Protection of Silent Diesel Generator Set under Loss Excitation

What are the protections for silent diesel generator sets in the event of loss of excitation? What are the high safety factors of silent diesel generator sets? Firstly, the loss of excitation protection serves as a loss of excitation fault protection for silent diesel generator sets with abnormal decrease or complete disappearance of excitation current. It is composed of criteria such as excitation low voltage Ufd (P), system low voltage, static stability impedance, TV disconnection, etc., which automatically change with active power according to the set value. It acts on signal sending and train de excitation respectively. The excitation low voltage Ufd (P) criterion and the static stability impedance criterion are both related to the static stability boundary, which can detect whether the silent diesel generator set has lost static stability due to loss of excitation. The static stability impedance criterion acts at the static stability boundary after loss of excitation.

Of course, there is also overexcitation protection, which is a protection against high magnetic density in the iron core of a silent diesel generator set caused by a decrease in frequency or high voltage. The overexcitation protection is divided into two fixed values: high and low. The low fixed value sends a signal and reduces the excitation voltage (the function of reducing excitation voltage and current is not currently used) after a fixed delay of 5 seconds. The high fixed value acts on the disconnection and demagnetization through an inverse time limit, with an upper limit of 5 seconds and a lower limit of 200 seconds.

In addition, stator grounding protection, as a single-phase grounding fault protection for the stator of a quiet diesel generating set, consists of two parts: the fundamental zero sequence voltage part and the third harmonic voltage part. The fundamental zero sequence voltage protection machine is used to protect the single-phase grounding fault of the stator winding in the 95% area of the tail of the machine, which is composed of reflecting the principle of zero sequence voltage of the silent diesel generator set. After a time limit of t1 (3s), it acts on the disconnection and demagnetization; The single-phase grounding fault of the stator winding in the 30% area from the tail to the engine of the third harmonic voltage protection is composed of the neutral point of the silent diesel generator set and the principle of the third harmonic of the engine. After a time limit of t2 (5s), it acts on the signal, and the two form a 100% stator grounding protection. The protection is equipped with PT disconnection blocking.

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