JPH0370425A - Circuit selective relay - Google Patents

Abstract

PURPOSE:To operate a circuit selective relay device normally regardless of an accident mode by correcting the phase of zero-phase active-component currents after an accident by using the phase difference of the quantities of polarity before the accident at every phase and the quantities of polarity after the accident. CONSTITUTION:The absolute values of each quantity of electricity and phase are obtained by an arithmetic processing section 20. The quadrature voltage of the quantities of polarity is generated in 21, and zero-phase active-component currents at every phase are arithmetically operated by 22 on normalcy. When an accident is generated, the generation of the accident is detected by 23, and quadrature voltage before the accident is stored in 24. The phase of zero-phase active-component currents after the accident is corrected so as to be made the same as the phase of the phase of the quantities of polarity before the accident by phase difference (the changing section of the phase of the quantities of polarity by the accident) measuring quadrature voltage stored in 24 and quadrature voltage after the accident by 25. Zero-phase active-component currents after the accident are arithmetically operated while using the corrected value as the quantity of correction. Accordingly, normal operation is enabled in a circuit selective relay even to an accident, in which the phase of the quantities of polarity is changed before and after the accident by a two-wire ground-fault accident, etc.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application! l'F) The present invention relates to an improvement of a line selection relay device, and in particular, to securely protect a faulty line even in the presence of zero-sequence circulating current. The present invention relates to a line selective relay device that is capable of selectively cutting off the line.

(Prior Art) In a parallel multi-circuit power system, typically two parallel lines, a considerable amount of zero-sequence current often circulates even during normal times. This is due to the unbalance of the self impedance of each phase and the mutual impedance between each phase.
If this zero-sequence circulating current cannot be ignored compared to the ground fault current at the time of an accident (this is particularly likely to occur in power systems with high resistance grounding), it may affect the detection sensitivity of the protective relay and cause an accident. There is a risk of misperception of direction, etc., and there is a problem that the protection operation cannot be made highly sensitive.

In order to solve this problem, line selection relay devices for ground fault protection of parallel two-line transmission lines have traditionally stored the value of the zero-sequence difference current between the two line currents before an accident, and A digital method has been put into practical use that determines a faulty line based on the difference between the zero-sequence difference current and the stored value.

Conventional digital relay one type time! For I selection relay,
The fault line is selected using the difference in the zero-sequence active component current before and after the fault, and the voltage between two phases that is in quadrature with the fault phase is used as the polarity quantity for determining the zero-sequence active component current. . That is, the zero-sequence effective current is calculated using the following equation. Moreover, this aspect is illustrated in FIG. 3.

a phase I = I −CO3θ8 0a O θ =1 to VbcZ90°O b phase I −I −cosθb b−0 θb ”” ' o AVcaZ90°a phase I. c=
Io-cosθ0 θ = 1 ^V, bZ90゜O The polarity of the current arithmetic equation requires finding one normal zero-phase circulating current, and one that has a constant output, and one that has a constant output.
One uses quadrature voltage because it requires something that will not be affected by a single-wire ground fault.

(Problem to be Solved by the Invention) By the way, the line selection relay that selects the fault relationship based on the difference in the zero-sequence active component current before and after the fault using the above-mentioned arithmetic formula is intended for operation in single-line ground faults. Normal operation is fully expected in the event of an internal 1-wire ground fault or normal non-operation in the event of an external fault, but if a 2-wire ground fault occurs, the amount of polarity will change, so there is a risk of malfunction. There is.

This situation is shown in Figure 4. Generally, in the event of a short circuit accident such as a two-wire ground fault, a short circuit priority circuit is provided using an undervoltage relay, etc., and the circuit is locked by this, but if short circuit priority is not applied. , there is a risk of malfunction. This is the fourth
This will be explained with reference to the figures.

FIG. 5 shows an example of a system configuration of two parallel lines. In the illustrated system, a first power transmission line 44a having circuit breakers 42a and 42c at both ends is provided between a power station bus 41a at its own end, which has a large power source 48 behind it, and a power station bus 41b at the opposite end. Circuit breaker 42b.

42d and a second power transmission line 44b are provided so as to constitute two parallel lines. The line current I flowing through the power transmission lines 44a and 44b on the electric station bus 41a side
, I are detected by the current transformers 43a and 43b, respectively, and the difference current (I - I) is detected by the current transformers 43a and 43b, respectively.

I) is introduced to the line selection relay 45 as an input current I. Further, the voltage of the bus bar is detected by a voltage transformer 46 and the voltage is introduced to an undervoltage relay 47 . In this system, if a two-wire ground fault occurs at point F, which is farther from the opposite end electrical station bus bar, the voltage of the line 41a at the opposite end electrical station will not drop because the power source is large. Therefore, the undervoltage relay 47 that introduces the voltage of the bus does not operate, and short-circuit priority locking is not performed.

On the other hand, the line selection relay that selects the faulty line based on the difference in the zero-sequence active current before and after the fault operates as shown in Figure 4.
When a line ground fault occurs, the amount of polarity changes, and the zero-sequence active current before and after the accident appears to be higher than the other, leading to the possibility of malfunction.

From the above, it is necessary to provide a line selection relay that will not malfunction even when short-circuit priority locking is not performed.

The present invention has been made to eliminate the above-mentioned disadvantages of conventional devices, and an object of the present invention is to provide a line selection relay device that can operate normally regardless of the fault mode.

[Structure of the invention] (Means for solving problems) The configuration of the present invention will be explained using FIG. 1.

As shown in Figure 1, there is a calculation process that converts the amount of electricity in each system into the signal necessary for the relay, an accident detection section that detects an accident, and an accident detector that stores the polarity amount before the accident occurs for each phase. The pre-occurrence polarity amount memory section and the phase difference between the memorized polarity amount before the accident occurrence and the polarity amount after the accident occurrence for each phase are stored.
It consists of a phase difference measurement section that measures the amount of change in the phase of the polarity amount due to an accident), and a polarity amount correction section that uses the detected phase difference to correct the phase of the zero-sequence effective current after the accident occurs.

(Function) Therefore, even after an accident occurs, the zero-sequence active current can be calculated using the same polarity amount as before the accident, and even in the event of an accident in which the phase of the polarity amount changes before and after the accident, the line The selection relay can now operate normally.

(Example) First, for convenience of explanation, a configuration diagram of a line selection relay device using a microcomputer will be described with reference to FIG.

In Fig. 6, the voltage and current of the power system are taken in through the input converter 61 that centralizes and houses the auxiliary PCT, and is filtered by a filter (Fl) that extracts only the commercial frequency components of the voltage and current. It will be done. Since each filter output is an analog signal, it is sent to the sample and hold circuit (S/I+) 63 and the multiplexer (HP
X) 64 to analog/digital converter (A/D
) 65 and converts it into a digital signal. The digital signals of voltage and current converted here are stored at one point in a data memory (RAM) 67 via a direct memory access (OH8) 66. CPU68
The current and voltage data stored in the RA) 467 are digitally processed according to the processing procedure stored in the read-only memory (ROM) 69, and the line selection relay is operated. 70 is an input/output device.

Here I! The calculation of the line selection relay that selects the faulty line based on the difference between the zero-sequence effective currents stored in 0869 before and after the fault is configured as shown in FIG.

FIG. 2 shows a specific example of means for realizing the present invention.

In FIG. 2, reference numeral 20 denotes an arithmetic processing unit that calculates the absolute value and phase of each electrical quantity using the voltage, current, and signals of the power system converted into digital quantities.

At 21, a quadrature voltage having a polarity amount used to calculate the zero-sequence effective current of each phase is created, and at 22 during normal times, the zero-sequence effective current for each phase is calculated.

On the other hand, when an accident occurs, the occurrence of the accident is detected at 23, and first,
24, the quadrature voltage before the accident is memorized.

Then, in step 25, the phase difference between the quadrature phase voltage memorized in step 24 and the quadrature voltage after the accident was measured, and the phase difference (change in phase of the polarity amount due to the accident) of the quadrature phase voltage after the accident was calculated. Correct it so that it is the same as the phase of the previous polarity amount, and use this as the polarity amount to calculate the zero-sequence effective current after the accident.

Note that in order to obtain the phase difference to be corrected, the zero-sequence voltage generated due to the accident and the memory of the polarity amount before the accident may be used.

Here, the means for calculating the change in the zero-sequence effective current before and after the accident is not directly related to the present invention, so it is omitted from the illustration.

[Effects of the Invention] As explained above, according to the present invention, the amount of polarity changes before and after the fault in a fault that becomes a problem between the fault line and the line selection relay that selects the fault line based on the difference between the zero-sequence active component current before and after the fault. This is a polar quantity that does not contribute to accidents. Therefore, regardless of the fault mode, changes in the zero-sequence active current can be accurately detected, and malfunction of the line selection relay due to an external fault can be prevented.

[Brief explanation of drawings]

Figure 1 is a block diagram for explaining the present invention, Figure 2 is a block diagram of an embodiment of the present invention, Figure 3 is a vector diagram of each phase showing the relationship between zero-sequence current and polarity, and Figure 4. is ab phase 2
A vector diagram of the sum of a showing the relationship between zero-sequence current and polarity at the time of a phase-to-ground fault, Figure 5 is a system connection diagram to explain short-circuit priority, and Figure 6 is a line selection relay using a microcomputer. FIG. 2 is a diagram showing an example of the configuration of a device. 1... Arithmetic processing section 2... Relay computing block 3... Accident detection section 4... Pre-accident polarity amount memory section

Claims (1)

[Claims] In a ground fault line selection relay device that selects a fault line based on the difference in the zero-sequence active current between each circuit before and after a fault in a parallel two-circuit transmission line in a high-resistance grounding system, the zero-sequence active current before the fault occurs a first means for storing a current derived polarity amount; a second means for detecting a phase difference between the polarity amount before the accident occurrence and the electrical quantity as the zero-sequence effective part current derived polarity amount after the accident occurrence;
and third means for correcting the phase of the zero-sequence active component current derived polarity amount after an accident occurs, using the phase difference obtained by the second means.