JP3207643B2 - Short circuit accident high-speed judgment circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit for determining a high speed in response to the rise of an excessive current caused by a short circuit, and more particularly to a protective relay.

[0002]

2. Description of the Related Art Conventionally, in a short-circuit protection relay, a short-circuit fault is determined when an excessive current level continuously flows. Therefore, a determination time of half a cycle or more is required. A time of several ms is required.

That is, as shown in FIG. 5, when a short-circuit current Z at the time of a short-circuit fault occurs with respect to a normal load current waveform A, the judgment is made based on the short-circuit current judgment value level L. A waveform K is obtained. At this time, the continuity of the excessive current is confirmed to prevent malfunction due to noise or surge. Therefore, short circuit determination is performed after an excessive current of several tens of ms flows.

[0004]

As described above, a short-circuit current flows through a load or an electric circuit for several tens of milliseconds during the protection operation, so that the measuring instrument or the protective relay may need to be replaced. Stress is occurring.

The present invention has been made in view of the above-mentioned problems, and provides a short-circuit accident high-speed judgment circuit which shortens a short-circuit accident judgment time of half a cycle or more, reduces stress on a load or an electric circuit, and minimizes damage of a short-circuit accident. Aim.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a half-wave rectifier circuit for rectifying only a half-wave of a detection voltage proportional to a load current, and a second circuit for inputting an output of the half-wave rectifier circuit. (1) an integration circuit and a delay circuit, a level detection circuit and a second integration circuit that receive an output of the delay circuit, an addition circuit that adds the outputs of the level detection circuit and the second integration circuit, and an output of the addition circuit And a comparison circuit for comparing the output of the subtraction circuit with a predetermined value.

Further, the present invention provides a half-wave rectifier circuit for rectifying only a half-wave of a detection voltage proportional to a load current, a first integration circuit and a delay circuit which receive an output of the half-wave rectifier circuit, A second integration circuit for receiving an output of the delay circuit, a subtraction circuit for obtaining an output difference between the first integration circuit and the second integration circuit, a comparison circuit for comparing the output of the subtraction circuit with a predetermined value, The gist is to have.

Further, the present invention has the above-mentioned configuration, and has a gist having a circuit configuration of two types of positive and negative polarities with respect to a load current, and obtaining an output by taking a logical sum of outputs of respective comparison circuits.

[0009]

Since the amount of change in excessive current due to a short circuit is determined based on the integrated value within the time Δt by the delay circuit, the short circuit can be detected before reaching the vicinity of the final short circuit current.
Since the determination is made based on the integrated value of time, malfunction due to an instantaneous level change such as noise and surge can be prevented, so that a determination output can be obtained immediately after detection. As a result, a short circuit accident can be determined based on the time Δt.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. In FIG. 1, a current transformer 1 is installed on an electric circuit, and the current transformer 1 is connected to an I / V converter 2. This I
The / V converter 2 converts a current proportional to the detected load current into a voltage.

The output voltage of the I / V converter 2 is processed separately in each of a positive half-wave route and a negative half-wave route. Here, the positive polarity route will be mainly described for convenience. .

A half-wave rectifier circuit 3 for rectifying only the positive voltage output from the I / V converter 2 is provided, and the output of the half-wave rectifier circuit 3 is connected to a first integration circuit 9 and a delay circuit 5. . The first integration circuit 9 obtains an integrated value (area) of the voltage, and the delay circuit 5 is used for measuring the time Δt.

The output of the delay circuit 5 is connected to a level detector 13 and a second integration circuit 10, and the level detector 13 outputs h
Performs level detection of ₁ × Delta] t (see FIG. 2), the second integrating circuit 10 performs integration of S ₁ (see FIG. 2).

Therefore, in the adding circuit 15, the output h ₁ × Δt of the level detector 13 and the output S
₁ is added. Then, the output of the adder 15 and the first integrator 9 are subtracted by a subtractor 17 to obtain a signal shown in FIG.
A hatched portion S ₂ - Request _{(S 1 + h 1 × Δt} ).
The output of the subtraction circuit 17 is compared with the value of the set value circuit 19 by the comparison circuit 10, and when the output exceeds a certain value, the output of the comparison circuit 20 is output. That is, the aforementioned S ₂ − (S ₁ + h ₁ × Δ
When t) exceeds a certain value, a comparison output is output. The discharge in the first and second integrating circuits 9 and 10 is as follows.
This is performed by the rising detector 8 along the route of the inverted half-wave rectifier circuit 4.

Similarly, in the route of the negative polarity, the inverted half-wave rectifier circuit 4, the first integrating circuit 11, the delay circuit 6, the level detector 14, the second integrating circuit 12, the adding circuit 16, the subtracting circuit 18, A comparison circuit 20,
It is output as the logical sum 22 of the output of 21.

In the configuration of FIG. 1, the operation is shown in FIG. 2. In FIG. 2, t ₁ is a short-circuit fault point, and t ₂ = t ₁ + Δ.
Let it be t time. When this FIG viewed as a positive voltage output waveform of the half-wave rectifier circuit 3 of the voltage, the area S ₁ until time t ₁ second
The area S ₂ up to the time t ₂ = t ₁ + Δt is the integrated value of the first integrating circuit 9. The output value of the level detector 13 is h ₁ × Δt = h ₁ × (t ₂
−t ₁ ). The output of the adder 15 is S ₁ +
(H ₁ × Δt). Therefore, the output value of the subtraction circuit is S ₂
− [S ₁ + (h ₁ × Δt)], that is, the hatched portion in the figure. The setting value circuit 19 in which the area of the hatched portion is predetermined
When the value exceeds the value, a (trip) output is output to the outside. Similarly, this figure is completely the same when the output waveform of the inverting half-wave rectifier circuit 4 of the negative voltage is viewed in the figure.

With the above configuration, it is possible to detect and determine a short circuit accident at time Δt before reaching the vicinity of the final short circuit current. 3 and 4 show another embodiment. This figure 3
In the example shown in FIG. 3, when the value of the predetermined set value is clearly larger between the maximum level of the overcurrent region × Δt and the value of the predetermined set value circuit, the circuit configuration of FIG. Is to simplify.

That is, FIG. 3 has a configuration in which the level detectors 13 and 14 and the adders 15 and 16 shown in FIG. 1 are omitted. Then, as the operation, the area of the shaded portion of the integrating circuit 9 or the integrated value difference of the integral values S ₁ of S ₂ and the integrating circuit 10 or 12 of the 11 (S ₂ -S ₁₎ i.e. in the figure as shown in FIG. 4 However, when the value exceeds a predetermined value of the set value circuit 19, an output is output to the outside.

[0019]

As described above, according to the present invention, as shown in FIG. 5, there is provided a protection relay for judging a short circuit accident before the current increases near the short circuit current and outputting the same to the outside. can do. Therefore, the stress on the load and the electric circuit can be reduced, and the damage in the event of a short circuit can be minimized. Further, since the change in the current is determined based on the integral value and the area, malfunction due to noise, surge, and the like can be prevented.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating the operation of the present invention.

FIG. 3 is a configuration diagram showing another embodiment of the present invention.

FIG. 4 is a waveform diagram illustrating the operation of another embodiment of the present invention.

FIG. 5 is a waveform diagram showing a difference between a conventional method and a method for detecting and determining a short circuit accident according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier 2 I / V converter 3, 4 Half-wave rectifier circuit 5, 6 Delay circuit 7, 8 Rise detection circuit 9, 11 First integration circuit 10, 12 Second integration circuit 13, 14, Level detector 15, 16 Addition Circuits 17, 18 Subtraction circuit 19 Set value circuit 20, 21 Comparison circuit

Claims (3)

(57) [Claims] 1. A half-wave rectifier circuit for rectifying only a half-wave of a detection voltage proportional to a load current, a first integrating circuit and a delay circuit for receiving an output of the half-wave rectifier circuit, and an output of the delay circuit. Input level detection circuit and second level detection circuit
An integrating circuit; an adding circuit for adding outputs of the level detecting circuit and the second integrating circuit; a subtracting circuit for obtaining a difference between an output of the adding circuit and an output of the first integrating circuit; A comparison circuit for comparing a predetermined value with a predetermined value. 2. A half-wave rectifier circuit for rectifying only a half-wave of a detection voltage proportional to a load current, a first integration circuit and a delay circuit which receive an output of the half-wave rectifier circuit, and an output of the delay circuit. A short circuit having: a second integration circuit to be input; a subtraction circuit for obtaining an output difference between the first integration circuit and the second integration circuit; and a comparison circuit for comparing the output of the subtraction circuit with a predetermined value. High-speed judgment circuit. 3. The high-speed short-circuit fault judging circuit according to claim 1, which has a circuit configuration of positive and negative polarities with respect to the load current, and obtains an output by taking a logical sum of outputs of the respective comparison circuits.