Abnormal problems found in the maintenance of the

Abnormal problems found during generator maintenance and their solutions

1 preface

Shandong Zhonghua Liaocheng Power Plant Phase I project adopts QFSN generator of Shanghai Steam Turbine Generator Co., Ltd., with rated power of 600MW, rated voltage of 20kV, rated current of 19245a and rated hydrogen pressure of 0.4MPa. The generator adopts water hydrogen hydrogen cooling mode, that is, the stator winding is water-cooled, and the rotor and stator core are hydrogen cooled

2 main problems

2.1 problems raised

in September 2005, Liaocheng Power Plant carried out level C maintenance of 1 unit. On September 12, one day after the backwashing of 1 generator stator cooling water system, the conical filter was untied and checked. It was found that there were a large number of bright yellow flakes, with a small amount of rust red on one side, and the maximum area was about 3 square centimeters. After many times of positive and negative flushing and standard mold test procedures, each time lasted for 24 hours, and more or less yellow flakes were found in the filtration

2.2 analysis process

after the problem occurred, professionals conducted a systematic analysis of the generator stator cooling system. Refer to the following figure for the cooling water circuit of generator stator

attached drawing sketch of generator stator cooling water system

2.2.1 stator cooling water circuit composition. Stator coil cooling water is a loop composed of water tank, water pump, water cooler, filter and generator stator bar. During the normal operation of the generator, the cooling water enters the annular main water inlet pipe in the stator base at the excitation end of the generator through the external water inlet pipe, one of which flows through the PTFE insulated water pipe. If the pot is not scraped, it is easy to cause the hollow wire in the stator bar with low strength, and then flows into the annular outlet pipe from the other end of the coil (steam end) through the insulated water pipe; The other way flows into the main lead of the stator coil through the insulated water diversion pipe. After the lead is discharged, it flows into the outlet pipe arranged in the outlet box through the insulated water diversion pipe, and then it also flows into the steam end annular outlet pipe through the industrial cluster pipe with the characteristics of organosilicon new materials developed by the upstream and downstream. The two-way flow finally flows out of the generator from the upper part of the steam end base and returns to the water tank through the main outlet pipe. When the unit is backwashed, through the switching of valves a and B, the cooling water enters the steam end of the generator first, and then returns to the water tank from the excitation end