A utility´s evaluation of a stator bar insulation system operating at increased electric stress

When considering acceptance of a new insulation system, an electric utility should employ caution, good judgment, risk analysis and extensive evaluation. These steps are especially important when the new insulation system operates at increased electric stress. The paper describes the accelerated aging tests which one utility has made on a number of single turn 13.8 kV Roebel stator bars as well as the online monitoring which is in progress on the hydro generator in which bars with the new insulation system have been installed under an agreement with the manufacturer. Comparisons are made to data on an existing insulation system from the same manufacturer for which there is extensive service experience