Diagnosing insulation of electrical machine windings by means of constant voltage

摘要

An equivalent circuit for insulation of electrical machines with thermally and electrically warm insulation is proposed. It can be used for developing methods of insulation tests and estimating the insulation technical condition. The diagnosticsmethod proposed is based on the following tests under constant voltage. 1. Obtaining the winding insulation leakage current time diagram when switching-on U{sub}nom. 2. Measuring steady-state leakage current when voltage rising from 0 to 2U{sub}nom anddetermining the characteristic of equivalent insulation resistance R{sub}e =f(U). 3. Charging insulation system up to voltage U{sub}nom then shortcircuiting with duration t{sub}s (t{sub}s depending on the insulation rated voltage and the degree of wearand tire of insulation, t{sub}s= 1-60s); determining the voltage recover' curve U{sub}r (t) after opening the chunt circuit. On the basis of results of the tests mention above it is possible to determine criteria for estimating the technical conditionalof insulation.