SU564678A1 - Device for limiting commutation overvoltage - Google Patents

Description

This invention relates to switching devices, namely, devices for limiting overvoltages based on vacuum arcing chambers in exhaust networks with both insulated and grounded neutral.

Devices for limiting overvoltages used in power supply schemes of industrial enterprises are known.

The closest to the technical essence of the invention is a device for limiting switching voltages, equipped with a discharge circuit of series-connected discharge resistance and a vacuum switch with an electro-magnetic drive connected to an AC power line 2 However, this device has limited use and is completely unapplicable MO in networks with insulated neutral at low ground fault currents (no more than AOA), so as to make sure that electrodes operate Sands drive

the value of the shock current must be much larger and reach several kiloamperes.

In addition to Torq, when cutting off small capacitive currents of a ground fault in a vacuum arcing chamber, current slices can occur (current drain in a vacuum switch to its natural passage through zero). These current slices lead to switching overvoltages, which affect the insulation of the electro-. equipment. Thus, this device in networks with an insulated neutral can self-serve as a source of switching

Puff overvoltages,

The purpose of the proposed invention is to improve the reliability of the device in networks with insulated neutral.

To this end, in the device for limiting switching voltages, the vacuum switch is equipped with normally open contacts, and an air trajectory is additionally introduced into the device

Claims (1)

a power cable installed on the Eloktroyedach line, a peak transformer installed in a discharge circuit, and a power source with capacitors, the air current transformer being connected to the turn-on coil of the electro-dynamic drive through the switch-on control unit, the peak-transformer through the switch-off control unit and the delay element connected to the disconnecting coil, and the power source connected in parallel to the capacitors and electrodynamic control coils. FIG. 1 shows a block diagram of the proposed device; in fig. 2 - schematic diagram. The device comprises a protected line 1 to which a series of discharge circuits is connected, consisting of a vacuum switch 2 and a discharge resistance 3 designed to dissipate energy, and a peak transformer 4 for generating voltage pulses when a ground fault current flows into the discharge circuits through zero. A known electrodynamic driven vacuum switch can be used as a vacuum switch. The vacuum switch is provided with normally open contacts for com tation and discharge current to the ground, one terminal of which is movable and is controlled by the electrodynamic drive coils 5 and incorporation disconnecting 6. On the movable contact is rigidly fixed disk 7 of non-ferromagnetic material. The electrodynamic drive enable coil 5 is connected to a control unit including an energy storage capacitor 8 with a thyristor 9, the control electrode of which is connected via a bridge circuit 10 to an air voltage transformer 11 which is connected to the protected line 1. The disconnect coil 6 is connected to another control unit, commanded from energy storage capacitor 12 with thyristor 13 for closing the capacitor discharge circuit to the disconnecting coil. The control electrode of the thyristor 13 through the bridge circuit 14 and the delay circuit 15, consisting of a potentiometer 16 and an electrolytic coi capacitor 17. A dinene with a peak - transformer 4, which is connected to the discharge circuit of the protected line i The electrodynamic coils are powered by water from the rectifier 18. The device works as follows When an overvoltage wave occurs in the protected line 1, the air transformer 11 produces a signal proportional to the level and rate of change of the voltage in the protected line, which through the bridge circuit 10 acts on the control electrode of the thyristor 9, which opens, and the precharged accumulator capacitor 8 is discharged through the coil voice coil motor 5 incorporating vacuum switch. Under the action of electrodynamic forces, the disk 7, which is rigidly connected to the moving contact, instantly starts moving and closes the normally open contacts of the switch 2, this leads to the closure of the protected line 1 to the ground through the resistance 3 and the vacuum switch. When the ground fault current is first transmitted through zero peak-j, the transformer 4 generates a voltage pulse, which through the mortar circuit 14 and the delay unit 15 acts on the thyristor 13. The thyristor 13 opens and the storage capacitor 12 is discharged through the disconnect winding 6. Under the influence of By means of electrodynamic forces, disk 7 opens the contacts of the vacuum switch. The opening occurs at the moment the discharge current passes through zero. The device tripping time is set by passing through the potentiometer 16, while the minimum overvoltage at which the device reacts is set by the potentiometer I9i. The gap between the moving and fixed contact of the vacuum switch 2 is set so that when the device control circuits fail the breakdown strength of the insulation of electrical equipment was higher than the breakdown strength of the vacuum gap. Claims An apparatus for limiting switching. rewired, containing an output circuit of successively connected discharge resistance and a vacuum switch with an electrodynamic drive connected to an AC power transmission line, characterized in that, in order to increase the reliability of operation in networks with isolated neutral, a vacuum switch equipped with normally-open contacts, and an air transformer TSSH installed on the power line, a peak transformer installed in the discharge enu, and a power source to the capacitors, wherein the air current through the transformer blszh yn.