Electrical Isolation

Definition - What does Electrical Isolation mean?

Electrical isolation is a method of corrosion control. Conductors are prone to corrosion from stray current that originates from dissimilar metals. Providing good isolation for these conductors manages the corrosion significantly.

Electrical isolation is achieved using a mechanical switch that isolates a section of a circuit from the main electrical power system as and when required.

Corrosionpedia explains Electrical Isolation

AM radio towers are an example of electrical isolators. Electrical isolation is used to shield the transmitting system from electrical pulses from the ground. The wire strain insulators from the ground completely cut the electrical path between the support on the ground and the tower. This completely eliminates the problem of galvanic cell corrosion, which is linked to the copper grounding systems.

Various electrical isolators can be used, depending on the requirements of the system. Some of types of isolators are:

  • Single break isolators - This type is divided into male and female contacts. The rotation of the post insulator moves the contact arms. Where both insulator stacks are rotated in opposite directions, the isolator is closed with the contact arm. Counter-rotation of both stacks causes the contact arm to open, and hence the isolator is turned off.

  • Double break isolators - Their constructional features are three post stacks where the central post is a tubular male contact that rotates horizontally. The rotation can be done manually using a lever at the base of the post, or by a motor that rotates the contact using a tie rod.

  • Pantograph isolators - This type of electrical isolation allows installation of modern switch gear with the least space required. It is comprised of an operating insulator and a post insulator.

Electrical isolators can be categorized differently, based on the position of the power system. The categorizations are:

  • Line side isolator - This type of isolator is fixed at the line of a feeder.
  • Bus side isolator - This kind of isolator is attached directly to the main bus.
  • Transfer bus side isolator - This type of isolator is attached directly to the transfer bus.

There is no arc-quenching technique used in an isolator, hence it must be operated when the circuit is free from any current. Opening or closing any live circuit by isolator is dangerous because there can be huge arcing between the contacts. A hand isolator can operate voltages that are up to 145kV, while higher voltages that are over 245kV require motorized isolators.

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