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HV cables

On High Voltage underground cables West Power is able to offer online measurement of partial discharges and sheaths test.

On-line PD measurement

Needed instruments
PD instrument and sensor

Available instruments
Techimp Portable PDCheck 2.4

Reference standard
IEEE Std 400.3
IEC 60885
IEC 60840
IEC 60270

Description
Partial Discharges (PDs) are electrical discharges localized inside or on the insulation surfaces, which only partially bridges the insulation distance.

In HV cables, the presence of Partial Discharges is associated with defects due to the manufacturing/installation phase, which should be detected during commissioning of the cable itself, or due to defects arising over time due to the electrical stress, particularly in the event of overvoltages.

An on-line PD measure, to be repeated each year (or two), if no defects are detected, can help in preventing long outages of line due to insulation ground failures.

The graph that compresses most information from PD is the Pattern (Amplitude vs Phase), which identifies the type detected phenomena.

Sheath test

Needed instruments
DC supply

Reference standard
IEC 60229-2007

Description
The purpose of this test is to verify the integrity of the cable outer sheath. Such sheath is intended to protect the cable from corrosion and as mechanical protection.

The test consists in DC voltage application for 1 minute, and is passes/does not pass. The test is passed when overcome when no insulation faults occurs during the application of the voltage.