values, that is, 1ΔIal:lΔIbl:lΔ1cl. A) and FIG. 10(A) are 0:1:1, respectively. White: 1:1 and 1:1:
This is when it is set to 1.

(1) A phase 1 wire breakage tt> (In formula 11j, multiplying JIc by 2 means rotating JIc counterclockwise by 120 degrees, so the vector ΔIa shown in FIG. 7 (A, )
, JIb and JIc are as shown in FIG. 7(B). As is clear from this figure, 1ΔIb-
Since ΔIc-al is rooster and 1ΔIal is 2, STa is ding.

(i) I will visit STb at this time as follows.0
If Δ■λ in equation 9 is rotated by 120 degrees as in (i), we get
The relationship between the vectors ΔIa, Δlb, and JIc shown in the 7th part is as shown in Figure 7 (q, 1Δlc−Δ■λ・a
Since l is a mountain and 1ΔIbl is 1, STb is small.

(ii) Furthermore, calculate STc at this time as shown below.

If JIb of the υ formula is rotated 1200 times in the same manner as (ri), the relationship between ΔIt, ΔIb and JIc in
As shown in Figure (D), IΔ■λ−Δ1b-al is a rooster, and 1ΔIcl is 1, so STc becomes V3.

+218C phase single-phase load release If the same procedure as described above is performed, FIG. 8(A) becomes FIG. 8(B), FIG. 8(C), and FIG. 8(D), respectively.

Further, both STb and STc are T=1.

(31AB-CA phase ■ Load release If you do the same as described above, Fig. 9(A) will correspond to Fig. 9(B), Fig. 9(C), and Fig. 9(D) (4), respectively.
3-phase load release 1-rubbing as described above, Fig. 10(A), Fig. 10(B), Fig. 10(C) and Fig. 10(
0), 1ΔIb-ΔIc-al, lΔI
c-JIa-al and 1ΔIu-ΔIb-al are both 0 (7) STa = STb = ST
c = Q'.

Here is the ST when one person/phase one wire is disconnected and various loads are released.
The values of a, STb, and STc are shown in Table 1.

Table 1 This table shows the calculated values of STa, STb, and STc when the human phase wire is disconnected and when the load is released under a three-phase balanced load. shows that they are different.

Therefore, the value for determining a disconnection is set to, for example, 1.5, and the disconnection conditions are STa, STb, and ST
If any two of c are thicker than 1.5 (however, the flash value is not taken), there is a disconnection, then as can be seen from Table 1, 11M in a three-phase balanced load.
Disconnection can be detected. Furthermore, in order to improve the detection of wire breakage, a value that is the sum of the three values STa, STb, and STc, for example, 4.0 (however, the value (1) is not taken) is determined as a wire breakage. You can also use it as

However, in the case of an unbalanced load, the values shown in Table 1 will change depending on the degree of unbalance.

In particular, when the human phase 1 wire is disconnected and when the AB-CA phase ■ negative load is released, these may overlap. Therefore, if you want to distinguish between a single wire disconnection and a V load release, you can set a certain range of unbalance, and under that condition, when the phase input single wire is disconnected and when the AB-CA phase ■ negative load is released. STa.

By calculating STb and STc, the value at which it is determined that the wire is disconnected must be determined.

The calculation of this value will be explained below.

(a) Phase A 1 wire disconnection ica Set Y=-1j-(>0), and apply this to equations (4) to (6).
) and roughly substitute these equations into equations 4 to (2) to obtain the following equations.

Also, ST = STa + STb 15Tc = fr
+-2Y cos (α-r-120°) (b) AB-C
A phase ■ Load release As shown in Figure 5 (C), each line current 1' after V load release
Since I'a=Q, a, I'b, and I'c become '=ibc eJβa2 I'c=-1bc eJβ·a2, and the changes in each current ΔIa, Δlb, and ΔIc are expressed by the following equations.

Δ1a=-iab ej"1ica eJr-a
−・・αηΔlb=iab eJ“
−UtOΔ1c=−ica eJr−
a - (191ca Here, set "=ta ball (>0) and convert this to 09 formula or 0
The equations obtained by substituting into Equation 9 and further substituting these equations into Equation 0 to Equation 0 are as follows.

Also, ST = STa しSTb +5Tc= 1
+Y2 Sat2YCO$(α-r+120°)' 1+Y”
+2Y Cos (d -7-120°5 +7 +
11-gl) STa, ST obtained in this way
For b and STc, STa and STb at Y0 and A phase 1 wire disconnection and V load open in the range of 30° from 1α-rl with (α-γ) as a parameter.
and the relationship with STc is drawn in a graph (not shown).

In this graph, a value A for determining a wire breakage is set in advance from the values of STa, STb, and S T c when Y=l, and the following three wire breakage conditions are considered based on the value A.

P; When any two of STa, STb, and STc (a) are larger than A, the wire is broken.

Q; When at least one of S"la, STb, and STc is greater than A, a wire breakage occurs.

However, the value of ■ shall not be taken.

R: When ST is thicker than A, the wire is broken. however,(
1) shall not be taken.

Therefore, in order to find the value for this (by changing A variously, 1α-rl-;
In order to satisfy each of the disconnection conditions P, Q, and K in the range <2, the range in which each disconnection can be detected and the range in which load release can be detected are tabulated from the graph (not shown) mentioned above (not shown). for example.

If a disconnection or load release can be detected, mark it with an ○; if it cannot be detected, mark it with an X.

From this table, it is possible to know the conditions for wire breakage P, Q, and conditions that will make the wire breakage detection range as wide as possible and minimize malfunctions when the V load is released. Next, based on each A, from the table (not shown) described above, the range in which a wire breakage can be detected and the range in which a load release can be detected is shown in a table with Y on the horizontal axis and (α-r) on the vertical axis. By creating this, it is possible to confirm the detection of a disconnection in one line of human phase in a certain range of Y and (α-r).

In this way, for the disconnection condition P, A=1.15
In this case, the conditions for Y and (α-r) are g, 4<:
Y<:2-0. 30°(:, a-r(+10°). Also, regarding the disconnection condition Q, A=1.63,
The conditions for Y and (α-r) at this time are 0.1≦Y −;
2.0, -30° and α−r≦+10°.

Furthermore, for the 2-disconnection condition K, A=356, and the condition of Y and (α-r) at this time is 0.5 < Y < 2.0
, −10° α−r×+a′0.

Therefore, if any one of the wire breakage conditions P, Q, and k is satisfied, it is possible to distinguish between a single wire break and a load release. This is clear from the fact that a disconnection in one wire of the A phase in a three-phase balanced load can be detected from the values shown in Table 1.

[Problems that the invention attempts to solve]

For example, when a load change occurs in which a three-phase load is released and a single-phase load is applied to the CA phase at the same time, the current vector detected at the substation will look the same as in the case of a single-wire disconnection accident. , the various disconnection conditions determined by the above-mentioned disconnection indices STa, STb, and S ``]''c may be met, and therefore, the disconnection may be erroneously detected at the time of the above-mentioned load fluctuation.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention adds means for detecting changes in zero-sequence voltage, and detects changes in zero-sequence voltage detected on the power supply side of the electric line. It is determined that a one-line wire breakage accident has occurred when both the magnitude and the values of wire breakage indices STa, STb, and STc based on conventional detection methods exceed predetermined values.

[Effect]

Disconnection index STa, ST based on the conventional disconnection detection power method
In addition to b and STc, the zero-sequence voltage that occurs when a wire is disconnected is larger than the zero-sequence pressure that occurs when the power line is healthy, so the change in zero-sequence voltage at that time is used as one of the disconnection detection elements. By adding this, it is possible to distinguish between 1-wire disconnection, single-phase load opening, load opening and 3-phase load opening on the power supply side, and for example, 3-phase load opening and CA phase single-phase load application at the same time When such a load fluctuation occurs, it is no longer determined that one wire is disconnected by vA, so the accuracy of detecting one wire disconnection can be improved.

〔Example〕

FIG. 1 is a block diagram of a device showing a first embodiment for implementing the disconnection detection method of the present invention.

In the figure, la~IC indicates the A-phase to B-phase electric lines, and current transformers 2z~ are installed at the power supply ends of the electric lines 1a~IC, respectively.
2C is installed, and signals indicating line currents 1a to Ic of phases A to C are obtained on the output sides of these current transformers, respectively.
These signals are converted into voltage signals by current-voltage converters 34-3c, and then manually input to storage devices 44-4C. 54 to 5C are current subtractors that input the outputs of the current-voltage converters 3a to 3C and the outputs of the storage devices 4a to 4C to calculate the current change of each phase; 5
This is a phase shifter for shifting the phase of the output of C by 120°. 7-7C are the output of phase shifter 6iL and current subtractor 5C, respectively.
This is a current change subtracter that calculates the difference between the output of the phase shifter σb and the output of the current subtractor 5a, and the difference between the output of the phase shifter 6C and the output of the current subtractor 5b. 8a-8
C is the ratio of the output for the current change subtractor 7 and the output of the current subtractor 5b, the ratio of the output of the current change subtractor 7b to the output of the current subtractor 5C, and the output of the current change subtractor 7C, respectively. This is a divider that calculates the ratio between the current subtracter 5a and the output of the current subtracter 5a. 9a to 9c convert the absolute values of the respective outputs of the dividers 84 to 8C into wire breakage indices S T a −S T
The DC converters 10&L to IOC which output the signal T of c are level detectors which output a logical value "1" when the outputs of the DC converters 94 to 9C are partially higher than the level. 11 is the level detector xoa, the output of 10b and the level detector 1
Input the inverted output of 0C! AND circuit, 12 is level detector 10m, 10 (output and level detector 10b)
13 is an AND circuit that inputs the inverted output of the level detector 10b, the inverted output of the level detector 10b, and the IOC.
14 is an AND circuit 11 to 13 which inputs
This is an OR circuit that inputs each output. The level detectors 101 to 10C, the AND circuits 11 to 13, and the OR circuit 14 constitute a disconnection condition setting circuit 25.

A grounding transformer 15 is also connected to the electric line 11C, and the zero-phase voltage Vo obtained from this transformer is inputted to a storage device 16. 17 is a zero-sequence voltage subtracter that inputs the output of the transformer 15 and the output of the storage device 16 and calculates a zero-sequence voltage change.

18 outputs a logic value "1" when the output of the zero-phase voltage subtractor 17 is higher than a certain level.A level detector 619 inputs the output of the disconnection condition setting circuit 25 and the output of the level detector 18. This is an AND circuit that outputs a disconnection detection signal.

Next, the operation of the device according to the present invention will be explained. First, the line current of A phase to C phase at time 2 [I ■λ ~ Ic
are stored in the storage devices 4a to 4C, respectively, and
Next, time 1. The time (,
, the signals indicating the line currents 1'a to I'c of the human phase to the C phase output at 1 time [, are respectively stored in the storage device 44-
'4C is added to and stored, and the storage device 41~
A signal indicating the line current Ihwlc read from 4C and the line current output from the current-voltage converter 34-3C! A signal indicating λ'-1C' or a current subtractor 54
~5C is input. In addition, if the disconnection condition described later is not satisfied, replace I, / ~ I'c with Ia-1c and newly store it, and I'a ~ I stored at time [,
The signal indicating 'c' is deleted.

On the output side of the current subtractors 54 to 5C, signals indicating current changes ΔIa to ΔIc per minute time Δ of the signal indicating the line current IawIc of the human phase to the C phase are obtained, and each of these signals is as follows. The phase is set to 120° by phase shifters 6a to 6c.
ΔI4·1 from the two phase shifters 64 to 6C, respectively.
．． Signals of ΔIb, a and ΔIc-a (m=e3N") are output. This signal of ΔIa-a is sent to the current subtractor 5C.
Since the current change is input to the subtractor 71 together with the output ΔIc, ΔIc - ΔIa・- is calculated, and the divider 8 directly calculates (ΔIc - ΔIa - 2) from the current subtractor 5b.
By dividing by the output Δlb, the calculation of (ΔIc−Δ14・S/Δib) is performed.

The absolute value is taken by the DC converter 9z and STb = Δlc
-Δ14+4 1 , □, 1 is output. Also, ΔIb-a
Since the signal is input to the current change subtractor 7b together with the output ΔIa of the xi subtractor 5a, here ΔI−−Δ
1b-a is calculated, and the divider 8b calculates (Δ14-Δ
lb-a) by the output ΔIc of the current subtractor 5C, the calculation of (ΔIw-ΔIb-li/Δlc) is performed, and the absolute value is taken by the direct converter 9b, and STc
=ΔIa−Δ■b a 1−1cho1c′ is output. Furthermore, ΔIc−
Since the signal No. 4 is input to the current change subtractor 7C together with the output ΔIb of the current g calculator 5b, here Δlb−
ΔIc-a is calculated, and the divider 8c calculates (ΔIb-
By dividing ΔIc・Li by the output ΔIa of the current subtractor 5, the calculation of (Δlb−ΔIc−a)/Δ1 is performed, and the absolute value is taken by the DC converter 9C and STa
Output Δlb −ΔIc@Todoroki=1, □4 1 . Now, the value of STa is 1
．． Thicker than 15 (, STb and STc values are 1.15
When the level is less than
Since J, rOJ, and rOJ are output, the AND circuit 11
.about.13 have a logical value of "o", and the output of the OR circuit 14 also has a logical value of "0".

However, when the value of STa is less than 1.15 and the value of STb and 5TC is greater than 1.15, the level detectors 10a-10C have the logical values rOJ,
rlJ.

Since "1" is output, both the outputs of AND circuits 11 and 12 have a logic value of "0", or the output of AND circuit 13 has a logic value of "1" and the output of OR circuit 14 also has a logic value. The value becomes "1". Ding, STa, S"l"C
When any two of the values are larger than 1.15, the output of any one of the ANI) circuits 11 to 13 becomes a logic value "1", and the output of the OR circuit 14 also becomes a logic value "1", causing a disconnection. The condition setting circuit 25 outputs a current disconnection signal, which is one of the disconnection detection signals.

- 10,000, the signal of the zero-sequence voltage Vo at the time [I mentioned above is stored in the storage device 16, and subsequently, at time t2, the signal of the zero-sequence voltage vO' output at the time [, is added to the storage device 16. and stored in the storage device 1.
The zero-sequence voltage V read from 6.

signal and the zero-sequence voltage V' output from the grounding transformer 15
0 is manually input to the zero-phase voltage subtractor 17. In addition, if the disconnection condition described later is not satisfied, V'0 is replaced with vO and newly stored.
The signal will be deleted.

A zero-phase voltage V is provided on the output side of the zero-phase voltage subtractor 17.

A signal of the zero-phase voltage change ΔvO per minute time Δ of the signal is obtained, and this signal is manually input to the level detector 18 that determines a certain level L, and when it is equal to or higher than the level L, it becomes a logical value "1" is output. In other words, 1 of the disconnection detection signal
A zero-sequence voltage disconnection IIM signal is output. The output of this level detector 18 and the output of the disconnection condition setting circuit 25 are input to the ANI) circuit 19, and the STλ~
Any two of the STc values are greater than 1.15,
When a part of the zero-phase voltage change ΔVo is equal to or higher than Bell L, a current disconnection signal and a zero-phase voltage disconnection signal are input to the AND circuit 19, and the AND circuit 19 indicates that a one-wire disconnection accident has occurred. Indicator T disconnection detection is outputted as number e. Note that the constant level L can be varied depending on the distance from the substation to the disconnection location so that disconnection at any location can be detected.

FIG. 2 is a block diagram of the main parts of a device showing a second embodiment of the wire breakage detection method of the present invention, and is completely the same as shown in FIG. 1 except for the wire breakage condition setting circuit 25. The block diagram of only the two-disconnection condition setting circuit is omitted.

In the same figure, both 201 to 20C have a lower limit of 1.63.
For example, when the values of S Ta to STc are both less than 1.63, the level detectors 2Oi1 to 20.
Since the logical value "0" is output to both 20C, OR
The output of the circuit 21 becomes a logical value "0". However, S
When the value of Ta is greater than 1.63 and less than 20.0, and the values of STb and STc are less than 1.63, the level detectors 20λ-20C each have a logical value r.
Since lJJOJ and rOJ are output, OR circuit 21
The output becomes a logical value "1". T, that is, S T a~
When at least one of the values of STc is larger than 1.63 and smaller than 20.0, the output of the OIL circuit 21 becomes a logic value "1", and the disconnection condition setting circuit 25 outputs an al current disconnection signal.

FIG. 3 shows the method for implementing the disconnection detection method of the present invention! J3
This is a block diagram of the main parts of the apparatus showing an embodiment of the present invention, and since the components other than the disconnection condition setting circuit 25 shown in the first figure are completely the same, the block diagram of only the disconnection condition setting circuit is omitted. In the same figure, 22 is L STa しSTb +S
It is an adder that calculates Tli, and 23 is the lower limit value 3.56.
and a level detector for determining the level of the upper limit value 20, 0, for example, which is output from the adder 22 (STa
+STb +STc)0) When the value is greater than 3.56 and smaller than 20.0, the output of the level detector 23 becomes a logical value “1”, and the disconnection condition setting circuit 25 outputs a current disconnection signal.

〔Effect of the invention〕

The change in zero-phase voltage that occurs when a wire is disconnected is detected as one of the disconnection detection elements.
By adding this as a single line, it is possible to distinguish between a single wire break and various types of load openings on the power supply side, and load fluctuations such as a three-phase load opening and a CA phase single-phase load application occurring at the same time can occur. This eliminates the possibility of erroneously determining that a single wire is disconnected when the wire is disconnected, so the accuracy of detecting a single wire disconnection can be improved, which is of great practical benefit.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus showing a first embodiment for implementing the wire breakage detection method of the present invention, and FIG. 2 shows a second embodiment for implementing the wire breakage detection method of the present invention. FIG. 3 is a block diagram of the main part of the device showing a third embodiment for carrying out the disconnection detection method of the present invention. FIG. Figures 5 (A) to (L)) showing the connected lines are A phase 1, respectively.
Equivalent circuit when wire is disconnected, equivalent circuit when BC phase single phase load is opened. AB-CA phase ■ A diagram showing the equivalent circuit when negative load is opened, and the equivalent circuit when 3-phase load is opened. Figures 6 (A) to (0) are respectively when a human phase 1 wire is disconnected when a 3-phase balanced load is affected. Vector diagrams of line currents in the substation when the BC phase single-phase load is released, the AB - CA phase■ negative load is released, and the 3-phase load is released, Fig. 7 (A), Fig. 8 (A), Fig. 9 LA) and FIG. 10(A) are vector diagrams showing vector value changes Δla, Δlb, and ΔIc in FIGS. 6(A) to (D), respectively, and FIGS. 7(B) to (1)). ffi 8 Figure CB) to (D], Figure 9 CB) to CD) OJ-Hi Figure 10 CB) to (D) are Figure 7 (A), Figure 8 (A), and Figure 9, respectively. 10 is a vector diagram obtained by rotating the vectors shown in FIG. 10A and FIG. 10A by 120 degrees in a counterclockwise direction. 1a~IC...electric line, 2o~2C...current transformer,
3a to 3C...Current voltage converter, 4a to 4C, 16.
··Storage device. 5a to 5C...Current subtractor, 64 to 6C...Phase shifter, 7o to 7C...Current change subtractor, 8a to 8C...
・Divider. 9-L to 9C... DC converter, 15... Grounding transformer, 17... Zero-phase voltage subtractor, 18... Level detector. 19...AND circuit, 25...Disconnection condition setting circuit. Agent Patent Attorney Hiroshi Nakai Figure 2 L-+ -'' Figure 4 (A) (El) (C)
(D) Figure 6 (A) (B) A,! 1!
M line B(, [M negative 4Ffl
release (() (D) ABC
Phase A 1 egg abundance 3 tree load comparison Figure 7 (A) (B) (C)
(D) (A) (B), Figure 8 (
C) (D)ΔIC・0 (A) (B) (C)
(0) Procedures Ne City Main Gate (Voluntary)

Claims (1)

[Claims] Zero-sequence voltage V detected at the power supply end of the 1st and 3rd phase electric lines
_0 and each line current Ia, Ib and Ic are respectively V'_
0 and I'a, I'b and I'c, the change in zero-phase voltage ΔV_0 = V'_0 - V_0 and the change in each current ΔIa = I'a - Ia, ΔIb = I'b From −Ib and ΔIc=I′c−Ic, the disconnection indices STa, STb, and STcSTa=
|ΔIb−ΔIc・a/ΔIa| STb=|ΔIc−ΔIa・a/ΔIb| STc=|ΔIa−ΔIb・a/ΔIc| is determined, and these values of STa, STb, and STc have a predetermined relationship. A wire breakage detection method for detecting a break in an electric line and determining that the wire is broken when the magnitude of the change ΔV_0 in the zero-sequence voltage exceeds a certain value. 2. The predetermined relationship is STa, STb and ST
The method for detecting disconnection of an electric line according to claim 1, wherein any two of the values of c are larger than 1.15. 3. The predetermined relationship is STa, STb and ST
The method for detecting disconnection in an electric line according to claim 1, wherein at least one of the values of c is larger than 1.63 (however, the value of ∞ is not taken). 4. The predetermined relationship is when the value of STa+STb+STc is larger than 3.56 (however, the value of ∞ is not taken).Disconnection detection of the electric line according to claim 1 Method.