Programmable UNITROL 1000 3BHE014557R0003 module communication system mechanical protection device

Description

UNITROL 1000 build-up excitation unit
Under normal conditions, the residual voltage of the generator is sufficient for excitation. The generator rotor has remanence. Generally, UNITROL 5000 can realize residual voltage excitation.
When the excitation is put into operation, the thyristor bridge will be triggered immediately. As long as the thyristor input terminal has 10-20V power supply voltage, the gate control unit can effectively control the thyristor rectifier bridge. If the residual voltage is lower than 10V and it is not enough to establish the generator voltage, after a certain time delay, the excitation device will be put into operation: the excitation loop will automatically close, flow current to the field winding, and the stator voltage building will begin.

UNITROL 1000 When the voltage reaches 10% of the rated value, the thyristor bridge can work normally, and the excitation switch is automatically disconnected. The soft build-up excitation process starts to raise the generator voltage to the rated voltage of 27KV, and the control and monitoring of the entire build-up excitation process are realized by AVR software.
When the output voltage of the rectifier bridge is higher than the DC system voltage, the diode in the excitation loop will prevent reverse current from flowing into the DC system.
The build-up excitation current is about 10% to 20% of the no-load excitation current, which depends on the series current limiting resistance R03.
Soft build-up excitation is used to prevent build-up excitation overshoot of terminal voltage. If the overshoot occurs, the voltage may be too high to cause overexcitation.
Deexcitation unit
When the protection relay detects the internal fault of the generator, the energy stored in the magnetic field must be released safely and quickly to protect the generator. De excitation function is realized by de excitation switch, jumper and de excitation resistor. The deexcitation switch is designed to safely cut off the excitation current under any fault condition. After the deexcitation switch is disconnected, a clear electrical isolation is also formed between the excitation transformer and the field winding.
The automatic de excitation device is installed on the DC side of the excitation circuit. The type of deexcitation switch is GERapid8007 2X2, the rated current is 8000A, and the breaking current is 120KA.
The excitation system has short-time overload capacity. For the static self shunt excitation system, the forced excitation multiple shall not be less than 2 based on 80% of the generator terminal voltage, and the allowable forced excitation time shall not be less than 10 seconds.
Deexcitation effect: In case of fault in the generator, outgoing line, high voltage auxiliary transformer, etc., although the protection device acts quickly to remove the fault, the induced electromotive force generated by the excitation current will continue to maintain the fault current. In order to quickly eliminate the fault and reduce its damage, the energy stored in the magnetic field must be released safely and quickly, that is, the magnetic field established by the current of the excitation winding must be rapidly reduced to the minimum.
Deexcitation requirements: 1. The deexcitation time shall be as short as possible (the time required for the generator terminal voltage to drop from the rated value Un to 5% Un is called deexcitation time). 2. The over-voltage at both ends of the excitation winding shall not exceed the allowable value (the requirement for overvoltage protection through jumper).
De excitation mode: inverter de excitation.
Deexcitation circuit: mainly composed of magnetic field switch, deexcitation resistor, thyristor jumper and related trigger elements. The deexcitation resistor is used to realize fast deexcitation of the generator. a. The nonlinear resistor R02 is connected in parallel and fixed in the generator excitation winding circuit, and is not controlled by the de excitation switch in the DC circuit. The attenuation process of excitation current depends on the characteristics of deexcitation resistor. The non-linear resistor has better de excitation characteristics than the linear resistor, and the excitation current decays faster. b. When the deexcitation switch is disconnected, the excitation current is instantaneously introduced into the deexcitation circuit by triggering the thyristor of the jumper, and the deexcitation process starts. c. When the generator operates normally, the thyristor of the jumper does not conduct, and the nonlinear resistance does not pass through the current; After the deexcitation switch is tripped, the thyristor of the jumper receives the trigger pulse to conduct, and the excitation current is instantaneously introduced into the deexcitation circuit until the magnetic field energy is released. d. The jumper is used as over-voltage protection for excitation winding and silicon controlled rectifier. Inverter deexcitation is completed within the opening time of deexcitation switch, generally within milliseconds. After the magnetic field switch is switched off, the field is de energized through a nonlinear resistor, and the de excitation time is short about 2-3s.

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