Prevention of slot discharge and on-line condition monitoring ofhigh voltage machine insulation

摘要

The various factors responsible for slot discharge damage arediscussed. The lowering of surface resistance in combination withlamination edges is shown to be an important factor in establishing theconditions of the initial discharge. Space charges on the free surfaceon the coil can cause the development of a large voltage when the coilvibrates in the slot. This leads to discharges to the coating. Amagnetic field effect in conjunction with a thermal effect can create afree surface or an isolated painted area responsible for the onset ofdischarges. A novel insulation technique has been developed whichpractically eliminates the slot discharge phenomena. The techniqueprovides a reliable and stable electrical path for allowing thecapacitive current of the main insulation to ground. An additionalfeature of this development is the provision of a simple onlinecondition monitoring method. Information can be obtained about anydischarging condition, ground fault in an isolated neutral system, andinterturn fault that could lead to ground insulation failure