JP2916148B2 - Line selection relay - Google Patents

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial application field) The present invention relates to a line selection relay device in a system where a zero-phase circulating current exists.

(Prior Art) In a parallel multi-line power system, there may be a zero-phase circulating current even at times other than the time of an accident due to imbalance between the self-impedance of each phase of the system and the mutual impedance between the phases. In a high-resistance grounding system or the like, this kind of zero-phase circulating current cannot be ignored compared to the fault current, and affects the detection sensitivity of the protection relay. That is, if the high sensitivity detection of the protection relay is aimed at, erroneous recognition of the direction of the accident occurs, and high-sensitivity and high-speed protection cannot be performed.

Generally, in a parallel two-circuit protection relay system, in a line selection protection relay used as a main protection relay, when an accident occurs near the opposite end of a parallel two-line transmission line, the currents of both lines are balanced. Therefore, the self-end line selection protection relay cannot operate, and is configured to cut off the self-end when an accident current is biased toward the accident line after the opposing end is cut off.

FIG. 10 is a connection diagram showing an example of a line selection and protection device in a two-terminal parallel two line. In FIG. 10, 1a is a bus of the own terminal substation, 1b is a bus of the opposite terminal substation, 2a, 2b, 2c, 2
d denotes a circuit breaker of a transmission line, 3a and 3b denote current transformers for supplying a current to the line selection relay 5a, and 4a and 4b denote transmission lines to be protected. Also, Ia, Ib, Is are the zero-phase current flowing through each transmission line 4a, 4b and the input current I of the line selection relay 5a.
This is the difference current between a and Ib. Here, there is a case where there is no zero-phase circulating current in both lines.

FIG. 10 (a) shows the state before the accident. If the line current is balanced, Is = 0, and FIG. 10 (b) shows the case where an accident occurs at point F near the opposite end. Since the fault current in this case is Is ≒ Ib, the input of the line selection relay 5a is Ia ≒ 0
And the line selection relay 5a at its own end cannot respond. Tenth
Figure (c) shows the case where the faulty terminal is cut off at the opposite end. In this case, the faulty current does not flow through the healthy line, but only the faulty line. The line selection relay input is only Ia, and Is = Ia. The selection relay 5a operates. Shutting off after such an opposite terminal is called sequential shutting. Normal line selection relay (hereinafter referred to as SG)
Therefore, it is necessary to take measures such as lowering the sensitivity to prevent malfunction due to the zero-phase circulating current when an external accident occurs, or providing a time limit until the external accident is eliminated. Therefore, high sensitivity and high speed protection cannot be performed.

Conventional line selection relays that have taken measures against zero-phase circulating current include a change detection line selection relay (hereinafter referred to as a change type SG) and a compensation type line selection relay (hereinafter referred to as a compensation SG). .

(Problem to be Solved by the Invention) Among the above-described conventional methods, the variation type SG stores the value of the zero-phase difference current of both line currents before the fault, and subtracts the stored value from the zero-phase difference current after the fault. The faulty circuit is determined by detecting the faulty line, or the change in the zero-phase difference current immediately after the fault occurrence is detected to determine the faulty line. This is based on the fact that a change in the zero-phase-difference current when an accident occurs in two parallel lines appears on the accident line side.

However, malfunction occurs when there is a change in the zero-phase circulating current due to a change in the system after the occurrence of an external accident. Therefore, in general, the system is locked within a certain time period after the occurrence of the accident. or,
Even in the case of an internal fault, if the zero-phase circulating current is larger than the fault current, the change in the zero-phase current of the differential line when the opposing end is preemptively interrupted may be on the healthy line side. The relay must be locked before the change. Therefore, when the variation SG is used, sequential blocking cannot be performed. So in this case,
Even if an ordinary line selection relay is used for sequential interruption, high sensitivity and high speed cannot be expected for the same reason as described above. For this reason, in a system where I _0th cannot be ignored with respect to the fault current, sequential interruption by a line selection relay cannot be expected. Often become.

In the case of the compensation type SG, the zero-phase circulating current I _0th from the induction line
And the _negative- phase circulating current I _2th have a constant relationship,
The zero-phase circulating current I _0th is compensated by the negative-phase circulating current I _2th , and the determination is made based on a change in the value from which the influence of the zero-phase circulating current I _0th is removed.

That is, in the compensation type SG, the current value _IE of the following equation is detected to identify the faulty line.

Also in the case of the above-mentioned compensation type SG, the load current is large, and if the load current has a negative phase component, the sequential interruption cannot be performed. This example will be described with a two-terminal system. Fig. 10 (c)
Is an example in which an accident is interrupted at the opposite end. In this case, the load current flows through a healthy line because one line has been interrupted, and the difference circuit current between the two lines, which is the input of the line selection relay 5a, includes the accident current component and the load. The current component flows. The repair-type SG compensates for the zero-phase circulating current using the negative-sequence current of this difference circuit current.However, if the negative-sequence current contained in the load cannot be ignored, normal compensation cannot be performed and erroneous selection is not possible. In some cases.

Generally, the negative-sequence component current included in the load is considered to be 8% or less, but if it is larger than the zero-sequence current to detect this, there is a risk of erroneous selection. Therefore, the compensation type SG needs to be locked after a fixed time similarly to the variation type SG, so that sequential shutoff cannot be performed. 3
In a terminal system, the same phenomenon occurs at a terminal that causes a change in load current after one terminal precedent cutoff.

For example, Japanese Patent Laid-Open No. Sho 60-234421 proposes an improvement of the line selection relay protection of the modified two lines having the zero-phase circulating current. However, this method has the same sensitivity problem as described above. .

The present invention has been made in view of the above circumstances, and in a modified two circuit with three terminals or less, a zero-phase circulating current is negligible with respect to a fault current, and is applied to a system. It is an object of the present invention to provide a line selection relay device which is capable of performing high-sensitivity and more reliable sequential interruption.

[Configuration of the Invention] (Means for Solving the Problems) In order to achieve the above object, in the present invention, the operation time varies according to the magnitude of the zero-phase active component current flowing through both lines to be protected in the event of an accident. First means 6 acting to
And a second means 8 for detecting a change in the difference between the positive-phase electric quantities of the two lines, and an operation for identifying whether or not the fault is within the protection zone by using the zero-phase sum current of the two lines as an input. And a fourth means 10 for detecting a ground fault. The trip output is derived when the conditions of the first to fourth means are satisfied.

(Operation) In the event of an external fault in a parallel two-line transmission line, the difference circuit current of the two circuits does not change, but it changes in an internal fault, and this is detected by the second means. At this time, if it is an internal accident, this is detected by the third means, and if there is an output by the first means, the trip condition is satisfied. In this case, the first means provided at each end is activated simultaneously after the occurrence of an accident. However, since the difference between the judgment currents of the correct judgment terminal and the erroneous judgment terminal is equal to the accident point current, the first means has a time limit of the first means. If the characteristic is a time limit characteristic in consideration of the current difference, the faulty line side can be correctly selected and cut off.

After the one end is selectively cut off, the fault current flows only to the faulty line side at the other end, and immediately after the preceding cutoff of the one end, the faulty line is operated and the faulty line is selected and cut off.

(Example) Hereinafter, an example is described with reference to drawings.

FIG. 1 is a connection configuration diagram of an embodiment of a line selection relay device according to the present invention, and shows a case where a changing part type SG relay is incorporated.

In FIG. 1, reference numeral 1a denotes a bus, and shows a state in which parallel two-line transmission lines 4a and 4b are connected via circuit breakers 2a and 2b.
5 is a variable SG relay, 6 is a time limit SG relay for sequential interruption, 7 is a ground fault direction relay (T67G) that identifies the direction of the accident, and 8 is a circuit that controls the output of the time limit SG relay 6 in the event of an external accident. Shows the differential electric quantity change detection relay (51DP). Reference numeral 9 denotes a conventional line selection relay in which the circulating current is set to a non-operating state, and when a fault current such as a complete ground fault fault is large, a shutoff output is derived at high speed. Reference numeral 10 denotes a ground fault detection relay, for example, using a ground fault overvoltage relay. Note that the CT3
a and 3b are cross-connected to form a relay input.

FIG. 2 is a relay sequence block diagram corresponding to the configuration of FIG. 1, and a lock circuit or the like at the time of a short circuit is omitted because the diagram becomes complicated.

The basic operation of FIG. 2 is to select the fault line in the event of an accident by using the change form SG5 and to sequentially cut off the remaining terminals at the time limit SG5. The conditions of the ground fault direction relay 7 and the change detection relay 8 are added in order to prevent unnecessary reaction and prevent unnecessary response due to a change in _I0th at the time of a start / guide system accident.
Since the load current of the preceding disconnection terminal at the time of preceding disconnection appears in the difference circuit current, a connection configuration that improves the detection sensitivity by using a change detection relay (51DP) of the positive-phase electricity quantity as the change detection relay 8. And

The operation will be described below based on the electrical phenomena of the three-terminal system.
FIG. 3 is a diagram showing a state in which a zero-phase circulating current I _0th flows as indicated by an arrow in the three-terminal system before an accident occurs. It should be noted that I _BL and I _CL are load currents at the B and C terminals, respectively.

FIG. 4 shows an example in which a one-line ground fault has occurred near the end C. The zero-phase circulating current I _0th is not changed, and the zero-phase current I _FA1 (zero-phase fault current on the line 1) ) And I _FA2 (zero-phase fault current on Line ₂ ) flow, and at the C end, the fault current from the A end Line 2 flows to the fault point of the Line 1 via the C end bus. In this example, it is assumed that the value of the change in the zero-phase difference current of both lines does not reach the sensitivity of the variation SG5 at the A-end and the B-end, and only the C-end reaches the sensitivity of the variation SG5. Therefore, at the C end, the variation SG5 operates and issues a shutoff command to the accident line side. In the state shown in FIG.
FIG. 5 shows a state in which is operated. In this state, in the relay sequence shown in FIG. 2, the variation SG5 at the C end is operated, and there is an input at one end of the AND circuit 11, and the other end is inputted by the inverter (the output of the ground fault detection relay 10 is the timer T1 Therefore, a trip output is generated in the OR circuit 13 by the output of the AND circuit 11.
In this case, the variation SG5 at the end A and the end B is locked by the timer T1 after the operation of the ground fault detection relay 10.
Also, A-end, by the C-terminal is cut off to the difference circuit of the B-end, the load current component I _CL which has been flowing to the C terminal appears as a sum of differences circuit electric quantity of A-end and B-end ( The positive phase component is almost the same as the load current component), and the change detection relay 8 that detects a change in the positive phase current or a change in the positive phase power operates. In addition, ground fault direction relay 7
As a result, the condition of the operation of the inward relay is satisfied at the power supply end, and the condition of the non-operation of the outward relay is satisfied at the non-power supply end.
If there is an output from the SG relay 6, the trip condition is satisfied. Incidentally, the time limit SG relays 6 at the A end and the B end are simultaneously activated after the occurrence of the accident by the timer T2 in consideration of the one end interruption.

Next, the magnitude of the fault line zero-phase determination current of each terminal in the state of FIG. 5 will be examined. In the figure, the zero-phase current
_{Assuming 0F} , A-end 1L judgment current (I _A1 ) = (I ′ _FA1 + I _0th ) − (I ′ _FA2 −I _0th ) = (I ′ _FA1 + I ′ _FA2 ) + 2I _0th A-end 2L judgment current (I _A2 ) _{= (I 'FA2 -I 0th)} - (I' FA1 + I 0th) = (I 'FA2 -I' FA1) -2I 0th B end 1L determination current _{(I B1) = (I '} FB1 -I 0th) - ( −I ′ _FB2 + I _0th ) = (I ′ _FB1 + I ′ _FB2 ) −2I _0th B end 2L judgment current (I _B2 ) = (− I ′ _FB2 + I _0th ) − (I ′ _FB1 −I _0th ) = − (I ' _FB1 + I' _FB2 ) + 2I
It becomes _0th . The "dash" attached to each equation means the zero-phase current at the fault point after the switch at the fault point is opened.

_{Here, | I 'FA2 | = |} I' FB2 | = | I 'FB1 | I' FA1 + I 'FB1 = I 0F I'FA1> I ' for an _{FA2, I A1 = I 0F -2I} ' FA2 + 2I _{0th I A2 = 2I 'FA2 -I} 0F -2I 0th I B1 = 2I' FA2 -2I 0th I B2 = -2I 'FA2 + 2I 0th next, zero-phase circulation current I phase the phase and the fault point current I _0F the _0th and then, and _{| I 0th |> | I '} FA2 | and that, in an accident maximum current of the pin for selecting the line correctly I _A1, maximum current of the terminal to be mistaken as an accident a healthy line will be I _B2. This I _A1
The difference between the magnitudes of I and I _B2 is always I _0F .

| I _A1 | − | I _B2 | = I _0F0F Also, _assuming that the phase of the zero-phase circulating current I _{0th and} the _fault point current I _0F are in opposite phases and | I _0th |> | I ′ _FA2 | at most I _B1 of the current terminal to correctly select the accident line, the maximum current of the terminal to be mistaken as an accident healthy line becomes I _A2, and the difference in size should always be I _0F of the I _B1 and I _A2 .

Since | I _B1 | − | I _A2 | = I _0F or more, the difference between the magnitudes of the judgment currents of the correct judgment terminal and the erroneous judgment terminal for the time limit SG relay 6 is only the _fault point zero-phase current I _0F. become. Therefore, if the characteristic of the time limit SG relay 6 is a time limit characteristic considering this difference in current, the faulty line can be selected and cut off correctly. In short, the maximum current at the terminal that correctly selects the fault line
FIG. 6 shows a state in which the end A has been cut off by the time limit SG relay 6 because it was I _A1 . In FIG. 6, the fault current flows only on the fault line side at the B end, and the zero-phase circulating current disappears at the same time as the A end is opened. At the terminal B, the time limit SG relay 6 operates immediately after the terminal A is cut off to selectively cut off the faulty circuit side at the terminal B, thereby eliminating the fault.

By the way, it is necessary to set the differential electric quantity change detection relay 8 to always operate in response to a change in the differential circuit electric quantity at the time of the termination of the internal accident. Therefore, next, a description will be given of a change in the difference circuit current in the three-terminal system at the time of one-end preceding cutoff.

FIG. 7 is a system diagram for explaining a change in the difference circuit current of the three-terminal system. FIG. 7 shows the line length from the branch point J to each terminal.
l _a, and l _b, l _c, power end to A end, B, and a C-terminal and load. In this power system diagram, Table 1 shows the current values appearing in the difference circuit of each terminal when each of A, B, and C is precedently cut off.

As is evident from Table 1, the change in the difference circuit current is smaller at the load-terminal pre-interruption than at the power-supply pre-interruption, and it is necessary to improve the detection sensitivity. For this purpose, a differential electric quantity change detection relay (51DP) 8 is used. Also, in order to determine whether the accident is in the direction of the target protection section, a ground fault direction relay 7 is provided.
Is provided.

FIG. 8 shows the time-delay characteristics of the reverse time-delay SG relay. In the figure, the vertical axis shows the effective component of the two-phase zero-phase current, and the horizontal axis shows time. I _0K is the maximum current set value at the start of the infinite time, which is a value obtained by adding a margin to the sum of the minimum fault currents to be detected, which is twice the maximum of the roughly zero-phase circulating current I _0th . I _0m is the detection sensitivity minimum value after the start of the time limit. When the time has elapsed to this value, the time limit stops, and the time limit SG relay maintains this sensitivity. This I _0m is the same as the sensitivity setting value of the conventional SG when there is no zero-phase circulation I _0th . The timer T2 takes into account the one-terminal shut-off time in the three-terminal system, and is determined from (operation time of the reverse time SG relay + operation time of the circuit breaker + review time of the reverse time SG relay). The slope I _Tr of the time limit is the ratio of the minimum _fault point current I _0F to be detected to the time from when the correctly determined terminal is cut off and the time limit SG relay of the incorrectly determined terminal is reset (counter reset). is there.

FIG. 9 shows the characteristics of the difference circuit positive phase component change detection relay.
(A) of the figure is for detecting a change in the positive-phase current.
(B) detects a change in the positive-phase power. In both cases, attention is paid to the fact that the change in load current at the time of one-time interruption and the positive-sequence current included in the circulating current are 0.3 to 0.5 or less as compared with those of the zero-phase.

Although the above embodiment has been described using a conventional analog relay, this can be realized by a digital relay using a microcomputer. Further, in the above embodiment, the example using the change type SG relay has been described.
The same applies when a relay is used.

[Effects of the Invention] As described above, according to the present invention, the fact that the relay for detecting that the positive phase change electric quantity of the difference current between the two lines is equal to or more than a certain value has been activated and the direction of the accident are detected. Since the faulty line is selected by the line selection relay having a time limit characteristic under the condition that the ground fault direction relay operates, a line selection relay device capable of performing a sequential cutoff with high sensitivity can be provided. .

[Brief description of the drawings]

FIG. 1 is a connection configuration diagram of an embodiment for explaining a line selection relay device according to the present invention, FIG. 2 is a relay sequence block diagram corresponding to the configuration of FIG. 1, and FIG. Fig. 4 shows a state in which a zero-phase circulating current is flowing, Fig. 4 shows a state in which a single-line ground fault has occurred near the C end, and Fig. 5 shows a state in which the breaker at the C end has been opened due to a one-line ground fault. Fig. 6 is a diagram showing a state in which the circuit breaker at the A-end is opened by the time limit SG relay, Fig. 7 is a system diagram illustrating a change in the difference circuit current of the three-terminal system, and Fig. 8 is a diagram showing the time limit of the time limit SG relay. FIG. 9 is a characteristic diagram of a time limit characteristic example, FIG. 9 is a characteristic diagram of a difference circuit positive phase component change detection relay, and FIG. 10 is a connection diagram of a conventional line selection relay in a parallel two-line configuration. 1a ... bus, 2a, 2b ... circuit breaker 3a, 3b ... current transformer, 4a, 4b ... transmission line 5 ... changeable SG relay, 6 ... time limit SG relay 7 ... ground fault direction relay , 8… Change detection relay 9… Line selection relay, 10… Ground fault detection relay 11, 12… AND circuit, 13… OR circuit

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masao Hori 1-1-1, Shibaura, Minato-ku, Tokyo Inside the head office of Toshiba Corporation (56) References JP-A-60-174016 (JP, A) JP-A-58-186325 (JP, A) JP-A-58-172924 (JP, A) JP-A-56-141723 (JP, A) JP-A-56-107731 (JP, A) (58) Fields investigated (Int .Cl. ⁶ , DB name) H02H 3/36

Claims (1)

(57) [Claims] 1. A line selection relay having a zero-phase circulating current countermeasure for protecting a three-terminal parallel two-line system in which a zero-phase circulating current is generated. A first means for operating to change the operation time according to the magnitude, a second means for operating to detect a change in the difference between the positive-phase electricity quantities of the two lines, and a zero-phase of the two lines. A third means for inputting the sum current to determine whether or not the fault is within the protection zone; and a fourth means for detecting a ground fault,
Means 10 wherein the trip output is derived when the conditions of the first to fourth means are satisfied.