SU736251A1 - Device for earthing protection in ac mains with insulated neutral wire - Google Patents

Description

37

the primary winding of the main current transformer of the zero sequence connected to the power supply side, and the aforementioned capacitors are connected to the line phases at the junction of the primary windings of the main and additional current transformers of the zero sequence, and the winding i of the polarized relay is connected in parallel to the additional rectifier bridge zero sequence current transformer, and brake - opposite, to the rectification bridge of the main zero current transformer flaxity

A schematic diagram of the proposed device for protecting a line against earth faults is shown in the drawing.

The device for protection of the line against earth faults contains zero-sequence current transformers - primary 1 and additional 2, to the secondary windings of which, via rectifying bridges 3, 4 with capacitors 5, 6, are connected, respectively, brake 7 and operating 8 windings of the polarized relay 9, Transformers current 1.2 is installed on the line 11 connected to the power source. Their primary windings are connected in series. Moreover, the current transformer 1 is installed on the side of the power source 1O. Between each phase of the line 11 and the ground at the point (point) of the connection of the primary windings of current transformers 1, 2, capacitors 12 are turned on, which generate (generate) an artificial capacitive current when one of the mains phases to ground. The braking winding 7 of the relay 9 to the rectifying bridge 3 is connected in opposite direction. In normal mode, the polarized relay 9 is de-energized and its contacts are in the neutral position,

. When a ground fault on line 11 through the current transformers of the zero sequence 1 flows capacitive current due to the capacity of the other lines of the network, and through the current transformer 2, in addition - the current due to the capacitance of the capacitors 12. As a result, the working winding 8 generated by the capacitive additional current current transformer 2 exceeds the amperages generated by the capacitive current osHOBHOt o current transformer 1. As a result, the relay 9 is activated and closes its closing contact, acting or off to off 1 chat.

l line, or neither sirpalzapik about the occurrence of zak b kani.

When an external circuit is applied, for example: the substation busses through the current transformer 1 flows a capacitive current equal to the sum of two currents - generated by capacitors 12 and line 11, and through the transformer 1 - current generated only by line 11. The ampere-turn of the brake winding 7 becomes larger ampere-turns of the working winding 8, In this case, the polarized relay 9 either does not work at all, or it works, but in the opposite direction.

Similarly, the relay operates when closed to another parallel. connected to the bus line substation.

The use of an additional current transformer, zero sequence connected by the primary current in series to the main current transformer of the zero sequence, installed on the side of the power supply, and switching on capacitors between all phases of the protected line and ground at the connection point of the primary windings of the main and additional zero sequence current transformers: as the selectivity and reliability of the work of a simple current protection, and its sensitivity after Olka t- eliminates the need for construction of the current operation of the protection of their own capacitive current line. No complex, e.g. directional, protection is required. Reliable protection of lines is ensured based on simple circuits and elements serially supplied by industry, and the reliability of power supply to consumers is increased.

Claims (2)

Invention Formula A device for protecting the line from earth fault in an electrical network of an alternating current with an insulated neutral, containing capacitors by the number of phases, connected between the respective phases of the network and the ground, a zero-sequence current transformer and an executive relay, characterized in that, in order to increase the selectivity in operation on the line with its own capacitive current, commensurate in magnitude with the total capacitive current of the other lines, it is equipped with two rectifying bridges, in addition to 573 ° n ° ndness, and Auxiliary relay is polarized, with the primary winding of the additional zero-sequence current transformer connected in series with the primary winding of the main zero-sequence current transformer connected from the mains side, and the above-mentioned capacitors are connected to the line phases at the connection of the primary windings of the main and additional current transformers zero sequence, and the working winding of the polarized relay is connected in parallel 16 to the rectifier at the bridge of dopapnigepno posletsovatelnosti zero current transformer, and the brake - counter to the rectifier bridge core transformer zero sequence current. Sources of information taken into account in the examination 1. Mavritsyn AM p tsr. Protection against single-phase ground closure in quarries. M., Nedra, 1968, p. 50. 2. Tsapenko, EF. Control of iso- tion in networks up to 1OOO V., M. Energi, 1966, p. 117.