JP2670291B2 - Protective relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a distance relay device applied to protection of back-up of a transmission line, wherein the distance relay device is a measuring transformer (hereinafter referred to as PD). )), The system voltage input from the transmission line via the AC
The present invention relates to a protective relay device that can reliably remove an internal short-circuit point near a protection system without malfunctioning even when a PD failure such as a disconnection of a secondary circuit of the PD occurs.

(Prior Art) In a protection system that protects a transmission line with two main protection and backup protection systems, when the main protection malfunction does not occur, the backup protection takes a timed trip with the main protection in time coordination.
In addition, when the main protection is not used, it is general that the first stage element of the back-up protection is instantaneously tripped and the accident is eliminated at high speed.

Considering the case where the system voltage becomes zero or a small accident voltage near the relay installation point short-circuit point in the protection relay device using the distance relay, the system voltage before the accident is set for the short-circuit distance relay. Is stored for several cycles, and measures are taken to ensure that the system can operate even in the case of a near-point accident.

However, as described above, in the case where the first stage element of the distance relay is operated in a timed manner as a measure against the main protection failure, the memory circuit holds the system voltage before the accident for only a few cycles in the case of the short-circuiting short-circuit accident. Therefore, the first-stage element output is also output only for a few cycles, and it is necessary to hold the first-stage element output for a time equal to or longer than the first-stage element time limit timer setting value. A holding circuit is provided.

An example of a conventional protective light electric device having a holding circuit will be described below with reference to FIG.

FIG. 2 is a trip block diagram of the first-stage element of the short-circuit distance relay, wherein 1 is the first-stage element of the short-circuit distance relay, 2 is the short-circuit overcurrent relay, and 3 is the short-circuit undervoltage relay (3, Four
Is for detecting accident elimination and returning the holding circuit. ), 4 is a short-circuit overcurrent relay as a fail-safe relay that operates in the event of a system fault, 5 is a condition in which the main protection relay is not used, 6 is a NAND logic, 7 is a flip-flop, and 8 and 12 are ORs.
Logic, 9 and 11 are AND logic, and 10 is an on-delay timer.

In FIG. 2, when an internal near point short-circuit accident occurs and the system voltage becomes zero or a small value close thereto, the first-stage element 1 of the short-circuit distance relay is activated by a built-in memory circuit.
The outputs are output for only a few cycles, and the short circuit overcurrent relay 2 and the short circuit undervoltage relay 3 detect an accident and operate, so that the output of the NAND logic 6 becomes "0" and the flip-flop 7 is set.

At this time, if the main protection relay device malfunctions and the accident continues, the short-circuit overcurrent relay 2 and the short-circuit undervoltage relay 3 continue to operate.
The (reset) terminal remains at “0”, and the flip-flop 7 is turned off when the memory voltage of the short-circuit distance relay is lost.
The operation is continued even if the output of the stage element 1 becomes “0”.

Therefore, the output of the OR logic 8 becomes “1”, the output of the short-circuit overcurrent relay 4 becomes “1”, and the output of the AND logic 9 becomes “1” until the fault is eliminated.
To continue. Here, in the main protection use state, since the logic of the condition 5 of not using the main protection relay is “0”, the AND logic 1
1 becomes “0” and the on-delay timer 10 becomes valid.

Therefore, the AND logic 9 activates the on-delay timer 10, outputs "1" after the settling time, and the OR logic 12 becomes "1", and thus outputs the breaker trip command.

Next, when the main protection relay device is not used, the main protection relay device non-use condition 5 becomes “1” logic, so that when the AND logic 9 becomes “1”, the AND logic 11 becomes “1” instantly and ORs. A trip command is output instantaneously via the logic 12, and the first-stage instantaneous trip is enabled.

After the trip command is output, the accident is eliminated, so the short circuit overcurrent relay 2 and undervoltage relay 3 are restored, the NAND logic 6 becomes "1", and the short circuit distance relay first stage element 1 is also restored. Therefore, the flip-flop 7 is reset.

By the way, if a PD failure such as PD secondary circuit disconnection occurs, the PD
When the voltage changes from the normal voltage to the zero voltage, the short-circuit distance relay first-stage element 1 outputs an unnecessary output for several cycles due to the memory voltage, the undervoltage relay 3 operates, and the short-circuit overcurrent relay 2 operates due to power flow. In this state, the output of the NAND logic 6 becomes "0" and the flip-flop 7 is set. In this state, when an external accident occurs, the short-circuit overcurrent relay 4 which is a fail-safe relay operates and the "1" output of the OR logic 8 and the AND logic 9 of the short-circuit overcurrent relay 4 become the output "1". At this time, if the main protection is not used,
Because condition 5 of not using the main protective relay device is "1"
The AND logic 11 instantaneously becomes "1" output, and there is a possibility that a trip command is erroneously output via the OR logic 12.

(Problems to be Solved by the Invention) As described above, in the holding circuit as a measure against near-point accidents of the first-stage element of the short-circuit distance relay, the output of the first-stage element is erroneously held at the time of a PD failure. In the event of an external accident, there was a possibility of a mistrip.

Therefore, the present invention can prevent mis-trip due to an external accident at the time of PD failure, even when PD failure such as PD secondary disconnection occurs, without the short-circuit distance relay first stage element holding circuit erroneously holding operation. In addition, it is an object of the present invention to provide a holding relay device that can reliably trip a circuit breaker in the event of an internal near-end accident.

[Configuration of the invention]

(Means for Solving the Problems) The protection relay device of the present invention is a protection relay device having an output holding circuit as a countermeasure for a near-point short-circuit accident at the output of a distance relay applied to transmission line back-up protection. , The output of the first stage element of the distance relay and the output of the relay that operates at the time of an accident in this transmission line system and does not operate due to a measurement transformer (PD) failure are established, and this accident is eliminated. An output holding circuit that holds the output until the output is held is provided.

At this point, the power transformer system operates in
D) A relay that does not operate due to a defect is an overcurrent relay that determines operation by using the system current, a current change width relay, or the like.If a relay with such an element is provided for a fail-safe relay as a relay device, The output of the fail-safe relay may be used.

(Operation) In the present invention, the output of the first-stage element output of the short-circuit distance relay and the relay that operates at the time of a system fault and does not operate due to a defective measuring transformer (PD), for example, a short-circuit overcurrent relay provided as a fail-safe relay. By maintaining the operation of the first element of the distance relay due to the short-circuiting short-circuit accident by the AND condition of 1), the backup operation is performed by the first step of the short circuit.

(Example) Hereinafter, an example is described with reference to drawings. Figure 1
FIG. 3 shows an example of a trip block diagram of the first-stage element of the short-circuit distance relay according to the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals, and the features of the present invention will be described here. In FIG. 1, reference numeral 13 denotes an AND logic. In the event of a near-internal short-circuit fault, the short-circuit distance relay operates with several cycles of the memory voltage, and the first stage element 1 outputs "1" until the memory voltage disappears. In addition, since the overcurrent relay 4 (which uses the overcurrent relay 4 provided for the fail-safe relay as a relay that operates due to a transmission line system failure and does not operate due to PD failure) operates due to the fault current, AND logic 13 Becomes “1” output.

At this time, the output of the NAND logic 6 is “0” because the short circuit overcurrent relay 2 and the short circuit undervoltage relay 3 operate, and the flip-flop 7 is in the set state, and the output causes the OR logic 8 to be “1”. Output and short circuit relay 4 is "1"
Since it is an output, the AND logic 9 outputs "1". Therefore, at this time, if the main protection is still malfunctioning in the main protection use state, the output of the AND logic 9 activates the on-delay timer 10, and the rear stock removal command is output via the OR logic 12. Then, the short circuit overcurrent relay 2 and the terminal undervoltage relay 3 are restored by the fact that the accident is removed by the rear trip removal, and the NAND logic 6 becomes “1” output,
Since the short-circuit distance relay first-stage element 1 has also returned, the flip-flop 7 is reliably reset.

Next, considering PD failures such as PD secondary disconnection, when the PD secondary voltage is lost and the PD soundness voltage goes to zero voltage, the memory voltage causes the short-circuit distance relay to respond unnecessarily for several cycles. Becomes "1", but does not operate due to PD failure.
The value 3 is still "0" output, and the flip-flop 7 is not set by mistake.

As described above, the flip-flop is set according to the AND condition of the short-circuit overcurrent relay output and the short-circuit distance relay first stage output that operates due to a system fault and does not operate due to PD failure. There is no mistaken setting of flip-flops even in the event of a loss.

In the above description, the first-stage operation is maintained by ANDing the short-circuit overcurrent relay and the first-stage output of the short-circuit distance relay, but as a fail-safe relay, the current change width is used instead of the short-circuit overcurrent relay. The same effect can be obtained even if a relay is used.

〔The invention's effect〕

As described above, according to the present invention, the short-circuit distance relay first-stage operation due to the near-point accident is held by ANDing the relay output and the short-circuit distance relay first-stage output that operate due to a system fault and do not operate due to a PD failure. Since it was done, the first when PD is defective
A protective relay device that does not maintain the unnecessary response of the step element, prevents mistrip due to an external accident when the PD is defective, and allows the circuit breaker to be reliably tripped in the event of an internal near point accident. Can be provided.

[Brief description of the drawings]

FIG. 1 is a trip block diagram of a short-circuit distance relay first stage element according to the present invention, and FIG. 2 is a trip block diagram of a conventional short-circuit distance relay first stage element. 1 …… Short circuit distance relay first stage element 2 …… Short circuit overcurrent relay 3 …… Short circuit undervoltage relay 4 …… Short circuit overcurrent relay 5 …… Main protection relay non-use condition 6 …… NAND circuit 7 …… Flip-flop circuit 8,12 OR circuit 9,11,13 AND circuit 10 On-delay timer

Claims (1)

(57) [Claims] 1. A distance relay which determines operation using a system voltage and a system current input from a transmission line via a measuring transformer and a current transformer, and a near-point short-circuit accident for application to transmission line back-up protection. In a protective relay device having an output holding circuit that holds the output of the distance relay until the accident is eliminated, provided that the relay that operates in the transmission line accident and does not operate in the measuring transformer fault operates. A protective relay device comprising a circuit that allows holding of output to the output holding circuit.