SU1705901A1 - Generator excitation circuit protective device - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to generator generator relay protection. The invention is an extension of functionality due to the detection of an open circuit and an increase in the security of the protection service. When, for example, a locking fault occurs, the magnitude of the rotor resistance decreases, and the automatic excitation control device (ODS) raises the excitation current so that the stator voltage does not decrease. The voltage at the output of the rectifier 10 increases and becomes greater than that at the output of the rectifier 9. The voltage at the output of the adder 11 will not be equal to zero, and the first threshold element 12 is triggered, and after the time relay 14 has been triggered organ 1b, and on the alarm unit there appears an indication of a winding short in the field winding. If, on the contrary, a breakdown of the contact of the conductor occurs, an arc occurs and, consequently, the resistance of the excitation circuit increases. Consequently, the voltage at the output of the rectifier 9 becomes greater than that at the output of the rectifier 10. The output voltage of the adder i1 changes its sign and the threshold element 13 is triggered, and when the time relay 15 is activated, the signal appears. The output of the actuator 16, and an indication of contact failure of the conductor appears on the alarm unit. 1 il. / e C Mi o ate CO O

Description

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This invention relates to electrical engineering, in particular, to generator generator relay protection.

A device for protection against an open circuit of an excitation winding of a direct current motor consisting of an excitation circuit current sensor, a thyristor converter, a grid occupied unit, an OR element, and a control unit J is known. When there is a current in the field winding, the signal from the current sensor is not present and the thyristor converter, controlled by the control unit, supplies voltage to the motor. In the case of J excitation current, the current sensor generates a signal which, through the OR element, goes to the control unit and blocks the thyristor converter, reducing the voltage on the 2 output to zero. But this device does not provide protection against coils in the excitation winding and short circuits between slip rings .2

It is also known a device for protecting the rotor winding of a synchronous generator against. coils, containing a transformer, the primary winding of which is connected in series with the field winding, in parallel to which a transformer winding is connected through a capacitor. The secondary windings of the transformer and transreactor through full-wave rectifiers are connected to the reacting organ. In normal mode, the voltage on the reacting organ is zero. In the event of a winding short circuit in the rotor winding, the inductance of the rotor winding changes. The voltage on the winding will not be equal to the voltage on the secondary winding of the transreactor and the difference between these voltages will trigger the actuator.

A disadvantage of this device is that it does not protect the field winding from a wire break.

The closest in technical essence to the invention is a device for protecting generator exciter circuits containing current sensors, rotor voltages and temperatures, a threshold element and an actuator. The principle of operation is based on the fact that when a short-circuit on the case at two points or directly of the turns of the excitation winding occurs, a violation occurs with 5 0 5

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the relationship between current and voltage of the excitation circuit. This change causes an imbalance that leads to the triggering of the threshold element and the executive body. If the rotor temperature has changed during operation, the resistance of the temperature sensor changes, the circuit does not unbalance, and there is no voltage at the input of the threshold element. The device protects the field winding from winding short circuits, but does not protect the field winding from a conductor break.

The purpose of the invention is to enhance the functionality by detecting an open circuit and increasing the security of the protection service.

This is achieved by the fact that the device for protection of the generator excitation circuit, containing current sensors, voltage and rotor temperatures, a threshold element and an actuator, additionally contains a matching unit, two rectifiers, an adder, two time relays, an alarm unit and a second threshold element, the voltage sensor output is connected to the first input of an auxiliary device, the second input of which is connected to the current sensor output, the first and second outputs of the matching unit are connected via the first and second rectifiers to the first and second inputs of the adder, respectively, the third, whose input is connected to the output of the temperature sensor, and the output of the adder is connected to the inputs of the first and second threshold elements, the output of the first threshold element is connected via the first time relay to the first inputs of the executive body and the alarm unit, and the second inputs the latter are combined and connected via the second time relay to the output of the second threshold element, while the matching unit has two channels, voltage and current, the voltage channel consists of a sequence About the connected level converter, low frequency filter and galvanic isolation element, the output of which is the first output of the unit, and the input of the level converter, its first input, the current channel consists of the galvanically separated isolation element and level converter, the output of the latter is output the matching unit, its second input is the input of the galvanically disconnected element

The essence of the proposal is that when the rotor damages due to the closure of the coils, the DC resistance of the rotor decreases, and if the contact of the conductor breaks, an arc occurs, which leads to an increase in resistance. The corresponding threshold elements react to these changes in the rotor resistance. The use of the matching signal ensures the galvanic isolation of the device from the excitation circuit, which will increase the safety of service of the device itself.

The proposed protection device comprises a matching unit 1, the inputs of which are intended to be connected to the terminals of the excitation circuit, and consisting of level converters 2 and 3, electrical isolation elements 4.5 and low frequency filter 6. Level conversion input 2 is the input of unit 1 matching, intended to supply the excitation voltage from the voltage sensor 7 to it, and the input of the galvanic decoupling element 4 is the input of the unit 1, intended to supply the voltage from the current sensor 8 to it, Voltage c in the level converter 2 travels through the low-frequency filter and the galvanic isolation element 5 to the input of the first rectifier 9, and from the output of the galvanic separation 4 through the converter, the damage n 3 is fed to the input of the second rectifier 10. The first 9 and second 10 rectifiers connected to the first and second inputs of the adder 11. The output of the adder is connected to the inputs of the first and second threshold elements 12 and 13, with each of them reacting only to its own polarity of the input voltage. The output of the first threshold element 12 through the first time relay 1 4 is connected to the first input of the actuator 16 and the first input of the alarm unit 17. The trigger of the second threshold element 13 via the second time relay 15 is connected to the second input of the executive body 16 and the second input of the alarm unit 17. The output of the actuator 16 affects the disconnecting circuit of the generator pg. The third input of the adder 11 is connected to the temperature sensor of the rotor 18, ko0

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Toryn eliminates the false triggering of vcTpo. jc.Tpa when changing the temperature of the rotor. The protection device is made on the known blocks described in the technical literature. During normal operation of the generator excitation system, the voltage coming from voltage sensor 7 is fed to the input of matching unit 1, where it is converted into the required voltage level, which is fed to low-pass filter 6, which does not pass high-frequency currents. The coi-electroplating element 5 produces an electrical separation of the excitation circuit and the semiconductor part of the device. The rectified voltage of the rectifier 9 and proportional to the voltage of the excitation - is supplied N. - i the first input of the adder 11. The voltage from the current sensor 8 goes to another input of the matching unit 1, where the electrical separation first takes place and then

5 receive the required voltage level in level converter 3. After rectifying with rectifier 10, this voltage is applied to the second input of the adder 11. To the third input

Q is supplied from the rotor 18 temperature sensor. The device is tuned so that in normal mode the voltage at the output of the adder 1 is zero. When, for example, a bead-closure occurs, the rotor resistance decreases, and the automatic excitation control device (APB) raises the excitation current so that the stator voltage does not decrease. The voltage at the output of the rectifier 10; increases and becomes greater, than., At the output of the rectifier 9. The voltage on. the output of the adder 11 will become non-equal to zero, and the first threshold element 12 is triggered, and after the time relay 14 trips, the output of the actuator 16 appears, and an indication of a short circuit in the excitation winding appears on the alarm unit. If, on the contrary, a contact fault occurs, then an arc occurs, and, consequently, the resistance of the excitation circuit increases. Under the influence of APB, the excitation voltage rises to maintain the current in the excitation winding circuit. Consequently, the voltage at the output of the rectifier 10. The output voltage of the adder 11 changes its sign and the threshold element 13 is triggered, and after the time relay 15 is activated, a signal appears at the output of the actuator 16, and on the alarm unit indication of contact disturbance.

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If for some reason the temperature of the rotor winding has changed, then at the output of the rotor temperature sensor there is a voltage of such polarity and value so that the voltage at the output of the adder is zero.

Installing the proposed device on the generator will reduce the amount of damage, reduce the time and cost of repairs.

Claims (1)

Invention Formula A device for protection of the generator excitation circuit, containing current sensors, voltage and rotor temperature, a threshold element and an actuator, characterized in that, in order to extend the functionality by detecting the excitation circuit, an additional matching unit is added Mittel, adder, two timers, alarm unit and the second threshold 0 5 o element, and the output of the voltage sensor is connected to the first input of the matching unit, the second input of which is connected to the output of the current sensor, the first and second outputs of the matching unit through the first and second rectifiers are connected to the first and second inputs of the adder, respectively, the third input of which is connected to the output temperature sensor, and the output of the adder is connected to the inputs of the first and second threshold elements, the output of the first threshold element is connected via the first time relay to the first inputs of the executive body and signal unit the second inputs of the latter are combined and connected via the second time relay to the output of the second threshold element, the matching unit has two channels — voltage and current; the voltage channel consists of a series-connected level converter, a low-frequency filter and an element whose output is the first output of the unit, and the input of the level converter by its first input, the current channel is formed by series-connected elements of galvanic isolation and level body conversion, the output the latter is the output of the matching unit, and its second input is the input of the galvanic isolation element.