SU1504715A1 - Method and apparatus for protecting three-phase consumer from asymmetrical modes - Google Patents

Abstract

The invention relates to electrical engineering and is intended for use in relay protection and automation systems. The purpose of the invention is to expand the functionality and increase reliability, increase the accuracy of protection operation. At the outputs of current sensors 1 included in the supply lines of the consumer phases, voltage pulses are generated with durations equal to the duration of dead time in the consumer phases. These pulses through full-wave rectifiers 5 are fed to the inputs of the element OR 2, from the output of which the voltage through the key element 3 is fed to the input of control unit 4, analyzing the duration of each pulse and pause at the output of the element OR 2. If any of these durations are exceeded, values form a consumer disconnect signal. The control of pulse durations and pauses of the pulse sequence at the output of the element OR 2 in the control unit 4 is carried out by a chain of serially connected frequency doubling unit 6, a pulse period to voltage converter 7 and threshold element 8, from the output of which the voltage enters the actuator. 4 il.

Description

my consumer phase. Block 4 of the counter-45 voltage U, formed on the voltage in the form of series-connected unit of frequency doubling 6, the transducer 7 of the pulse period to voltage and the threshold element 8,

during the course of the element OR 2. A double pulse of double frequency from the output of the frequency doubling unit 6 is fed to the converter pulse input converter 7 7

wherein the input of the frequency doubling unit 6, JQ is in voltage. At the output of converter 7, a series of voltage pulses U. is formed. At the moment a short pulse arrives at the input of converter 7, the voltage at the output of this converter is almost instantly reset to zero, after which the next voltage rise process U at the output of this converter Etc

serves as an input, and the output of the threshold element 8 - at the output of the control unit 4. The current sensor 1 is connected to counter-parallel-connected thyristors 9 connected to the consumer's 5-phase power line, while the primary winding of the transformer 10 is turned on parallel to the thyristors, the secondary winding of which serves as the output of the element 2 OR 2. Two short pulses the frequencies from the output of the doubling frequency block 6 are fed to the input of the converter 7 of the pulse period

in tension. At the output of the converter 7, a series of sawtooth pulses of voltage U. is formed. At the moment a short pulse arrives at the input of the converter 7, the voltage: at the output of this converter is practical. is instantly reset to zero, after which the next voltage rise process U- begins, at the output of this converter.

In the normal mode of power supply, the consumer pulse sequence at the output of the OR 2 element is complete, and the durations of the pulses and pauses in this sequence are equal to each other. Therefore, the voltage at the output of the converter 7, which enters the input of the threshold element 8, does not have time to increase to voltage, the setpoints of the comparator 31 operation. At the output of the comparator 31, a voltage level indicating the normal power supply of the consumer is formed.

If at time t the breakdown of thyristor 9 in phase A (phY3) occurred, there is no current-free pause in the graph of current 1 of phase A of the consumer in the corresponding time interval. As a result, the sequence of voltage pulses U, for-. The output element OR 2 is produced by a pulse, the pause between two adjacent pulses of this sequence increases, which leads to the formation of a frequency doubling sequence 6 of voltage pulse U with an increased pause time between two adjacent pulses. At the output of the converter 7, the voltage exceeds the voltage of the setpoint for the operation of the comparator 3 1, the latter triggers, and a voltage pulse C / is generated at the output of the control unit 4, indicating an abnormal power supply of the user. The voltage Ug from the output of the block 4 is fed to the input of the executive body, which makes a protective disconnection of the consumer

In the event of a crash at time tg. the control electrode of the thyristor 9 of phase A or another accident resulting in the loss of the half-wave of the consumer supplying the current phase (Fig. A), the duration of the current-free pause in this phase of the consumer is equal to the half-period of the network. In the pulse sequence of the voltage I1, formed at the output of the element OR 2, impulses appear, whose durations are equal to the half-period of the network, and in the sequence of voltage pulses U appear the intervals between the pulses, also equal to the half-period of the network. As a result, the voltage and, at the output of the converter 7, exceeds the voltage of the setpoint

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the comparator 31 srabatshan, the last one srabatshat and gives impulse to the executive body, carrying out a protective shutdown of the consumer,

Claims (2)

The operation of the device in case of malfunctions in other phases of the consumer is similar to that described. Invention Formula 1. A method of protecting a three-phase consumer from asymmetrical power supply modes, which consists in forming pulses with durations equal to the time intervals of zero values of the consumer's power supply phases, the logical summation of the pulses of all phases and the time control of the resulting pulse sequence, characterized in that in order to extend the functionality and improve the reliability of operation, they control the duration of each pulse and pause of the specified sequence and, if necessary, Juba are formed a predetermined value, a trip signal wearer. 2. Device for protection of a three-phase consumer from asymmetrical modes, containing in number of phases current sensors with input terminals for switching on each sensor in the power supply of the corresponding consumer phase, a three-input OR element, a key element and a control unit, and the output of the OR element is connected to the input the key element, the output of which is connected to the input of the control unit, the outflow of which serves to connect to the input of the executive body, is, in particular, in order to increase the accuracy of protection operation in the device The operation introduced by the number of phases single-phase full-wave rectifiers, AC inputs connected to the output of the corresponding current sensor, and DC outputs - to the corresponding input of the OR element, each sensor made in the form of an inverter driver, the voltage at the output of which is zero in the presence of current in the controlled phase of the consumer, and the control unit is made in the form of a series-connected frequency doubling unit, a pulse period-to-voltage converter and a threshold element, moreover stroke frequency doubling unit is input, and an output of threshold element - output control unit.