SU815827A1 - Device for protective disconnection of electric equipment in electric network withinsulated neutral wire - Google Patents

Description

(54) DEVICE FOR SAFETY SHUTDOWN

ELECTRICAL INSTALLATIONS IN ELECTRIC NETWORK

ISOLATED NEUTRAL

zero-sequence power, a load current transformer 5, a signal generation unit 6 according to the rate of change of the load current, a prohibition block 7, an actuator (relay element) 8 acting on the switching device 9 of the consumer 10.

The device works as follows.

In the normal state, the contacts of the switching equipment 9 are closed, the executive body 8 is de-energized. When a person touches one of the phases in the protection zone, output 2 of the block 2 generates a signal that passes the inhibitor block 7 and triggers the actuator 8. The latter acts on the switching device and disconnects the consumer 10 from the network.

In the event of a short circuit outside the zone at the output of block 4, a signal arrives at the inhibitory input of block 7. As a result, the signal from block 2 to the executive body 8 does not pass, i.e. the device does not respond to external short circuits.

When the device is turned on, a jump in the natural leakage current occurs, which causes a false disconnect of the consumer. Since this jump is accompanied by a jump in the load current, block 6 at the moment of switching on generates a signal at the prohibiting input of block 7 of the prohibition and false disconnection does not occur.

Thus, the proposed device allows to ensure the selectivity of operation of protective disconnect devices in three-phase networks with insulated neutral, and ultimately, increase the reliability of the power supply of the protected consumer.

Claims (2)

Invention Formula Safety shutdown device electrical installations in the electrical network with isolated neutral containing a zero-sequence current transformer with a signal-shaping unit connected to it according to the rate of change of leakage current, a load current transformer with a signal-shaping unit connected to it according to the rate of change of current Q load, prohibit unit, to the first prohibitory input of which the output of said signal shaping unit is connected by the rate of change of load current, and the enabling input is the output of said signal shaping unit by rate of leakage current change, the actuator whose input is connected to the output of the aforementioned prohibition unit, and the switching device in the circuit of the protected electrical installation, the input of which is connected to the output of the said executive body, characterized in that, in order to increase the reliability of its operation, the voltage transformer of the zero sequence and the signal shaping unit are inversely introduced into it 5 to the zero-sequence power symbol, two inputs of which are connected respectively, one to the said zero-sequence current transformer, the second to the newly introduced voltage transformer zero-sequence, and the output of which is connected to the second prohibitory input of the prohibition unit. Sources of information taken into account in the examination 5 1. USSR author's certificate number 476633, cl. H 02 H 5/12, 1972. 2. USSR author's certificate number 465690, cl. H 02 H 3/14, 1973.