Remote diagnosis of insulator strings using radiated emission

Considerable numbers of glass, ceramic and non-ceramic insulators strings are used on transmission and distribution overhead lines. Defects that commonly occur on this type of high voltage equipment are often associated with the presence of the corona discharges or gap discharges and therefore could be diagnosed using the electromagnetic signature of such phenomena. The paper investigates the correlation of the Radio Interference Voltage (RIV) measured in a standard CISPR circuit to the emitted radio frequency disturbance received by a high frequency electric field isotropic probe, placed in different locations around the insulator string under test. The results show that the radio frequency emission is strongly correlated to the RIV level, i.e. to the disturbing current injected by the discharge in the line conductor, confirming the possibility to develop a remote sensing diagnosis technique based on RF emission.