JPH0223025A - Distance relay - Google Patents

Abstract

PURPOSE:To discriminate between inner fault and outer fault reliably by limiting the period of polarity amount corresponding to the system voltage below a predetermined value and judging the overlap angle between the polarity amount and an electrical amount obtained through combination of voltage and current. CONSTITUTION:Output K2V from an auxiliary transformer 1 is connected with a polarity amount circuit 3 in order to obtain a polarity amount VP, while output K1I from an auxiliary current transformer 2 is combined with the output K2V to produce an operational amount K1I-K2V. The polarity amount VP and the operational amount K1I-K2V are converted through conversion circuits 4, 5 into square waves. The VP converted into square wave and a signal limited 8 within 180 deg. are employed for inhibition 9. The operational amount K1I-K2V converted into a square wave and the output from the inhibit circuit 9 are fed to an AND gate 6 in order to detect overlap of the polarity amount VP and the operational amount K1I-K2V thus judging whether they are overlapped more than 90 deg. through a time measuring circuit 7. By such arrangement, duration of DC transient component produced from the auxiliary transformer 1 is limited resulting in prevention of erroneous function.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a protective relay, and particularly to a protective relay with measures to prevent malfunction.

(Prior Art) FIG. 5 is a schematic diagram of a Moh type relay, which is a type of conventional power system protection distance relay, and FIG. 6 is a waveform diagram of each part for explaining the operation of FIG. An overview of the operating principle of this Moh type relay will be explained.

An alternating current voltage V proportional to the voltage and current of the power transmission line, and an alternating current The output of the auxiliary transformer 1 is introduced into the polarity circuit 3, and the output of the auxiliary transformer 1 is introduced into the polarity circuit 3, and the output of the auxiliary transformer 1 is in the same phase as KV
Outputs a polarity amount of V, which is proportional to . Su, KI and 2
2V is used as the operation amount in the combined electricity amount of v, and the operation of the relay is determined. In this way, it is determined whether the gain phase difference is within 90°.

That is, 2V is introduced into the square wave converting circuit 4.5 to ■ and K I-, respectively, and the square waves (V, )' and (K I-
2V)' and is introduced into the AND circuit 6 at the next stage. In AND circuit 6, (V,)' and (K T- 2V)
The time measurement circuit 7 measures the time of -2V) when both 1 and 1 are 1, and if it is 90 degrees or more, the Moo-type relay is in a working state.

FIG. 7 is a vector diagram illustrating the above operation, and shows the operating limit of voltage V with respect to current {circle around (2)}. That is, ■, Toni 11
The phase difference between the electric quantities K2 V is represented by θ in FIG. 7, and if this phase difference θ is within 90°, the device will operate, and therefore the operating range will be within the circle in FIG.

In FIG. 8, a Moo type relay 8 similar to that shown in FIG. 5 is applied to the power source P8 end of a transmission power source, which generally has power sources P s and P R at both ends. Assume that the current is P, flowing from the end side to the PR end. Failure at point A of power transmission line ■5, i.e.
In the event of an internal failure, the Moh type relay 8 operates as described above and becomes operational. In the case of a failure at point B or point B, that is, an external close point failure, the voltage V becomes zero as shown in the waveforms of each part in Figure 9, and the polarity V also becomes zero, so the Moh type relay It becomes inactive.

In other words, the normal response is to operate in case of an internal failure, but not to operate in case of an external failure.

(Problem to be Solved by the Invention) However, as is well known, in the auxiliary transformer 81 of the 1A electric appliance shown in FIG. This will generate a transient DC component. This will be explained using the equivalent circuit of the auxiliary transformer shown in FIG. First, before a failure occurs, an excitation current flows through the excitation impedance Z due to the input voltage ■, and excitation energy is stored. However, when the input voltage V instantaneously becomes zero, the excitation energy stored in this vjJ magnetic impedance Z1- is released to the secondary side as shown by the arrow, so the secondary side output v' instantaneously becomes zero. Instead, a transient DC component (1) occurs as shown in FIG.

The transient DC component V□ generated by the auxiliary transformer 1 adversely affects the response of the conventional MoW type relay, causing it to malfunction due to an external failure.

That is, when an accident occurs at point B of the power transmission line in Fig. 8, the voltage V becomes zero as described above, but the output V' of the auxiliary transformer 1 does not immediately become zero, and the transient DC component 1 remains. The response of the motor type relay in this state is as shown in FIG. That is, since the polarity amount V- is the output of the auxiliary transformer 1 multiplied by 2V by a predetermined coefficient, the waveform becomes proportional to 2V. Since the 2V transient DC component remains in the output of the auxiliary transformer 1 for a while after the accident occurs, the polarity NVp becomes as shown in FIG.

The fault current ■ is in the opposite direction to the current, so it reverses at the time of an accident as shown in Figure 12. If this fault current ■ is sufficiently large compared to the KV mentioned above and the influence of K2V can be ignored, then K I
- and 2V are set as shown in Fig. 12.

When these are converted into square waves, (V, )' remains ``1'' continuously while the transient DC component remains, and remains ``1'' only during the period of 180° (2V in K I-). Therefore, the output vAND of the AND circuit 6 becomes a 180° square wave output for each cycle, and the output of the time measuring circuit 7, that is, the output V. This will result in erroneous output.

As described above, the conventional Moh type relay has the drawback that the transient DC component generated by the auxiliary transformer causes the malfunction of a part that should not normally operate in the event of 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 Moh-type relay, was lost.

The present invention has been made to solve the above-mentioned drawbacks, and an object of the present invention is to provide an electric appliance with a distance M@j that does not malfunction due to the transient DC component generated by the auxiliary transformer of the relay.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention uses polarity UV corresponding to the voltage from the power system, and the amount of electricity <K, T- Distance Mi! to determine whether the overlapping angle of (2) is within a predetermined value. 1! The electric appliance is configured to include a circuit that limits the period of the polarity amount Vp to a predetermined value or less.

(Function) By limiting the period of the polarity amount, the transient DC component Il! generated from the auxiliary transformer of the relay is reduced. Continuation opening time 1
It can be limited to the equivalent of 80 degrees, preventing relay malfunctions.

(Example) Examples will be described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a Moh type relay according to the present invention. In FIG. 1, the output of the auxiliary transformer 1 is connected to the polarity circuit 3 to obtain the polarity K 2 V,
The introduction into the square wave conversion circuit 5 is the same as in the case of FIG. The output of the square wave conversion circuit 4 is introduced into the input terminal of the next-stage input bit circuit 9 and the time measurement circuit 8,
Furthermore, the output of the time measuring circuit 8 is introduced into the in/out bit terminal of the in/out bit circuit 9.

2V is also introduced into the square wave conversion circuit 5 to the operating amount K I-. Then, each output of the bit circuit 9 inputted to the square wave conversion circuit 5 is subjected to an operation judgment in an AND circuit 6 and a time measuring circuit 7 to obtain a relay output. Components with the same reference numerals in FIG. 5 and FIG. 1 have the same symbol.

Next, the operation of the negative type relay according to the present invention will be explained.

FIG. 2 shows waveforms of various parts to explain the operation of the Moh type electric appliance of the present invention shown in FIG. Point B on the power transmission line shows the behavior when an external accident occurs. As mentioned above, if an accident occurs outside the closest point behind the Moh type relay installation point, the voltage at the relay installation point on the power transmission line becomes zero.

However, the output of the auxiliary transformer 1 of the relay does not become completely zero, and because a transient DC component is generated, the output becomes 2V as shown in Figure 2. Also, since the post-failure current ■ is the opposite of the power flow,
When the operating amount K I- is 2V, a waveform as shown in FIG. 2 is obtained.

Therefore, as shown in Fig. 2, the operating amount (K I- is 2V
) is converted into a square wave by the square wave conversion circuit 5, and a 180° square wave is output for each cycle.

However, the output of the square wave conversion circuit 4 due to the transient DC component of the polarity vp is a long-duration "1" output while the DC component is generated.

is introduced into the time measuring circuit 8. The time measurement circuit 8 is a so-called time-limited operation circuit in which the output becomes "1" after a predetermined time has elapsed since the input changed from "0" to "1".
Here, the time limit is expressed as an electrical angle equivalent to 180°, which corresponds to a half cycle of the input. Therefore, as shown in Fig. 2, the output of the time measuring circuit 8 in steady state is "O", and after the input <v, )' becomes continuous "1", it becomes continuous "1" after a time equivalent to 180゛ has elapsed. The output v2 of the time measuring circuit 8 is an inhibit input to the inhibit circuit 9 in the subsequent stage, so when ■2 is "0", it is input and the other input of the bit circuit (V, )' is If it is “1”, the input bit circuit output is “1”, and if the inhibit power v2 is “IH”, the output of the inhibit circuit 9 is always “0”, so the output V of the inhibit circuit 9 is the second The result will be as shown in the figure.

The output V[ of this inhibit circuit 9 and the operating amount are AND
Since the AND is performed in circuit 6, the output is VAN shown in the second part, and the time width of this is equivalent to 90 degrees in electrical angle.
The time measurement circuit 7 measures whether or not the voltage is higher than or equal to (V,
)' continuous "1" output influences the output V of the time measurement circuit 8.
, so there will be no malfunction. That is,
Malfunctions due to transient DC components generated in the auxiliary transformer 1 at the time of external failure can be prevented.

In addition, in distance relays, the phase of 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 positive half wave of the AC quantity of electricity,
Separate square wave conversion circuits, AND circuits, etc. are used for the negative half wave and negative half wave, but these have been omitted in the explanation so far to simplify the explanation, but for the negative wave Of course, it can be considered in the same way.

By suppressing the output of the square wave conversion circuit 4 to which the polarity is input within 180 degrees in this way, there is an advantage that malfunctions can be prevented in the event of an external failure.

In addition, in the embodiment of this proposal, we have described the effects caused by the transient DC component and P, ) transient of the auxiliary transformer in the iJ electric appliance, but separately from this, we have described the effect caused by the transient DC component of the auxiliary transformer in the iJ electric appliance. An embodiment of the present invention can also be applied to transients that occur. Other examples of actual rods include those shown below.

(a) In the above embodiment, the time measurement circuit 8 and the inhibit circuit 9 have been described as circuits that limit the width of the transient DC component of the auxiliary transformer 1, but the present invention is not limited thereto. For example, as shown in FIG. 3, a similar effect can be expected by combining the one-shot pulse circuit 10 and the AND circuit 6-1.

(b) Furthermore, in the above embodiment, the voltage input to the relay.

The explanation has been made based on the assumption that the current is in the same phase (for example, R phase).

However, the present invention is not limited thereto. For example, taking advantage of the characteristics of a three-phase circuit, protection of the R phase @1 S as an electric appliance
A similar effect can be expected by inputting the T-phase voltage and using the amount of electricity phase-shifted by 90° as the polarity amount.

This embodiment is shown in FIG. In Figure 4, 11 is 90
° Phase shift circuit is shown.

〔Effect of the invention〕

As explained above, according to the present invention, even when a transient DC component occurs in an auxiliary transformer of an electric appliance,

It is possible to provide a distance relay that can reliably distinguish between internal and external accidents by simply adding a simple device without malfunctioning when an external failure occurs.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment of a distance relay according to the present invention;
Fig. 2 is a diagram showing the response to an external close f4 accident of the distance a electric appliance shown in Fig. 1, Fig. 3 is a configuration diagram of another embodiment for limiting the width of the transient DC component, and Fig. 4 is a diagram of the present invention. A block diagram of still another embodiment according to the invention, FIG. 5 is a top view of a conventional distance relay, FIG. 6 is a diagram showing the response to an internal accident of the distance relay shown in FIG. 5, and FIG. 7 is an operation diagram. Characteristics diagram, Figure 8 is a diagram of applying a distance relay to a power system, Figure 9 is a waveform diagram showing the response to an external close point fault, Figure 10 is an equivalent circuit of an auxiliary transformer, and Figure 11 is a transient DC component. FIG. 12 is a waveform diagram showing the response of the conventional distance relay shown in FIG. 5 to an external close point accident. 1... Auxiliary transformer 3... Polarity circuit 6... AND circuit 9... Inhibit circuit 2... Auxiliary current transformer 4.5... Square wave conversion circuit 7.8... time measurement circuit

Claims (1)

[Claims] The polarity amount V_p corresponding to the voltage from the power system and the amount of electricity (K_1I-K
What is claimed is: 1. A distance relay that determines whether an overlapping angle of _2V) is within a predetermined value, comprising a circuit that limits the period of the polarity amount V_p to a predetermined value or less.