Fault Solution for Excitation System of Diesel Generator Set

Excitation system provides magnetic field current to the rotor winding of diesel generator. Its main function is to keep the generator voltage at a given level, reasonably distribute reactive power and improve the operation stability of power system. It can be seen that maintaining and debugging the excitation system is of great significance to ensure the safe operation of electricity production.

However, we also know that any equipment may have faults in operation. How to quickly diagnose and eliminate faults is an important responsibility and task of maintenance personnel, and the excitation system is no exception. Therefore, this article discusses the common faults and countermeasures of diesel generator excitation system.

1. Common faults and countermeasures of diesel generator excitation system

1.1 excitation failure

When the generator cannot establish the initial voltage after the excitation system issues the excitation command, which is called excitation failure.Because there are many models of diesel generator excitation system, and there are differences in parameter setting and signal display.For example, EXC9000 excitation system,when generator terminal voltage is still lower than 10% of the generator rated voltage within 10s, the regulator display screen will report "excitation failure" signal.

There are many reasons for the failure of build-up excitation, and the common ones are:

(1) There are omissions during startup inspection, such as excitation switch, de excitation switch, safety seat switch of synchronous transformer, etc. are not closed.

(2) The excitation circuit is faulty, such as loose lines or damaged components.

(3) Regulator failure.

(4) the operator is unfamiliar with operation, and the time of pressing the excitation button is too short, less than 5s.

Solution:

(1) Check the boot status strictly in accordance with the procedures, review all links to avoid omissions.

(2) Observe carefully. If you suspect that the excitation circuit is faulty, judge by observing the activation of the excitation contactor and the sound of the pull-in. If there is no sound, may be a circuit failure; if it is a regulator failure, you can observe the switch indicator light of the regulator board. Whether the input indicator light is always on, and if the light is off, check the wiring and whether the host computer command is issued.

(3) After the equipment is overhauled, check whether the excitation mode of the man-machine interface is appropriate, and restart the machine by adjusting the excitation mode or changing the channel.

(4) Many of the failures after maintenance and repair are left over from previous operations. If you patiently recall what you have moved, you can find some signs, such as whether the rotor and the excitation output cable are connected reversely.

2.2 Unstable excitation

During the operation of the generator, the excitation fluctuation is too large. For example, the operation data of the excitation system increases, but sometimes it is normal and irregular, and the adjustment of addition and subtraction can still be carried out.

The possible reasons are:

(1) The output of phase-shift pulse control voltage is abnormal.

(2) The environmental temperature changes and the components are affected by vibration, oxidation and malfunction.

Solution:

For the first reason, first check whether the excitation power supply is normal, and check whether the given value and the measured value (generator voltage or excitation current) processed by the adaptation unit are normal.

For the second reason, use an oscilloscope to observe whether the rectified waveform is complete, and then use a multimeter to check whether the performance of the thyristor is normal. This type of failure will occur when the wire welding status and component characteristics change, and the maintenance and debugging should be strengthened and replaced in time. Problematic components can reduce the probability of such failures.

2.3 Abnormal de-excitation

After the diesel generator set is disconnected from the power grid, the de-excitation device should attenuate the residual magnetization in the excitation device as soon as possible. Demagnetization methods include inverter demagnetization and resistance demagnetization. The reasons for the failure of inverter demagnetization include circuit reasons, SCR control pole failure, abnormal AC power supply, and too small leading trigger angle of the inverse conversion phase. Therefore, the solution is to strengthen daily maintenance, regularly clean the dust in the equipment, and then apply conductive paste to the de-excitation fracture, arc extinguishing grid and other parts to prevent the mechanism from jamming.

To keep the excitation system of a diesel generator in good condition, in addition to strengthening maintenance and management, regular dust removal, testing and testing, attention should also be paid to the analysis and summary of common faults. Just like emergency plans, clearing out common troubleshooting procedures and methods can greatly reduce the troubleshooting time and lay a solid foundation for ensuring the safe production of diesel genset and improving power generation efficiency.