Comparison of PD Patterns Obtained by Conventional Conducted Signals Measurement and TEV Sensor during Electrical Ageing Tests

The conventional Partial Discharges (PDs) measurement systems, IEC60270 compliant, normally use a quadripole as coupling device to convert the current pulses to output voltage signals when the system bandwidth is in the frequency range from 40 kHz to 1 MHz. This kind of measurement usually needs an off-line measure and an invasive procedure to connect the objects under test to the measurement system. Other measurement systems based on non-invasive sensors like High Frequency Current Transformer (HFCT) and Transient Earth Voltage (TEV) could be used if the provided results give comparable response. Focusing on TEV sensors, they can be coupled to measurement systems having a frequency bandwidth out of the range defined in IEC60270 standard. The comparison among TEV measurement system and those IEC60270 compliant can be based on the derived and statistical quantities computed starting from the PD pattern. PD Patterns have been collected during electrical ageing test applied to twisted pair located in an air insulated medium voltage switchgear (AIMVS).