JPS6016123A - Distance 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 [Technical Field of the Invention] The present invention relates to a distance relay that receives the voltage and current of each phase of a power transmission line as input and detects the distance and direction to a fault point from the magnitude and phase relationship.

[Technical background of the invention and its problems]

The prior art will be explained with reference to the drawings. FIG. 1 is a block diagram showing a conventional Maw type distance relay, and FIG. 2 is a vector diagram showing its operating principle.

The distance relay receives the voltage and current at its installation point as input, and determines whether an accident has occurred within the protected area based on the magnitude and phase relationship between the two. As shown in FIG. 1, the voltage input (hereinafter referred to as 9) and the current input (hereinafter referred to as i) are connected to input transformers T1 r T11, respectively.
DC components and harmonic components are removed by a filter (hereinafter referred to as FIL). FIL
The output of , is introduced into the phase shift circuit PSl which shifts the alternating current electrical quantity in the leading direction by the phase angle ψ generated between the current and voltage due to the impedance of the power transmission line, and the difference between its output and the output of FIL□ is subtracted. The circuit S is connected to the square wave conversion circuit LD! It is converted into a square wave. On the other hand, the output of FIL is introduced into a memory circuit M, and a polarity voltage ψP corresponding to voltage 9 is derived. As the polarity voltage 9P, for example, a healthy phase voltage may be used instead of using the memory circuit M1. The electric quantity 9F is converted into a square wave by the square wave conversion circuit LD1, and LDl and LD! The outputs of both are AND circuit AN
The overlapping angle is determined by D□, AND, when the output is 90° or more in electrical angle, the timer TDE for determining whether the overlap occurs
, is configured to obtain the output.

When the output is obtained from TDEl, the delay circuit 'I'D
D.

to obtain a serialized output.

FIG. 2 is a vector diagram showing the principle of obtaining the Moh characteristic.

Here, iku is P8. 2 shows the output, and iM-v shows the output of Sl. When i and vr are input such that the overlapping angle of 9P and iz-* is 90°, as shown in FIG. 2, the relay output is at its operating limit.

In Fig. 1, the outputs of T, , T, are FILl, F
After the DC component and harmonic component are removed by IL2,
It is guided by a circuit that realizes the Mo characteristic.

The reason why FILl and FIL are necessary is as follows.

The characteristics of a distance relay are obtained from the magnitude and phase relationship of the fundamental waves of the input voltage and input current, respectively. When an accident occurs in the power system, as is well known, the input voltage and input current of the distance relay have DC components and harmonic components superimposed, and the computation required to obtain the Moh-shaped characteristics described earlier is necessary. may cause problems. Therefore, it is included in the amount of human electricity.
! ! FI is used for the purpose of removing frequency components other than the fundamental wave.
L, , FIL.

is provided.

The above is the operating principle of the Moo type distance relay. By the way, distance relays have characteristics called current-distance characteristics, as an example of which is shown in FIG.

This means that if enough input current is given, accurate calculations will be made that are equal to the ratio of input voltage and input current, that is, the distance from the installation point of the distance relay to the fault point, but conversely, if the input current is small, accurate calculations will be performed. This means that the distance to the accident point is judged to be farther than it actually is (hereinafter referred to as underreach). In FIG. 3, lm1n represents the minimum operating current value, and Imax represents the maximum allowable input current value.

Next, the reasons why Imin, Imax and the above-mentioned underreach occur will be explained.

FIG. 4 shows the signals of each part of the configuration shown in FIG. 1, and θ indicates the phase difference between ν and i. And M,
The outputs 9P and 81 outputs 19-9 are converted into square waves by LD, LD, and AN, respectively.
The phases are compared by D, , T'DB, and a distance relay output is obtained.

now,? The phase difference θ between and i is equal to ψ and the magnitude is equal, that is, iz−? Assuming that is zero, the second
As is clear from the vector diagram in the figure, the distance relay reaches its operating limit.

On the other hand, at this time, inside the distance relay, the amount of electricity corresponding to iλ-9 must exceed the detection level of the LD and be large enough to obtain an operation determination angle of 90°.

Now, when adjusting the characteristics of the distance relay, it is done by setting i, 9, which is sufficiently larger than the detection level of the LD, such as its rated input value. The bar representing the operating limit of the distance relay shown in Figure 2 is LD, which is sufficient to ignore the value of the detection level. .So, if we give such large i and V and then gradually decrease i without changing the ratio and phase difference ψ, 1
Since the z-vO value also decreases by 1〉 ・°゛, the output width of the LD becomes narrower and the distance relay becomes inoperable.Next, change the ratio of i and V and change only 9 to a smaller value. If the value of 1z-v becomes large again, the distance relay will operate again. This clearly shows that the distance relay has an underreach characteristic. The tendency of this underreach characteristic is that when i is small, For example, as shown in FIG. 3, when the fourth flow is 1, an underreach characteristic of about 20 inches is exhibited.

If j-2 is further decreased, even if 9 is set to zero, the output width of LD2 will not reach 90 degrees and the distance relay will become inoperable. i at this time is the minimum operating current value lm1n.

When trying to protect a long-distance power transmission line with the characteristics shown in Figure 3, the current value given to the distance relay will be greatly different depending on whether there is an accident at a far point or an accident at a close point], and the dynamic range required for a distance relay is 1,000 times greater. Sometimes. For this reason, there has been a problem in that it is difficult to apply conventional distance relays to such long-distance power transmission lines. Furthermore, even if the dynamic range required for a distance relay is hundreds of times larger, if the impedance behind the relay installation point is large and the current due to an accident is small, the operating principle will cause
The underreach characteristic shown in the figure occurs, which causes the problem that the distance to the accident point cannot be calculated accurately.

As a countermeasure for this, use a small current range, for example '4 current.

In order to improve the underreach characteristic when
It is conceivable that the output width of the circuit LD (p) can be made large even when the magnitude of v is small.

However, as shown in Figure 1, distance relays have F
IL, , FIL□M,, P8. These circuits generally use operational amplifiers. There is a phenomenon in operational amplifiers that even if the output voltage is zero, an output voltage (offset voltage) is generated due to temperature changes, etc. If the detection level of the circuit LD is made too sensitive, this offset voltage will be generated. Since the distance relay malfunctions due to the amount of noise, there is a limit to how high the sensitivity of the detection level of the circuit LD can be made, and it is not possible to make the detection level of the square wave conversion circuit LD2 high enough to improve the above-mentioned underreach characteristic.

[Purpose of the invention]

The present invention was made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a distance relay with improved underreach characteristics.

[Summary of the Invention] In order to achieve the above object, the present invention C reduces the voltage 9 at the installation point.
, 4 currents i are detected by the input transformer and by the phase shift circuit)
Obtain the electrical quantity 1z (z is the impedance of the power transmission line), the polar quantity voltage 9P by the polar quantity voltage generation circuit, and the electrical quantity iz-v by the subtraction circuit, and transfer these to the square wave conversion circuit. ,V, ,IZ-V Tol,Claim,C(2) Electrical quantity IZ,V,.

K is designed to generate a relay output when the overlapping angle of IZ-V is equal to or greater than a predetermined electrical angle. In addition, the detection level of the electric quantity IZ is set to a level where the offset electric quantity becomes a problem,
Further, the detection level of the quantity of electricity IZ-V is set to be more sensitive than the detection level of the quantity of electricity IZ.

[Implementation sequence of the invention]

An embodiment of the present invention will be described with reference to FIGS. 5 to 8.

In FIG. 51, a square wave conversion circuit LD3. inputs the output signal iz-v of the subtraction circuit S□. A square wave conversion circuit LD, which inputs the output signal iλ of the phase shift circuit PS, and an AND circuit AND, which inputs the output signal of the square wave conversion circuits LD, LDs, and LD, are provided. In addition, LDs
The square wave conversion level of LD4 is set to have high sensitivity compared to the square wave conversion level of LD4.

Next, the operation of this embodiment will be explained.

The square wave conversion circuit LD3 receives the output signal iz of the subtraction circuit 8□.
-: is input. Since the square wave conversion level of the LDs is made more sensitive than the square wave conversion level of LD2' in FIG. 1, the underreach characteristic is improved as described above. In addition, the square wave conversion circuit LD includes a phase shift circuit P8. The output signal i of is input. L.D.

The square wave conversion level of ゛ is set to a level that detects the offset electrical quantity. When the input t exceeds this set level, an output IZ is produced. This output ■Z eliminates the influence of the offset amount of electricity.

The phase relationship is as follows. Therefore, it can be seen that even if the electric quantity i is introduced, the motor characteristics are not affected.

FIG. 7 is a diagram explaining the above, in which the signal ``Z'' is the AND (IZ-V) of the signals IZ-V and ``V''.

The signal IZ does not affect the overlapping angle determination based on the signal (IZ-V)·V.

FIG. 8 shows the current-distance characteristics of the distance relay having the configuration shown in FIG. 5, and for comparison, the characteristics according to the configuration shown in FIG. 1 are shown by a chain line. The underreach characteristic at current 11 is significantly improved from point B to point A. The current 11 is a value determined by the conversion level of the circuit LD in the configuration example shown in FIG.

According to this embodiment, the underreach characteristics are improved by making the square wave conversion circuit LDs highly sensitive. Furthermore, by introducing the electric quantity iM, the influence of the offset electric quantity can be removed.

Note that instead of providing the square wave conversion circuit LD as in this embodiment, an overcurrent relay may be added and the breaker tripped by the AND of the outputs of the distance relay and the overcurrent relay.

Compared to this method, this embodiment is superior in the following points.

In this embodiment, a square wave conversion circuit LD is provided in the apparatus shown in FIG.
It is possible to improve the underreach characteristic with a very simple circuit configuration.

Additionally, adding an external overcurrent relay as described above not only increases the circuit size but also reduces the operating time.

Although there are drawbacks in terms of return time characteristics, such as the need for time coordination with a distance relay, the device of this embodiment does not have such problems.

Next, another embodiment of the present invention will be described with reference to FIGS. 9 and 10.

In the above embodiment, the case where the present invention is applied to a Moh characteristic distance relay has been explained.

However, the present invention is not limited thereto, and can also be applied to distance relays with offset mow characteristics or impedance characteristics.

FIG. 9 shows a configuration when applied to a distance relay with offset mow characteristics, and compared to the configuration shown in FIG. 5, the memory circuit M1 is replaced with an adder circuit A1. .

The adder circuit A1 calculates the electrical quantity K11z from the electrical quantities 9 and iz.
Ten? This is the first relay characteristic.
It becomes a figure.

In FIG. 9, the portion surrounded by a dashed line is a square wave conversion circuit LD for improving underreach characteristics according to the present invention, and an AND circuit AND!, which is similar to the configuration shown in FIG. 5. It is.

Square wave conversion circuit LD1. The reason why the detection level of LD3 is more sensitive than that of square wave conversion circuit LD is the same as in the case of the configuration shown in FIG.

As is clear from Fig. 10, the quantity of electricity i stops is the quantity of electricity i
z−v and quantity of electricity x, iz+? Therefore, for the same reason as shown in FIG. 7, the introduction of the magnetic quantity t does not affect the offset motor characteristics.

Also, in Fig. 10, is there a difference between the two? If the scalar coefficient of is set to 2l, it is clear that the present invention is applicable to an impedance characteristic distance joint.

Note that the present invention is also applicable to the modification of the mho characteristics shown in FIGS. 11 to 14 obtained by changing the timer time of circuit TDK in the configuration diagram of FIG. 5.

In the configuration diagram of FIG. 5, a voltage in which the system voltage is stored is used as the polarity voltage VP. However, without being limited to this, for example, a composite voltage of a faulty phase voltage and 4 voltages storing the faulty phase voltage, or a combination of a voltage obtained by rotating a faulty phase voltage and a healthy phase voltage by an appropriate angle vector. Various methods such as voltage may be used.

〔Effect of the invention〕

According to the present invention, as described above, it is possible to provide a distance relay with improved underreach characteristics.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing a conventional Moh type distance relay, Fig. 2 is a Moh characteristic diagram of the device shown in Fig. 1, Fig. 3 is a custom-made flow-distance diagram of the device shown in Fig. 1, and Fig. 4 is 1, FIG. 5 is a configuration diagram showing an embodiment of the present invention, FIG. 6 is a phase characteristic diagram of the device shown in FIG. 5, and FIG. 8 is a waveform diagram showing the operation of the square wave conversion circuit, FIG. 8 is a current-distance characteristic diagram of the device shown in FIG. 5, FIG. 9 is a configuration diagram showing another embodiment of the present invention, and FIG. Phase characteristic diagram of the device shown in Fig. 1.
1 to 14 are characteristic diagrams of relays to which the present invention can be applied. Tl + "2...Input transformer, M, , A, ・Polarity voltage generation circuit. ps, ・Phase shift circuit, SI... Subtraction circuit, ■・D, , LD2. LD3. LD, ,, Square wave conversion circuit, ANDl, TDE, , TDD,...
Output circuit. (7317) Acting Patent Attorney Kensuke Chika (and 1 other person) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 13 × Figure i2 Figure 14

Claims (1)

[Claims] (1) An input transformer that inputs the voltage and current of the power system, and the current signal output from this input transformer is input and the phase is shifted in the leading direction by the phase angle determined by the impedance of the transmission line, and the magnitude of the impedance is adjusted. a polarity voltage generation circuit that receives the voltage signal output from the input transformer and outputs a polarity voltage, and the output signal of the phase shifter circuit and the polarity amount. a subtraction circuit that inputs the polarity voltage output from the voltage generation circuit and outputs the difference therebetween; and a first circuit that inputs the voltage signal output from the input transformer.
A second square wave conversion circuit which inputs the output signal of the phase shift circuit and a second square wave conversion circuit which generates an output when the offset electric quantity is equal to or higher than the detected level, and inputs the output signal of the subtraction circuit. When a third square wave conversion circuit having higher sensitivity than the second square wave conversion circuit and the output signals of the first to third square wave conversion circuits are input and the overlap angle thereof is equal to or greater than a predetermined electrical angle. and an output circuit that produces a relay output.