JPH04200222A - Protective 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 [Object of the Invention] (Industrial Application Field) The present invention relates to a protective relay that determines operation based on the magnitude relationship between the amount of operation and the amount of suppression.

(Prior art) Normally, a protective relay that has the ability to determine the direction of an accident inputs multiple electrical quantities, calculates the amount of operation and amount of suppression according to a predetermined determination principle, and determines the operation based on the magnitude relationship between the two. .

As an example, the principle formula for determining the operation of current differential * electric appliances is (1)
This is expressed by the formula, which is known as the ratio characteristic,
The operating amount is the vector sum (Id) of each current input, and the suppression amount is a predetermined ratio (K) to the scalar sum (Σ!■1) of each current input.
is multiplied by the sensitivity term (Ko
), the relay is activated.

Id≧1 Σl I l +KO-...-(1) Fourth
The figure shows the ratio characteristics of a widely used current differential relay.The ratio characteristics 1a, which allows faults to be detected with high sensitivity in areas where the fault current is small, and the ratio characteristics, 1b, which allow for highly sensitive detection of faults in areas where the fault current is large, are This is an example in which the operation of a relay is determined by combining two different ratio characteristics, which are designed to prevent the relay from operating within minutes. Here, if we focus on the relay response in a transient state when an accident occurs or when recovering from an accident, in accident 2, which is in the non-operating area close to the operating area shown in Figure 4, the relay should not operate even in a transient state. , it is necessary to add measures to prevent malfunction.

A conventional transient response measure for a relay will be explained using the functional block diagram shown in FIG. 3a and 3b are input converters that input the amount of electricity to be protected to the relay. Reference numeral 4 denotes an input circuit for an electric quantity used for calculating the amount of operation, and 5 denotes an input circuit for an electric quantity used for calculating the amount of suppression, which includes a filter circuit using an operational amplifier and the like.

The output of each input circuit is input to the operation amount calculation circuit 8 @ 6 and the suppression amount calculation circuit 7 to calculate the operation amount and the suppression amount.

In the case of a digital relay, the signal is preprocessed by a digital filter to remove harmonic components and DC components prior to calculation of the operating amount and the suppression amount.

In order to prevent relay malfunction in the event of an accident, it is necessary to establish the suppression amount faster than the operating amount. For this reason, the transient response time of the prefilter on the suppression amount side should be made faster than on the operating amount side. The response time of the suppression amount calculation circuit is increased.

On the other hand, in order to prevent malfunctions during recovery from an accident, it is necessary to delay the suppression amount by a predetermined period of time using the suppression amount delay circuit 8 so that the movement amount does not become larger than the suppression amount during the process of attenuation of the operation amount and suppression amount. Alternatively, a method is used in which the operation determination circuit 9 performs the operation determination of equation (1) using the maximum value of the suppression amount for a predetermined time in the past. With this measure,
How the operating amount and suppression amount of the relay change when an accident occurs or when the accident is recovered will be qualitatively explained using the locus of the calculation amount on the ratio characteristic in FIG. 6. The current before the simple accident is set to zero, and the fault point is set to 10.

If no countermeasures are taken, the transient locus of the operating amount and suppression amount will be approximately a straight line 11, passing through the operating range, leading to malfunction of the relay. If measures are taken to establish the suppression amount earlier than the operating amount, the trajectory at the time of the accident will be 12, and passing through the operating range can be avoided, but conversely, when the accident recovers, the trajectory will be 13.
It passes through and tends to malfunction. Therefore, if a measure is taken to delay the attenuation of the suppression amount, the trajectory becomes 14 and passes through the non-operation area, so that malfunctions during recovery from an accident can also be prevented.

(Issues to be solved by the invention) According to the above method, the measures to prevent malfunction in the event of an accident are as follows:
As shown in the suppression amount calculation result No. 15 in the figure, since the suppression amount is also attenuated quickly, this works in a disadvantageous direction for cooperation during accident recovery. In order to take into account this effect and achieve coordination, it is necessary to extend the amount of suppression for a sufficient period of time as shown in 16. However, the more the attenuation of the amount of suppression is delayed, the more the operating time of the relay tends to be delayed. In particular, if there is a sufficient amount of suppression before the accident, such as an accident under heavy load or an internal accident immediately after an external accident, the operation will pass through a trajectory like 17 in Figure 6. There will be a significant time delay, and in some cases, the delay in clearing the fault may have a serious impact on the stability of the power system.

The present invention has been made in order to solve the above problems, and provides a protective relay that does not significantly impede operating time in the event of an accident and does not malfunction in a transient state when an accident occurs or when recovering from an accident. The purpose is to

"Configuration of the Invention" (Means for Solving the Problems) The configuration of the present invention will be explained with reference to the functional block diagram of FIG. 1 corresponding to the embodiment. Another operation amount calculation circuit 2 that inputs the electric quantity of , and calculates the operation amount with a faster transient response time than the operation amount calculation circuit.
0 and another level determination circuit #I22 for determining the level of the calculation result of the other operation amount calculation circuit described above, and is configured so that the output of the operation determination circuit 9 is invalidated by the output of the other level determination circuit 22. did.

(Function) As a result, when the accident recovers, the operation amount of the operation amount calculation circuit output with a faster response time is attenuated in a short time, and the level detection output is restored, so that the relay operation judgment is disabled. Therefore, it is only necessary to coordinate so that the amount of suppression is greater than the amount of operation in the time it takes for the level detection output to return, and the delay time of the amount of suppression can be shortened, making it possible to minimize the amount of time required for relay operation. .

(Example) An embodiment of the present invention will be described with reference to FIG.

In FIG. 1, parts that are the same as those in FIG. 5 are given the same numbers and their explanations will be omitted.

In FIG. 1, the operation amount calculation circuit 20 calculates the operation amount 21 by inputting the same electric quantity as the operation amount calculation circuit 6.
A circuit is used in which the response time of the calculation result is faster than that of the operation amount calculation circuit 6 with respect to fluctuations in the input electric quantity. Movement amount 2
1 is used to detect recovery from an accident, and therefore does not need to be highly accurate. Therefore, an arithmetic circuit with a quick response time can be used without being restricted by arithmetic accuracy. For example, in the case of a digital relay, specific methods include narrowing the window of sampling data used in a digital filter, and calculating an amplitude value by comparing instantaneous values.

The operation amount 21 is determined by comparing the judgment value with 1 in the level judgment circuit 22, and if it is below the judgment level, the output 23 is set to "O".
”, the AND circuit 24 disables the output of the operation determination circuit 9 and controls the relay output to be restored.Here, the determination value 1 means that the accident detection range of the level determination circuit 22 is in the steady state and the operation is detected. The level is set so that it is equal to or higher than the accident detection range of circuit 9.

Next, the response in the above embodiment when an accident occurs and when recovering from an accident will be explained with reference to the time chart shown in FIG. 2. 25 shows the change in the output 21 of the operation amount calculation circuit 20, and because the response time is faster than the output of the operation amount calculation circuit 6, the value settles to the value after the state change in a short time both when an accident occurs and when the accident is recovered. When recovering from an accident, the output of the level detection circuit 22 is restored at time T, so after time T, the relay output is controlled to the restoration side.

Therefore, the extension of the suppression amount by the suppression amount delay circuit 8 may be coordinated so that it becomes larger than the operating amount for the period of time T, and long-term coordination as shown in FIG. 7 is not necessary. Therefore, it is possible to minimize the delay in operating time of the relay due to delaying the amount of suppression.

Next, another embodiment will be described with reference to FIG.

In FIG. 3, parts similar to those in FIG. 1 are given the same numbers and their explanation will be omitted. In FIG. 3, the input electric quantity of the operating quantity calculation circuit 20 is individually introduced from the output of the input converter 3a via the input circuit 26. Therefore, if a pre-filter with a fast response time is used in the input circuit 26, the recovery time of the level detection circuit 22 at the time of recovery from an accident will be even faster, the coordination time T will be shortened, and the relay operating time will be further reduced. The speed can be increased.

[Effects of the Invention] As described above, according to the present invention, in addition to the operation amount calculation circuit for determining the operation of the relay, there is provided an operation amount calculation circuit with a fast response time during transients and the operation of its output. A circuit for determining the level of the amount is installed, and the relay output is controlled to return when the operating amount is less than the level value, so the delay time of the suppressed amount is reduced to prevent transient malfunctions during accident recovery. To provide a protective relay that can minimize the time required, does not significantly delay operating time even in an accident under heavy load or an internal accident immediately after an external accident occurs, and does not malfunction when an accident occurs or when recovering from an accident. be able to.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing one embodiment of the protective relay according to the present invention, FIG. 2 is a time chart explaining the operation of the protective relay according to the present invention, and FIG. 3 is a functional block diagram showing another embodiment of the present invention. Block diagram, Figure 4 is a ratio characteristic diagram of a current differential relay, Figure 5 is a block diagram of a conventional protective relay, Figure 6 is a ratio characteristic diagram for explaining operation, and Figure 7 is a diagram of a conventional protective relay. It is a time chart explaining the operation. 1a, 1b... Ratio characteristic 2.10... Accident 3a, 3b... Input converter 4, 5.26...
Input circuit 6.20... Operation amount calculation circuit 7... Suppression amount calculation circuit 8... Suppression amount delay circuit 9
...Movement determination circuit 11, 12.13.14.17...Locus of movement amount/suppression amount 21, 25...Movement amount 15.16...
Suppression amount 22...Level judgment circuit 23...Level judgment circuit output 24...AND circuit helmet 1M Z helmet 3 figure suppression @! ΣITI Man 4 figure

Claims (1)

[Claims] In a protective relay having a circuit that calculates an operation amount by an operation amount calculation circuit and a suppression amount by a suppression amount calculation circuit from an input electrical amount, and determines operation based on the magnitude relationship between the operation amount and the suppression amount, the operation amount calculation circuit The operation determination is performed on the output of the other operation amount calculation circuit and the other operation amount calculation circuit that inputs the same electric quantity as the input and calculates the operation amount after a state change faster than the operation amount calculation circuit. A protective relay comprising another level determination circuit that performs level determination with a detection sensitivity equal to or higher than the determination level of the circuit, and in which the output of the operation determination circuit is invalidated by the output of the other level determination circuit.