SU405085A1 - MEASUREMENT METHOD OF RESTORING - Google Patents

Description

one

The invention relates to the field of research of high-voltage switches and can be used in laboratories for testing high-voltage switches for switching capacity.

Despite their critical importance, methods for measuring the characteristics of restoring electrical strength (CDW) of switches due to methodological and technical difficulties have not yet found wide application, and there is no generally accepted method for measuring HEBs.

By a known method, an alternating current with a frequency of 50 Hz is passed through the circuit breaker under study and before the current passes through zero this voltage is applied to the switch from a high-resistance (ohm) high-voltage source (probe generator). Using an auxiliary switch, the AC circuit opens at the current zero and after the disappearance of the residual conductivity in the switch under study at its contacts shunted by a small capacitance (voltage divider, wire capacitance, etc.), the voltage increases exponentially until a spark breakdown occurs.

Breakdowns occur every time when the applied voltage reaches the value of the VEP switch. Thus, the VEP characteristic is described in the process of experimenting with the envelope of the sawtooth probe voltage pulses.

However, when this method is carried out, the test switch before probing the HEP is switched off by an auxiliary switch, which affects the shape of the current curve in the test loop in the zero-current region and introduces distortions

in measured value. Character made

distortion depends on the size of the disconnected

current, voltage of the current source and arc-suppressing properties of the auxiliary switch.

In addition, it is impossible to measure VEP

in the presence of significant residual conductivity of the switch being investigated due to a large voltage drop on the high-resistance internal resistance of the probe generator.

The method does not allow residual current to flow, which limits its use only to air circuit breakers that do not have this current. It is designed only for the use of a small shunt capacitance.

The switch under study, otherwise large energy emitted during the breakdown of the chalk of the contact gap, can greatly distort the measured VAL.

To reduce the distortion of processes in

test switch in zero area

the current acting on the VEP characteristic should be excluded from the influence of the auxiliary switch, and the measurement of the VEP should be started immediately after the expected termination of the residual current flow.

For this, but the proposed method uses a fast-saturated choke in the AC circuit, which, together with the switch being tested, is short-circuited after the residual current disappears.

VEP switch sounding is produced by short high-voltage impulses, for which the unsaturated choke separating the switch from the short-circuited area represents a large resistance.

The drawing shows a scheme for measuring HEP switches according to the proposed method.

The order of measurement of VEP is as follows.

The switching device 1 closes the circuit of the current circuit consisting of the generator 2, the current-limiting reactor 3, the throttle 4 of the saturation of the studied switch 5, the peak transformer 6.

When the current passes through zero, the peak-transformer supplies a voltage pulse to the switching-on unit 7, which, with a delay determined by taking into account the time of the residual current flow, turns on a high-speed short circuiter 8 and a generator 9 of probe pulses.

When the current loop is short-circuited with a short circuit, the saturation throttle is de-energized and the switch under study is disconnected from the shorting circuit and the C / 10 circuit with a high inductance of unsaturated droplets.

After turning on the generator with low internal resistance, a spark gap 11 is punched, and a series of short voltage pulses are applied to the circuit breaker under test, each of which causes the breaker to break down in the process of restoring the strength of the hot gap, fixed by oscillographic circuit 12.

Subject matter

The method of measuring the restorative electric strength of a high-voltage switch, with which a current is passed through the switch under study from an alternating current source and after passing this current through a zero to the switch being investigated, a series of short high voltage pulses is given, in order to approximate conditions to real areas of current zero, a saturable choke are included in the current circuit, which, together with the switch being tested, is shunted after the residual current disappears.