JPS5819570A - Controlling device for impression of voltage for inspecting ground fault point of distribution line - Google Patents

Abstract

PURPOSE:To facilitate firing of an incomplete grounding point and maintain a proper value of a current after completion of the firing, by maintaining an appropriate value of a voltage impressed on a fault section of a distribution line by means of an automatic control circuit containing a bidirectional thyristor and a bidrectional diode. CONSTITUTION:When a power switch 2 is charged, an AC voltage is impressed on an boosting transformer 3 and a triode bidirectional thyristor 5, and thereby a current flowing through an automatic boosting circuit is increased to change a value of R3. Thereby the time constant of a circuit 7 is changed, a time required for a bidirectional trigger diode 6 to reach a breakover voltage is changed and a phase control of the thyristor 5 is conducted. In a boosting process, the rise of a primary current of the transformer is sharpest at a point whereat a firing angle is 90 deg., and there a crest value induced on the secondary side is large. When a fault point is in the state of incomplete grounding, an impressed voltage becomes vibrant and the firing is facilitated by an intermittent discharge current. When said point is near to the state of permanent grounding, grounding resistance decreases and the energy of the circuit is consumed by resistance. Therefore a vibrating part attenuates and thus a stable current flows.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power charging control device for detecting a ground fault point in a power distribution line, which improves the efficiency of detecting a ground fault point and reduces the size and weight of the device.

In general, the ground fault current when a single line ground fault occurs in a high-voltage distribution line differs greatly between before and after the ground fault point. Focusing on this, the ground fault point can be found by applying an appropriate high voltage to the distribution line in the section where the ground fault has occurred, examining the current distribution along the line, and searching for sudden changes in the current. ing.

However, if the fault point is in an incomplete ground fault state, the power is cut off by the protective relay operation, and once the ground fault current disappears, the insulation will temporarily recover, and after the period during which the fault remains, it will become permanent. This often leads to ground faults, leading to interruptions in power supply.

Therefore, in the case of intermittent ground faults, the incomplete ground fault is forcibly burned out by applying high voltage, and the fault progresses to a permanent ground fault. After that, the fault point is detected by a detector and the faulty part is quickly repaired. It is desirable to do so.

The present invention is used for power charging control of an earth fault point detection device based on the above principle, and is composed of an automatic control circuit including a bidirectional thyristor and a bidirectional diode, and controls the voltage applied to a fault section of a distribution line. The current is maintained at an appropriate value to promote firing of the incomplete ground fault location, and after firing is completed, the current flowing from the exploration device to the fault location is maintained at a value suitable for detection.

FIG. 1 shows the configuration and operating principle of an embodiment of the ground fault point detection system and the power supply control device according to the present invention. This is the part that becomes. In Figure 1, 1 is an alternator with a gasoline engine used as a power source, 2 is a power switch,
3 is a step-up transformer, 4 is a single-phase full-wave rectifier circuit, 5 is a 3-pole bidirectional thyristor used as an AC switch for opening/closing the primary (low-voltage side) circuit of the step-up transformer, and 6 is a 3-pole bidirectional thyristor. Timing control (phase control) of switching operation of
7 is a capacitor and resistor for adjusting the turn-on phase of the bidirectional trigger diode, 8 is a conversion circuit (for example, a photocoupler) that converts current changes into a resistance value, 9 is an automatic booster circuit, and 10 is a constant voltage regulator. In the current control circuit, 11 is a detection circuit for detecting the current flowing from the power supply section to the distribution line, and 12 is a relay circuit for automatically switching between the automatic booster circuit 9 and the constant current control circuit 10.

Reference numeral 13 designates a portable live-line ammeter used to measure ground fault current flowing in a power distribution line, such as an optical fiber insulated high-voltage ammeter (see Japanese Patent Application Laid-Open No. 138661/1983).

First, the general operation of the ground fault point detection system to which the power charging device according to the present invention is applied will be explained. In FIG. 1, when the power switch 2 is turned on, an AC voltage of 100 delt and 60 hertz is supplied from the generator 1 with gasoline engine to the primary side of the step-up transformer 3, and the secondary side (high voltage side) of the transformer 3.
An alternating current voltage is generated according to the excitation current flowing to the primary side by turning on and off the thyristor alternating current switch 5.

This voltage is converted into a pulsating high voltage by the single-phase full-wave rectifier circuit 4 and applied to the faulty section of the distribution line. If the fault point is in an incomplete ground fault state, this pulsating high voltage burns the fault point and transitions it to a permanent ground fault state. The current value flowing into the distribution line during the firing period and after transition to a permanent ground fault is maintained at a preset value by the constant current control device of the power supply control device. Therefore, the fault point can be determined by examining the distribution of the 120 Hz AC component included in the ground fault pulsating current along the distribution line using the portable live-line ammeter 13 and finding the point where this current component suddenly changes.

Next, the operation of the power charging control device that is the target of this development will be explained.゛First, when the voltage switch 2 is turned on, a 60 Hz 100° sine wave AC voltage is applied from the AC generator 1 to the step-up transformer 3 and the 3-pole bidirectional thyristor 5;
A current that gradually increases according to the integral time constant of the automatic booster circuit 9 flows into the current-resistance value conversion circuit 8 and changes the value of the resistor R3. Along with this, capacitor c1. c2 and resistance R
Since the charging/discharging time constant of the circuit 7 consisting of 1, R2*R3 changes, the time for the bidirectional trigger diode 6 to reach the breakover voltage changes, and the bidirectional trigger diode 6
Phase control of the r-to control signal output from the three-pole bidirectional thyristor 5 is performed. Therefore, the firing phase of the 3-pole bidirectional thyristor is set to 1 before the power supply control device is powered on.
80° and the firing phase is gradually shifted in the direction of θ° according to the time constant of the automatic step-up circuit, the secondary voltage of the transformer 30 and therefore the voltage applied to the distribution line will automatically rise. . Figure 2 shows the transition state of the waveform of the transformer primary current during the step-up process. ), (3), and (4) each have a firing angle of 135”.

In the case of 90° and 45°, (1), (2),
The actual high value of the transformer secondary voltage increases in the order of (3) and (4). In the step-up process, the rise of the primary current of the transformer is the steepest at the point of the 90° firing angle, so the change in the magnetic flux of the transformer is large, and the peak value of the voltage induced on the secondary side of the transformer is large. Therefore, if the fault point is in a state of incomplete ground fault and the ground fault resistance is large, the voltage applied to the line near the firing angle of 90° becomes oscillatory as shown in Figure 3, and this voltage An intermittent discharge current flows to the end point of the unfinished metal base to promote firing. As firing progresses and approaches a permanent ground fault state, the resistance at the ground fault point decreases, and as the energy of the circuit is consumed by the resistance, the oscillations of the current are attenuated and the current continues stably until the ground fault point is reached. It becomes flowing. The secondary voltage of the transformer is determined so that the peak value of the oscillating voltage is sufficiently lower than the shock discharge starting voltage of the lightning arrester to prevent malfunction of the lightning arrester due to the oscillating voltage.

Next, the operation of the automatic constant current control circuit will be explained. The magnitude of the current flowing out of the distribution line 5 due to the application of the pulsating high voltage is extracted as a voltage in the detection circuit 11 of FIG.
After being converted into direct current by the smoothing circuit, it is guided to the comparator of the relay operation circuit 12. When the magnitude of this voltage becomes larger than the set voltage value of the comparator, the relay is energized and switching from the automatic booster circuit 9 to the automatic constant current control circuit 10 is performed. The automatic constant current control circuit 10 calculates the difference between the DC voltage corresponding to the current setting value and the output DC voltage of the detection circuit, and converts a current proportional to this difference voltage into the current-resistance value conversion circuit 8 of FIG. The firing phase of the three-pole bidirectional thyristor is controlled so that the current flowing out to the distribution line is always maintained at a constant value based on the above-mentioned principle. Therefore, all voltage and current controls are automatically performed after the power supply control device is powered on. If the state of the ground fault point is close to a permanent ground fault and the ground fault resistance is small, the relay circuit operates without going through the above firing process to maintain the ground fault current at a value suitable for detection.

As explained above, by using the power supply control device according to the present invention, the efficiency of ground fault point detection is improved and the monitoring burden on workers is also reduced. In addition, it is possible to reduce the capacity of the power transformer and power supply alternator, making it possible to reduce the size and weight of the device.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a power charging control device according to the present invention and a distribution line fault detection system to which the power charging control device is applied. Figure 2 is a diagram of the primary current waveform of the step-up transformer during the automatic step-up process, and (1) is the 3-pole bidirectional thyristor firing angle α = 18
0°, (2) α=135°, (3) α=90°, (
4) shows the case where α=45°. FIG. 3 shows an example of the voltage waveform on the secondary side of the step-up transformer during firing of the unfinished metal terminal. 1...Sine wave alternator with gasoline engine, 2...
・Power switch, 3...Step-up transformer, 4...Single-phase full-wave current circuit, 5...3-pole bidirectional thyristor, 6...
Bidirectional trigger diode, 7-- Bidirectional trigger diode turn-on phase adjustment circuit, 8-- Current-resistance value conversion circuit, 9-- Automatic booster circuit, lO-- Constant current control circuit, 11-- - Current detection circuit, 12... Relay operation control circuit, 12a, 12b... Relay a contact and b contact, 13... Optical fiber/insulated high voltage ammeter. Figure 2, l-\, 45' Figure 3

Claims (1)

[Scope of Claims] A bidirectional current control circuit inserted into the primary side circuit of a step-up transformer in a power supply section, a current detection circuit that detects a current flowing from the power supply section to a distribution line, and the current While the magnitude of the detection current of the detection circuit is smaller than a certain set value, the firing angle is set at around 90° in order to generate a voltage on the secondary side with a peak value that promotes firing of the incomplete ground fault point. an automatic booster circuit for igniting the bidirectional current control circuit; and an automatic booster circuit for igniting the bidirectional current control circuit; and an automatic booster circuit for igniting the bidirectional current control circuit; A power charging control device for detecting a ground fault point in a distribution line, comprising: an automatic constant current control circuit for controlling a forward current control circuit.