JPS6028719A - Protecting 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 The present invention relates to a protective relay that responds based on a DC component generated as a result of integrating two AC quantities.

For the sake of convenience, the tortoise distance relay will be described as a conventional device as shown in FIG. 2 in the figure, (1) (2
) are transformers that convert electric quantities such as voltage and current from the power system into voltage signals, (3) is a subtractor that subtracts two voltage signals, and (4) is an integrator that integrates two voltage signals. , (No. 5 is a low-pass filter that extracts the DC component and effectively attenuates the second harmonic and above, and (6) is a level detector that operates when the human input signal is positive.

The following operation will be explained. The amount of electricity input from the power system Et I Ex is respectively E, = I sin
(ωt), E2=vSLII (ω is 10θ). However, ω is the angular frequency, and θ is the phase angle of the voltage V with respect to the current ■. Also, Z is a constant having a phase angle α with respect to the current ■, and K
is converted into a proportional constant, transformer (2) converts E2 to vg =
- If it is converted to V (ω is 10), the output of the subtractor (3) is vs”'
vt Therefore, the output of the integrator (4) becomes the harmonic component Va)s(2
ωt+20)-ZIa)s(2a+t+θ+α) and the DC component ZIccs(α-β)-V are superimposed.

Therefore, when the low-pass filter (5) is higher than the second harmonic, the level detector (6) will operate if the human input signal j2 is positive, so if we set the condition for lt to be positive, we can form the following inequality: holds true.

ZIClys(α-β)≧V If this inequality is shown on the R-X diagram, as shown in Figure 2, it becomes the Moh characteristic represented by a circle that passes through the origin, has a diameter of Z, and whose center lies on the line of angle α. Become.

In other words, by detecting that the DC component that is the output of the low-pass filter (5) is positive, the Moh type distance relay has a Moh characteristic that has an operating range when V falls within a circle with a diameter of Z. will be obtained.

Conventional protective relays are configured as described above, so
Sufficiently attenuate the second harmonic from the output of the integrator (4),
In order to effectively extract the DC component, the cutoff frequency of the low-pass filter (5) must be set to a fairly low value, such as 2ω or less, for example -. Therefore, the output response of the low-pass filter (51) is slow. This has the disadvantage of slowing down the operation speed.The reason is that the output response time of a low-pass filter is generally one point below the cutoff frequency.
This is because it is proportional to the cycle time, and therefore, the lower the cutoff frequency is set in an attempt to attenuate the second harmonic, etc., the slower the operating speed becomes.

This invention was made for the purpose of eliminating the drawbacks of the conventional ones as described above, and it is a protective relay that can operate extremely quickly by converting the output of an integrator into a rectangular wave and detecting the pulse of the rectangular wave. I will provide a.

An embodiment of the present invention will be described below with reference to the drawings. 8th
In FIG. 3, (1) to (4) are exactly the same as the conventional one in FIG. (7) is a rectangular wave converter that outputs a positive rectangular wave P when the output 11 of the integrator (4) is a positive wave, and a negative rectangular wave P when it is a negative wave; A pulse width detector that outputs a detection signal when the value exceeds the value.
(9) is a time-limited return circuit that extends the input signal for a predetermined period.

Icos (2a+ 10+α) 10ZILxs (α-β)
-V) If it is detected that the DC component contained in is positive, it can be determined that the accident is within the protected area.

Here, signal I! If the DC component of The pulse becomes a rectangular wave with To=- as shown in FIG.

2ω At this time, the composite wave when a positive DC component is superimposed on the harmonic component with an angular frequency of 2ω is a square wave converter (7) because the waveform moves in the positive direction as shown in Figure 4 (Q). As shown in Figure 4 (D), the output becomes a rectangular wave of 10 or more during the positive pulse.Also, when a negative DC component is superimposed on the harmonic component, the output becomes a rectangular wave of 10 or more during the negative pulse. It becomes a square wave.

Therefore, if the pulse width detector (8) operates when To=- or more during the positive pulse of the input rectangular wave signal P, the output l! of the 2ω integrator (4)! It can be detected that the DC component contained in 1 is positive, and therefore an accident within the protected area can be determined.

At that time, the output of the pulse width detector (8) becomes a minute pulse as shown in Figure 4 (8), so if the signal is thinned out by 2To for one period in the time-limited return circuit (9), it becomes a continuous signal. This signal can be used to trip a breaker (not shown) forming a protection zone.

In this embodiment, since the DC component can be determined without using a low-pass filter, there is no delay in response time and high-speed operation can be expected.

In addition, in the above embodiment, the explanation was given by applying it to a distance relay, especially one having a Moh characteristic, but other protective relays may also be used, and the relay responds based on the DC component generated as a result of integrating two AC quantities. If this is the case, the same effects as in the above embodiment can be achieved.

As described above, according to the present invention, since the output of the integrator is converted into a rectangular wave and the response is performed based on the pulse width of the rectangular wave, a protective relay that operates extremely quickly can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a conventional protective relay, FIG. 2 is a characteristic diagram showing the operating range of a Moh-type distance relay, FIG. 8 is a block diagram showing a protective relay according to an embodiment of the present invention, and FIG. FIG. 2 is a waveform diagram illustrating the principle of an embodiment of the present invention. In the figure, (4) is an integrator, (7) is a rectangular wave converter, (8) is a pulse width detector, and (9) is a timed return circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Agent Masuo Oiwa Figure 2 X Figure 4 = 83-

Claims (4)

[Claims] (1) An integrator that integrates two alternating current electrical quantities, a rectangular wave converter that converts the output of this integrator into a rectangular wave, and when the output pulse of this rectangular wave converter exceeds a predetermined value, it is within the protection zone. A protective relay equipped with a pulse width detector that determines an accident. (2) The protective relay according to claim 1, wherein the rectangular wave converter outputs a rectangular wave corresponding to the polarity of the input waveform. (3) The protective relay according to claim 2, wherein the pulse width detector responds when the pulse width of the positive rectangular wave is equal to or greater than a predetermined value. (4) A patent characterized in that when the angular frequency of two alternating current quantities of electricity is ω, the predetermined value of the pulse width is -.