SU1495893A1 - Device for differential current phase protection of buses - Google Patents

Abstract

The invention relates to power generation, in particular, to relay protection devices. The purpose of the invention is to increase the reliability of the protection by improving the selectivity of the phase organ. The goal is achieved by the fact that the phase circuit is additionally connected via a rectifying diode to the secondary winding of the transreactor, the primary winding of which is included in the differential circuit of the device. So A current of unbalance of the differential circuit is supplied to the input of the phase organ in case of external damage, which, in turn, leads to the failure of the phase organ when one of the current transformers is saturated. 2 Il.

Description

FIELD OF THE INVENTION The invention relates to power engineering, in particular, to relay protection devices for power plants and substations of power systems.

The purpose of the invention is to increase the reliability of the protection effect by improving the selectivity of the phase organ.

FIG. 1 shows a block diagram of a device for differential current phase protection of tires j in FIG. 2 - graphs of the change of secondary currents from current transformers of connection of the protected bus system.

The protection device contains high-voltage circuit breakers 1, current measuring transformers 2 (CTs), transreactors with primary winding 3 and secondary winding 4, which include rectifying diodes 5, current element 6 connected to the output

a differential circuit for the circulation of currents, a phase element 7 at the output of the phase circuit and reacting for a given duration of pauses between the positive (or negative) half-waves of the current (voltage) short circuit (SC) in the busbar connections circuit 8, realizing the logical operation p with an amplifying circuit and an output relay affecting the opening of the connection switches.

The device works as follows.

; With an internal short circuit on the tires in the protection zone at point K, the geometric sum of the secondary currents from the CT 2 and the current element 6 is triggered for current circulation in the differential circuit. In dan4

i sd

oo with

In the mode, the output of the phase circuit. After the half-wave rectification, current pulses appear (voltage from currents I ,, (, and unbalance current iin (o which are approximately in phase with each other (.fig .. 26). In this case, pauses with duration tj, the magnitude of which is greater than the setpoint of the response of the phase organ 7 reacting to the duration of the Douz between the pulses in the phase circuit, occur between the positive pulses under consideration. after which outlet body 8 is a signal to circuit breakers 1 connections protected bus system.

With an external short circuit at the point Kj, the currents I ,, l | are in antiphase at one of the connections, a fundamentally phase organ 7, due to the small pairs of bonds between the impulse of the ground current I (voltage), does not work in the phase circuit. Therefore, even when the current organ is processed from the unbalance current in the differential circuit, the false disconnection of the switches 1 does not occur, since in this case the signal from the organ 7 at the second input of the circuit 8 does not coincide and

I With a short circuit (at point K), the secondary current TT of the faulty connection is strongly distorted (FIG. 2a). In this case, the value of pauses t at the level of a re;

ItM, i.e., t tu, and organ 7 falsely works,

To ensure proper operation of the protection, an additional current transreactor is introduced into the device, which is connected to the differential circuit to circulate currents, in the secondary winding of which is included in the phase circuit, high current pulses (voltage) proportional to the current i)) magnetizing TT 2 damaged connection with short-circuit at point Kj ,,

You can write that,

then (o1 where is the undistorted secondary current from the measuring TT of the faulty connection, i is the distorted secondary current from the same TT of the damaged input, 0 0

50

five

0

five

five

Dineni at their saturation, "(o) the magnetizing current TT,

Assuming that i / ji-. ,, i-zfn-ii the output of the differential circuit for the circulation of currents, the currents (o and (o) (fig. 26) are supplemented in the phase protection circuits by the distorted currents i and ij The pause t "is reduced to the normal value of t (Fig 2a), in this case the protection does not work falsely, because tn to. With internal short circuits (the point Kp in the zone of action of protection under reJC conditions the current form at the output of the phase circuit has the form , shown in FIG. 2b. Here, too, the distorted current 11, “complements P, (

with the magnetizing current i-jfjCo), the pause value t is reduced to the normal value t as with sinusoidal, undistorted current pulses in the phase bus protection circuit. In this case, the bus protection reliably works as the necessary conditions are met. H where I s (b) actuation current of the body 6, 1a is the differential current at the circuit output.

The advantage of the proposed technical solution is to increase the reliability of the differential current phase bus connection by improving the selectivity of its operation at strongly distorted current pulses (voltage) in the phase contour due to the deep TT of the damaged connection with external short circuits.

Claims (1)

Invention Formula The device of differential current phase protection of tires, containing trans-current transformers intended for installation in each phase of each connection, in series with which primary windings of transreactors are included, indicated chains of like phases of all connections are connected in parallel, the first common output of the combined secondary windings of transformers is connected to current .the first input of the current organ is secondary, the windings of the transreactors of the same phases through diodes are connected in parallel and their general conclusions under lyucheny to the inputs of the phase body, and current outputs faz.nogo bodies are connected respectively to first and second inputs of AND member, the output which is the output of the device, differing from the fact that, in order to increase the reliability of the protection by way of improving the phase organ, the diodes and the transreactor are additionally included, the primary winding which is connected between the common output of the primary windings of the transreactors and the second input of the current organ, and the secondary windings in series with the diodes are connected in parallel with the inputs of the phase organ. ESESE FIG. J iZn (0