JPS6223314A - Protection system for power system - 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 generally relates to power system protection systems, and in particular to TLGs and power grids equipped with phase comparison relays that take measures against malfunctions caused by magnetizing inrush currents or power system transient currents. Concerning grid protection systems.

[Conventional technology]

FIG. 3 is a block diagram showing the configuration of a phase comparison relay of a conventional power system protection system published in Japanese Unexamined Patent Publication No. 59-099924.

In Figure 3, 1 is a current transformer (hereinafter referred to as rCTJ) that introduces the transmission line current into the relay, 2 is an auxiliary transformer that converts the secondary current of the CTI into a voltage signal,
3 is a filter F that removes high frequency components contained in the voltage signal output from the auxiliary transformer 2 and passes only the fundamental frequency component of the power transmission line, and 4 is a third filter among the signals output from the filter F3. A slice level SLH circuit outputs only a portion larger on the positive side than the slice level SLH shown in FIG. B (II) as a rectangular wave signal as shown in FIG. 3 B (1), 5 is the slice level S
Similarly to the LH circuit 4, only the portion of the signal output from the filter F3 that is larger on the positive side than the slice level SLL shown in FIG.
This is a slice level SLL circuit that outputs a slice level SSL signal as a rectangular wave signal as shown in FIG. The slice level SLL circuit 5 is configured to transmit the rectangular wave output signal portion to the relays R and Y at the other end.

Reference numeral 6 denotes a slice level 8 for reproducing the slice level SLL signal of the other end transmitted from the other end relay RY.
An LL signal reproducing circuit 7a is configured to reproduce the slice level SLL signal outputted from the signal reproducing circuit 6 and the slice level S
Slice level SLH of the own end output from the LH circuit 4
An AND circuit 8 is an AND circuit which calculates the logical product with a signal and outputs it, and when a signal of logic level rH is outputted from the AND circuit 7a, the on-time width of the signal is longer than the preset clock time t1. 9 is a return timer circuit that resets the relay Y operated by the operation timer circuit 8 when a preset clock time t2 elapses; The above-mentioned phase comparison relay has a configuration that ignores the so-called transmission delay time until the signal is transmitted from the other end, and the slice level value SLH and slice level value SLL are usually as shown in FIG. 3B. As shown in (II), it is set so that the relationship 5LH)lSLIno1,SL,L<0 holds true.

Next, the operation of the above-described configuration will be explained below, mainly with reference to FIG. 3B, which shows a timing chart when the power transmission line is in a healthy state. As shown in Figure 3B (1), this relay B
Consider the case where the power transmission line in section AB is protected by Y.

If the power source is the A terminal, and the current flows from the person to B when the transmission line is healthy, each CTIA at the A end and B end,
1B are connected with mutually opposite polarities, the output signal of the auxiliary transformer 2 described above has a voltage waveform with a phase shift of approximately 180° between the A terminal and the B terminal in FIG. 3B (it). The signals with slice level values 8LH and SLL at the A end and B end, respectively, due to the input of the voltage waveform are shown in FIG. 3B (
(lit) and as illustrated in FIG. 3B (lv). The SLL signal illustrated in FIG. 3 (1v) is
As shown in FIG. BM, each signal is transmitted to the other end via a transmission device, and the AND circuit 7a performs a logical product with the own end slice level SLH signal. Figure 3B
As is clear with reference to (1) and FIG. 3B (v), when there is no overlap between the own end slice level SLH signal and the opposite end slice level 8LL signal, the AND circuit 7a A signal of logic level "H" is not output (see Fig. 3B (vll)). That is, AND
If the circuit 7a does not output a signal of logic level rHJ, it means that the power transmission line is in a healthy state. Contrary to the above, if there is a fault between the A terminal and the B terminal, the fault current flowing to the B terminal will be reversed, so the output voltages of the auxiliary transformer 2 at the A terminal and B terminal will have approximately the same polarity. So, A N
Since the D circuit 7a outputs a signal of logic level rHJ whose on-time width is the width of the SLH signal, the (
If the on-time width of No. 1 is wider than t1, a trip occurs.

[Problem that the invention seeks to solve]

Conventional power system protection systems are configured as shown above, so when the power transmission line is in good condition, terminals A and B are
The secondary voltage waveforms of the auxiliary transformer 2 in the end relays should be out of phase, whereas when the transmission line fails, the secondary voltage waveforms should be in phase.

However, if the transmission line is covered with cables or is a long-distance transmission line, the ground capacity C of the transmission line cannot be ignored, and for example, the B-end transformer TR
When recovering from an external ground fault F, a resonance phenomenon occurs between the transmission line and transformer's resistance and ground capacity, and there is a risk that the relay BY may malfunction due to the resonance phenomenon. That is, if the high frequency components generated at the A end and the B end are different as shown in FIG. 4 (11) due to the resonance phenomenon, the second wave having the same peak value as the fundamental wave on the A end side
and the third harmonic are superimposed, and on the other hand, on the B end side, the second harmonic having the same wave height value as the fundamental wave is superimposed. In an actual system, when the ground capacity C is large, the frequency of the high-frequency component drops to the order of several 1001 (z), and the frequency of the transformer's magnetizing inrush current is approximately IQQI (near z). It has been observed that the time is on the order of several 100 ms to several S. Therefore, on the A-end side.

High frequency components with different waveforms are generated due to the difference in resonance conditions on the B end side, and when these high frequency components enter filters F3 in relays R and Y as shown in FIG. 3A, the corresponding Filter F3 is a number 10 whose frequency is close to the fundamental wave.
Since input signals of about 0 Hz cannot be completely cut and are output, the A-end slice level SLH signal and the B-end slice level SLH signal are separated as shown in Figure 4 (vl).
There is a possibility that the end side slice level 5LLB signal overlaps in the AND circuit 7a, causing the relay BY on the A end side to malfunction, and similarly, the B end side slice level SLH signal and the A end side slice level 5LLA signal overlap in the AND circuit 7a. There has been a problem in that it is difficult to further improve the reliability of the system as a whole, such as the risk that relays R and Y on the B end side may also malfunction due to overlapping.

This invention was made to solve the above-mentioned problems, and provides a power system protection system that can prevent malfunctions caused by superimposed high frequencies, thereby further improving reliability. The purpose is to obtain.

[Means for solving problems]

The power system protection system according to the present invention includes a phase comparison relay that protects the power transmission line by detecting a failure occurring in the power transmission line by comparing the phases of the transmission currents at one end and the other end of the transmission line; a transmission means for transmitting and receiving signals between the phase comparison relays, wherein at least one of the phase comparison relays is provided with an undervoltage detection means for detecting and outputting a drop in the power transmission line voltage; First signal processing for detecting a fault in the power transmission line based on the output signal from the undervoltage detection means and the output signal from the other phase comparison relay applied to one phase comparison relay via the transmission means. a second phase comparison relay for outputting an output signal from the phase comparison relay and an output signal from the undervoltage detection means to the other phase comparison relay via the transmission means; It is equipped with signal processing means.

[Effect]

The first signal processing means in this invention detects a failure in the power transmission line based on the output signal from the undervoltage detection means and the output signal from the other phase comparison relay given via the transmission means, and the second signal The processing means outputs the output signal from one phase comparison relay and the output signal from the undervoltage detection means to the other phase comparison relay via the transmission means.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a phase comparison relay used in a power system protection system according to an embodiment of the present invention, and FIG. 2 (1) is an outline of a power system protection system according to an embodiment of the present invention. 2(11) to (vm) are timing charts showing the operation of the power system protection system according to an embodiment of the present invention. Note that the reference numbers 1, 2° 3.4, 596.7 &, 8.9 in FIG. 1 are exactly the same as those shown in FIG. 3A, so their explanation will be omitted.

In Fig. 1, 10 indicates the voltage on the A side of the power transmission line through relay R
Voltage converters P and T that convert to voltage for Y input.

11 is an auxiliary voltage transformer that converts the output voltage from the voltage converters P and T into a signal for the internal circuit of the relay RY; 12
The undervoltage detection means, that is, the undervoltage detectors U, V, 7b provided in the relay RY on the A end side are connected to the slice relay z.
A second signal processing means for ANDing the SSL signal output from the SLL circuit 5 and the output signals from the undervoltage detectors U and V, i.e., AND circuit 7e is the undervoltage detector U. , V, and the output signal from the recovery timer circuit described above.
This is a signal processing means, that is, an AND circuit.

Next, the operation of the above-mentioned configuration will be explained below, mainly with reference to FIG. 2 (11) to FIG. 2 (vii+) showing operation timing charts of each part.

Assuming that the continuing ground fault at point F shown in Figure 2 (1) is restored at time t = 0, the power transmission line and transformer T
A resonance phenomenon occurs between the reactance of R and the ground capacitance. Due to this resonance phenomenon, the high frequency components generated at the A end and the B end may be different, as shown in Figure 2 (Fig. 11).
and the third harmonic are superimposed, and the second harmonic having the same wave height value as the fundamental wave is superimposed on the -10,000B end side. As mentioned above, the frequency of the high frequency component K, in an actual system, drops to the order of several 100 Hz when the ground capacity tC is large, and the frequency of the excitation inrush current of the transformer TR is approximately i.
o It's around OH2, and the duration is several o
It has been observed that it ranges from 0 ms to several S. When such high frequency components enter the filter F3 in the relay RY arranged on the A end side and the B end side as shown in FIG. 1, the filter F3 has a frequency close to the fundamental wave. Since it is not possible to completely cut an input signal of about 100 Hz, the waveform shown in FIG. The input signal on the A end side shown in FIG. As shown in FIG. 2 (-), only the large signal portion is output as a rectangular wave signal to the AND circuit 7a of the A-end relay BY.
Slice level # S L L In the circuit 5, only the signal portion larger on the positive side than the slice level SLL is processed as shown in Fig. 2 (
As shown by the leap, it is output as a rectangular wave 1g to the AND circuit 7b of the A-end relay RY. Said Figure 2 (11
The input signal on the B-end side shown in j is also subjected to signal processing similar to that on the A-end side described above in the B-end relay 1 (Y), and the input signal from the slice level SLH circuit 4 on the B-end side is processed as shown in FIG. A rectangular wave signal as shown in FIG. 2 (1v) is output from the slice level SLL circuit 5, and a rectangular wave signal as shown in FIG.

When the above-mentioned ground fault at point F is restored, the line voltage that had been decreasing will return to its original level, so the undervoltage detectors U, V, and 12 will operate as shown in Figure 2 (vii). The operation will be restored. Output signals from the undervoltage detectors U, V, and 12 are output to AND circuits 7b and 7C, respectively. The 5LLB signal shown in FIG. 2 (V) transmitted from the slice level SLL circuit 5 on the B end side to the A end relay RY via the transmission line and transmission device is AND
In the circuit 7a, the AND circuit 7a is logically ANDed with the SLH signal on the A end side shown in FIG.
A signal having an on-time width as shown in FIG.
It is output to circuit 7C. The signal shown in FIG. 2 (VIJ) and the signal shown in FIG.
The logical AND is performed in C. As is clear from the A side in Figure 2 (vl) and the A side in Figure 2 (vii), the on-time widths of both signals do not overlap in time, so the trip occurs. does not occur. Therefore, the output signal from the AND circuit 7c is determined by the second factor (v+++
) as shown on the A end side.

On the other hand, the undervoltage detectors U, V, l2 shown in FIG. 21 (vii) and the slice level SLL signal on the A end side shown in FIG. 2 (1v) are the AND of the A end side.
A logical product is performed in circuit 7b. The 5LLA signal shown in FIG. 2 MK outputted from the AND circuit 7b by this logical product is transmitted to the B-end side relay RY via the transmission line and transmission device, and is applied to the B-end side AND circuit 7a. FIG. 2 (IiiiJ
The SLH signal shown in FIG.
A logical AND is performed at a. As is clear from the B end side of Figure 2 (iiiJ) and Figure 2 (B end side of VJ), a trip occurs because the on-time widths of both signals do not overlap in time. No. Therefore, the above A
The output signal from the ND circuit 7a is as shown in FIG.
As shown in the figure on the B end side.

In one embodiment according to the present invention described above, an undervoltage detector tJ,
Although the outputs of V and l2 are given to the AND circuit 7C, the same effect can be achieved by giving the outputs of the detectors U, V and 12 to the AND circuit 7a on the A end side. Furthermore, in the above-mentioned embodiment, the undervoltage detectors U, V, and 12 were installed only in the relays RY at one end of the power transmission line, but of course they can also be installed in the relays RY at both ends. In that case, trip control at the own end can prevent malfunctions when the power transmission line is restored from a fault, but adding transmission line control to the other end doubles the measures against malfunctions and increases reliability. improves.

〔Effect of the invention〕

As described above, according to the present invention, a failure in a power transmission line is detected based on the output signal from the undervoltage detection means and the output signal from the other phase comparison relay given via the transmission means, and one The output signal from the phase comparison relay and the output signal from the undervoltage detection means are outputted to the other phase comparison relay via the transmission means, thereby preventing malfunctions caused by superimposition of high frequencies. This has the effect of providing a power system protection system that can further improve reliability.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a phase comparison relay used in a power system protection system according to an embodiment of the present invention, and FIG. 2 (1) is a block diagram of a Hoto system for a power system according to an embodiment of the present invention Outline diagram, Figure 2 (1s+ (tj)
+ Ovl + (v) r (four l (Vii) l
(Viii) is a timing chart showing the operation of a power system protection system according to an embodiment of the present invention, and FIGS. 3A and 3B show the configuration of a phase comparison relay used in a conventional power system protection system. FIG. 4 is a timing chart showing the operation of a conventional power system protection system when different high frequency components are input to one end and the other end of the power transmission line. It is. In the figure, 1 is a current transformer or C, T, 2 is an auxiliary transformer, 3 is a filter F, 4 is a slice level SLH circuit, 5 is a slice level SLL circuit, 7a is an AND circuit,
7b is an AND circuit, 7C is an AND circuit, 8゛ is an operation timer, 9 is a recovery timer, 10 is a voltage converter or P, T, etc.
11 is an auxiliary voltage transformer, 12 is an undervoltage detector U, V
, is. In each figure, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A device is installed at one end and the other end of the power transmission line, and detects a failure occurring in the power transmission line depending on whether the phases of the transmitted currents at one end and the other end of the power transmission line are in phase or opposite to each other. In a power system protection system comprising a phase comparison relay that protects a power transmission line, and a transmission means for transmitting and receiving signals between the phase comparison relays, at least one of the phase comparison relays is connected to the transmission line. Undervoltage detection means for detecting and outputting a drop in voltage is provided, and an output signal from the undervoltage detection means and an output signal from the other phase comparison relay are applied to the one phase comparison relay via the transmission means. a first signal processing means for detecting a failure in the power transmission line based on the output signal; A protection system for an electric power system, characterized in that a second signal processing means for outputting the signal to the other phase comparison relay via the transmission means is provided.