SU1224890A1 - Device for current protection of transformer against short circuit - Google Patents

Abstract

The invention is intended for current protection against short circuit (SC) of a power transformer. The purpose of the invention is to increase the reliability of operation by increasing the sensitivity. The device contains an intermediate relay (PR) 16, two current transformers installed in phases A and C of a high-voltage supply network and connected in an incomplete star circuit, to the rays of which two current relays (RT) are connected in series to form a star. (P U- + 7 b-d 1 b-w w 20 - Mark.

Description

The increase in sensitivity is ensured by including the winding of the intermediate relay (PR) 16 into the operative supply circuit through a three-phase rectifier 2, closing the contacts (K) 4 ,, 5, 6, opening K 7, 8, 9, opening K 13, 14, 5 RT and resistors 18, 9, 20. Connecting the PR 16, you

The invention relates to relay protection, namely to current protection, made from the highest voltage of transformers of distribution networks having a triangle-star connection group.

The purpose of the invention is to improve the reliability of operation by sensitivity.

FIG. 1 shows the current circuit protection circuit; in fig. 2 scheme of its operational circuits.

The current transformer protection includes the first 1, second 2 and third 3 current relays with closing contacts 4 5, 6 and opening contacts 7, 8,; 9, respectively, the fourth 10, n - 1 and sixth 2 current relays with different | 13, 14 and 5, respectively, intermediate relay | (3 with closing contact J7, resistors 13, 19 and 20f three-phase two-phase rectifier 21 with three inputs and two outputs and two current transformers 22 and 23, connected according to the incomplete stars.

The detuning of the relay is carried out so that the current relay 1, 2, 3 is from the super-front current of a three-phase short circuit behind the transformer, the current relay 10, P, 12 is from a current of 0.58, which corresponds to the single-phase short-circuit mode on the star side. The size of the resistors 18 "19 and 20 is chosen such that the intermediate relay 16 of the three-phase short circuit works only when the currents flow through two or three resistances, and when the current flows through one resistance does not work.

The device works as follows.

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The choice of resistance values of resistors 18 ,, 19 5 20 ensures that the PR 16 operates only with the flow of currents of one or three resistances, and at the same time revealed the following emergency conditions. power transformer - single-phase short-circuit KZ 5 two-phase short-circuit in the protection zone n three-phase. KZ 2 Il.

ifpH single-phase short-circuit in transformer e, for example, in phase L, the current relay 10 operates, which opens its contact 7j, and the current relay 12, which

opens its contact 9. As a result, the contact of relay 12 and two resistors connected in parallel, a current flows sufficient to trigger an intermediate relay 6. Relay 16

triggers and closes its contact 17 3 disconnecting circuits.

With a two-phase short-circuit in the transformer, for example, between the phases of the IC and the accumulator, the current relay is 3 to 12. The contacts 5 of these relays are opened and the coil of the relay 16 via the contact 6 and two current in parallel to the resistors will flow enough to operate. The contact 17 of the intermediate relay 16 closes and supplies a shutdown voltage. In case of short circuit in the same phases, but outside the protection zone, only current relay 12 triggers and contact 3 is opened. However, opening only one contact 15 does not trigger relay I6, therefore, in a two-phase short circuit outside the protection zone, the device does not trigger .

at dv gkhfaznom KZ on the findings of higher voltage transformer .; For example, in phases 8 to C, the current relays 3 .. 2, II and 2 are triggered. The contacts of these rales 9, 8, 15 become blunt, and A and B and 5 are closed. Coil of PrO1 1ZhZ tschnogo relay 16 floor: takes into account the power through the contacts 6 and 5 l three soprotiBlenm. Contact 17 of intermediate relay 16 closes and provides a signal for deviation.

With a three-phase short circuit, all current relays are triggered ,, and intermediate relay 6

gets i ita} those through pins 4

31

6, 5 and three parallel resistors. In case of a three-phase circuit, current relays 1, 2 and 3 do not operate outside the protection zone.

Simultaneous opening of the contacts 13, 14 and 15 of the current relay 10, 11 and 12 does not trigger the intermediate relay. Therefore, in case of a three-phase short-circuit fault, the protection does not work out of the zone.

Thus, the current protection of the transformer distinguishes one, two | and three-phase internal short-circuit in the transformer and has the same high sensitivity to each of them.

Claims (1)

Invention Formula Device for current protection against short-circuit of a transformer with a delta connection group on the side of the supply network with an insulated neutral and a star with a grounded neutral on the side of the receiving network containing in the transformer circuit on the supply side a switch with a tripping coil and a two-pole operational source , the first and second current transformers with the primary winding of each in the circuit of the corresponding phase of the network on the supply side of the transformer, the first and second overcurrent relay with a circuit they each contact, as well as an intermediate relay with a closing contact, while the inputs of the windings of the first and second overcurrent relays are connected to the polar terminals of the secondary windings of the first and second current transformers, respectively, the non-polar currents of the secondary windings of the first and second transformers are connected to each other other, one pole of the closing contacts of the first and second overcurrent relay and the intermediate relay are combined with each other and connected to the first pole of the operating current source, and the other The capping contacts of the first and second overcurrent relays are integrated with each other and connected to the input of the coil of the intermediate relay, characterized in that, in order to increase the reliability of operation by increasing the sensitivity, a third overcurrent relay with closing and opening contacts is added to it, the fourth , fifth and sixth overcurrent relay with open 24890 each contact, as well as fuse contacts in the first and second overcurrent relays, the first, second and third resistors and the three-phase output 5 r micler with the first second and third inputs and the first and second outputs, while the output winding of the third relay the maximum current is connected to the winding input of the fourth maximum current relay, the VIDEO of which is connected to the aforementioned unpolarized wires of the secondary windings of the first and second current transformers, the winding input of the first maximum current relay to the output of said first winding overcurrent relay sixth overcurrent relay coil input connected to the output of said The windings of the second overcurrent relay, the windings of the fifth and sixth overcurrent relays are combined with each other and connected to the winding input of the third maximum current relay, one pole of the fourth and fourth trip contacts of the sixth maximum overload relay are connected with each other and connected to the mentioned first pole of a two-pole, source of operating current, another pole of the disconnecting contact of the fifth overcurrent relay connected to one pole of the disconnecting contact of the second relay; maximum current The other pole of which turnkey combined to each other with one pole of the first resistor and the first input of the three-phase vtr mite- l, the other pole of the fourth relay break contact maximum  current is connected to one pole of the open contact of the first maximum current relay, the other pole of which is connected to one pole of the second resistor connected to each other  : And the second input of the three-phase rectifier, the other pole of the opening contact of the sixth overcurrent relay is connected to one pole of the third-contact relay of the maximum current, the other pole of which is connected to the third resistor and the third input of the three-phase connectors connected to each other, the other poles first, 55 of the second and third resistors are connected to each other and connected to the second pole of the two-field operational current source. the first output of the three-phase output miter pdc is connected to the aforementioned winding input of the intermediate relay, to the output of which the second output of the three-phase voltage miter is connected, one pole of the closing contact of the third maxiABC The maximum current is connected to the said first pole of the two-pole operating current source, and the other pole of the make contact of the third overcurrent relay is connected to the input winding of the intermediate relay. P Editor M. Bandura Compiled by V. Molchanov Tehred I. Veres Order 1958/52 Circulation 612 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Ra usushka nab. 4/5 -Production and printing company, Uzhgorod, Projecto st., 4 Proofreader M. Demchik