JPS61273125A - Phase comparator/relay - 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 relates to a phase comparison relay, and more particularly to a phase comparison relay that takes measures against malfunctions caused by excitation inrush current or transient current in a power system.

[Conventional technology]

FIG. 3 is a block diagram of a conventional phase comparison relay disclosed in, for example, Japanese Unexamined Patent Publication No. 59-099924. In the figure, 1 is a current transformer (hereinafter abbreviated as CT) for introducing the transmission line current into the relay, 2 is an auxiliary transformer that converts the secondary current of the CTI into a voltage signal, and 3 is an auxiliary transformer that converts the secondary current of the CTI into a voltage signal. Filter F and filter 4 remove high frequency components included and pass only the fundamental frequency components of the power transmission line. Filter F and 4 are filter outputs that convert only the positive side of the slice level (8LH) into a rectangular wave signal and output it. SLH)
Circuit 5 is a slice level (8LH) circuit similar to circuit 4,
Slice level 8LL of filter output of filter 3
A slice level 8LL circuit outputs only the signal larger on the positive side as a rectangular wave signal, and transmits the rectangular wave output signal to the other end relay RY. 6 is a slice level SLL signal reproducing circuit of the other end which is transmitted from the other end, and this and the S of the own end of the slice level SLH circuit 4.
The LH signal is synthesized by an AND circuit 7a, and an AND output signal is output. This output is introduced into the operation timer circuit 8a,
The output of this operation timer circuit 8a is sent to the recovery timer circuit 9.
Introduce into a. If the output lWA of the AND circuit 7a is longer than the measured time t1 of the operation timer circuit 8a, the relay RY
comes to work.

However, the configuration here ignores the so-called transmission delay time until the signal is transmitted from the other end. Pottery 1
Normally, each slice level value SLH and SL of the slice level SLH circuit 4 and the slice level SLL circuit 5
I, are set in the relationship of 5LH), 18LLl, and 8LL (0, respectively).

Next, the operation will be explained with reference to the timing diagram of the operation time chart shown in FIG. As shown in FIG. 4 (1), section A is set by relay RY.

Consider the case of protecting power transmission line B. With the power supply end as the A end, send 1! Assuming that a healthy special current flows from the A terminal to the B terminal, the output signal of the auxiliary transformer 2 will be as shown in the figure (
1:), the voltage waveforms have a phase shift of approximately 18σ at the A end and the B end.

Slice level value SLH of each of the A end and B end.

The SLL signals are as shown in the same figure) and Qv). The same figure (V
) is the slice level SLL transmitted from the other end.
Signal in the same figure (4 is the AND output signal of the AND circuit 7a, which has the own end slice level 8LH and the opposite end slice level S)
When there is no overlap with LL, no output signal is output.

This means that the power transmission line is in good condition, and Figure 4 shows
The time chart of this healthy state is shown, but conversely, end A, end B
If there is a fault between the terminals, the fault current flowing to the B terminal is reversed, so the output voltages of the auxiliary transformer 2 at the A terminal and B terminal have almost the same polarity.The AND output of the AND circuit 7a Since the width of the SLH signal is output as a signal, the width is 1. If it is larger, it becomes a trip.

[Problem that the invention seeks to solve]

Since the conventional phase comparison relay is configured as described above, when it is healthy, the auxiliary transformer 20 in the A-terminal and B-terminal relays
The secondary voltage waveforms are in opposite phase, and in the event of a failure, they must be in phase.

However, when the transmission line is composed of cables or when it is a long-distance transmission line, as shown in Figure 4 (1), the ground capacity C of the transmission line cannot be ignored, and for example, at the B end When a ground fault F outside the transformer TR is restored, a resonance phenomenon occurs between the transmission line and the transformer's actance and ground capacity.

Fig. 5 (11) - (VO is an operation time chart of the phase comparison relay showing the situation at this time. Fig. 5 (11)
As shown in the figure, the high frequency components at the A end and the B end may be different. In an actual system, the frequency of this high frequency component drops to several 100 Hz when the ground capacity is large, and is close to the 100 Hz frequency of the transformer's excitation inrush current. It has been observed that the duration ranges from several hundred meters to several seconds. Such high frequency components generate different waveforms depending on the difference in resonance conditions on the A end side and the B end side.

Therefore, when the above-mentioned high frequency component enters the filter circuit 3 in the relay as shown in Fig. 3, the filter circuit 3 cannot completely cut out the human power of about several hundred Hz, which is close to the fundamental wave, and outputs it. As shown in the NX5 diagram (VO), the slice level SLH signal and the B-end slice level 8L
There are problems such as overlap with the LB signal, which may cause the relay BY at the A end to malfunction, and overlap between the slice level SLH signal and the A end slice level 5LLA signal, which may cause the relay RY at the B end to malfunction. Ta.

This invention was made to solve the above-mentioned problems, and it is an object of the present invention to provide a phase comparison relay that can prevent malfunctions due to high frequency superimposition.

[Means for solving problems]

The phase comparison relay according to the present invention changes the self-end slice level SLH depending on the high frequency/fundamental wave ratio, and prevents malfunction due to the difference in high frequency current between the A end and the B end, such as when recovering from an external accident. Yes [Operation] The phase comparison relay according to the present invention changes the value of the slice level SLH by calculating the ratio between the output of the high frequency detection circuit and the output of the fundamental wave detection circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1, in which the same parts as in FIG. 4 are denoted by the same reference numerals.

In FIG. 1, 10 is a fundamental wave detection circuit that detects only the fundamental frequency component and generates an output proportional to its value, 11 is a high frequency detection circuit that detects only the high frequency component and generates an output proportional to that value, and 12 compares the outputs of the fundamental wave detection circuit 10 and the high frequency detection circuit 11, and only when the ratio of the two exceeds a preset value, the self-end slice level 5L is set.
This is a high frequency/fundamental wave ratio comparator that outputs a control signal to increase H4.

The operation will be described below with reference to the timing diagram of the operation time chart shown in FIG.

Now, in Figure 2 (1), suppose that the ground fault that continued at point F at time 1 = 0 has been restored.
As shown in 1), the second and third v4 waves having the same peak value are superimposed on the fundamental wave on the KA end side, and the second harmonics having the same peak value are superimposed on the fundamental wave on the B end side. Since the filter 3 cannot sufficiently remove such low-order harmonics, it is assumed that the waveform shown in FIG. 2 (110) is transmitted as is to each slice level circuit 4, 5.

On the other hand, the harmonics are detected by a high frequency detection circuit 11, and the output thereof and the output of the fundamental wave detection circuit 10 are compared by a high frequency/fundamental wave ratio comparator 12). Now, since the ratio of the high frequency to the fundamental wave is sufficiently higher than the set value, a control signal is output from the high frequency/fundamental wave ratio comparator 12.
This control signal changes the slice level 5LH4 to a large value as shown by the broken line. The output sliced at slice level 5LH4 is shown in FIG. 2 (IIIJ).

Comparing with the conventional phase comparison relay Fig. 5 (Ill),
The time width of the SLH output has become smaller, and the number of outputs has also decreased on the A end side. Figure 2 (Iv) +1v)
(V) is the same as FIG. 5 (lvl, (vl). Therefore, as shown in FIG.
No false trip signals are generated.

Further, in the above embodiment, the case of slice level SLH has been described, but slice level SLL may also be used, and the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, the phase comparison relay is configured to change the value of the cis slice level depending on the high frequency content, so malfunctions such as when recovering from an external accident can be prevented and highly reliable. It has the effect of getting something.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a phase comparison relay according to an embodiment of the present invention, FIG. 2 is a timing diagram showing an operation time chart, and FIG. 3 is a block diagram of a conventional phase comparison relay. Fig. 5 is a timing diagram showing an operation time chart when input signals with different high frequency components are input to a conventional phase comparison relay;
0... Fundamental wave detection circuit, 11... High frequency detection circuit, 12... High frequency/fundamental wave ratio comparator O. Note that the same reference numerals in the drawings indicate the same or corresponding parts.

Claims (1)

[Claims] Each power transmission current at the A end side and the B end side is detected, and the A end side power transmission current is set to a first slice level value, and the B end side power transmission current is set to a second slice level value. A phase comparison relay that compares each output slice level signal and trips based on an AND condition determination signal of each output slice level signal includes a fundamental wave detection circuit that detects only a fundamental frequency component from the power transmission current and generates an output proportional to that value; A high-frequency detection circuit that detects only high-frequency components from current and generates an output proportional to that value, and a high-frequency detection circuit that compares the outputs of both detection circuits and outputs a control signal when the ratio exceeds a preset value. A phase comparison relay comprising: a fundamental wave ratio comparator, wherein the first slice level value or the second slice level value is changed by the control signal.