Commissioning and Test Procedure of Power Cable and Equipment

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

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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.

HVDC or HVAC, Which Test is the best for XLPE Power Cable?

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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

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.

              sn’t need the equipment to make 1.7 U0 for testing

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.

ü  Because of space charge, unequal electrical stress caused by defection can be released so We can’t detect even big problem when we take DC Test