A Partial Discharge analysis is an ideal solution to control MV switchgear HV systems in operation.
A set of techniques to discover possible damage in dielectrics and connections of HV substations and MV switchboards.
Partial Discharge is an electrical discharges that does not completely puncture the insulation between conductors and only occur in the medium and high voltage range.
The size of these discharges is usually small, but slowly the Partial Discharge is able to irreparably damage the insulation, up to the formation of destructive arcs.
The non-destructive diagnosis of Partial Discharge, if made early and regularly, identifies these sources of potential irreparable damage.
If they are not identified, Partial Discharge will evolve to destructive plant damage, causing production losses and high costs and, above all, may become a risk for personnel.
Paradoxically, the diagnosis of Partial Discharge is often much simpler than people think.
The search for Partial Discharge, for the majority of the plants, does not require production stoppages or high investment costs.
You simply need to have the right tool, with dedicated algorithms and “listen”.
The sensors “perceive” three types of signal:
TEV sensor – Transient Earth Voltage
When a partial discharge occurs inside a switch, it generates electromagnetic waves that can only escape through the openings present.
Crossing the structures these waves generate “Transitory Voltage to Earth” (TEV) which can be detected from the outside by a contact probe.
EVT graph with data interpretation
Ultrasound sensor “Airborne”
Partial discharges also emit acoustic waves, especially ultrasound, as they generate turbulence in the air.
The instrument has the highest sensitivity around 40 kHz, when it can pick up ultrasounds that pass through even the smallest openings in the casing of the components examined and around the connections.
Partial discharge ultrasound graph
RCFT – Radio Frequency Current Transformer
When a partial discharge occurs in an MV cable, current pulses are created and propagate from the discharge point through the ground cables.
When possible, the RCFT ring is placed on the ground cable connected to the MV cable sheath and can therefore detect the presence of discharges in the cables.
RCFT ring for MT cable control