SU1381645A1 - Device for protecting instrument voltage transformer against damage - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is to increase the efficiency of protection with single-phase arc locks on the ground. The device contains a measuring voltage transformer (ITN) 1, fuse 2, resistors 3 and 4, relay 5, diode 6, ballast resistor 7, opening contact 8, closing contact 9, diode 11, capacitor 12 and opening contact 10. With single-phase arc Closing x on resistor 4 increases the voltage drop until the relay 5 trips. At the same time, contact 10 opens and resistor 3 is introduced into the circuit, which limits the current through ITP 1 to the allowable value. 1 il. - cl

Description

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The invention relates to electrical engineering, in particular, to relay protection, and can be used to protect against damage to transformer isolation control transformers (TNKI).

The aim of the invention is to increase the effectiveness of protection during single-phase arc faults to earth.

The drawing shows a single line diagram of the device.

The device for protection of the measuring-voltage transformer 1 (IST) contains, installed in each phase of the windings of the high voltage ITS 1, a circuit consisting of a series-connected fuse 2, a current limiting 3 and a low-impedance 4 resistance, a relay 5, a diode 6 and a ballast resistor 7. The first terminal of the winding of the relay 5 is connected to the point of connection of the first terminals of the current-limiting 3 and low-resistance 4 resistances. The second terminal of the relay coil 5 is connected through a series-connected diode 6 and the first disconnecting contact 8 of the relay is connected to the second output of low-resistance 4. The common connection point of diode 6 and the first disconnecting contact 8 is connected to the second output of the current-limiting resistor 3 through a series-connected ballast resistor 7 and a closing contact 9 of relay 5. A second disconnecting contact 10 of the relay shunts the current-limiting resistance 3, a diode 11 connected in series with diode 6, is installed to increase reliably ty of the device from the breakdown of one of them with power relays voltage drop across the high-resistance resistor. Capacitor 12 plays the role of a smoothing filter. The value of the current limiting resistor 3 is selected from the condition of current limiting through the voltage transformer during arc faults to ground to an acceptable value, i.e. about 50-100 kOhm. Fuse 2 is designed to protect the IH from short circuit.

The device works as follows.

In the normal operating mode, the current-limiting resistance 3 is shunted by the break contact 10 of relay 5, and the resistance does not affect the error of the voltage transformer, which operates in

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given accuracy class. The working currents through the TNKI flow through the low-impedance resistors 4 and the main shredder 2. With single-phase arcs, when the currents through the TNIs exceed the permissible (but less than the melting current of the fuse insert 2), the voltage drop increases at low resistance 4 when the threshold is reached, relay 5 turns on. In this case, the contact 10 of the relay 5 is opened. After this, a current limiting resistance 3 is introduced into the circuit, which provides current limiting through TNKI 1 to an acceptable value, the voltage drop on the low resistance 4 decreases. To hold the relay 5 in the on position, the contact 8 opens, and the contact 9 closes and the relay 5 connects to the current-limiting resistance 3. The relay 5 remains in the on-position. After elimination of the circuit in the network (or self-arcing of the arc circuit), the currents in the phases of TNKI 1 are reduced to an acceptable value. The voltage drop on the current-limiting resistance 3 decreases sharply and becomes much less than the relay trip voltage. Relay 5 is turned off. This opens the opening contact 10, shunt the current-limiting resistance 3, and opens the contact 8 and opens contact 9 of the relay 5. The safety device assumes the initial position.

When k.z. In transformer 1, fuse-links fuse 2 are burned, thereby breaking the supply circuit of TNI.

Thus, by introducing a low-impedance resistor with a relay winding diode connected to it, which opens the contact bypassing the current-limiting resistance included in the high voltage winding circuits of the measuring voltage transformer, the current in the transformer is automatically limited to the acceptable value of the arc to ground supply network, which contributes to the effectiveness of protection for the specified type of damage.

Claims (1)

The invention The device for the protection of the measuring transformer voltage from five 0 five 0 five 313816454 fault, containing for each connected to the point of connection of the first phase a circuit consisting of series-on leads of a current-limiting and low fuse and current-limiting-ohm resistances, a second output resistance having a terminal: a relay winding through a series to connect a diode and The first disconnect of the measuring voltage of the trans contact of the relay is connected to the second of the voltage transformer, which distinguishes the low-impedance water, in common with the fact that, in order to and the connection of the diode and the first protection efficiency with single-phase Q1 1 relay contact through the arc arc to ground, the low impedance co-resistor and the relay contact of the relay, connected in series with the second terminal, are terminally connected to the ballast with a current limiting resistance, a shunt, a diode, a ballast resistor, and a second break contact, the first winding of which is a relay.