NONLINEAR OVERVOLTAGE LIMITER APPLICATION FOR INTERNAL OVER-VOLTAGE PROTECTION IN AVERAGE VOLTAGE NETWORKS

Abstract

Review of internal over-voltages in distribution networks 6…10 kV and means of their limitation has been carried out. One of the most efficient remedy for reduction of over-voltage at arcing ground is resistive neutral grounding. In order to estimate an influence of a nonlinear over-voltage limiter (NOL) on over-voltage reduction at ground an experimental research of varistor characteristics with 2,4 and 3,8 kHz frequencies has been carried out.Parameters of the NOL dynamic model have been determined. The main peculiar feature of the model is an account of m-lag time constant.A mathematical modeling of transitional processes in distribution networks with NOL has been made.Over-voltages in the calculative experiment at arcing ground for load diagram have accounted for 3.2 Uf, that corresponds to the results of field tests.