SU67658A1 - Device for protecting electrical installations from atmospheric overvoltages - Google Patents

Description

In order to ensure reliable isolation of high-voltage apparatuses from atmospheric overvoltages, it is necessary to have a sufficient interval between the volt-second characteristics of the insulation being protected and its protective discharge. Typically, the value of such an interval is limited by the need to prevent the operation of arresters with possible switching overvoltages in the system. Modern advanced dischargers (tirite and partly tubular) tend to be designed so that the discharge voltage at pulses is as close as possible to discharge voltage at an industrial frequency. For this purpose, special shapes of spark gap electrodes and special circuits with shunting of individual spark gaps with resistance are used. In this case, it is possible to achieve a favorable distribution of the voltage applied between the discharge between the gaps and obtain a very reasonable volt-second characteristic, but the discharge itself turns out to be expensive and complicated.

All existing discharges are characterized by the fact that in them the sum of the voltages at the individual spark gaps of the discharge is equal to the voltage applied to the whole discharge.

- The proposed spark gap is radially different from the known ones in that the sum of the stresses St // is greater than the voltage applied to the whole discharge voltage and is on individual spark gaps of the spark gap, and also depends on the speed

dUo increase voltage

dt dUo

In this case, the more

those dt

Sf / n

more and in the limit in the case of

and about

overvoltage square wave, 6 / "with two parallel branches x (in the diagram shown in the drawing), ilU ,, sibUo with three parallel branches x, etc.

This is achieved, according to the invention, by the fact that in the proposed gage two or more parallel circuits, consisting of each of the series-connected spark gap and capacitance, are driven to the line one — by capacitance.

and the other, by the spark gap, and the midpoints of these circuits are connected through the spark gap, shunted by resistance.

The drawing shows a diagram of the proposed device composed of two parallel branches, in each of which the spark gaps PI and 2 small capacitances C2 (or € -2) are connected in series with relatively large capacitances Ci Cr (or). The mutual arrangement of C / and Co in the second circuit relative to the phase and the earth back to the location of Ci and C-, in the first circuit.

The midpoints of both branches are interconnected by a spark gap RZ, shunted by equalizing resistance Z.

The values of Cj, C / and Z can be taken such that the losses from the surge current are not of practical importance.

The scheme is given for the case of a gadget with two parallel branches, but if desired, the number of parallel branches can be increased, which will give a corresponding improvement in the protective characteristics of the gaps.

With rapidly flowing atmospheric overvoltages, the surge current / does not have time to significantly equalize the voltages f /, and, i.,:

and, 0 and U ,,

(since the voltages are distributed across the capacitances Ci and Cf, with Cl Ca and the capacitance C / and, and moreover).

Spark gaps P, P PI appear to be turned on, as it were, in parallel to the total voltage Uoi / piSS 7p2 6p3S Uo.

With relatively slow mutation overvoltages and with a voltage of industrial frequency, the equalizing current // almost completely equalizes the voltage t / it / 2, and the voltage distribution occurs across the capacitances Ci - and C /, and the spark gaps PI, RE and RHs are turned on as if sequentially for the voltage Uo:

f / pl + p2 + t / p3S; / o.

In particular, with C / sC,

, 5Hw; f / pssO. Thus, the discharge gives a fundamental opportunity to bring the pulse coefficient:

a) with two parallel branches x to k, - 0.5;

b) three parallel branches x to / Cg 0.33, etc.

As the inventor points out, approximate calculations made have shown that for all voltage classes to get a gaiter of this type with a pulse coefficient at a full wave of 1.5 / 40as X; 0.7- .- 1.0.

This arrester provides reliable protection against atmospheric overvoltages of high-voltage devices and masks of 6-220 kV, including:

1) isolation protection of rotating machines b-10 kV, working on. air network;

2) protection of the isolation of equipment 35 and 110 kU without thyrites;

3) protection of equipment isolation of 154 kV and above without the use of tirit gaps and using tubular gaps of 110 kV and below.

At the same time, as the PI, PZ and PZ gaps, one can install tubular (thyrite) dischargers of the lower class of insulation or their combination with rod and ball spacing gaps, which will make it possible to quench with an accompanying current of industrial frequency. As capacitances Ci and C /, it is possible to install reinforcements of high-capacity insulators (for higher insulation classes) or special capacitors (for protection of rotating machines).

Thus, the proposed type of discharge:

1. Provides a reliable threat of isolation of all classes of voltages.

2. Allowing or completely refusing the use of expensive

Tyrites dischargers or significantly simplify and cheapen them (in case of protection of rotating machines).

3. Unload the electric industry from the manufacture of very labor-intensive and complex thyrite gaps.

- subject invention

Device for protection of electrical installations from atmospheric overvoltages, consisting of a system of spark gaps, capacitances and resistances and included

between the line and the ground, characterized in that two or more parallel circuits, consisting of each of the series-connected spark gap and capacitance, are adhered to the line by one eq, and the other is an spark gap, and the midpoints of these circuits are connected through a spark The resistance-shunt gap, so that the sum of the voltages on the spark gaps during overvoltage exceeds the magnitude of the applied voltage all the more, the greater the voltage rise rate.

 (Ci Ci C2- C24i: 3) 50ji