JPH0213272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a grounding fault display circuit of a high voltage pulse application device used for searching for grounding fault points on overhead and underground power distribution lines using a high voltage pulse application method.

When a ground fault occurs on a high-voltage overhead power distribution line,
Selective opening and closing can be performed using the substation's grounding relay and the divisional switch of the above-mentioned distribution line to shorten the area where a ground fault occurs, or the high-voltage pulse of the high-voltage pulse energizing device can be connected to the three distribution line wires all at once, and connected to the ground. The earth fault fault area is narrowed by displaying the ground fault indicator and selectively opening and closing the distribution line sectional switch. In order to find the fault point in this narrow ground fault section, a high voltage pulse is applied to two wires of the distribution line at once, as described above, between them and the ground, and this high voltage pulse causes the distribution line to It has been considered to detect the flowing current with a detector and search for the point of a ground fault.

This exploration will be explained below using diagrams.

FIG. 1 is a diagram showing the principle of detecting a ground fault point in a power distribution line and the internal basic circuit of a conventional high voltage pulse charging device. The main components of this power supply device 1 are a main capacitor C ₁ , an output resistor R ₃ , a contact S ₁ of an electromagnetic switch that repeatedly opens and closes, a waveform adjustment capacitor C ₂ , a resistor R ₁ , and a line grounding resistor. R ₂ , a line current detector 6, a timer circuit 7a that outputs after a time T ₁ for the detector output voltage to converge with a time constant determined by the line characteristics, and a ground fault based on the output of this timer circuit 7a and its output polarity. A display device 8 for displaying information, and the like.

In such a power supply device 1, the voltage of a high voltage power supply is applied to the main capacitor _C1 through a current control resistor to store energy, and this energy is transferred to the main capacitor C1 through a current control resistor.
A voltage is applied between the contact S ₁ connected to the R ₁ side and the overhead power distribution line 2 via the lead wire 4 . and,
After a certain period of time, the coil of the switch is demagnetized to bring the contact S ₁ into the resistor R ₂ side, and the energy applied to the distribution line 2 via the discharge resistor R ₂ is discharged and consumed. In this way, a high voltage pulse is applied and discharged, and the output of the detector 6, which detects the current flowing at that time as a voltage value, is detected by the timer circuit 7a at a time _T1 after the high voltage pulse is applied. is output as an instantaneous value, and the display 8 displays the detection of a ground fault on the distribution line 2 and the extent of the fault. The next display is similarly displayed again as an instantaneous value by applying the next high voltage pulse.

To explain this in more detail, in the figure, Rg is the ground fault resistance at ground fault point 5, Cg is the line capacity from fault point 5 to terminal 9, and switch S ₁ is R ₁
The output current I ₁ from the high-voltage pulse energizing device 1 when the line is closed is divided into a current Ig ₁ flowing through the ground fault resistance Rg and a charging current Ic flowing through the line capacitance Cg at the fault point 5. In addition, past the ground fault point 5, the fault current Ig ₂ flows in the opposite direction to the charging current Ic, so this negative fault current -Ig ₂ and the charging current Ic
The sum of current I ₂ will flow. At this time, the current flowing through the detector 6 is, of course, the current _I1 .
Furthermore, when the switch S ₁ switches and closes on the resistor R ₂ side, the current I ₁₂ discharged from the capacitance Cg of the distribution line 2 is combined with the current Ig ₁₂ flowing through the ground fault Rg and the high voltage pulse charging device. 1, and the current I ₁₁ also flows through the detector 6 in the opposite direction to _the current I ₁ .

The earth fault display circuit outputs the current detected by the detector 6 after a time T1 by the timer circuit _7a , and directly inputs the output to the display 8 for display. When there is no ground fault on the distribution line, the output current will be as shown in Figure 3 a-1,
For the display to show zero, the timer circuit time T ₁
must be set to the time when the current is zero between the charging current on the positive side and the discharging current on the negative side. but,
The time constant in the line characteristics of the distribution line 2 is almost unknown, and the optimum T ₁ may not be known, and depending on the type of indicator 8 (for example, an ammeter), there may be a negative discharge after T ₁ in addition to the instantaneous current. Current may be displayed, which may result in incorrect display.

In addition, if there is a ground fault Rg on the distribution line,
The output current flowing to the detector 6 is as shown in Figure 3 b-1, and the timer circuit's time T ₁ is the peak value of the positive charging current and the negative discharging current. It is necessary to set the time when the fault current Ig, which is a small value between the peak values of , is flowing.
However, in this case as well, the error will be displayed for the same reason as when there is no ground fault.

As the line capacity of the power distribution line increases, the number of erroneous indications increases, and in some cases, there is a risk that the display may be mistaken for a ground fault.

In order to eliminate these drawbacks, this invention adds a self-holding circuit and a lock circuit to the display circuit, thereby eliminating false indications when there are no faults on the power distribution line and initial false indications at the time of a ground fault. The purpose of this invention is to provide a device that can reliably grasp the magnitude of a ground fault accident. The ground fault fault display device for power distribution lines according to the present invention calculates the current value generated by applying and discharging high voltage pulses to the power distribution line, and calculates the time for the current to converge using a time constant determined by the application time of the high voltage pulse and the line characteristics. Integration is performed by the integrating means for a certain period of time, and the integrated current value signal of the integrating means is stopped being fed to the display for the certain period of time, and after the feeding is stopped, the signal is displayed on the display for a certain period of time. is sent by the locking means, the signal value of the locking means at the time of the start of the signal feeding is held, and this is sent to the display by the holding means.

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 2, 6 is the charging and discharging current detector (for example, a resistor) of the distribution line, and 7 is the main capacitor C ₁
The accumulated energy of the electromagnetic switch is applied during the application of high voltage pulses generated by the opening/closing operation of contact _S1 of the electromagnetic switch for a certain period of time during which the current converges with a time constant determined by the line characteristics. An integrator that integrates the current value generated by discharge, 8 is a display (for example, an ammeter), 10 and 11 are amplifiers, R ₄ and C ₃ are resistors and capacitors for holding the display voltage, and R ₅ is a self-holding _D1 is a holding voltage blocking diode,
_S2 is a switch for locking for a certain period of time and holding the display for a long period of time (for example, 2 seconds).

In addition, Fig. 3 a shows the case where there is no ground fault, and Fig. 3 b
represent the waveforms and operating conditions of each part during a ground fault accident. In each figure, the line 1 is the waveform of the charging/discharging current flowing to the detector 6, and the line 2 is the integral of the charging/discharging current value. The line diagram 3 is a diagram of the operating state of the switch _S2 , and the diagram 4 is an output voltage waveform diagram of the amplifier 11.

In the above configuration, when there is no ground fault on the distribution line, the charging/discharging current flowing through the line is:
As shown in Figure 3 a-1, the polarities are opposite and the total sum is zero, and if we look at this in Figure 3 a-2, the output voltage of the integrator 7 shows that after a certain period of time (e.g. becomes zero at T ₍₁ second). Lock switch S ₂
is a current flowing through the distribution line for a certain period of time (for example, T ₁
2 seconds), clamping the input of amplifier 11 to zero voltage, and then locking switch S ₂
acts as an open circuit and serves to release the input of the amplifier 11 from zero voltage. Therefore, for a certain period of time (T ₁ second)
Even if the output of the subsequent integrator is input to the self-holding circuit, it is zero, so the display 8 does not display at all, and no erroneous display occurs.

Furthermore, if there is a ground fault in the distribution line, a current flows to the point of the ground fault, so the sum of charging and discharging currents in the distribution line has positive polarity due to the relationship I ₁ > I ₁₁ . The output voltage waveform when this is input to the integrator is shown in Fig. 3b-2.

If the output voltage of this integrator is input to a self-holding circuit and the switch _S2 is opened after a certain period of time (for example, T ₁ second) to self-hold, the voltage value corresponding to the ground fault condition will be held and is displayed on the display 8. Then, when the switch _S2 is closed after a long period of time (for example, after 2 seconds) and the input of the amplifier 11 is clamped to zero potential, the self-holding is also released and the display becomes zero. Therefore, the display 8
The display operation no longer ends in a momentary short period of time, and the possibility of erroneous display is also eliminated.

In the above embodiment, only one pulse of high voltage application was explained, but the same operation occurs when the application is repeated continuously.

Further, the contact _S1 of the switch may be either an air switch or a vacuum switch, and the lock switch _S2 may be a semiconductor switch (for example, a transistor) to obtain the same effect.

As described above, the present invention integrates the current value generated by applying and discharging a high voltage pulse for a certain period of time during which the current converges with a time constant determined by the application time of the high voltage pulse and the line characteristics. An integrating means, a locking means such as a locking switch that locks the display for a certain period of time from when a high voltage pulse is applied, low resistors R ₄ and R ₅ that hold the integrated output value immediately after the lock is released, and a capacitor C ₃ amplifier 10. 11
The power distribution lines are not only overhead lines, but also have many underground distribution lines and underground drop-in lines with a large line capacity, so it is possible to detect ground faults on distribution lines with a large total line capacity. Even in cases where a ground fault is detected, it is possible to reliably detect a ground fault without making a misjudgment due to erroneous display. In particular, the integral value of the integrating means is not affected by the distribution line and is proportional to the resistance value of the ground fault. By holding and displaying the integral value, the magnitude of the ground fault can be clearly recognized, and reliable and appropriate exploration can be carried out. In addition, the instructions change accordingly depending on the situation of the ground fault, and stable instructions over a long period of time enable reliable understanding of the ground fault.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing a conventional high-voltage pulse energizing device equipped with a ground fault fault display circuit and the flow of current when a high voltage pulse is applied to a distribution line, and Fig. 2 is a ground fault according to the present invention. FIGS. 3a and 3b are block diagrams showing one embodiment of the accident display circuit, and are timing diagrams showing voltage waveforms and operations of various parts of the circuit according to the present invention. In the figure, the same symbols indicate the same or corresponding parts, 6 is a detector, 7 is an integrator, 8 is a display,
S ₂ is a switch.

Claims (1)

[Claims] 1. By applying high voltage pulses to and discharging the distribution line, and detecting the resulting signals such as current, the presence or absence of a ground fault on the distribution line can be determined.
In a distribution line ground fault accident display device that displays the extent of the accident on the display, when the current value generated by the application and discharge of the high voltage pulse is determined by the application time of the high voltage pulse and the line characteristics. an integrating means that performs integration for a certain period of time during which the current converges with a constant, and an integral current value signal of the integrating means that stops feeding the integrated current value signal to the display for the certain period of time, and after the stop of the feeding is released, a predetermined value. It is characterized by comprising a locking means for sending the signal to the time display, and a holding means for holding the signal value of the locking means at the time when the signal transmission starts, and sending it to the display. A ground fault indicator for power distribution lines.