SU1372451A1 - Arrangement for protecting one of parallel-operating transformers of distribution networks with insulated neutral wire - Google Patents

Abstract

The invention relates to the field of electrical engineering and can be used in relay protection devices. The purpose of the invention is to increase the sensitivity for internal damage to the transformer. A power relay 2 is used as a reacting element, the working winding of which is connected to current transformers T installed on the high voltage side of the power transformer, the polarizing power relay 2 winding is connected via a saturable intermediate transformer 5 to current transformers 3 and 6 installed on the low side voltage power transformer. The power relay operates only when current flows through the polarizing winding of the power relay in the direction corresponding to a short circuit inside the power transformer. 1 il. (L

Description

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The invention relates to electrical engineering and is intended to protect power transformers of distribution networks with insulated neutral.

The purpose of the invention is to increase the sensitivity of protection in case of internal damage in power transformers.

The drawing shows a diagram of the device.

The current transformers 1 on the supply side are connected in an incomplete star circuit and connected to the operating winding of the power direction relay 2. On the lower voltage side, the secondary winding of one of the current transformers 3, for example phase C, is connected to the primary winding of the second intermediate current transformer 4. The primary winding of the first intermediate Naschennogo transformer 5 is included in the sum of the secondary currents of current transformers 4 and 6. The secondary winding of the first intermediate transformer 5 includes a phase-shifting circuit formed in series by a second capacitor 7 and a resistance 8, and through the first capacitor 9 a polarizing winding of the power direction relay 2. The current passing through the operating winding of the relay 2 varies only in magnitude.

The direction of the EMF of the secondary winding

intermediate saturating transformer 5 varies by 180 ° depending on the location of the short circuit.

The polarizing winding of the power relay is connected in such a way that when

damage to transformers 3 and 6 of the current relay is not valid, and to transformers 3 and 6 closes its contacts to disconnect the switches of the power transformer. The installation of the second intermediate transformer 4 ensures the protection action during a short circuit on the low voltage side between phases A and C. Except

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 , 5 20 25

35

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In addition, during three-phase short circuits on the low side of the transformer, the phases of the currents in the operating winding of the power relay 2 and the primary winding of the intermediate transformer 5 are alpha-

Capacitor 9 serves to obtain maximum torque at the power relay. Capacitor 7 and resistance 8 cut off voltage peaks dangerous to the insulation. The design of the intermediate transformer 5 with an instantaneous voltage allows the relay 2 to be supplied to a polarizing relay 2 of practically constant voltage regardless of the type of damage.

Claims (1)

Invention Formula A device for protection of one of the parallel operating power transformers-distribution networks with insulated neutral, containing phase current transformers installed on both sides of the power transformer, intermediate current transformers, reactive organ, characterized in that, in order to overcome sensitivity, the first capacitor was additionally introduced, phase-shifting chain of series-connected second capacitor and resistor, while the reaction body is designed as a power relay with whose and polarizing windings, the working winding is connected to the secondary windings of current transformers connected according to the incomplete star scheme, on the higher voltage side the polarizing winding is connected through the first capacitor to the secondary winding of the first intermediate current transformer, made with a crossed, phase-shifted phase-shifting circuit, the primary winding of the winding The intermediate current transformer is connected via the second intermediate current transformer.