JPS60234421A - Channel selecting relaying device - 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 [Technical Field of the Invention] The present invention relates to an improvement in a line selection ground fault detection device in a system where a zero-phase circulating magnetic current exists.

[Technical background of the invention and its problems]

In a power system with parallel multi-circuit lines, zero-sequence circulating current may exist even during non-fault situations due to unbalanced self-impedance of each phase of the system and mutual impedance between each phase. This zero-sequence circulating current cannot be ignored compared to the fault current at the time of an accident. In flat resistance grounding systems, etc., there is a problem in that if high sensitivity detection is aimed at because it affects the detection sensitivity of the protection relay, misidentification of the direction of the accident may occur, making it impossible to provide high sensitivity and high speed protection. By the way, in a line selective protective relay device that is generally used as a main protective relay with one type of protection relay for two parallel lines, in the event of an accident occurring near the opposing ends of the two parallel line power transmission line 9, the currents in both lines will be balanced. Therefore, the line selection protection relay at the own end can operate, and the breaker at the opposite end is configured to cut off the own end when the fault current is biased toward the fault line.

1 to 8 are connection diagrams showing an example of a line selection protection device for two parallel lines with two terminals.

In Figs. 1 to 3, 13 is the bus bar of the electric station at its own end, 1b is the bus bar of the opposite electric station, 2a, 2b, 2c, and 2d are the circuit breakers of the respective transmission lines, and 8a and 8b are the line selection relays 5a. Current transformers 4a and 4b respectively indicate the power transmission lines to be protected. Also, Ia, Ib,
Is is 4 o it flowing through each of the four sending wires 4a, 4b, and Ia which is the input commutation of the line selection relay 5a.
, Ib.

Figure 1 shows the state before the accident, J'j: L, and if the line current is balanced, Is-〇, and Figure 2 shows the case where an accident occurs at point F near the opposite end. . In this case, the fault magnetic current is Ib in Ia, and the input I of the line selection relay 5a is
A is 0, and the line selection relay 5a at the own end cannot respond.

Figure 8 shows the case where the fault line is cut off at the opposite end. In this case, the fault current does not flow through the healthy line, only the fault line remains, and the line selection relay human power is only Ia, and l5 = Ia, so line selection The state in which the relay 5a operates, as shown in FIG. 8, where one end operates later than the opposite end and is able to shut off is called sequential shutoff. With ordinary line selection relays (hereinafter referred to as 8G), in order to prevent malfunction due to zero-sequence circulating current when an external fault occurs, it is necessary to take measures such as making it low sensitivity or setting a time limit until the external fault is removed. do. Therefore, it has high sensitivity.

Cannot provide high-speed protection. In order to solve the above-mentioned problem, the change detection type line selection relay (hereinafter referred to as change type SG) stores the value of the zero-sequence difference current of both line withstand currents before the accident, and uses that memory from the zero-sequence difference current after the accident. The faulty line is determined by subtracting this value.

Alternatively, a method is adopted in which a change in the zero-sequence difference current immediately after the occurrence of a fault is detected to determine the faulty line. this is,
This method utilizes the fact that if there is a fault in two parallel circuits, the zero-sequence difference current will change, and the amount of that change will appear on the faulty circuit side.

However, since malfunctions occur if there is a change in the zero-sequence circulating current when an external accident occurs, a method is generally adopted in which the lock is locked for a fixed period of time after the accident occurs. In addition, even in the case of an internal fault, if the zero-phase circulation 3t4 current is larger than the fault current, the change in the difference circuit zero-sequence current when the opposite end is cut off in advance may be on the healthy line side, so the opposite end may be in the lead-off state. It must be locked before it is cut off.

Therefore, sequential cutoff using the variation form SG is not possible. When using a variable SG, high sensitivity and high speed cannot be expected for the same reason as mentioned above even if a normal SG is used for sequential transmission. In systems where th cannot be ignored relative to the fault current, sequential cutoff by line selection relays cannot be expected, and final cutoff is often performed by backup protection ground fault direction relays with limited operation times.

In the case of compensation type SG, zero-phase circulation 'magnetic current I from the induction line
. Since th and the negative phase circulating current I, th have a constant relationship, the negative phase circulating current I, th causes a zero sequence circulating current I. Compensate for th and zero-sequence circulating current■. Remove the influence of th and its zero-sequence circulating current■. Judgment is made based on the amount of change in value that is affected by th.

For compensation type SG, the surge value is the following formula. In order to detect the change in , if one terminal is cut off, I, th = 0, and the current value is reduced. is only the fault current, and sequential cutoff is possible with two terminals.

I,,,I. /: Fault current I, th, I at the time of failure. th: Circulating magnetic current at the time of failure t + IQ
S difference current (when one line is grounded, I, = I, etc.) However, even in the compensated type 8Gi2, there is a problem in the case of eight terminals, which will be explained next.

Figures 4 to 7 are connection diagrams showing an example of a one-way type line selection protection relay for two parallel lines with three terminals. In Fig. 4, 10 is the bus bar at the other end, 2e and 2f are power transmission line breakers, and 3f is C, which provides magnetic current input to the line selection relay 5c.
It is T. Ic, Id, Is' are currents flowing through the respective power transmission lines 4a, 4b and line selection relays 5b.
This is the difference current between the input currents Ic and Id.

FIG. 4 shows the state before the accident, and if the line'-flow is balanced, Is = Q and l4 = O.

Figure 5 shows a case where an accident occurs at point F near one terminal. In this case, the fault current is 1b in Ia, the input Is of the line selection relay 5a becomes 0, and the line selection relay 53 cannot respond.

If the other terminal is not grounded, it is Ic, Id, 0, and ■
The line selection relay 5b cannot respond due to the 4-kiO condition. Also, even if the other terminal is also grounded, it is Ic and Id, and Is
' is set to 0, and the line selection relay 5b cannot respond.

Figure 6 shows the case where the fault line near point F is cut off.
If the other terminal is ungrounded, Ib = I
c = Id. Depending on the location of the branch point, it is determined whether one terminal or both terminals are sequentially cut off at the same time.

Figure 7 shows a case where only one terminal is sequentially cut off in Figure 6, and the remaining terminal is Ia=Is
Therefore, the sequential cutoff occurs.

4 to 7 are obtained when the zero-phase circulating current Ioth is protected by a line selection relay when the fault current can be ignored. If th cannot be ignored with respect to the fault current, change type SG and compensation type SG
It depends on the following.

In the case of the variable type SG, the state shown in FIG. 6 is reached, but since it is blocked after a certain period of time after the accident occurs, sequential disconnection of the remaining two terminals is not possible.

In the case of compensation type SG, the situation shown in Fig. 6 will also occur, but if an unbalanced load current occurs, it will affect the negative phase circulating current r2th, so normal compensation may not be possible and malfunction may occur. If the change in the negative phase circulating current I, th is large, it will be blocked, and in that case, the remaining two terminals cannot be sequentially cut off. Even in the case of compensated type SG, complete protection cannot be expected with three terminals alone.

[Purpose of the invention]

The present invention performs sequential cutoff of variable type SG and compensated type SG in two parallel three-terminal lines in which the zero-phase circulation ° current cannot be ignored against fault current, and also enables highly sensitive line selection. The present invention provides a relay device.

[Summary of the invention]

The present invention provides a first means for detecting a change in the differential current between both lines in the event of a system failure in a line selection switching device with zero-phase circulating current countermeasures for protecting a multi-terminal power transmission line with two parallel lines. A line selection relay with zero-phase circulating current countermeasures, characterized in that the first means controls the output of the second means and selects a faulty line, comprising a second means whose operating time changes depending on the size of the relay. The first means is an OR operation of the changes in the scalar quantities of the zero-sequence current and the negative-phase magnetic current of the electrical quantities of the two line difference circuits.
A line selection relay device as a condition, a line selection relay device in which the first means is a scalar sum of changes in each of the scalar quantities of the zero-sequence current and the negative-sequence current of the difference circuit electrical quantities of both lines; A line selective relay device whose means is a scalar sum of changes in each phase current of the electrical quantity of the difference circuit between the two lines, a line selective relay device whose second means is an inverse time-limited characteristic, and a second means which is a proportional time-limited characteristic. The present invention provides a line selection relay device which integrates a zero-sequence difference current from the time of occurrence of an accident and selects a faulty line as a second means.

[Embodiments of the invention]

Next, examples of the present invention will be explained. FIG. 8 shows two sets of power transmission lines 4a that transmit AC power in the same phase.

4b, two sets of current transformers 8a and ab installed on the power transmission lines 4a and 4b, and whose secondary sides are connected in a star connection, and the secondary of current transformers 8a and 8b. A ring-shaped connecting wire consisting of a neutral point connecting wire 32 in which the neutral point 81a and Blb of the side star-shaped connection are shorted together, and an in-phase connecting wire 34 in which the secondary side in-phase terminals 88a and 83b are shorted together, and a power transmission line. 4a.

4b through a transformer (not shown), and the zero-sequence voltage V at the time of a ground fault. A ground fault overvoltage relay 8 is connected to the neutral point connection line 32 and the in-phase connection line 34, and is connected to the , furthermore, a change detection type line selection relay 6 that selects a line based on the zero-sequence voltage V., and a change detection type line selection relay 6 are connected in series, and the operating time depends on the magnitude of the zero-sequence difference magnetic current I.th. This figure shows a line selection relay device comprising inverse time-limited line selection relays 7a and 7b for sequential cutoff in which the voltage changes.

That is, FIG. 8 shows an example of the configuration in combination with the variation form SG, and is represented by a three-line diagram. In this configuration example, the zero-sequence current of the ground fault relay is represented by the residual circuit of CT.
The same result can be obtained even if a tertiary circuit of T is used.In Fig. 8, 6 is a relay that detects the zero-sequence difference between the two lines when an accident occurs, and a relay that detects the change in current. Indicates a limited time SG. Reference numeral 9 indicates a reverse phase difference current relay for blocking and locking the reverse time limits 5G7a and 7b in the event of an external fault. 8 shows a ground fault overvoltage relay for accident detection.

FIG. 9 is a block diagram of the configuration shown in FIG. 8, in which the terminals near the fault point are detected by the change signal SG6, and the fault line is cut off by the trip signal 13.The remaining terminals are connected after the ground fault overvoltage relay 8 operates. After a certain period of time has elapsed by the timer T2, the inverse time limit S G 7a, 7b is activated, and the fault line at one terminal is first cut off by the trip signal 14. Input titE difference I with 2 terminals. When comparing the two terminals, one terminal has a zero-phase circulation "magnetic current I." th is added to the accident amount, and the other terminal is the zero-phase circulating electricity it I. Since th is subtracted from the accident amount, the input current difference is ■. The terminal with the larger value always correctly selects the fault line side. Figure 11 shows the input current difference between both terminals when there is no zero-phase circulating current roth. , and FIG. 12 shows the zero-phase circulating current I. Input current difference I when there is th. 2, Fig. 11 and Fig. 12, 21 is A.
The difference IO, 22 is B difference. , the edict is on the IL side ■. , Sae is 2L
Side siding. It shows. Reverse time limit 5G7a and 7b are the input current difference■. The operating time changes as shown in Figure 13 depending on the size of Can be done. In Figure 13, P
indicates the active zone and Q indicates the non-active zone. However, even in the case of an accident outside the protected area, the zero-sequence circulating current I. Due to the influence of th,
Since the anti-time SG operates, as a countermeasure in case the fault removal time for an out-of-section accident is slower than the operation time of the anti-time SG,
Input current difference■. An internal accident can be determined by ORing the change in and the difference I, and by setting this condition as an AND condition in the tripping circuit, there is no possibility of malfunction due to an out-of-section accident. In addition, the above measures are zero phase circulation 3314 style I. If only the change in th is considered, the input current difference I for the fault. When the change in phase and the change in 2×Ioth when changing from 3 terminals to 2 terminals are in opposite phase, the tripping circuit remains locked despite an internal fault.

Therefore, the input '1M, the change in the flow difference (2)6, and the change in the difference I2 are set as an OR condition. This results in zero-phase circulating current■ during normal times. Since th and reverse phase circulation EJ '4 current l2th are generally not equal, the input current difference I for the fault. 2XI when changing from 8 terminals to 2 terminals. Even if it is canceled by the change in th, from FIG. th and the negative sequence circulating current l2th for the fault are 1. I, th in th, and the change in the difference I due to the accident is not canceled by 2XI, th when changing from 3 terminals to 2 terminals. In FIG. 9, when the timer TI changes from 3 terminals to 2 terminals in the change amount SG, a trip lock is applied to prevent malfunction, and switching to protection by inverse time limit S() is also used. The timer T2 is used to start the inverse time limit sG, and by setting the timer to a value equal to or longer than the one-terminal trip time due to the variation SG, the influence of the input current difference ◎ at the time of three terminals is eliminated.

In FIG. 14, 5 indicates normal phase, 26 indicates reverse phase, and 27 indicates zero phase.

As a result of the above, zero-sequence circulating current ■ in two 8-terminal parallel circuits. Even when th is large, the change is 9G and the inverse time SG
However, the same effect can be obtained by using a variable sensitivity SG instead of an inverse time SG. This is because, as shown in FIGS. 15 and 16, the setting value changes to the lower setting side with time, and the terminal that correctly selects the fault line is tripped first.

Figure 15 shows when t = 0, Figure 36 shows 1=T1
17 is 1-1, and FIG. 18 is t =
3 +7) indicates the time.

Further, the same effect can be obtained by using an integral type SG instead of a counter-timed SG. This is a relay that adds the sampled currents as shown in FIGS. 17 and 18, and operates when the added current exceeds a set value. Naturally, the input current difference is ■.

This is because the larger the value, the smaller the number of samplings required to reach the set value, so the terminal that correctly selects the fault line will trip first. Here, the relay operation time is the product of the sampling time and the number of sampling times.

Further, the same effect can be obtained by using a proportional time limit SG instead of an inverse time limit SG. This means that the relay operation time becomes faster in proportion to the magnitude of the input.

FIG. 19 shows an example of a configuration in combination with a compensation type SG, and 8
It is represented by a line diagram. In this configuration example, the zero-phase difference current of the ground fault relay is represented by the CT residual circuit, but the CT 8
The same is true even if the following circuit is used.

In FIG. 19, 6a indicates compensation type SG, 'Ia, Tb
indicates the counter-time SG of the sequential new moon.

8 shows a ground fault overvoltage relay for fault detection. FIG. 20 is a block diagram of the configuration shown in FIG. The remaining terminals are cut off by the compensating type S G 5a if the change in the negative phase circulating current I, th is small, and if the change in the negative phase circulating current I, th is large, activation is applied to the reverse time limit S G 7a, 7b. The fault line of one terminal is first cut off by the trip signal 14. Note that the tripping of the remaining two terminals and the determination of an internal accident are the same as those described above. [Effects of the Invention] From the above, conventionally, when variable type Sa is used, sequential disconnection is not possible for two and three terminals. normal SG
However, by applying the present invention, high-sensitivity and high-speed protection becomes possible.

In addition, in the case of compensation type SG, when conventionally applied to 8 terminals, the change in negative phase circulating current I, th is large, so
Since the sequence cutoff relies on ordinary 8G, it has been difficult to achieve high-sensitivity and high-speed protection, but by applying the present invention, high-sensitivity and high-speed protection becomes possible.

Note that the same effect can be obtained by using a proportional time SG and an integral type SG instead of the inverse time 8G.

[Brief explanation of the drawing]

Figures 1 to 3 are connection diagrams of a conventional line selection protection device for two parallel lines, and Figures 4 to 7 are three-terminal parallel two line connection diagrams.
A connection diagram of a conventional line selection protection device in a line, FIG. 8 is a connection diagram of a line selection protection device showing an embodiment of the present invention,
Figure 9 is a block explanatory diagram of Figure 8, Figures 10 to 18
8 is a diagram illustrating the operation of FIG. 8, FIG. 19 is a connection diagram of a line selection protection device showing another embodiment of the present invention, and FIG. 4 is a block explanatory diagram of FIG. 19. 6... Change detection type line selection relay 6a... Compensation type line selection relay 7a, 7b... Reverse time limit line selection relay 8... Earth fault overvoltage relay 9... Reverse phase change detection relay substitute Person Patent Attorney Noriyuki Chika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 9 Figure 10 IC Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Figure 18

Claims (1)

[Claims] A parallel two-circuit transmission line consisting of two sets of three-phase power transmission lines transmitting AC magnetic force of the same phase, and each magnetic transmission line of this parallel two-circuit transmission line is installed, and the secondary side is connected to a star-shaped connection. Two sets of alternating current transformers, a neutral point connection line in which the neutral points of the secondary side star-shaped connections of these two sets of current transformers are shorted together, and an in-phase connection line in which the secondary side in-phase terminals are shorted together. a ground fault overvoltage relay connected to the power transmission line via a transformer to detect zero-sequence voltage in the event of a ground fault, and connected to the neutral point connection line and the in-phase connection line; detecting a zero-sequence difference current, a negative-sequence current, or a change in a zero-sequence difference magnetic current corrected by the negative-sequence current flowing on the secondary side of the current transformer; A line selection relay that selects a line based on the directionality of the zero-sequence plate pressure, and a zero-sequence differential current, a negative-phase magnetic current, or a negative-sequence current that is A line selection relay device comprising a sequential reverse time limit line relay whose operating time changes depending on the magnitude of phase difference current.