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June 22, 2020
The rotor is an important component of the hydroelectric generator. As a rotating part, its main function is to generate magnetic field, transform energy and transmit torque. Some hydro-generators have suffered one-point grounding faults and even two-point grounding accidents due to the aging of the rotor insulation during many years of operation. So how do you troubleshoot these problems? Let's discuss it below.
The one-point ground fault of the rotor in the hydro-generator set generally has no obvious traces and is difficult to find. The traditional search method for hydropower stations is to open the stator air box cover and remove the upper and lower wind shields, use a soldering iron to divide the number of rotor poles in two, use a 500V insulated shaker to determine which side the fault is on, and then there will be a ground fault The magnetic pole on the other side is divided into two, and then use a 500V insulated rocker to determine which side the fault is on until the last two magnetic poles are divided to find the faulty magnetic pole. This method may seem simple, but in practice it is very time-consuming and laborious. If the rotor of the hydropower station has a little ground fault, it shall be shut down according to the requirements of the regulations. If the peak load period is positive, the scheduled maintenance time is very short, and it is difficult to complete the task using traditional methods. You can use the magnetic pole flux to generate magnetic current phenomenon, using the following method, the fault will be quickly eliminated.
The method to eliminate the rotor fault in the hydro-generator set is as follows:
First disassemble the rotor carbon brush, use a 500V shake meter to measure whether the ground fault is on the connection cable of the carbon brush and the exciter. If not, open the stator air box cover and remove the upper windshield, connect the wire, and slide the rheostat to make The coil passes a current of 5 to 10A, and uses an iron block (or wrench) to approach one by one from the magnetic pole where the current first flows.
(1) If all magnetic poles of the rotor have no magnetic force or have magnetic force, the fault should be on the positive or negative lead.
(2) (2) If there is no magnetic force on a magnetic pole (referred to as the B magnetic pole), the fault point is on the previous magnetic pole (referred to as the A magnetic pole) or its connection line with the A magnetic pole. At this time, only need to weld the two magnetic level connection wires, and then connect the wires according to the figure to try the magnetic force of each magnetic pole above the B magnetic pole. If there is a magnetic force, it means that the fault is on the A magnetic pole. If there is no magnetic force, it means that the fault is in Connecting line of B pole and A pole.
The above is how the rotor failure in the hydro-generator set ends. According to the above method, when the fault point is found on the negative pole of the rotor, the rotor support pad is re-insulated, so that the problem can be solved quickly.