JPH0546772B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a digital distance relay, and particularly to a digital distance relay that is a combination of a Moh-type distance relay and a reactance-type distance relay.

[Technical Background of the Invention] Distance relays with various characteristics have been used for the purpose of power system protection. In particular, a system that combines a Moh type distance relay and a reactance type distance relay is widely and generally applied. As shown in FIG. 5, the Moh type distance relay is a relay with circular characteristics whose diameter is on the straight line of the maximum sensitivity angle of the relay installation system, and has excellent direction discrimination ability. On the other hand, as shown in Figure 6, reactance-type distance relays are relays with linear characteristics that are defined only by reactance components, and have superior distance measurement ability in the event of a failure compared to transmission lines that are considered to be based on almost pure reactance components. ing. Therefore, as shown in FIG. 7, in order to take advantage of the advantages of both, the Moh characteristic and the reactance characteristic are superimposed, and an operation determination output is produced under the AND condition of these characteristics.

FIG. 8 is a flowchart for determining the operation of a reactance element using a conventional digital calculation method. First, in step 81, it is determined whether the impedance seen from the reactance relay is within the operating range of the reactance relay as a result of digital calculation. If it is within the operating range, proceed to step 82a; otherwise proceed to step 82b. In step 82a, the motion determination counter is incremented by 1 because the detection is on the active side, and on the other hand, in step 82b, the motion determination counter is decreased by 1 because the detection is on the non-operation side. In step 83, it is determined whether or not the operation counter is 2 times or more. If it is 2 or more times, the process advances to step 84a and sets the operation output; otherwise, the process advances to step 84b and sets the non-operation output. Here, the upper limit value of the operation judgment counter is 3, and
The lower limit value is clamped to 0. The operation of a normal digital relay is determined with the above configuration.

FIG. 9 shows the change in impedance seen by the distance relay in the event of a system failure. It goes without saying that the mission of a protective relay is to never output an operation judgment output in the event of an external failure, but in the event of an external failure as shown in Figure 9,
Unnecessary output is considered to occur when the impedance seen by the relay changes from point A to point B when a fault occurs, and when the impedance seen by the relay changes from point B to point A when the fault is recovered.

[Problems with the background art] When considering each of the cases in which the above-mentioned unnecessary output may occur, it is found that in the above case, the operating time (SU-PU) of the motor element and the return time (OI-DO) of the reactance element are the problems. Therefore, unnecessary output occurs when SU−PU<OI−DO. However, since the operation time (SU-PU) of the Moo element is usually slower than the recovery time of the reactance element, this coordination is not particularly problematic.

In the above case, the return time (SU−
DO) and reactance element operating time (OI−PU)
becomes a problem, and unnecessary output occurs when SU−DO>OI−PU.

That is, time coordination becomes a problem because the return time (SU-DO) of the MO element is slower than the operating time (OI-PU) of the reactance element.

Conventionally, as a countermeasure against these problems, a method has been used to coordinate the outputs of the Moor elements or reactance elements by setting a time limit, but this results in a delay in operation time. I didn't like it as such.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems, and provides a digital distance relay that can coordinate the time of the Maw element and the reactance element without delaying the operating time of the relay. is intended to provide.

[Summary of the Invention] In the present invention, when it is detected for a certain period of time that a failure point is in the operating range of the Moh characteristic and in the non-operating range of the reactance element, the number of times the reactance element operation judgment is confirmed is n times more than usual. I try to coordinate my time by doing more.

[Embodiments of the Invention] Examples will be described below with reference to the drawings. FIG. 2 is a block diagram of an embodiment of the digital distance relay according to the present invention constructed using a digital processing device such as a microcomputer.

Each phase current I^・ _R , I^・ _S , I^・ _T of the power system is supplied from current transformer 1, and each phase voltage V^・ _R , V^・ _S , V^・ _T
are introduced from the transformer 2 to the digital distance relay 4 via the input converter 3, respectively. After removing harmonic components from each of the introduced amounts of electricity using a filter circuit (FIL) 5, the sample and hold circuit (S/H)
6. Multiplexer (MPX) 7 and analog
It is converted into a digital quantity via a digital conversion circuit (A/D) 8 and stored in a random access memory (RAM) 9. The operating output of the relay is
Using the amount of electricity stored in the random access memory (RAM) 9, the digital arithmetic circuit (CPU) 10 performs the calculation described later, and the judgment result is sent to the output interface circuit (I/
F) Output via 11.

FIG. 1 is a flowchart for arithmetic processing, and the operation will be explained using this.

In this embodiment, a "cooperative memory" is set when it is detected for a certain period of time that the impedance seen by the relay is in the operating range of the motor element and in the non-operating range of the reactance element, and this "cooperative memory" is set. Only when there is, the number of times the reactance element's operation judgment is confirmed is increased n times to realize time coordination with the Mo element, and does not affect the operation judgment time of normal reactance elements for which "cooperation memory" is not set. This is how it was done.

Therefore, first in step 11, it is determined as a result of digital calculation whether the impedance seen from the Moh relay is within the operating range of the Moh relay.
If it is in the operating range, proceed to step 12a, otherwise proceed to step 12b to reset the cooperative memory. In step 12a, it is determined whether the impedance seen from the reactance relay is within the operating range of the reactance relay. If it is within the operating range, proceed to step 13a; otherwise proceed to step 13b.
In step 13b, it is detected that a certain period of time has elapsed, and if it has elapsed, the process proceeds to step 14c and the "cooperative memory" is stored.
Set. In step 13a, the set state of the cooperative memory set in step 14c is checked. If the cooperative memory has not been set, the process advances to step 14a, and if it has been set, the process advances to step 14b. In step 14a, since the cooperative memory has not been set, the count number is set to the normal m times (because this is the operating range of the reactance element).

On the other hand, in step 14b, since the cooperative memory is set, the count number is set to m+n times, which is n times more than usual (because this is the operating range of the Mo element and the non-operating range of the reactance element). In step 15a, counting is performed on the active side, and in step 15b, counting is performed on the non-active side. In step 16, the operation is determined based on the count results in steps 15a and 15b. That is, if the counter is greater than or equal to a predetermined number of times, the process advances to step 17a to set the operating output of the reactance element, and conversely, if it is less than the predetermined number of times, the process proceeds to step 17b to set the non-operational output of the reactance element. Here, the predetermined number of times means the number of times set in step 14a or step 14b. That is, if cooperative memory is set, m+
n times, and m times if it is not set.

FIG. 3 is a characteristic diagram when a blinder element is added to a combination of a Moh element and a reactance element, where 12 shows the Moh element characteristics, 13 shows the reactance element characteristics, and 14 shows the blinder characteristics. The sloped portion in the figure indicates the operation determination area of the reactance element.

An example in which a blinder element is added will be described using the flowchart shown in FIG. In step 11, as a result of the digital calculation, it is determined whether the impedance seen from the Moh relay is within the operating range of the Moh relay. This is similar to the case in FIG. If it is in the operating range, proceed to step 41, otherwise proceed to step 12b to reset the cooperative memory. In step 41, it is determined whether the impedance seen from the blinder relay is within the operating range of the blinder relay. If it is in the operating range, proceed to step 12a; otherwise proceed to step 12b.

The processes after steps 12a and 12b are the same as those in the flowchart of FIG. 1, and their explanation will be omitted.

As explained above, even when a blinder element is added to the combination of a Moo element and a reactance element, the operational coordination of the reactance relay can be realized.

[Effects of the Invention] As explained above, according to the present invention, the operation of the reactance element is controlled on the condition that it is detected for a certain period of time that the failure point is in the operating range of the Moh characteristic and in the non-operating range of the reactance element. Since the number of judgment confirmations is calculated n more times than usual, time coordination between the Moh element and the reactance element can be easily achieved even in response to impedance changes that occur during recovery from an external fault, and the operation time of the normal reactance element can be easily achieved. can provide a digital distance relay without delay.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for determining the operation of a reactance element included in a digital distance relay according to the present invention, and FIG. 2 is a diagram showing a case where the digital distance relay according to the present invention is constructed using a digital processing device such as a microcomputer. Embodiment configuration diagram, FIG. 3 is an operation characteristic diagram when a blinder element is added to a combination of a Moo element and a reactance element, and FIG. 4 is a flowchart for determining the operation of a reactance element when a blinder element is added. Figure 5 is an operating characteristic diagram of the Moo element, Figure 6
The figure shows the operating characteristics of the reactance element, Fig. 7 shows the operating characteristics of the AND condition of the Moh element and the reactance element, Fig. 8 shows a flowchart for determining the normal operation of the reactance element, and Fig. 9 shows the case of an external failure. FIG. 3 is a diagram showing impedance changes. 1... Current transformer, 2... Transformer, 3... Input converter, 4... Digital distance relay, 5... Filter circuit, 6... Sample hold circuit, 7... Multiplexer, 8... Analog... Digital conversion circuit, 9...RAM, 10...Digital arithmetic circuit, 11...Output interface circuit, 12...
...Mho characteristics, 13...Reactance characteristics, 14...
...Blinder properties.

Claims (1)

[Scope of Claims] 1. A digital system that periodically samples a plurality of electrical quantities related to voltage and current from a protected power system at the same time and performs protection calculations using each of the electrical quantities converted into digital quantities. The relay includes a first element having a mho characteristic for determining the direction of a failure point, and a second element having a reactance characteristic for limiting a failure range, and the failure point is caused by the operation of the first element. and the second element is in the non-operating area for a certain period of time, the number of times the operation determination of the second element is confirmed is increased n times than usual. Features a digital distance relay. 2. The digital distance relay according to claim 1, wherein a blinder characteristic is superimposed on the first element having a Moh characteristic.