Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Hydroelectric Generator and Generator-Motor Insulation Tests

This report is a general treatise on insulation testing for Corps of Engineers hydroelectric generators and generator motors. Included are descriptions of the basis for generator ratings, the effect of operating and service conditions, types of insulation systems, and a complete description of visual inspections and electrical tests. Tests covered are the routine and special tests accepted by the industry for insulation systems for the generator stator, rotor, and stator core. A discussion and recommended criteria for rewinding generators are included in this report along with detailed guidance on criteria for generator uprating. The field offices with responsibility for hydropower were surveyed about current routine generator insulation testing. Presents practices by the Districts and Divisions are summarized. A recommended routine inspection and test program is included. Also included is a summary of the Corps of Engineers experience with thermosetting insulation. Experience from the early 1950s with Westinghouse polyester insulation to the present with epoxy impregnated insulation is included.