Commissioning and Test Procedure:
Testing methods for power cable insulation depend basically on type and material of cable insulation. Cross-linked Polyethylene (XLPE) is now spreading widely for power cable insulation at the rated voltage of 66 to 500 kV world-wide.
Quick and easy understanding for commissioning test for transmission line and major equipment. Here specially focused on underground power transmission line, underground cable megger testing, cable fault location and main causes of cable fault, some manufacturing fault. You also find some megger test procedure for transformer or circuit breaker or common methods for insulation test or megger test.
To see the slide view click below link,
Commissioning and Test Procedure of Power Line
Sponsored:
Typical Electrical Test for Power Cable
01. Resistance measurements through bolted connections with a
low-resistance ohmmeter;
02. Insulation-resistance test individually on each conductor
with all other conductors and shields grounded. Apply voltage in accordance
with manufacturer’s published data;
03. Shield-continuity test on each power cable;
04. In accordance with ICEA, IEC, IEEE and other power cable
consensus standards, testing can be performed by means of direct current, power
frequency alternating current, or very low frequency alternating current. These
sources may be used to perform insulation-withstand tests, and baseline
diagnostic tests such as partial discharge analysis, and power factor or
dissipation factor.
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HVDC or HVAC, Which Test is the best for XLPE Power Cable?
We propose to take HVAC test1.
HVAC Soak Test is also suitable way for testing insulation as per IEC 62067 There are 2 ways of HVAC Test mentioned in IEC 62067
(1.7 U0 HVAC Test / U0 HVAC Soak Test)
2. HVAC Soak Test doesn’t require additional cost for equipment and complex testing progress, It is the way to keep the testing cost as HVAC Soak Test doe.
We not recommend to take HVDC test
We not recommend to take HVDC test
There are
several reports that DC Testing is ineffective and could even be dangerous for the
system under test.
v IEC 62067 : The clause
regarding HVDC Test for insulation is changed to HVAC Test for insulation after
it is revised
v IEEE 400 : HVDC is not
effective in detecting certain types of insulation defects in a bable system
when compared with AC Test.
1. DC test
can’t detect some problems which can be detected during in HVAC Test.
ü AC Electrical
stress is influenced by capacitance in insulation instead DC Electrical stress
is influenced by resistivity
ü So, the problems
in AC system can be different with DC system because of Electrical stress
difference.
ü The reason of some
problem in AC system can’t be detected in DC test.
2. DC test
can’t detect some problem regarding partial discharge which can be the worst
problem in Cable system.
ü AC voltage makes
many kinds of partial discharge pulses in 1 cycle of AC current and it’s
repeated
ü But, DC voltage
makes constant value so the number of partial discharge pulses and the value
are very normal as compared with AC voltage.
ü So, even big
defection can’t be detected in DC voltage test.
3. Space
Charge
ü In the case of
applying DC voltage, Normally Space charge is accumulated in insulation layer.
ü However, when
there is a defection, more charges got into the insulation layer and will be
accumulated more than in normal situation because of unequal electrical stress
as compared with equal electrical stress.
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