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ERIENCE ON LOCALIZATION &
PINPOINTING OF PARTIAL DISCHARGE
DEFECTS IN 33 kV UNDERGROUND CABLES
USING ONLINE MONITORING TECHNIQUES
RITABAN GHOSH, SOUMALYA ROY
CONDITION MONITORING CELL
Abstract
The service life of a cable can be significantly reduced if it has been expected to operate outside of the optimal
operating conditions it was designed for. The ageing process usually results in embrittlement, cracking and
eventual failure of the insulating and sheathing materials, exposing the conductor and risking a potential short
circuit, a likely cause of electrical fire. There are several reasons why the sheathing material may degrade,
including excessive heat or cold, chemicals, weather conditions, and abrasion of the sheath. All of these factors
can ultimately cause electrical failure as the insulated cores are no longer protected by the sheathing as
originally designed. Moisture ingress can also cause significant problems including short circuit and corrosion
of the copper conductors. Excessive heating of the cable will cause degradation of the insulation and sheathing
material and premature failure. The heat may come from an external source or may be generated by the
resistance to current flow in the conductor - a particular problem if the cable is overloaded and/or underrated
for the application.
This Paper introduces two new technologies to detect any 33kV Underground Cable Insulation degradation prior
to cable fault - Spot Measurement and Online Measurement. Relevant field trials in di erent suspected cable
sections will be continued which would help to minimize Underground cable faults.
Faults on underground power cables are almost always disruptive and costly to fix. So, there’s a very big
incentive to minimise the risk of such faults occurring. One of the most e ective ways of doing this is to use
partial discharge (PD) testing and mapping, partial discharge activity is an indication of incipient insulation faults
and is widely regarded as one of the best ‘early warning’ indicators of deterioration in medium and high voltage
insulation.
INTRODUCTION Medium voltage cables have three distinct phases to
their lifecycle: (1) new — just manufactured, still in the
CESC 33kV network mostly comprises of XLPE Cables and factory; (2) installed — ready for commissioning but
PILC old cables. We started Field Trials to pre-locate the not yet energized; and (3) aged — in-service for some
defect points in a 33kV buried Underground XLPE Cables. period of time. These different periods of their life provide
31
PINPOINTING OF PARTIAL DISCHARGE
DEFECTS IN 33 kV UNDERGROUND CABLES
USING ONLINE MONITORING TECHNIQUES
RITABAN GHOSH, SOUMALYA ROY
CONDITION MONITORING CELL
Abstract
The service life of a cable can be significantly reduced if it has been expected to operate outside of the optimal
operating conditions it was designed for. The ageing process usually results in embrittlement, cracking and
eventual failure of the insulating and sheathing materials, exposing the conductor and risking a potential short
circuit, a likely cause of electrical fire. There are several reasons why the sheathing material may degrade,
including excessive heat or cold, chemicals, weather conditions, and abrasion of the sheath. All of these factors
can ultimately cause electrical failure as the insulated cores are no longer protected by the sheathing as
originally designed. Moisture ingress can also cause significant problems including short circuit and corrosion
of the copper conductors. Excessive heating of the cable will cause degradation of the insulation and sheathing
material and premature failure. The heat may come from an external source or may be generated by the
resistance to current flow in the conductor - a particular problem if the cable is overloaded and/or underrated
for the application.
This Paper introduces two new technologies to detect any 33kV Underground Cable Insulation degradation prior
to cable fault - Spot Measurement and Online Measurement. Relevant field trials in di erent suspected cable
sections will be continued which would help to minimize Underground cable faults.
Faults on underground power cables are almost always disruptive and costly to fix. So, there’s a very big
incentive to minimise the risk of such faults occurring. One of the most e ective ways of doing this is to use
partial discharge (PD) testing and mapping, partial discharge activity is an indication of incipient insulation faults
and is widely regarded as one of the best ‘early warning’ indicators of deterioration in medium and high voltage
insulation.
INTRODUCTION Medium voltage cables have three distinct phases to
their lifecycle: (1) new — just manufactured, still in the
CESC 33kV network mostly comprises of XLPE Cables and factory; (2) installed — ready for commissioning but
PILC old cables. We started Field Trials to pre-locate the not yet energized; and (3) aged — in-service for some
defect points in a 33kV buried Underground XLPE Cables. period of time. These different periods of their life provide
31
