JPS58224518A - Protecting relay with second harmonic wave suppressor - 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 The present invention relates to a protective relay for protecting an electric power system, and more particularly to a protective relay with second harmonic suppression for protecting a transformer, which is an important device in the electric power system.

A conventional relay of this type is shown in FIG.

In FIG. 1, 1 is a suppression input terminal, 2 is a differential input terminal, 3 is a suppression circuit, 4 is a differential circuit, 5 is a first comparison circuit, 6 is a suppression circuit 3. A ratio element consisting of the differential circuit 4 and the first comparator circuit 5, 7 is a fundamental component derivation circuit, 8 is a second harmonic component derivation circuit, 9 is a second comparison circuit, and 10 is a fundamental component derivation circuit. 7. A second harmonic detection element 11 consisting of a second harmonic derivation circuit 8 and a second comparison circuit 9 operates only when the output of the second harmonic detection element 10 is not sent out. 12 is an output terminal of the first AND circuit which outputs the result.

Symbol II in Figure 1 is the differential input, a is the output of the ratio element 6, 2 is the fundamental portion of the differential input, 3 is the second harmonic of the differential input, and b is the second harmonic. The output of the detection element, C, indicates the final output, and these waveform operations are shown in FIGS. 2 and 3, where the alternating current amount is shown as a dotted line, and the rectification and smoothing amount is shown as a solid line.

Next, the operation will be explained using FIGS. 2 and 3.

FIG. 2 is an operating waveform diagram when the inrush current of the transformer flows as a differential input. The inrush current of a transformer is the current that occurs when the transformer is turned on with no load, and is not a fault current, but a current that must not operate as a protective relay. In general, in-rush current contains a large amount of second harmonics, and it is common to suppress the output by detecting this content, and the device shown in Figure 1 also uses this output suppression method. are doing. As shown in FIG. 2, the output a of the ratio element 6 operates if the differential amount is above a certain value, and the second harmonic detection element 100 outputs the second harmonic component 3 and the fundamental component 3.
It is working because the ratio with 2 is large. Therefore, the output C of the first AND circuit 11 will rise as shown by the dotted line if the output is not sent, but no output appears because the output condition of the first AND circuit 11 is not satisfied for the output. .

FIG. 3 shows the waveform operation when a differential current occurs (internal failure occurs), and the fundamental wave current changes to the differential current 11 at time tx.
If the flow is as follows, the basic yield ■2 will occur. Since the basic liquid component deriving circuit 7 generally uses a filter circuit, the basic distribution (2) gradually increases as shown in the figure with a delay in the start-up 9.

In addition, since the input is originally only the fundamental component 2, the second harmonic component output 13 is not generated, but the second harmonic component deriving circuit 8 also uses a filter circuit, and the sharpness of the filter circuit is Normally, the sharpness is higher than that of the basic liquid component deriving circuit 7, and due to the transient phenomenon characteristics due to changes in input, it shows a rapidly decreasing state like a mountain shape as shown in Fig. 3. As a result, the output a of the sill ratio element 6 operates when the differential amount is above a certain value, but the output of the second harmonic detection guide 10 and the second harmonic component output ■3 as described above are initially Output is sent for a certain period of time, but the first
The rise of the output C of the AND circuit 110 is delayed. This is because the operating time is delayed by the second harmonic detection element 10.

Next, a case will be described in which the differential current suddenly decreases at time t2 using the waveform operation diagram of FIG. 3. If the differential current suddenly decreases within the operating range of the ratio element 6 at time t2, the fault point has moved within the operating range, so the output originally continues to be in the sending state, but due to a change in the input, the If the second harmonic output component I3 changes in a mountain shape due to the transient phenomenon of the harmonic component deriving circuit 8, and the value of this second harmonic output component ■3 is larger than a certain ratio of the value of the fundamental component I2, then , the output of the second harmonic detection element 100 rises, and in response to this output, the first
There was a phenomenon in which the output C of the AND circuit 11 was temporarily stopped.

The movement of the differential current within the operating range of the ratio element 6 as described above is caused by the occurrence of a system fault during inspection by applying the test current of the protective relay, and the subsequent removal of the test current (by applying the test current of the protective relay). This operation does not result in a circuit breaker coil energization output, so it is necessary to stop the inspection, or the inspection current must be removed), making it difficult to set the inspection sequence.

The present invention has been made in order to eliminate the drawbacks of the conventional ones as described above.
The output of the harmonic detection element is used as a suppressing force, and even if the output of the second harmonic detection element continues to be sent for a predetermined time or more, the output is suppressed, and the output is suppressed within the operating range of the ratio element. It is an object of the present invention to provide a protective relay with second harmonic suppression in which the output of a first AND circuit is not cut off due to sudden changes in differential current.

An embodiment of the present invention will be described below with reference to the drawings. 1st
In FIG. 4, parts that are the same as those shown in the figure are designated by the same reference numerals. In FIG. 4, 16 is a monostable multivibrator circuit that continuously sends out an output for a certain period of time when the ratio element 6 sends out an output, and 14 is a monostable multivibrator circuit 16. A second AND circuit 15 sends out the output of the second harmonic detection element 10 only when the second harmonic detection element 10 is sending out an output. A timer circuit 16 which operates when the wave detection element 10 continues outputting, obtains the logical sum of the output of the second AND circuit 14 and the output of the timer circuit 15;
An OR circuit that suppresses the output of the first AND circuit 11, symbols d-f in FIG. 4 represent the output waveforms of each part of the circuit, and their operating states are shown in FIGS. 5 and 6. .

Figure 5 shows the operating waveforms for the input conditions corresponding to Figure 3.
Figure 6 shows the case where the inrush current of the transformer is input (
The input conditions corresponding to FIG. 2 are shown.

Next, the operation of the present invention will be explained. In Figure 5,
Waveforms a and b are omitted because they are similar to the operations described in FIG. 3. When the differential current 11 flows at time tl, the ratio element 6 sends out an output a, and the monostable multivibrator circuit 16 operates to send out an output d for a certain period of time. As a result, the second AND circuit 14 sends out the output e of the second harmonic detection element 10 as an output e which performs a suppressing operation. Therefore, the output C of the first AND circuit 11 is outputted with a time delay as explained in FIG. In this case, the time limit circuit 15 does not send out any output since the output of the second harmonic detection element 10 does not reach the fixed time T.

Next, a case where the differential current It suddenly decreases within the operating range of the ratio element 6 at time t2 will be described. Output a of ratio element 6 continues and monostable multivibrator circuit 1
6 sends no output. Therefore, since the output e of the second AND circuit 140 does not rise, the output of the second harmonic detection element 10 is different from that in FIG. 3, and is not an output that suppresses the output of the first AND circuit 11. I can't do it. Also, at this time, the timer circuit 15 measures the output f of the second harmonic detection element 100, but since the predetermined time T has not been reached, the output f is not sent out.

Therefore, at time t2, the output C of the first AND circuit 11
will never return.

Next, the operating waveforms shown in FIG. 6 will be explained. Input current 11
When is the inrush current of the transformer, the operations of the output a of the ratio element B and the output of the second harmonic detection element 100 are the same as those explained in FIG.

Therefore, the monostable multipipe rake circuit 16 sends out a pulse output d of constant width. As a result, the second AND circuit 14
takes the AND of the output of the second harmonic detection element 10 and the output d of the monostable multivibrator circuit 16, and sends out an output e that suppresses the output of the first AND circuit 11.

In this state, the output C of the first AND circuit 11 is the output e
rises as shown by the dotted line as the fall of T rises. However, since the time limit circuit 15 that clocks the output of the second harmonic detection element 100 sends out the output f after a certain period of time T, this output f causes the The output C of the 1-AND circuit 11 cannot rise. That is, even in one embodiment of the present invention, malfunction does not occur when a transformer inrush current is input.

The time T measured by the time limit circuit 15 is the output time of the second harmonic detection element 10 when the differential input suddenly decreases (it is determined by the circuit constant of the second harmonic detection element 100 and the sudden amount of input). It is necessary to set the output pulse width of the monostable multivibrator circuit 13 to be longer and shorter than the output pulse width of the monostable multivibrator circuit 16, and the output pulse width of the monostable multivibrator circuit 13 must be set to detect the second harmonic when the differential input suddenly decreases. Any time longer than the output time of element 10 can be set.

In the above embodiment, a fundamental wave component derivation circuit and a second harmonic component derivation circuit were shown as the second harmonic detection element, but a so-called second harmonic detection relay (which detects the second harmonic component and The same effect can be achieved even when applied to a relay used for locking a relay, etc.

As described above, according to the present invention, the output of the second harmonic detection element is made valid only when the differential amount increases, and the output of the second harmonic detection element is made valid after timing. This configuration increases the stability of the protective relay,
This has the effect of providing a highly reliable protective relay.

[Brief explanation of drawings]

Figure 1 is a block diagram of a conventional protective relay, Figures 2 and 3
The figure is a waveform diagram showing the operating status of a conventional protective relay, Figure 4 is a block diagram of a protective relay showing an embodiment of the present invention, and Figures 5 and 6 are waveform diagrams showing the operating status of an embodiment of the present invention. FIG. 1... Suppression input terminal, 2... Differential input terminal, 6
... Suppression circuit, 4... Differential circuit, 5... First
Comparison circuit, 6... Ratio element, 7... Fundamental wave component deriving circuit, 8... Second harmonic component deriving circuit, 9... Second comparison circuit, 10... Second harmonic detection Element, 11.
...First AND circuit, 16... Monostable multivibrator circuit, 14... Second AND circuit, 15...
Time limit circuit, 16...OR circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Makoto Kuzuno - (1 other person) (5) No. 2 Figure 1A3 No. 5 Mazuki 6 Written amendment in secret procedure (spontaneous) Mr. Commissioner of the Japan Patent Office 1, Indication of the case Patent application No. 109206/1986 2
, Title of the invention Second harmonic suppression protection relay 3, Relationship with the case of the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Corporation Representative Katayama Jinhachibe 4, Agent Address: 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo, Detailed explanation of the invention in the statement of subject matter of the amendment 6 Contents of the amendment + 11 Specification 1 Page 4, Ladle 14 1: The phrase [output is sent out for a certain period of time] is corrected to "because output is sent out at a fixed period of time." (2) Page 6 of the specification, 2nd to 3rd ladle (2) ``Suppress the force, ... sudden iI: against'' is replaced with ``with the force as a restraining force, within the operating range of the ratio element. For sudden changes in the differential current E, the correction is made as follows.

Claims (1)

[Claims] In a protective relay with second harmonic suppression, which has a ratio element that compares a differential current amount and a suppressed current amount, and includes a second harmonic detection element that detects a second harmonic content rate in the differential current,
a monostable multivibrator circuit that sends out an output for a certain period of time when the ratio element sends out an output; a second AND circuit that receives the output of the monostable multivibrator circuit and the output of the second harmonic detection element; a time limit circuit for timing the output of the second harmonic detection element, and a logical product of the output of the ratio element and the output of the ratio element, receiving the output of the time limit circuit and the output of the second AND circuit; A protective relay with second harmonic suppression, comprising: an OR circuit that outputs an output to a first AND circuit forming a first AND circuit.