SU883758A1 - Transient reguperating voltage determination method - Google Patents

Description

(54) METHOD FOR DETERMINING TRANSITIONAL RESTORING

VOLTAGE

I

The invention relates to the measurement of electrical quantities, in particular, to methods for measuring the parameters of a voltage that is restored when an electrical circuit is opened.

There is a known method for determining the transient recovery voltage in the network, in which a short-circuit is in effect in the operating network at the reference voltage, disconnect the short-circuit current by the switch and oscillograph the voltage at the breaker contacts.

The disadvantage of this method is the need for a short circuit device in an existing network. The closest in technical essence to the present invention is a method for determining a transient recovery voltage, in which a sinusoidal current of low amplitude is supplied to an electrical circuit under study from an external power source and oscillograph the voltage at the input of the circuit under study. However, the known method does not allow g The required measurement accuracy of the recovered voltage in the investigated electrical

high-capacity circuits due to its significant distortion of the current pulse shape.

The purpose of the invention is to improve the measurement accuracy of the transient regenerative voltage at the capacitance of the circuit under study.

ten

This goal is achieved by the fact that, according to the method of determining the transition voltage in the electrical circuits, by applying a current pulse to the circuit under study

15 and measuring the voltage at the input of the circuit under study provide an additional current pulse of opposite polarity by discharging the capacitance of the circuit under study, and the restoring voltage is measured after the additional current pulse has ceased, and an additional current pulse is supplied with an adjustable time delay for assigning it to the main pulse current.

Claims (2)

The second current pulse is determined only by the parameters of the circuit under study, its shape is not distorted, and the accuracy of measurement of the reducing 30 from the voltage is detected. The drawing schematically shows a device that implements the proposed method. The voltage source 1 circuit through the current limiting reactor 2 (or resistor) includes two series-connected valve elements 3 and 4 controlled from the control circuit 5. The valve elements 3 and 4 are included in such a way that the direction of current flow in them with respect to source 1 is consistent. Parallel to the controlled valve element 4, an input circuit 8 is switched on by means of the input terminals 6 and 7, which in this case represents the circuit of the restoring voltage of the synthetic circuit for testing the circuit breakers. The circuit under study consists of two branches connected in parallel with the input terminals 6 and 7, one of which is formed by a series-connected capacitor 9 and a reactor 10, and the other is a series-connected capacitor 1 and a resistor 12. A recording device, such as an oscilloscope, is turned on between terminals b and 7 Not shown in Fig. 3. Normally, the valve elements 3 and 4 are closed. To determine the transient, the restoring voltage of the electric circuit 8 provides the first current pulse in the valve element circuit 3 on the signal from the control circuit 5. As a result, the capacitors 9 and 11 of the circuit under investigation are drawn. After the voltage at the input of the circuit under study reaches a certain level and the current through it drops to zero, the valve element 3 turns off the circuit under study from the source. this or with a predetermined time delay from the control circuit 5, a trigger pulse is applied to the valve element 4, the latter is opened and the capacitor 9 is recharged through the reactor 10, as a result of which a half-wave sinusoid is formed in the circuit under study Current ceiling elements of opposite polarity, relative to the first current pulse. When the current passes through zero, the valve element 4 is closed and at the terminals 6 and 7 of the circuit 8 under study, a transient recovery process occurs, which is recorded by the oscillator graph. The adjustable time delay of the moment of switching on the valve element 4 allows for the necessary time to reliably lock the valve element 3. Instead of the valve element 4, any switching device or special switching circuits can be used to ensure the closing and opening of the circuit at certain points in time. The first current pulse, specified by the source of the GND 1H, is determined by the resistor 2, the block diagram and the parameters of the circuit 8 under study, and can differ significantly from the sinusoidal one. The second (additional) current pulse, which determines the transient recovery voltage, practically does not differ from the sinusoid, since it is formed by the discharge of the capacitance of the circuit under study through its irregularity, as a result, the accuracy of the measurement of the restoring voltage increases. The sinusoidal nature of the second current pulse is ensured regardless of the shape of the first current pulse, so the first pulse can be obtained by switching on the input circuit of the studied DC source (supra miter), which expands the capabilities of the proposed method. Using the control circuit 5, both pulses can be applied periodically, for example 50 times per second, in order to obtain on the oscilloscope screen a stable image of the self-regenerating voltage of the circuit under study. The use of an inductor based on the proposed method eliminates the need for experiments to measure the recovery voltages at high voltages, and provides the necessary accuracy of measurements with capacitive resistance of the circuit under study. Claim 1. The method of determining the transitional voltage in electrical circuits by applying a current pulse to the circuit under study and measuring the voltage on the input circuit, characterized in that, in order to improve the measurement accuracy with the capacitance of the circuit under study, provide an additional current pulse opposite polarity by discharging the capacitance of the circuit under study, and the restoring voltage is measured after the termination of the additional current pulse. 2. A method according to claim 1, characterized in that the additional current pulse is supplied with an adjustable time delay with respect to the main current pulse. Sources of information taken into account in the examination 1. M. Akodis. et al. Determination of the voltage recovery on switch contacts. Energy, 1968, p. sixteen. 2. In the same place 17 (prototype). oiWxTn