Page 75 - Practical Power System and Protective Relays Commissioning

72 Practical Power System and Protective Relays Commissioning

One can also classify cables based upon their construction:
Conductor: aluminum or copper.
Conductor shield.
Insulation.
Insulation shield.
Filling material: plastic or PVC.
Armor.
Jacket or sheath.

6.3.1 High-Voltage Cables
Most high-voltage cables are:

Paper-insulated oil-filled cables up to 500 kV AC. This type of cable is
not good for the environment and requires maintenance.
XLPE cables up to 525 kV AC. These cables can be in service for more
than 20 years, with reliable good insulation, being maintenance free and
good for the environment.

6.3.2 High-Voltage Cables: End Terminations
The ends of high-voltage cables can be terminated in a variety of ways:
Outdoor sealing end.
Transformer sealing end.
SF6 Switchgear sealing end.

6.4 TESTING AND COMMISSIONING OF EXTRA-HIGH-
VOLTAGE AND HIGH-VOLTAGE CABLES AT SITE
6.4.1 Continuity and Phasing Checks

The continuity test is done after completion of all joints and termination
installations to ensure that there are no broken conductors in any phase. This
test is undertaken using a Megger tester, connecting one lead of the Megger
to one phase of the cable and the other lead to the other phase. Each phase is
tested as shown in Fig. 6.4.
The phasing test is done after completion of all joints and termination
installations to ensure the cable phase is the same at both ends of the cable.
This test is undertaken using a Megger tester, connecting one lead of the
Megger to one phase and the other end of the cable phase to the earth. The
other end of Megger tester is to be connected to the earth. By this test we
identify the cable phases R, Y, and B at both sides of the cable as shown in
Fig. 6.5.