RU2442238C2 - The noncontrollable gas-discharge arrestor - Google Patents

Abstract

FIELD: electrotechnical equipment.

SUBSTANCE: innovation is designated for the application to schemes for measuring parameters and the control of quality of the electrotechnical equipment and presupposes application of a noncontrollable gas-discharge arrestor as a protecting device for DC circuit installments having inductivity due to inductive current arising during the DC circuit break as a result of self inductance; after the arrestor discharge caused by the discharge voltage, the burning of the normal glow discharge is supported by the diminishing (due to the putout of the energy accumulated in the inductance) inductive current until the current is able to support the glow discharge; the glow gas discharge transforms into the dark discharge; the amperage and the voltage are diminishing to nil in proportion of the energy putout accumulated in the inductance.

EFFECT: enhancement of the efficiency of the equipment protection from the inductive current irrespective the polarity of the operation voltage and electromotance.

1 cl, 5 dwg

Description

The technical field to which the invention relates.

The invention relates to uncontrolled discharge arresters and can be used to protect equipment from induction current in direct current circuits, in particular in circuits for measuring parameters and quality control of electrical equipment.

The level of technology.

A simple and reliable device for protecting equipment from induction current in a direct current circuit is known - a semiconductor diode, which is turned on in the opposite direction and does not affect the operation of the circuit at high voltages, and when the DC circuit breaks, it turns on in the forward direction relative to the induction current and shunts the circuit.

This device cannot be used when the diode at low voltages on the reverse branch of the current-voltage characteristic has a low resistance in operating mode and shunts circuits with high resistance.

Another device is known - an uncontrolled gas discharge arrestor, designed for another purpose: to protect the circuits of direct and alternating current equipment, lines and communication equipment from pulsed electrical overloads on voltage (Electronic devices for protecting REA from electrical overloads: Reference / Cherepanov V.P., Khrulev A.K., Bludov I.P. - M.: Radio and communications, 1994; p.96-128). Its task is to limit the high-voltage voltage to a level corresponding to the breakdown voltage of the spark gap.

Its main drawback when used for its intended purpose is that, performing the main function, the spark gap simultaneously closes the current from the power source of the protected circuit. This current, having a value above a certain value, after the arrester performs its function, is able to hold it in the on state for an arbitrarily long time. In this case, for its intended purpose, the circuit is inoperative. The arrester can be brought out of this mode only by disconnecting the power source of the protected circuit.

In order to prevent a prolonged short circuit in the invention "US 2007/0223171 A1, Lafon Guy, Herve Lindeperg. Protector Device with Improved Capacity to Break Follow Current ”uses a non-inductive resistor. It limits the short-circuit current to a level at which the arrester immediately, after performing its function of protecting against an overvoltage pulse, independently returns to its original high-resistance state, that is, all subsequent processes are excluded.

Disclosure of the invention.

The objective of the invention is to protect the equipment in the DC circuit from induction current resulting from self-induction when the DC circuit breaks, both when the circuit is turned off by a circuit breaker and during an emergency circuit breakdown occurring on any part of the circuit: in wires, in soldered and bolted connections, and in the pressure contacts of the switching devices.

This is achieved by the fact that the previously known device is a gas-discharge uncontrollable spark gap, it is used for a new purpose.

Description of the drawings.

Figure 1. The use of a spark gap in the circuit for measuring the ohmic resistance by the direct current of the reactor winding.

I is a direct current source,

S - manual circuit breaker simulating an open circuit,

L is the winding of the reactor,

P - spark gap uncontrollable

A is an ammeter,

V is a voltmeter.

Figure 2. Oscillograms of voltage at the R-350 spark gap at operating current: 10 A (1), 5 A (2) and 1.5 A (3). Scale: 40 V / div. and 20 ms / div.

Figure 3. Oscillograms of the current through the R-350 spark gap at an operating current of 10 A (1), 5 A (2). Scale: 1.5 A / div. and 20 ms / div.

Figure 4. Oscillograms of voltage at the 4378D spark gap at an operating current of 2.7 A (1), 1.4 A (2). Scale: for (1) 50 V / div., 20 ms / div. and for (2) 50 V / div., 10 ms / div.

Figure 5. Oscillograms of the current through the 4378D spark gap at an operating current of 2.7 (1) and 1.4 A (2). Scale: for (1) 1 A / div. and 20 ms / div. and for (2) 0.5 A / div. and 10 ms / div.

The implementation of the invention.

Protection against induction current using an uncontrolled gas discharge spark gap has features.

1. An uncontrolled gas discharge arrestor has no limitation on the lowest operating voltage, in contrast to a diode discharge circuit. Before the breakdown, it has a high insulation resistance from “not less than 10 MΩ” to “not less than 5000 MΩ”, depending on the type of arresters. After the breakdown, its resistance is units of Ohms.

2. For well-known reasons, the supply voltage of the protected circuit should not exceed the breakdown voltage of the spark gap, and the amplitude value of the induction current should not exceed the maximum permissible current of the spark gap anode. These are the main conditions when choosing a spark gap to protect the circuit.

3. When the circuit is broken from a direct current source, in the circuit having inductance, due to the inductance property, to prevent any change in the magnitude of the current flowing through it, the induced induction current at the first moment is the largest and equal to the operating circuit current. He is safe for her and his restriction is not required. Moreover, current limitation, as in the case of overvoltage protection, is not possible for the induction current - at the first moment it saves the working current, regardless of the resistance of the circuit, and installing a resistor in series with the spark gap does not give the desired effect.

4. At the moment of circuit breaking at the point of breaking (with high resistance), the current retains its value and a voltage surge occurs, the amplitude of which is many times higher than the operating voltage in the circuit. Its limitation is required. This voltage is limited by the arrester at the level of the breakdown voltage of the arrester.

5. It includes a spark gap, that is, it performs the action necessary for a short circuit for the induction current, on which the operation of the device for protection against induction current is based, in contrast to the harmful effects of a short circuit for the power source of the circuit to be protected when protected against pulsed electrical overvoltage . The turn-on time is determined by the breakdown delay time.

6. The induction current itself maintains for itself the short-circuit mode of the arrester in time for as long as is required for the inductance discharge. If the process of spending the energy stored in the inductance were not completed, due to the short-term operation of the protective device, then repeated surges of voltage could occur, dangerous to the circuit.

7. The arrester immediately, after fulfilling its function of protecting the circuit from the induction current, independently returns to its original state with a high insulation resistance. The performance of the circuit is restored.

The device operates as follows. At the moment of breaking the DC circuit, having inductance, the current in it retains its value and at the place of the gap, which has a large resistance, voltage arises.

It is limited by the arrester, shunting the circuit, at a level corresponding to the breakdown voltage. At the same time, it performs the function for its intended purpose.

After the breakdown, the arrester works for a new purpose. The arrester goes into a state of normal glow discharge. It is supported by the induction current flowing through the arrester. As the energy stored in the inductance is consumed, when it is scattered by the ohmic resistance of the inductance itself, the current gradually decreases. Moreover, in the spark gap, at a constant current density, the cross-sectional area along which the current flows in the gas gradually decreases. At some point, it becomes so small that the steady burning of a normal glow discharge becomes impossible. In this mode, the voltage across the arrester remains almost constant and minimally necessary to maintain a normal glow discharge, that is, this is the voltage at which the electron acquires kinetic energy sufficient for a single impact ionization of the filler atom.

Next, the discharge in the gas goes into a dark (quiet) discharge. In this case, the gas ionization remains still excessive compared to the initial ionization (before the arrester is triggered) and the voltage drop is much less than the breakdown voltage of the arrester. Current and voltage drop to zero when the energy stored in the inductance is completely consumed. After that, the spark gap, without outside interference, returns to its original high-resistance state: restores its performance.

As an example of the use of a spark gap, we cite its operation in a circuit for measuring the ohmic resistance of direct current of the windings of power transformers and reactors according to the "ammeter-voltmeter" method with the protection of the voltmeter from induction current (Fig. 1).

A winding of the RZDPOM-760/10 type with an inductance of 0.40 G and an ohmic resistance of 0.2 Ohms is used. An open circuit is modeled by a manual circuit breaker. Changes in voltage and current over time are recorded by an oscilloscope. Oscillograms are shown in FIGS. 2-5.

The breakdown voltage of a P-350 discharger with argon filling is approximately 350 V, and that of a 4378D with neon filling is 90 V. The voltages on the dischargers in the short circuit mode for the induction current correspond to voltages at which the electron acquires kinetic energy sufficient for a single shock ionization of free unexcited neutral gas atom (for argon - 15.76 eV, for neon - 21.56 eV) (figure 2 and figure 4).

The discharge time of the induction current and its initial value depend on the operating current of the circuit. The initial current is slightly less than the operating current of the circuit, because during the breakdown of the spark gap during the delay of the breakdown, part of the energy stored in the inductance is consumed (Fig. 3 and Fig. 4).

In this circuit, in the absence of a spark gap, the current through the voltmeter at break of the current circuit could reach 10 A, and the voltage - 10 kV. When using a spark gap 4378D, the amplitude value of the voltage pulse does not exceed 90 V for a duration of 2 ms, determined by the breakdown delay time.

Modern arresters have a breakdown delay time of 0.15-1.3 μs, which allows to reduce voltage pulses in separate parts of DC circuits using frequency filters.

Claims (1)

The use of an uncontrolled gas discharge arrester designed to protect communication lines and circuits of direct and alternating current equipment from pulsed electrical overloads by voltage, as a device for protecting circuits of direct current equipment having inductance from induction current arising from self-induction when the DC circuit breaks.

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