SU773810A1 - Device for short-circuiting protection of ac equipment - Google Patents

Description

one

The invention relates to electrical engineering and can be used to protect energy objects in high-voltage networks, as well as as a measuring body in the automatic network dividing network (AODS) during short circuits with currents exceeding the breaking capacity of installed switches.

According to the main author. St. No. 693501 10 a device for protection of an AC electrical installation against a short circuit is known, which contains a current sensor, the output of which is connected to the input of the first phase-turning element, the second phase-turning element, the outputs of which are connected to the comparator through the appropriate quadrants and the executive body, in which the input of the executive authority 20 and the output of the comparator is switched on to include the first input of the newly introduced logic element I, the second input of which is connected to the output of p & 25 consisting of two rectangular pulse formers and their outputs connected to an adder via a second absolute value formers, and the input of the square wave 30

respectively, are connected to the outputs of the current sensor and the first phase-turning element, and the input of the second phase-turning element, l, is connected to the output of the latter.

A disadvantage of the known device is the impossibility of taking into account the aperiodic component at the point of short closure, which can lead to some redundancy in its response.

The purpose of the invention is to improve the accuracy and expansion of functionality.

This goal is achieved by the fact that the device for protection of electrical installation of alternating current from short circuit is additionally equipped with a third and fourth adders, a second absolute value generator, a differentiator, a second and third comparators, an automatic setpoint adjustment unit, a pulse expander, NOT and AND elements, and a second when the executive body, with this input, the third adder is connected to the outputs of the current sensor and the second phase shifter / output of the third adder via the second generator spruce absolute values connected to one

From the inputs of the fourth adder directly and with another input through the differentiating authority, the output of the fourth adder is connected to the input of the third comparator, the output of which is connected through the serially connected pulse expander and the element NOT connected to the first input of the second element I, one of the inputs of the second comparator is connected to the output the second absolute value generator, another input is connected to the output of the first adder via the automatic setpoint adjustment unit, the output of the second comparator is connected to the second y input of the second AND gate, the third input of which is connected to the output of the first absolute value formers, and the output of AND gate is connected to the second operating body.

FIG. 1 shows a block diagram of the proposed device; in fig. 2 block diagram of the automatic adjustment of the setpoint of the second measuring unit.

The device contains a current sensor 1, the first 2 and second 3 phase-shifting elements, respectively, each of which performs the leading phase shift of the input signal by an angle close to 90, quadrants 4 and 5, the first adder b, the first comparator 7, the first element 8 And with two the inputs, the first actuator 9, the formers 10 and 11 of the rectangular pulses, the second adder 12, designed to form a different gender p-. pulses in the coincidence intervals of the corresponding polarities at its inputs, the first absolute value generator 13, the third adder 14 for extracting the aperiodic component of the short-circuit current, the second absolute value generator 15, the second comparator 16, the comparator setpoint automatic control unit 17,. differentiator 18, fourth adder 19, highlighting. voltage proportional to the difference between the set and the current value of the constant network time, the third comparator 20, designed to block the second comparator 16 at a constant network time below the set value, the expander 21 pulse to eliminate the premature reset of the blocking signal from the comparator 20, the HE element 22 , the second element And 23 and the second executive body 2

The automatic adjustment unit 17 contains a proportional ratio unit 25, designed as an amplifier with limited output voltage at a given level, a max detector 26 for selecting the largest input signal, the first sensor 27 of the threshold voltage, the second sensor 28 of the threshold voltage, and an output adder 29.

The device works in the following way.

If the periodic component of the short-circuit current exceeds the trigger setpoint of the comparator 7, the first actuator 9 is triggered at intervals when signals from the generator 13 to the second input of element 8 And signals are received that coincide in time with the unit signals from the comparator 7.

If in this mode the short-circuit current contains an aperiodic component, it is released at the output of the adder 14 and, after being straightened on the shaper 15, enters the input of the comparator 16, the setpoint of which is selected according to the condition that by the time the contacts of the switch do not diverge exceeded the allowable value determined by the ratios below.

The breaking capacity of high-voltage circuit breakers is provided when short-circuit conditions are met.

eleven

and)

but

t,

(2-)

  ) but

de 1 is the effective value of the periodic component of the short-circuit current;

 but the rated current of the circuit breaker (actual value); fb - y is the relative content of the aperiodic component in the short circuit current; 1- - the value of the aperiodic component in the short-circuit current at the time of the contact of the switch with the breaker nominal value

for a given switch. Installation in the operation of the device is chosen as the smaller of the two

 I 1.L C)

ep c.

but

i

K, 1b

Y (4)

but

where K.j 1.1 -1.2 safety factor. At the same time, if the time constant, the primary network is more than nominal, i.e., the calculated one (for a short-circuit with the maximum aperiodic component; condition (A) appears.

From the condition (2) we have

BUT

(five

Claims (1)

1. USSR author's certificate in application 2503928 / 24-07, n 02 H 3/38, 1978. , ЁЁН / 7 P