JP2703354B2 - Digital short-circuit distance relay - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a digital short-circuit distance relay device for protecting a transmission line.

(Prior art) The use of computers for power system protection and control has been remarkable in recent years, and has been studied by various manufacturers. Among them, analog data is converted into digital data, and AC voltage,
There is a mo relay that calculates the impedance proportional to the distance from the current to the fault point of the power system, and if this is within a certain value, issues a shut-off command to the corresponding breaker. In the case of this relay, in order to judge the fault point, a reference amount that does not change the phase even in the event of an accident is required. The idea was to sum with previous data.

The above-described method is called a cyclic method because a comparison result between the current sampling data and the data before a predetermined time is fed back to the current sampling data.

(Problems to be Solved by the Invention) When the above method is adopted, if a value that causes an error, such as noise, occurs in data before a certain period of time, the error is mixed into the current data even after recovery from the accident. It is calculated many times as it is. Moreover, these errors are accumulated during normal times.

The present invention eliminates the disadvantages of the prior art and provides a digital short-circuit distance relay that eliminates an error factor generated by the cyclic method by introducing a current sampling value as a polarity quantity after recovery from an accident. The purpose is.

[Configuration of the Invention] (Means for Solving the Problems) In the present invention, in the normal state, the polarity amount uses the sampling data at the current time, and on the condition that the output of the short-circuit detection element operates at the time of the short-circuit accident, A new polarity quantity is obtained from the data several cycles before and the data at the present time, and the data is switched to the current data after the recovery from the short-circuit accident. The operation equation in this case is equation (1),
Equation (2) is the amount of polarity at normal time and at the time of recovery from a short-circuit fault, and equation (3) is the polarity amount at the time of a short-circuit fault.

_{(IZ O -V) V p>} 0 ...... (1) V pm = V m ...... (2) V pm = k 1 V pm-N + k 2 V m ...... (3) where, V _p ... polarity voltage Amount V _m … Current sampling voltage amount V _pm … Current polarity voltage amount V _pm-N … Predetermined N cycles before polarity voltage amount k ₁ … Constant k ₂ … Constant (operation) Switching by output of short-circuit detection element Without (3)
In the case where the polarity amount is determined only by the equation, in equation (3), V
If an error occurs in _pm-N (polar voltage amount by sampling before the predetermined cycle) due to some factor, V _pm is calculated as the polar voltage amount including the error even after recovery from the accident, and the direction determination may be incorrect. Become.

According to the present invention, by switching to the equation (2) after the recovery from the short-circuit fault, the above error can be eliminated, and the direction can be accurately determined after the recovery from the short-circuit fault.

(Example) Hereinafter, an example is described with reference to drawings. FIG. 1 is a block diagram of an embodiment according to the present invention. FIG. 2 is an example of a flowchart for digitally processing the short-circuit distance relay device 6 in FIG.

In FIG. 1, 1 is a short-circuit detecting element for inputting a current I and detecting a short-circuit accident, 2 is a voltage and current input, and a distance relay element for realizing characteristics by arithmetic processing. 4) An element for realizing, by arithmetic processing, the polarity voltage amount shown in the expression as the polarity amount of the current sampling data, and 4 is a constant for the data before the predetermined sampling shown in the above expression (3). An element that realizes in the arithmetic processing that the amount obtained by multiplying the multiplied amount and the amount obtained by multiplying the current sampling data by the constant is used as the polar amount, and 5 is an arithmetic processing that switches the polar amount based on the output from the short-circuit detecting element. , 6 indicates a digital short-circuit distance relay including 1-5.

In FIG. 2, step S11 is determined whether the sampling data, step S12 is short circuit relay operates, the step S13 the calculation of _{V pm = k 1 V pm-} N + k 2 V m, the step S14 is V _pm = calculation of V _m, the step S15 is calculated in IZ _O,
Step S16 the calculation of IZ _O -V, step S17 is IZ _O -V>
The determination of 0, step S18 shows the operation processing, and step S19 shows the return processing.

In FIG. 2, the voltage I and the current V
Are sampled, and it is determined in step S12 whether or not the short-circuit detecting element 1 in FIG. 1 operates.

In a normal state, the short-circuit detecting element 1 shown in FIG.
Is a non-operation, the processing in step S14 is performed in FIG. 2, and the polarity voltage amount shown in the above equation (2) is
The current sampling data is calculated as the polarity amount. In the event of a short-circuit accident, the short-circuit detecting element 1 in FIG.
The polarity amount is calculated by adding the amount obtained by multiplying the data constant before the predetermined sampling shown in the above equation (3) and the amount obtained by multiplying the current sampling data by the constant.

Further, at the time of recovery from a short-circuit accident, the short-circuit detecting element 1 in FIG.
In step S14, the polarity voltage amount shown in the above equation (2) is calculated using the current sampling data as the polarity amount. If this is replaced with FIG. 1, the switch 5 is normally in the position a and becomes the position b in the event of a short circuit, and the switch 5 is in the position a after recovery from the short circuit, and the polarity is switched.

In addition, the step S15 in FIG. 2, to calculate the IZ _O, the IZ _O -V calculated in step S16, step S17
In, (IZ _O -V) in the above (1) V _p> 0
Is performed, the output determination processing of the distance relay element 2 in FIG. 1 is performed. If the determination in step S17 is satisfied,
In step S18, the distance relay element 2 in FIG. 1 obtains a circuit breaker trip output. If the determination in step S17 is not satisfied, the process returns to step S19, and the output of the distance relay element 2 in FIG. 1 does not operate.

Further, the sampling process of the next step S17 is performed, the same process as described above is performed, and the process returns.

In general, the polarity amount V used for the determination in step S17
_pm is switched to the sampling value including the current sampling value and the value before the predetermined cycle according to the determination condition of the short-circuit detection element 2 in step S12.

By switching the polarity amount between the normal state and the short-circuit accident as in the above-described embodiment, it is not necessary to continuously calculate the error at the time of the short-circuit accident, and it is possible to perform the normal direction determination.

In the above embodiment, the term short-circuit detecting element is used. However, there is no limitation as long as it is means for detecting a short-circuit accident. FIG. 3 shows another embodiment. The same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The same applies when the short-circuit detecting element 1 in FIG. 1 is installed outside the distance relay 6 as the short-circuit relay 1-1. The internal processing of the short-circuit relay 1-1 is not limited to digital processing, but may be a transistor type, an induction type, or the like.

Further, the polarity amount switching in steps S12 to S14 in FIG. 3 is performed immediately after the sampling process in step S11. In the present embodiment, the switching is performed immediately after the process in step S16. Is as shown in FIG.

[Effects of the Invention] As described above, according to the present invention, the polarity amount at normal time is used as the current sampling data, and when a short circuit occurs, the constant multiplied by the data obtained by multiplying the data before the predetermined sampling by the constant and the constant at the current sampling time. Since the multiplied amount is configured to be the added amount, it is possible to provide a short-circuit distance relay device capable of accurately determining an accident without leaving any error factor in the polarity amount after the recovery from the short-circuit accident.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of a digital short-circuit relay according to the present invention, FIG. 2 is a flowchart showing the processing contents of the short-circuit relay in FIG. 1, and FIG. 3 is another embodiment. FIG. 4 is a flowchart showing the processing contents of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1 ... Short-circuit detection element, 2 ... Distance relay element 3,4 ... Polarity 5 ... Polarity changeover switch 6 ... Short-circuit distance relay

Claims (2)

(57) [Claims] In a digital short-circuit distance relay device for protecting a power system, a short-circuit detecting element for detecting a short-circuit accident, first means for making the current sampling data a polarity amount, and a constant for the current sampling data. And a second means for setting the amount obtained by adding an amount obtained by multiplying the amount obtained by multiplying the amount by a constant to the amount of polarity before the predetermined sampling, and outputting the amount of polarity of the first means in a normal state to the short-circuit detecting element. Switching means for switching the amount of polarity from the first means to the second means when a short circuit accident is detected, and a distance relay element for determining operation using the polarity amount from the switching means. Digital short-circuit distance relay. 2. The digital short-circuit distance relay device according to claim 1, wherein said switching means switches the polarity amount from said second means to said first means after recovery from a short-circuit fault.