SU743111A1 - Method of selective disconnection of ac mains - Google Patents

Description

This goal is achieved by the fact that when implementing the method of selective disconnecting the AC network, which consists in disconnecting a short circuit in any area, of the network, by turning on a fast-acting head short circuit, disabling the current of the feeder switch and then automatically restarting the automatic recloser by disabling the short circuit, The mentioned switching on of the short-cutter is made for the time sufficient to activate the protection of the damaged feeder, in the event of an unsuccessful PV tklyuchayut shorting and include it by the time equal degree of selectivity, the switching cycles and interrupting short-circuiting is repeated a number of times equal to the number of stages of selectivity.

FIG. 1 shows a diagram of the device that implements the method; figure 2 shows a timing diagram of the current flowing through the short circuit. The power supply system contains transformer 1, conductor 2. Between transformer 1 and conductor 2, a thyristor short circuit 3 is turned on, containing two groups of bipolarly connected thyristors and current-limiting resistors. They are connected to the conductor through switches 4 and 5 of a motorized substation. For example, two substations are shown containing switches 6-11 and motors 12-17. The proposed method is applicable to any number of substations.

As can be seen from FIG. 1, there are no reactors in the power supply system. In this case, the switching capacity of the switches in the power supply system is less than the short-circuit power, for example, at points K and K ,.

In the normal operation of the power supply system, the thyristor short circuiter 3 is disconnected and the electric power supply of the electric motors 12-17 is provided.

When an accident occurs, for example, a short circuit at the point K ;, the thyristor short circuiter 3 is triggered at the first wave of the short circuit current. In the first interval 1, the thyristor short-circuiter remains on for two periods of alternating current, diverting the shock wave of the short-circuit current from the switch b. On this operating interval, the shorting time of its on state can be regulated, but as a rule, in networks b, 10 kV of alternating current, two periods of alternating current are practically sufficient to attenuate the aperiodic component of short-circuit short-circuit current.

After that, the short-circuit breaker 3 is disconnected - the second interval of operation. This interval is necessary for reliable operation of the relay protection devices of the switch 6. In the power supply system there can be situations when the electric motors 13-17 fully or partially are turned off. In case the feed currents are insufficient or absent, the relay protection of the switch b may not work, since the thyristor shorting switch 3 transfers the short-circuit current. in your circuit, including almost instantly. In this case, the damaged feeder with switch b may not be disconnected.

In the presence of the second interval of operation, the protection of the feeder with switch b acts reliably, namely: in the absence of a make-up current, from the network current, in the presence of a make-up current, from the sum of the mains and make-up current.

Then, to ensure selectivity, the thyristor short circuit is switched on again - the third interval of operation. In this case, the current is switched by the switch b. Due to the current diversion to the short-circuit breaker, the switch 6 switches only the make-up current. Really to the contour A part of the power from the network can also be supplied, which is determined by the value of the resistances included in the short-circuit 3 circuit.

In the event of termination, the cycle of the selective shutdown system ends with the disconnection of the switch 6 and the short-circuit switch 3.

In case k.z. the shortcut is not eliminated to remain off and is turned on after a time t D t - t off,

where dt is the degree of selectivity;

off time off. tel.

In the case under consideration, this interval of operation takes place, for example, at KZ, at point K and leads to switching of switch 4, which has a selectivity level. In this case, the switch 4. also switches the reduced power of the short circuit.

With the & in the power supply system of additional selectivity levels, such a cycle is repeated a number of times equal to the selectivity level.

Claims (3)

This method of selective disconnection in the AC network is very simple and provides a selective disconnection of the switch in the power supply system. In addition, each of the switching devices switches limited power, which significantly increases the reliability of the power supply system. The reliability of the method of selective disconnection in the case of a motor and mixed load is significantly higher compared with the prototype, since after the elimination of a short circuit. the power supply system is under full voltage, which ensures the restoration of the normal operation of the power supply system elements. A method for selectively disconnecting an AC mains power, consisting in disconnecting a short circuit at any part of the network, by turning on a quick-acting head short-circuit switch, disconnecting the current of the damaged feeder switch and then automatically restarting it (AR) by turning off the short circuit breaker, characterized by In order to improve the reliability of the power supply to consumers, the mentioned switching on of the short coil is made for a time sufficient to allow A short-circuit current wave, then disconnect the short circuit breaker for a time sufficient to activate the protection of the damaged feeder, re-enable the short circuit breaker at the switching time of the damaged feeder switch, if unsuccessful, disable the short circuit breaker and turn it on after a time equal to the selectivity stage, and the on / off cycle the short circuit is repeated a number of times equal to the number of selectivity steps. Sources of information taken into account in the examination 1.N. Chernobrov Relay protection. Energie, M., 1974. 2. USSR author's certificate number 504274, cl. H 02 H 7/26, 1974. 3.- USSR Author's Certificate No. 2574655 / 24-07, cl. H 02 J 3/00, 1978.