SU983870A1 - Device for protecting from single-phase earthing in network with insulated neutral - Google Patents

Description

one

The invention relates to the distribution of electrical energy, namely, devices are protected against single-phase earth faults in a network with an insulated neutral.

There are known devices for 2 protection against earth faults in networks with insulated neutral, whose work is based on monitoring capacitive currents of network connections and introducing into the mouth, Q devices are different): additional elements blocking the protection operation during external short circuits to ground l.

However, the known devices have insufficient selectivity — in networks with a J5 low earth fault current and with a connection with its own capacitive current, comparable in magnitude to the total earth fault current of the network.

The closest to the proposed technical entity is a protection device containing a zero-sequence voltage transformer, in terms of the number of connections to a trap {zero-current circuit with additional primary coils and connected in series and connected to a voltage transformer via a phase-shifting circuit zero sequence, trigger unit, rectifiers & cells, indicator of greatest parallel action, coincidence, and performer s organs.

In this device, the current account of the additional primary windings achieved an increase in the transducer sensitivity of the current of zero mS sequence 2.

However, the bias current in the weighing device is not adjustable and remains unchanged with possible variations in capacitance of both individual connections and the entire network, which complicates the selectivity of the protection. The aim of the invention is to increase the selectivity of the protection. The goal is achieved by the fact that the device containing, at each connection, zero-sequence current transformers, connected to the corresponding executive bodies and provided in additional primary windings, which are connected via a photoelectric element with a zero-sequence voltage transformer, is equipped with additional phase-shifting devices according to the number of connections elements, additional zero sequence current transformers, rectifiers and current regulators, And this is the output of additional current transformers of the zero-sequence through rectifiers connected to the controllers: to the 1 inputs of the corresponding current regulators, whose inputs are connected to the output of the phase-shifting elements, and the outputs to the additional primary winding of the corresponding zero-sequence current transformers. The drawing shows a diagram of the proposed device. A device for protection against single-phase short circuits in an insulated neutral network consisting of several connections 1, nx) connected to the busbar 2 of the substation contains, for each connection, the first transformer 3 of the zero-sequence current with an additional primary winding 4, to the secondary winding of which an executive relay 5 is connected, a second transformer 6 of the zero-sequence current, an additional winding 4 is connected to the output of the current converter 7, the control input of which is connected through a rectifying h yku 8 to the secondary winding of the transformer current July 6, its other input to the transformer 9 poutsshyuchen voltage zero sequence. The composition of the current converter 7 includes a phase-shifting element 10 and a regud current torus 11. The device operates as follows: at a single-phase earth fault, a zero-sequence voltage appears at the output of the transformer 9. In the primary circuit of transformers 3 and 6 of each) connection, a zero-sequence current flows. In undamaged joints, this current pajeeH is its own coupling current and lags in phase from the neutral bias voltage. This angle is close to 90, which depends on the ore COOT of the conductivities of this connection relative to the earth. On the Damaged connection, this current is equal to the sum of the currents of all intact connections and is ahead in phase of the neutral bias voltage by an angle of about 900. The voltage from the transformer 9 is applied simultaneously to the current converters 7 of all connections. In each converter 7, this voltage is converted by a phase-shifting element 10 into a current that is out of phase in the direction of advance by an angle close to 90. This angle can be adjusted for each connection separately. The resulting current is fed into the additional transient winding 4 of the current transformer 3 The magnitude of this current, under the action of a signal fed to the current controller 11 of the converter 7 through the rectifier cell 8 from the current transformer 6, is automatically set equal to the zero sequence current of this connection. If the number of turns of the additional winding 4 is more than one, the current value of the converter should be reduced in proportion to the number of turns. The phase of the current in the winding 4 on the damaged connection coincides with the phase of the zero-sequence current of this connection, and on intact connections of the phase, the currents are opposed. As a result, magnetizas. The primary and secondary primary windings of the transformer 3 of the current at the damaged connection are added, and at the intact ones they are subtracted. For this, the current in the winding and the additional relay 5 on the damaged connection is doubled compared with the case where there is no current in the winding 4. This ensures reliable operation of the damaged connection relay. At all neprevrez-. In the current connections, the current in the windings of the executive relays 5 is equal to the sky-, lance current. It is close to zero in magnitude and is due to the unbalance of the magnetizing forces of the transformer 3 current. This ensures a reliable interlock on the operation of the relay intact connections. 5S The choice of the current for the operation of the new protection can be made on the basis of the inequality of Shore:) 7 / 3c; 7 l PHj5. - the total current of a single-phase zaksykan to the earth network; - own current of the dead line; - the primary unbalance current of the transformer 3 current of the intact attachment; K ,,, cKch-, respectively, the safety factors and sensitivity. In the device, using the phase shifting element 1O and the current regulator 11 of the converters 7, it is possible to ensure that the unbalance current is no more than 5-10% of the intrinsic current of any connection. The proposed protection provides a high selectivity of action in networks as with a low own current connection. neniy, so And with the current of a separate connection, commensurate with the total current of the short circuit to the ground network. The device can be manufactured using standard elements produced by industry. In the circuit of adjustable current transducers, the required phase shift can be used & string known phase-shifting elements, and the current can be varied, for example, using a controlled throttle or similar elements. The application of the invention allows to increase reliably, st and electrical safety of power supply systems. 76 Claim 1 A device for a single-phase ground fault in a polished neutral network, containing at each connection a transformer | Zero-sequence curtains connected to the corresponding IMO actuators in a supply with 1 additional wiring in the primary windings that are connected to a section of the first section; An element with a transformer is of zero sequence, characterized in that, in order to increase the selectivity of the sesht action, it is supplied according to the number of connections; Auxiliary switches, additional zero-sequence current transformers, rectifiers and current regulators, the outputs of additional current transformers of zero sequence are connected to controllers with the first inputs of the corresponding current regulators, whose inputs are connected to the output of phase-shifting elements, which are connected to the terminals of the corresponding current regulators, the inputs of which are connected to the output of phase-shifting elements. the outputs are to the additional primary winding of the corresponding zero sequence current transformers. Sources of information taken into account in the examination 1. Bukhtorov V.F. Nseye devices for protection against short circuits to earth, in electrical networks of cuts. M., ZNIEIugol, 1976, p. 4. 2. USSR author's certificate No. 51797О, кп. H 02 H 3/16, 1976.

Claims (1)

I A device for protection against a single-phase earth fault in a network with an isolated neutral, containing on each connection zero-sequence current transformers connected to the corresponding executive bodies and provided with additional primary windings that are connected through a phase-shifting element to a voltage transformer well. left sequence, characterized in that, in order to increase the selectivity of the action of protection, it is equipped with the number of connections additional phase-shifting elements, additional current transformers of zero sequence, | rectifiers and current regulators, this means that the outputs of additional zero-sequence current transformers are connected through rectifiers to the controlled inputs of the corresponding current regulators, the inputs of which are connected to the output of the phase-shifting elements, and the outputs to the additional primary winding of the corresponding zero-sequence current transformers.