1. Generator loss of excitation protection
Dongguan generator maintenance tells you that the loss of excitation protection serves as a loss of excitation fault protection for generators with abnormal decrease or complete disappearance of excitation current. Composed of criteria such as excitation low voltage Ufd (P), system low voltage, static impedance, TV disconnection, etc., which automatically vary with the active power according to the set value, they respectively act on signal generation and train de excitation.
2. Generator overexcitation protection
Overexcitation protection is a protection that reflects the high magnetic density of the iron core of a generator caused by a decrease in frequency or high voltage.
3. Generator stator grounding protection
The generator stator grounding protection, as a single-phase grounding fault protection for the generator stator, consists of two parts: the fundamental zero sequence voltage part and the third harmonic voltage part. The fundamental zero sequence voltage protection protects the single-phase grounding fault of the stator winding in the 95% area from the machine end to the tail of the machine.
4. Generator stator interturn protection
The protection is composed of longitudinal zero sequence voltage and negative sequence fault direction criterion, with PT disconnection blocking measures set as the main protection for internal inter turn and inter phase short circuits of the generator and stator winding open welding.
5. Out of step protection
The protection adopts a three impedance element, and the engine detects the number of sliding poles and determines the position of the oscillation center through the trajectory change of impedance.
6. Low frequency accumulation protection
The low-frequency accumulation protection reflects the cumulative effect of a decrease in system frequency on the steam turbine. The protection consists of sensitive frequency relays and counters, which are locked by the auxiliary contact of the outlet circuit breaker (i.e. the low-frequency accumulation protection also exits operation when the generator exits). The accumulated system frequency is below the frequency setting value of 47.5Hz, and when the accumulated time reaches the set value of 3000 seconds, it acts as a signal after a delay of 30 seconds.
7. Excitation circuit overload protection
The excitation circuit overload protection is used as a protection for overcurrent or overload in the rotor excitation circuit, connected to a three-phase type, consisting of a fixed time limit and an inverse time limit.
8. Generator rotor one-point grounding protection
The one-point grounding protection of the generator rotor is used to reflect a one-point grounding fault in the generator rotor circuit. The protection adopts the ping-pong switching principle and takes turns sampling the positive and negative voltage of the rotor circuit to ground. By solving two different grounding circuit equations, the rotor grounding resistance and grounding position are calculated in real-time.
9. Generator symmetrical overload protection
The protection device consists of a fixed time limit and an inverse time limit, with the fixed time limit acting on the signal after a time limit of 5 seconds.
10. Generator negative sequence overload protection
The protection device consists of two parts: a fixed time limit and an inverse time limit. The fixed time limit action current is set according to the long-term allowable negative sequence current value of the second-hand generator set and the current value of the negative sequence current filter under maximum load, and acts on the signal after a time limit of 3 seconds.
11. Generator overvoltage protection
Before the generator is connected to the grid, if the terminal voltage reaches 1.3 times the rated value, the generator overvoltage will be triggered by a 0.5 second delay to disconnect and de-excitation.
12. Generator longitudinal differential protection
According to the different input currents on both sides of the differential element, it can be classified into two categories: complete longitudinal differential protection and incomplete protection.