Electrical Engineering ⇒ Topic : Classification of cables

CLASSIFICATION CABLES:-

Low voltage (LT.) cables                   :             operating- voltage upto 1 kV

High voltage (H.T.) cables                 :            operating voltage upto 1.1. kV

Super tension (S.T.) cables               :            operating voltage upto 33 kV

Extra high tension (E.H.T.) cables     :            operating voltage upto 66 kV

Extra super voltage power cables      :          operating voltage beyond 132 kV.

Insulation resistance of a single core sheathed cable

Insulation resistance of a single core sheathed cable is given by

where

R = insulation resistance

p = resistivity of dielectric

r₁ = conductor radius ; and

r₂ = sheath radius.

The insulation resistance of a cable can be measured by the following two methods :

• Galvanometer method
• By meggar