Measurements of RIV on Large EHV Apparatus in High Voltage Laboratory

North American practice for the measurement of Radio Interference Voltage, (RIV), on EHV apparatus is specified by the NEMA 107 Standard. The recommended measurement frequency is 1 MHz but at this frequency physically large test circuits do not represent the service condition. The measured levels of RIV for EHV apparatus may be unrealistically high at 1 MHz. This phenomenon is caused by an increase of RIV signals due to an internal resonance in the test circuit. This increased reading cannot be corrected by the application of the Circuit RIV Factor "p" since the circuit responses of the calibration and test set-ups are different.