SU1365227A1 - Method of protecting synchronous generator with controlled exciter from stator overcurrent - Google Patents

Abstract

The invention relates to electrical engineering. The purpose of the invention is to increase the speed and reliability of the protection when the generator is operating in parallel with an unstable voltage or frequency network. This is achieved by using relay 2 of the maximum current to control the current of the stator 1. Relay 2, when the stator current exceeds the setpoint, triggered as soon as the stator winding current is less than the release current of the relay, it sends a signal to the And 5 element without a time delay. On the element And 5 already there is a signal from the block 3 of the damping field. At the output of the element And 5, a signal appears to turn off the switching device 4. 1 sludge. with " /)

Description

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The invention relates to electrical engineering and can be used to protect against current overloads, including short circuits of self-excited synchronous generators.

The purpose of the invention is to increase the speed and reliability of the protection operation when the generator is operating in parallel with an unstable voltage or frequency network.

The drawing shows the block diagram of the device.

The stator winding current of the generator 1 is controlled by means of a maximum current relay 2 with a time delay independent of the current value, the output of which is fed to block 3 of switching on the field of the generator excitation winding (for example, the winding) of the intermediate relay, the closing contact of which bypasses the field winding and to disconnect the switching device 4 through the element 5.

The device works as follows.

In the event of a short circuit or overcurrent, the stator current is greater than the set value of relay 2, and after a short time, it triggers and turns on the field excitation winding unit 3. In this case, unit 3 becomes self-blocking and switches the generator to the unloading mode based on the stator current. As the excitation current decreases, the stator winding current decreases, and as soon as it becomes less than the release current of relay 2, it disappears without time delay and outputs a signal to the input of element 5, where there is already a second input signal from the output of block 3. If the signals from the blocks coincide At the output of element 5, a signal appears to shut off the switching device 4, which breaks the current close in magnitude to the nominal one. Thus, the dimensions of the switching device can be selected by the rated current of the generator. Unit 3 may have an output to activate the alarm. If a short circuit or current overload lasts less than the time delay of relay 2, then the signal at its output does not appear, and, consequently, there will be neither field quenching nor switching off of the switching device.

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3652272

In parallel operation of the generator with an unstable industrial network and in cases of an increase in the network voltage before the generator goes into operation with capacitive cosq and overloads it with capacitive current or decreases the frequency of the network voltage before the generator is overloaded with active current, the stator current load after the generator the operation of unit 2 is made according to an increase in the generator excitation current or a decrease in the supply of energy to the primary

1g. engine generator.

When using the proposed method, the time from the moment of operation (switching on the output relay) of unit 2 to switching off the switching

2Q apparatus 4 is different and is proportional to the stator overload current of the generator. The longest time delay after fixing the presence of an overload will be at short-circuit currents in the chain of the stator of the generator.

The proposed method of protecting a generator with self-excitation is advisable to protect low-power synchronous generators in mobile electric power engineering, which must withstand short-circuit currents for 5 s which the field quenching time (until the stator current drops) is short.

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Claims (1)

Invention Formula The method of protection of a synchronous generator with a controlled exciter overcurrent stator by measuring the stator current, comparing it with a given setpoint, fixing the presence of an overload when the stator current exceeds the setpoint, switching the generator to the stator current unloading mode and detecting the signal to turn off the switch with a time delay after an overload has been detected, characterized in that, in order to increase the speed and reliability of the protection during parallel operation a generator with an unstable voltage or frequency network, the specified signal to turn off the switch is applied at the time when the stator current decreases to a value less than the current of the specified setpoint.