JPS6023919Y2 - Lightning arrester discharge counting device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a discharge counting device for a lightning arrester installed on the line side of a gas-insulated switchgear in a substation.

Conventionally, in order to protect line side equipment of high voltage substations such as 275 kV or 500 kV from overvoltage such as lightning impulses, an air rod gap has been installed between the high voltage side terminal of a circuit breaker and the ground.

However, as SF6 gas insulated equipment has come to be used as switchgear in substations in recent years, SF6 gas insulated equipment has become more effective against steep waves that occur when lightning strikes several times from a substation.
6 Gas has a flat discharge V- characteristic compared to air, so in normally designed gas insulated equipment, the breakdown voltage value will be lower than the discharge voltage value of the air gap, so protection is required. does not fulfill its role.

Therefore, as an alternative to the air rod gap, a method has been adopted in which the protective gap is installed in SF6 gas to improve insulation coordination, similar to gas insulated equipment. .

This gas gap lightning arrester is different from the air rod gap type arrester because it is a sealed type, so it cannot be maintained visually.

Therefore, in the case of lightning impulses, it is important as a maintenance management criterion to count the number of short-circuit currents (arcs) following a lightning impulse.

In addition, discharge counters have been used to count the discharge of lightning arresters using air rod gaps, but
In this lightning arrester, the follow-on current from the system that flows after the snow impulse becomes a pulse due to the current limiting effect of the lightning arrester itself, so what is required of the discharge counting device is the ability to count pulses.

On the other hand, in a gas gap lightning arrester, when operated while the grid is energized, a short circuit current following a lightning impulse flows for several cycles.

For this reason, a discharge counting device for a lightning arrester using a gas gap is required to have the ability to count the conduction of commercial frequency short-circuit currents in addition to the pulse counting ability.

The present invention has been made in consideration of this point, and an object of the present invention is to provide a discharge counting device for a lightning arrester that counts discharges due to lightning impulses and energization of short circuit currents.

An embodiment of a discharge counting device for a lightning arrester according to the present invention will be described below with reference to the drawings.

In the figure, numeral 2 indicates the discharge counting device of this embodiment.

1 is a lightning arrester using a gas cap, 1a is a grounding terminal, and 1b is a grounding conductor that electrically connects the grounding terminal 1a and the earth.

3 is a main current transformer that passes through the ground conductor 1b as a primary side.

4 is a counter capable of counting the discharge due to electric impulses, and is connected between both ends of the first capacitor 5.

Further, a metal varistor 6 for overvoltage protection is connected between both ends of the first capacitor 5.

Further, one end of the first capacitor 5 is connected to the cathode of the current generator 7, and its anode is connected to one end of the secondary side of the main current transformer 3.

The other end of the first capacitor 5 is connected to the other end of the secondary side of the main current transformer 3.

One end of a second capacitor 8 is connected to the anode of the current generator 7, and the other end of the first capacitor 8 is connected to the other end of the first capacitor 5.

Further, a beam axle 9 is connected between both ends of the second capacitor.

Reference numeral 10 denotes an auxiliary current transformer that passes through the conductor that connects one end of the second capacitor 8 and the reactor 9 as a primary side. A current relay 11 is connected.

12 is a metal varistor connected between both ends of the secondary side of the main current transformer 3, which functions as overvoltage protection for the device 2.

Here, the first and second capacitors 5 and 8 and the reactor 9
The impedance relationship is set such that the impedances of the first and second capacitors 5 and 8 are sufficiently low against lightning impulses, and the impedance of the axle 9 is sufficiently low against commercial frequencies.

Next, the operation of the discharge counting device of this embodiment configured as described above will be explained.

The rectifier 7 is connected to the polarity shown, and now the lightning arrester 1
Suppose that a positive impulse current flows through.

The secondary current of the main current transformer 3 flows through Ica to the first capacitor 5 through the current generator 7, and (2) flows to the second capacitor 8.

b, and are divided into first and second capacitors 5 and 8, respectively.
to charge.

In this case, since the above-mentioned impact current is shunted into Ica and Icb, when the above-mentioned impact current is particularly large, the current burden on the rectifier 7 and the first capacitor 5 is reduced, and those with small capacity and withstand capacity can be used. It's advantageous.

The electric charge charged in the first capacitor 5 is transferred to the main current transformer 3 and the reactor 9 by the reverse biased rectifier 7.
Since it is not discharged to the counter 4 but is discharged only to the counter 4, it is possible to count the positive impulse current.

Note that the electric charge charged in the second capacitor 8 is gradually discharged through the accelerator 9.

Also, when a negative impulse current flows, the rectifier 7 is reverse biased, so the indicated current is ■.

The secondary current of the main current transformer 3 is entirely the current I flowing to the second capacitor 8.

b, and charges the second capacitor 8.

And when the shock current is gone, the second capacitor 8
The charge attempts to discharge into the reactor 9 under oscillatory conditions, but after half a period determined by the second capacitor 8 and the reactor 9, the voltage reverses, so the rectifier 7 conducts and the current
- flows and charges the first capacitor 5.

Therefore, negative impulse currents can also be counted.

At this time, if the first and second capacitors 5.8 are made to have the same capacity, the positive and negative shock currents can be counted with the same value.

Further, at the time of such an impact current discharge, the current flowing through the reactor 9 is small, so the overcurrent relay 11 does not work.

On the other hand, when a short-circuit current flows in the grid following the shock current, a large current flows through the handle 9, so the auxiliary current transformer 1
The overcurrent relay 11 is operated by the secondary current of 0, and the conduction of short circuit current can be detected.

Incidentally, when discharging the impact current, the first and second capacitors 5,
There is a risk of charging too much voltage to 8, but this can be protected by a metal varistor 6.12.

As described above, the discharge counting device for a lightning arrester according to the present invention includes a main current transformer whose primary side is a ground conductor that electrically connects the ground side terminal of the lightning arrester to the earth, and this main current transformer. 2
A circuit in which a rectifier and a first capacitor are connected in series between both ends of the circuit, a second capacitor connected between both ends of this circuit, and an accelerator connected between both ends of this second capacitor. and an auxiliary current transformer whose primary side is a conductor connected between one end of each of the reactor and the second capacitor, and the discharge due to a lightning impulse connected between both ends of the first capacitor is counted. It consists of a counter and an overcurrent relay connected between both ends of the secondary side of the auxiliary current transformer, and when a positive impulse current flows through the ground conductor, the secondary side of the main current transformer A current is charged to the first capacitor through the rectifier, and the charged charge is counted by the counter, so that the positive impulse current can be counted.In addition, a negative impulse current flows through the ground conductor. If
The secondary current of the main current transformer is charged to the second capacitor, the charged electric charge is charged to the first capacitor via the rectifier, and the first capacitor is charged. The charge is counted by the counter to enable counting of the negative impact current, and further, when a short circuit current flows through the ground conductor, the secondary current of the main current transformer is energized to the reactor, The secondary current of the auxiliary current transformer operates the overcurrent relay to detect the short circuit current, and since the positive impact current is divided into two systems, the positive impact current When the impact current is particularly large, the current burden on the rectifier and the first capacitor is reduced, and it is advantageous to use one with a small capacity and withstand capacity.

[Brief explanation of the drawing]

The drawing is a circuit diagram showing a discharge counting device for a lightning arrester according to an embodiment of the present invention. 1... Lightning arrester, 3, 10... Main and auxiliary current transformer, 4... Counter, 5, 8...
- First and second capacitors, 6, 12...metal varistor, 7...rectifier, 9...reactor, 11...overcurrent relay.

Claims (1)

[Scope of utility model registration request] A main current transformer whose primary side is a ground conductor electrically connected to the ground side terminal of the lightning arrester and the earth, and a rectifier and a first capacitor connected between both terminals of the secondary side of this main current transformer. is connected in series, and a second circuit is connected between both ends of this circuit.
a capacitor, an auxiliary current transformer whose primary side is a conductor connected between both ends of the second capacitor or an accelerator, a conductor connected between one end of each of the reactor and the second capacitor, A discharge counting device for a lightning arrester comprising a counter connected between both ends of the capacitor No. 1 and an overcurrent relay connected between both ends of the secondary side of the above-mentioned auxiliary current transformer. .