JPH02184221A - 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 relay that responds to changes in the amount of input electricity,
In particular, it relates to improving the operational reliability of relays for ground fault protection in ungrounded systems or high resistance grounded systems with improved frequency characteristics.

(Prior art) Conventionally, in relays that convert the input electrical quantity into a digital quantity and derive the change, the input is sampled at regular time intervals, and the difference between the current sampling value and the sampling value several times ago is calculated. By doing so, the amount of change was derived. However, with this method, if the frequency of the input electricity changes,
There was a problem in that an error component occurred and the input electrical quantity was mistakenly interpreted as having changed.

In order to eliminate this drawback, Japanese Patent Application Laid-Open No. 61-106021
In this issue, the line-to-line voltage, positive-sequence voltage, etc. of the power system, which has little fluctuation during a one-line ground fault, is used as the reference voltage, and by using this specific phase instant as the sampling reference, even if a frequency change occurs, the difference A relay that generates less is proposed.

A configuration diagram of an embodiment of the prior art is shown in FIG. In the figure, B is the busbar, CT is the current transformer, CB is the breaker, or distribution line, PTl and PT2 are the potential transformers, 1 to 3 are the input converters, 4 is the specific phase discriminator, and 5 is the sampling device. It has a built-in multi-breather. Reference numeral 6 denotes an A/D converter (analog-digital converter), 7 a protection arithmetic unit composed of a digital arithmetic unit such as a microprocessor, and 8 a trip device.

Zero-sequence current in distribution lines 1. Electricity proportional to I.

is supplied to the sampling device 5 via the current transformer CT and the input converter 1. Further, an amount of electricity V□' proportional to the zero-sequence voltage Vo at the distribution line terminal is supplied to the sampling device 5 via the voltage transformer PTI provided on the bus B and the input converter 2. Note that the potential transformer PT1 may be provided at a terminal portion of the distribution line instead of being provided at the bus bar B. Each input converter 1 and 2 converts the electrical quantity Io' into a normal voltage and supplies it to the sampling device 5.

The instantaneous values of the electric quantities Io' and Vo' are sampled by a sampling device 5, and the sample value 11 is converted into a digital value 12 by an AD converter 6.

The protection calculation device 7 calculates the difference (sum) using the digital value 12, performs protection calculation using these, and produces one output if an internal accident is determined. Trip device 8 is i3
When this happens, an output cam is generated and the circuit breaker CB is cut off.

Furthermore, 1 of the line voltage, positive sequence voltage, etc. obtained from bus B
The electrical quantity Vs', which is proportional to the reference voltage ■S, which has little fluctuation in the event of a line-to-ground fault, is input to the specific phase discriminator 4 via the potential transformer PT2 and the input converter 3; The specific phase of the electrical quantity vs' is determined and the output pulse VSS is sent to the protection calculation device 7, and the sampling device 5 that receives the signal from here generates an electrical quantity proportional to the zero-sequence voltage using the signal VSS as a reference. V□' and an electrical quantity IO' proportional to the zero-sequence current are sampled.

(Problem to be solved by the invention) However, with this method, if a sudden change in phase occurs in the reference voltage waveform due to system operation or an external short-circuit accident, an error component occurs and the input electrical quantity is mistakenly interpreted as having changed. There is a problem. I will explain this point in detail to my father-in-law with reference to FIG.

- As an example, in a method in which the zero-sequence voltage Vo is sampled based on the point where the reference voltage waveform is Oo in electrical angle, and the change is derived by taking the difference at one sampling interval, the reference voltage waveform is 10 degrees. Assuming that there is a sudden phase change (delay), find the error component at that time. Let the time point of t be θ in electrical angle, and the sample value at that time is P1,1
Copy the sample values after the sampling interval has elapsed, and calculate the peak value of the zero-sequence voltage. 10, the sample value V1.
Vx is as follows.

tt1=r6sinθ v2=r6sin(θ+10°) Therefore, what is the difference? /2-Zr1= JN 2101 sin (θ+
10°)-sin θ), and the maximum error is around θ=0°. Calculating the difference based on the standard without setting θ0° is ar"I?/1l) (5in10°-5inO°' x
loo = 24.6 degrees [%] If a sudden 10° phase change occurs in the reference voltage waveform, it will be approximately 2
4.6 [%] Error. As the sudden phase change angle increases, this error further increases, and in some cases, the relay may operate unnecessarily during system operation or an external fault.

The present invention has been made to eliminate the above-mentioned drawbacks.
It is an object of the present invention to provide a highly reliable relay that does not operate unnecessarily even when a sudden phase change occurs in a reference voltage waveform and an error occurs.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention uses a power system voltage as a reference voltage, and includes a first means for determining a specific phase instant of this reference voltage waveform; a second means for sampling at least one of a zero-sequence voltage or a zero-sequence current of the electric power system a predetermined plurality of times within the reference voltage cycle; and a sample value obtained by the second means and a sample value of the sample value. a third means for calculating the value of the period (sum of the previous R value (k = positive integer));
The fourth step is to perform a protection operation using the value obtained by the method.
and a fifth means for determining whether a change in the phase of the reference voltage is equal to or greater than a predetermined value, and a first sampling time point of the second means is determined by the first means. at a specific instant or after a scheduled time, and the second of the second means
The second (and subsequent) sample time is after the scheduled time of the first (previous) sample time, and when the phase change of the reference voltage exceeds a predetermined value, the operation is inhibited for a predetermined period. It was configured as follows.

(Function) The voltage Vs, which has little fluctuation during a one-line ground fault, such as the line voltage or positive sequence voltage of the power system, is used as the reference voltage, and the specific phase instant of this reference voltage waveform is determined by the first means, and the power At least one of the zero-sequence voltage Vo or the zero-sequence current 1 of the system is sampled a predetermined number of times by means of the tube 2 within the period of the reference voltage Vs, and the sample value obtained by this second means and its The value of the sample value (the sum of samples before the period (k: positive integer)) is calculated by a third means, and the value obtained by this third means is used to perform a protection operation by a fourth means. Furthermore, a fifth means detects a phase change in the reference voltage waveform, and when the phase change exceeds a predetermined value, the operation is inhibited for a period in which a predetermined cycle has elapsed.

(Embodiment) FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, the same symbols as in FIG. 6 indicate the same things. In addition, 9 is a device for detecting a phase change in the electrical quantity Vs' proportional to the reference voltage Vs, and is composed of, for example, a period counter. Reference numeral 7' denotes a protection arithmetic unit which can also introduce the count results of this period counter.

Figure 2 shows an example of a periodic change when the electrical quantity Vs' proportional to the reference voltage VB suddenly changes phase by 10°.
At this time, if the rated frequency of the power system is 50[)12] and the clock frequency of the period counter is 1 [MHz], the normal period T is ) occurs, the period change ΔT is ΔT2 and -T = 555. If a sudden phase change occurs in the reference voltage Vs such as 0 or more, the count result of the period counter is processed by the protection calculation device. It can be detected by sequentially importing the data and calculating the difference between them.

Next, the operation of the present invention will be explained with reference to the flowchart of FIG. 3 and the time chart of FIG. 4. Step 5101 is the reference electricity quantity Vs obtained from the -g# line B.
A signal VS9 is generated by determining a specific phase (for example, a zero point) of the signal. In the next step 5102, sample 10 after C1 and set the sample value to 1. shall be. At 5103, Vo is sampled after ti from 5101, and the sample value is set to tr, ). 5104 samples the IO after a time corresponding to t, which further corresponds to 90' in electrical angle, and sets the sample value to 420. 5ios samples Vo after a time corresponding to 90" in electrical angle from ti, and sets the sample value to υ2o. Stellar 78106 has a periodic change of 1ΔT in the reference quantity of electricity VB.
This is a step of determining whether 1 is greater than or equal to a predetermined value, and if it is greater than or equal to a predetermined value, step 810 is performed.
7, the relay output is restored, and step 510
Proceed to step 8 to update the memory contents every cycle. 5109 is a step for determining whether n+1 cycles have elapsed since 1ΔT1 or less; if not, proceed to step 8108; and when n+1 cycles have elapsed, proceed to the next step 3110; 8110 is a step of calculating a change sample value using each sample value, and a change in the zero-sequence current and zero-sequence voltage is calculated by the following formula using the IIIigN from n cycles ago and the new value.

t1Δ""two tln V 2Δ=υ20 t'2A From the variation sample values separated by 90 degrees shown in equation (1), the amplitude of the change component of the input electric quantity is calculated by equation (2).

106P = tlh) + (t2Δ) 2)
(2) VQAP = (t/+Δ) 2+(υ2Δ) Here, IQ6P and VωP are amplitude values of changes in zero-sequence current and zero-sequence voltage, respectively.

Next, in step 5111, a relay calculation is performed using the calculation formula shown in equation (3), for example.

I k1ΔV OA P However, φ is the angle θ at which IoΔP advances from VωP is the settling angle (
(constant angle) k, ko, and 4 are constant expressions, and if θ is set to +90°, as shown in Figure 5, the zero-phase voltage change vector amount VOAP is the reference phase, and the zero-phase current change vector amount l0AP operates as shown. A ground fault directional relay is obtained which operates when within the range.

According to the embodiment described above, when a sudden phase change occurs in the reference voltage waveform, it is detected, the relay output is restored, and the sample value is changed to the data sampled at the new reference phase after the sudden phase change. By not performing differential calculations until all of them are updated, it is possible to obtain a variable rectangular ground fault directional relay that does not require unnecessary response due to errors caused by sudden phase changes.

In addition, in the explanation of the above embodiment, a variable rectangular ground fault direction relay that responds to changes in both zero-sequence voltage and zero-sequence current has been described, but the present invention is not limited to this, and the present invention is not limited to this. May be used.

For example, exactly the same effect can be expected in the case of a variable square ground fault overvoltage relay that responds to a change in zero-sequence voltage or a variable square ground fault overcurrent relay that responds to a change in zero-sequence current.

[Effects of the Invention] As described above, according to the present invention, even if there is a frequency change, the amount of change as an error is small, and moreover, when a sudden phase change occurs in the reference voltage waveform and an error occurs, It is also possible to obtain a highly reliable relay that does not operate unnecessarily.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining a method for detecting sudden phase changes, FIG. 3 is a flowchart showing processing of an embodiment of the present invention, and FIG. The figures are waveform diagrams showing sampling points in the flowchart shown in Figure 3, Figure 5 is a characteristic diagram showing one embodiment of the present invention, and Figure 6 is a waveform diagram showing sampling points in the flowchart shown in Figure 3.
The diagram shows the configuration of the prior art, and FIG. 7 is a waveform diagram for explaining the drawbacks of the prior art. 1 to 3... Input converter 4... Specific phase discriminator 5
...Sampling device 6...A/D converter 7...
・Protection calculation device 8...Trip device 9...Period counter

Claims (1)

[Claims] a first means for determining a specific phase instant of a reference voltage waveform using a power system voltage as a reference voltage; and a first means for determining a specific phase instant of the reference voltage waveform; a second means for sampling times, and a sample value obtained by the second means and k of the sample value.
The difference (or k-
[1/2] A third means for calculating the value of the sum of the sample value of the previous cycle), a fourth means for performing a protection calculation using the value obtained by the third means, and the reference voltage and fifth means for determining whether the change in phase of is equal to or greater than a predetermined value,
The first sample time of the second means is at the specific instant determined by the first means or a scheduled time after that, and the second (and subsequent) sample time of the second means is the first sample time.
A relay characterized in that, when a scheduled time after the second (previous) sample time and the phase change of the reference voltage exceeds a predetermined value, the relay stops operating for a predetermined period.