JPS6120211B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Description of the technical field The present invention is an improvement regarding measures to prevent malfunction of a Mo-type protective relay (hereinafter abbreviated as a Mo-type relay) for power system protection.

(b) Description of Prior Art FIG. 1 is a diagram showing an outline of a conventional power system protection motor-type relay 8, and FIG. 2 shows waveforms of various parts explaining the operation of FIG. 1. The outline of the operating principle of this motor-type relay is as follows. In other words, the AC voltage V proportional to the voltage and current of the power transmission line
and alternating current I are respectively introduced into the auxiliary transformer 1 and the auxiliary current transformer 2 of the motor-type relay, and the quantity of electricity K ₂ proportional to V and the quantity of electricity proportional to I
K ₁ I is obtained. Further, the output of the auxiliary transformer 1 is introduced into the memory circuit 3, and the electrical quantity V _P having the same phase as V is used as the polarity quantity of the Morph type relay, and the sum of K ₁ I and K ₂ V The electrical quantity K ₁ I−K ₂ V is used as the operating quantity to determine the operation of the relay. Furthermore, the memory circuit 3 stores the phase of the voltage V before a failure in the power system, and even if a failure occurs near the relay installation point and the voltage V becomes zero as described later, the memory circuit 3 Therefore, even after a failure, the polarity amount V _P can be obtained, and the operation of the relay can be determined. The phase difference between the polarity amount V _P obtained in this way and the operation amount K ₁ I−K ₂ V is 90
Determine whether or not it is within °. That is, V _P and K ₁ I−K ₂ V are square wave conversion circuits 4 and 5, respectively.
is introduced into the square wave (V _P )′ and (K ₁ I−
K ₂ V)' and is introduced into the AND circuit 6 at the next stage. In the AND circuit 6, (V _P )′ and (K ₁ I−
An output is produced only when both K ₂ V)' are "1", and an output of (V _P )'.(K ₁ I-K ₂ V)' is obtained. If (V _P )'·(K ₁ I-K ₂ V)' is measured by the time measuring circuit 7 and exceeds 90°, the Mo-type relay is in an operating state. FIG. 3 is a vector diagram explaining the above operation, and shows the operating limits of voltage V with respect to current I. That is,
The phase difference between the electric quantities V _P and K ₁ I−K ₂ V is represented by θ in Figure 3, and if this phase difference θ is within 90°, it will work, and therefore the circle in Figure 3 is This is the operating range. Figure 4 shows a typical power transmission line L with one non-power supply end.
A Mo-type relay 8 similar to that shown in FIG. 1 is applied to the power source end of the power source. In the case of a failure at point A of the power transmission line L, that is, an internal failure, the Mo-type relay 8 operates as described above, and the relay 8 becomes operational.
Further, in the case of a failure at point B, that is, an external failure, both the voltage V and the current I become zero, as shown in the waveforms of various parts in FIG. 5, and the Mo-type relay 8 becomes inoperable. In other words, the normal response is to operate in the event of an internal failure and inoperative in the event of an external failure.

However, as is well known, even if the input voltage V becomes zero, the auxiliary transformer 1 of the relay shown in FIG.
The output V' on the secondary side does not become completely zero, but generates a transient DC component. This point will be explained using the auxiliary transformer equivalent circuit shown in FIG. First, before a failure occurs, an excitation current flows through the excitation impedance Z _L due to the input voltage V, and excitation energy is stored. However, when the input voltage V instantaneously becomes zero, the excitation energy stored in this excitation impedance Z _L is released to the secondary side as shown by the arrow, so the secondary output V does not instantaneously become zero. First, as shown in FIG. 7, a transient DC component V _T is generated. The transient DC component V _T generated by the auxiliary transformer 1 of this relay has an adverse effect on the response of the conventional motor-type relay, causing it to malfunction due to an external failure. That is, if a failure occurs at point B of the power transmission line in Fig. 4, both the current I and the voltage V become zero as described above.
The output V' of the auxiliary transformer 1 does not immediately become zero, and the aforementioned transient DC component V _T remains. The response of the Mo-type relay 8 in this state is as shown in FIG.
In other words, the polarity V _P continues to memorize the phase of the voltage V even after a fault occurs, and the polarity V P continues to memorize the phase of the voltage V and the current I after the fault occurs.
becomes zero, but since the transient DC component remains for a while in the output V' of the auxiliary transformer 1, the operating amount becomes K ₁ I−K ₂ V in FIG. When this is converted into a square wave, (V _P )′ is “1” only for a period of 180°.
Therefore, (K ₁ I−K ₂ V)′ remains “1” continuously while the transient DC component remains. Therefore, the output of the AND circuit 6 is
Since the output is a 180° square wave, the output of the time measuring circuit 7, that is, the output of the Morph type relay, will produce an erroneous output once per cycle. still,
Malfunction of the Mo-type relay due to this transient DC component is caused by the voltage or current remaining even after the fault occurs when the power transmission line in Figure 4 is at both ends, so the operating amount K ₁ I-K ₂ V is It is larger than the transient DC component and does not occur. However, in a system where both the voltage and current become zero after a failure occurs, as shown in FIG. 4, malfunction will occur.

As mentioned above, the conventional motor-type relay has the drawback that the transient DC component generated by the auxiliary transformer causes the malfunction of the relay when it should not operate due to an external failure. Although the malfunction phenomenon has been explained above with respect to the auxiliary transformer of the relay, a similar phenomenon may also occur in the capacitor-type voltage transformer circuit. This was also a fundamental drawback in that the direction discrimination function, which is the basic response of the Mo-type relay, was lost.

(c) Object of the Invention The object of the present invention is to provide a motor-type relay that does not malfunction even in response to such a transient DC component generated by an auxiliary transformer.

(d) Structure of the Invention FIG. 9 is a block diagram showing one embodiment of a motor type relay according to the present invention. The output of the auxiliary transformer 1 is connected to the memory circuit 3 to obtain the polarity V _P , and the output K ₁ I of the auxiliary current transformer 2 and the output K ₂ V of the auxiliary transformer 1 are combined to obtain the operating amount K ₁ I−K ₂ V is obtained and introduced into the suppression circuit 9. This suppression circuit 9 has a coefficient multiplier -K ₃ , sets the output V _P of the storage circuit 3 to -K ₃ V _P , applies suppression to the operating amount K ₁ I-K ₂ V, and outputs K ₁ I-K ₂ V−K ₃ V _P is obtained. Note that the magnitude of the suppression amount −K ₃ V _P is selected to be slightly larger than the magnitude of the transient DC. Then, these electric quantities V _P and K ₁ I−K ₂ V−K ₃ V _P are introduced into square wave conversion circuits 4 and 5 to become square waves, and further, an AND circuit 6 and a time measurement circuit 7 determine the operation. is executed and the output is obtained. Components with the same numbers in FIG. 9 and FIG. 1 have similar functions.

(c) Effects of the invention The effects of the Mo-type relay according to the present invention will be explained below.

FIG. 10 is a waveform of each part explaining the operation of the Mo-type relay of the present invention shown in FIG.
The operation will be shown in the same fault condition as the conventional motor-type relay shown in the figure, that is, when an external fault occurs at point B on the power transmission line L in FIG. As mentioned above, if a failure occurs outside the power supply side of the installation point of the Mo-type relay, both the voltage and current of the power transmission line become zero. However, the output of the auxiliary transformer 1 of the relay does not become completely zero, and because a transient DC component occurs, the output becomes like V' in FIG. 10. Furthermore, since the current I is zero after the failure, the operating amount K ₁ I−K ₂ V has a waveform equivalent to that of a transient DC component. Moreover, the polarity amount continues for a while like V _P due to the memory effect. By the way, from the output of the memory circuit 3, the suppression circuit 9 generates an opposite phase suppression amount - which is proportional to the polarity amount _VP .
K _{3 VP} is obtained, and the operation amount K ₁ I−K ₂ V is suppressed by this suppression amount −K _{3 VP} .

Therefore, as shown in FIG. 10, K ₁ I−K ₂ V becomes (K ₁ I−K ₂ V−K ₃ V _P ) due to the suppression. These two electrical quantities V _P and (K ₁ I−K ₂ V−
K ₃ V _P ) is converted into a square wave by the square wave conversion circuits 4 and 5, and (V _P )′ and (K ₁ I−K ₂ V−
The waveform becomes K ₃ V _P )'. (V _P )′ becomes a square wave output of 180° every cycle, and (K ₁ I−
Due to the suppression from the memory circuit 3, K ₂ V-K ₃ V _P )' does not become "1" continuously, but there is a period in which it becomes "0" every cycle. Moreover, this “0”
There is a point at 90° after the 180° square wave output of (V _P )'. This is because the polarity amount V _P and the suppression amount −K ₃ V _P are in opposite phases. Therefore, these (V _P )′ and (K ₁ I−K ₂ V−K ₃ V _P )′
The period in which both are "1" is always less than 90 degrees, as shown in the AND circuit output in FIG. Therefore, the time measuring circuit 7 cannot measure the time at 90 degrees, and no output is produced. In other words, malfunctions due to transient DC components generated in the auxiliary transformer 1 at the time of an external failure can be prevented by the suppression from the memory circuit 3. As is clear from the previous explanation, the magnitude of this suppression amount K ₃ V _P should be slightly larger than the magnitude of the transient DC component; Since the value is small, the amount of suppression only needs to be small. Furthermore, as mentioned above, the attenuation speed of the memory circuit can be changed arbitrarily by changing the circuit constants, and the relay's operation is only related to the phase, which has almost no relation to the attenuation speed. It can be adjusted to the attenuation time constant of the transient DC component. In the above explanation, we have discussed the case where the voltage and current of the transmission line become zero due to the response of the Mo-type relay to an external fault.However, if the voltage or current remains even after the fault, it is possible to use the conventional Mo-type relay. It is clear that it will not work in exactly the same way. in this case,
There is no difference other than the fact that a non-operating state is reliably obtained. Also, in the case of an internal failure, the amount of operation is much larger than the amount of suppression, so normal operation is possible, just like the conventional response.

In addition, in distance relays, the phase of the current I is generally advanced within the relay by that angle in consideration of the impedance angle of the transmission line, and in order to speed up the operation, the phase of the current I is advanced separately for the positive and negative half waves of the AC quantity of electricity. The square wave conversion circuit, AND circuit, etc. of This is a moot point.

In this way, the present invention can prevent malfunctions in the event of an external failure by using the output of the memory circuit as a suppression amount, and since the memory circuit is always necessary for conventional motor-type relays, it is possible to prevent malfunctions due to external failures. Another feature of the present invention is that it can be used without the need for complicated additional circuits.

(f) Other embodiments In the explanation so far, the operation amount K ₁ I−K ₂ V of the Mo-type relay 8 is suppressed to reduce K ₁ I−K ₂ V−
K ₃ V _P was obtained, but as shown in Figures 11 and 12, even if we suppress the electrical quantity before obtaining the composite electrical quantity, that is, K ₁ I or -K ₂ V, exactly the same behavior will occur. It is possible. Moreover, it goes without saying that the same effect can be obtained even if the three electrical quantities of K ₁ I-K ₂ V-K ₃ V _P are simultaneously combined and suppressed as shown in FIG. 13.

In Fig. 9, the time measurement circuit 7 of the Mo-type relay 8 is measured at 90 degrees, but this measurement time is 90 degrees.
It doesn't have to be ゜. For example, if the time measurement is made at an angle greater than 90 degrees, the characteristics of the Maw-shaped relay will become leaf-shaped as shown in FIG.
It is clear that the present invention can be applied even in that case.

(g) Overall effect As explained above, according to the present invention, even if a transient DC component occurs in the auxiliary transformer of a relay, there will be no malfunction in the event of an external failure, and by simply adding a simple device. Therefore, it is possible to obtain a motor-type relay that can reliably discriminate between internal and external failures.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of a conventional motor type relay, Fig. 2 is a waveform of each part explaining the operation of Fig. 1, and Fig. 3 is a vector diagram explaining the operating principle of Fig. 1. Figure 4 shows an example of a system to which the Mo-type relay shown in Figure 1 is applied, Figure 5 shows the waveforms of various parts when the Mo-type relay shown in Figure 1 malfunctions, and Figure 6 explains the auxiliary transformer. Figure 7 shows the waveform when a transient DC component occurs in the auxiliary transformer shown in Figure 6, Figure 8 shows the waveforms of various parts when the Mo-type relay shown in Figure 1 malfunctions, and Figure 9 shows the waveform of the present invention. FIG. 10 is a block diagram for explaining one embodiment. FIG. 10 is a waveform of each part explaining the operation of FIG. 9. FIGS. It is a figure which shows an example. 1... Auxiliary transformer, 2... Auxiliary current transformer, 3...
Memory circuit, 9... Suppression circuit, 4, 5... Square wave conversion circuit, 6... AND circuit, 7... Time measurement circuit.

Claims (1)

[Claims] 1. Means for inputting voltage and current from an AC system via a voltage transformer and a current transformer, and synthesizing the voltage and current to obtain an operating amount, and inputting the voltage to a storage circuit to obtain a polarity amount. In the device in which the operation is determined based on the means and the amount of movement and polarity output from these means,
A Morph type protective relay characterized in that an output electricity quantity of the memory circuit is inputted to obtain an electricity quantity larger than a transient DC component of the voltage transformer, and the operating quantity is suppressed by this electricity quantity.