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High Voltage DC Test is Killer for XLPE Insulated Power Cable
High Voltage DC test is
alternately referred as Hi-Po test. High voltage DC (Direct Current) testing method is performing for long time on cable insulation systems, especially
for field test which broadly known as SAT (Site Acceptance Test) for users and
contractors .
But recent research has shown that DC testing is the causes to certain types of defects and that it can make worse the deteriorated condition of some aged cables insulated with extruded dielectrics and affected with electrical-tree and water-tree. That’s way our article question “Is High Voltage DC Test Killer for XLPE Insulated Cable”.
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But recent research has shown that DC testing is the causes to certain types of defects and that it can make worse the deteriorated condition of some aged cables insulated with extruded dielectrics and affected with electrical-tree and water-tree. That’s way our article question “Is High Voltage DC Test Killer for XLPE Insulated Cable”.
Sponsored:
LVDC or Low voltage DC testing is covering
voltages up to 5 kV and HVDC high voltage dc testing covering voltage levels
above 5 kV.
Type of DC Hi-Po Test:
DC Withstand Test: DC withstand test is
such a Hi-Po test where voltage at a prescribed
level is applied for a prescribed duration. The cable system will be considered
to acceptable if no breakdown occurs.
Leakage Current Tests:
Leakage current test is a Hi-Po test with function of time where total apparent leakage output current is recorded to a prescribed voltage level. Not the absolute value, but the variations of leakage current with time is recorded what presents the diagnostic information of the cable system.Voltage Test:
Voltage test is also known as Leakage Current Tip-up Tests where voltage is increased in small steps while the steady-state leakage current is recorded, until the maximum test voltage is reached. The relationship graph between current and voltage denotes the insulation system is defective or not.Weak Points of DC Hi-Po test for Power Cable:
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A. This test is blind to certain types of defects,
such as clean voids and cuts.
B. May not replicate the stress distribution
existing with power frequency ac voltage. The stress distribution is sensitive to temperature
and temperature distribution.
C.May cause undesirable space charge
accumulation, especially at accessory cable insulation interfaces.
D.May adversely affect future performance of
water-tree affected extruded dielectric cables.
Though DC Hi-Po test is simple and easy
recently experts are thinking DC high voltage test is keeps some signs that
bring bad effect for cable at aged. Consequently we can say above mentioned
disadvantages of DC Hi-Po test turn itself as a
killer for XLPE insulated power cable.
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