High Voltage Terminations & Splicing

Question 1

In the installation of high voltage cables, what precautions must be observed when handling and pulling cables?

Answer 1

• Use extreme caution when moving cable reels to prevent any physical damage to cables.
• Always clean (or Mandrill) all cable ducts or conduits before installing cables.
• Use the appropriate pulling tools (i.e. pulleys, winches, trucks).
• Set the reels, pulleys, etc. in the appropriate locations.
• Pull the cable slowly to avoid any excessive stress.
• Use an approved type of lubricant when pulling.
• Keep both cable ends sealed at all times.
• Leave enough slack in manholes to allow for cable movement (and splicing).
• Avoid any cable crossings in manholes.
• Avoid any sharp bends.
• Whenever storing cable, it must be kept in a cool, dry location (do not leave outdoors).

Question 2

What are the two common types of stress relief used in high voltage terminations?

Answer 2

1. Geometric stress relief - A factory-made stress cone is used to build up the thickness of the insulation in the region of high electric stress
2. Capacitive stress relief - is a prefabricated stress termination that uses a capacitive method of overcoming the problem of high electric stress in the insulation. The manufacturer calls the insulating material used in the tube Hi-K

Question 3

The IEEE defines three classifications of high voltage termination: Class 1, Class 2, and Class 3, what are the differences?

Answer 3

Class 1 termination requires stress relief, anti-tracking, and a seal to the environment.
Class 2 termination requires stress relief and anti-tracking.
Class 3 termination requires stress relief only. Used for an indoor cable termination in a clean, dry environment.

Question 4

What are three high voltage termination types

Answer 4

1. Pothead - has been traditionally used on PILC (paper-insulated-lead-covered) cables
2. Stress cone
3. Hi-K

Question 5

What three things could make a high voltage splice fail?

Answer 5

1. The shields are not put back in place
2. Air gets trapped in between layers of insulation
3. The splice is not watertight