SU993375A1 - Device for single-phase protection in three-phase network with insulated neutral wire - Google Patents

Description

The device contains voltage relays 1–3 with closing contacts 4–9, respectively, current transformers 10–12, current relays 13–15, and disconnecting terminals 16–18, respectively, and a capacitor 19.. The single-phase protection device operates as follows. In the normal operation of a three-phase network 20, a relay 1–3 voltages are under the nominal phase voltage of the respective phases, and their normally open contacts are open. With a single-phase circuit, for example, phase A of a three-phase network 20, the voltage of phase A with respect to earth decreases and the relay 1 of the voltage of the damaged phase does not work, and the voltages of the other two phases B and C increase, causing the relay 2 and 3 to trip. wives The operation of the relay 2 and 3 voltage leads to the closure through the closing contacts 6 and 8 of the artificial (controlled) closure circuit. To the earth of the phase A. As a result, the short-circuit current is. distributed in two branches: the branches of the emergency short-circuit. and branches of controlled k.s. After elimination of the emergency circuit k. the entire short circuit current flows through the branch controlled by k.3 i, causing the current relay 15 to trip. The contact 18 is opened and the protection device automatically returns to its initial position (minimizing the current flow time of the n branch of the controlled short-circuit). The device is reliable in operation economically in operation and allows

CD

T y y

Claims (2)

V I Y To elevate electrical, fire, and explosion-proof in electrical installations with an insulated or compensated neutral. The invention The device for protection against single-phase closure in a three-phase network with insulated neutral, containing three voltage relays, the windings of which are connected to the corresponding phases of the protected network by one terminal, and the other terminals are connected to the initial position through the series-connected capacitor ground bus, serially connected closing contacts of two voltage relays connected between the corresponding phase of the protected network and the ground bus, differ luminant in that in order to provide automation devices return to the initial position, the element returns to its original position device configured as a series-connected normally closed contacts of three current relay whose winding is connected to the phase included in the network protected by the current transformer. Information sources,. taken into account during the examination 1.N. High-speed grounding of the damaged phase with insulated neutral. - Industrial-. on energy, 1977, No. 5, pp.37-38. 2. USSR author's certificate number 785804, cl. G 01 R 31/02, 1978.