Electrical Isolator Types, Function, Symbol, Diagram


Electrical Isolator is a piece of equipment or an arrangement used in devices and power systems to isolate two circuits or load from the power supply. The main function of an electrical isolator is to isolate two different circuits from each other. Or to isolate a part of the circuit from a power system. Generally, an electrical isolator mainly indicates a mechanical switch and they also designed with electrical arrangements. The main design consideration is its contacts should be open to visible.

There are so many electrical equipments, devices such as circuit breakers, contactors, etc are available. They also can isolate the circuits. Then why we required Electrical Isolators. The main reason is visibility. We cannot see the contacts of the circuit breaker or contactor if they are open or close. To make sure the circuit is completely disconnected, electrical isolators are used.


Types of Electrical Isolator


Electrical Isolator Types, types of isolator



There are three types of electrical isolator according to applications,

  • Single Break Isolator
  • Double Break Isolator
  • Pantograph Type Isolator




Single Break Isolator


An isolator is connected between two circuits or between a power circuit and load circuit. That there are two sides of an isolator available. So the single break isolator is one that disconnects or isolates at one side only. It isolates the power supply circuit side of the circuit from which another circuit is to be a disconnect.

Single Break Isolator Symbol, symbol of isolator



In the above symbolic diagram of the isolator, you can see there one side of the isolator is always connected and another side subjected to close or open.
The two contacts in a single break isolator are known as male and female contacts. These contact arms are fixed on a movable post insulator arrangement. So when the post insulator is rotated by a motor or manually by hand the contacts are become close or open according to the rotation.




Double Break Isolator


Double Break Isolator Symbol, symbol of isolator



The double break isolator is designed to connect and disconnect on both two sides. In the above symbolic diagram also you can see. A double break isolator is bigger in construction than the single break isolator but it provides more safety, more features, and smooth operations.

Double Break Isolator Diagram, Diagram of Isolator



In the double break isolator arrangement, there are three stacks of post insulators available. The center post insulator is subjected to movable or rotation. In that center post insulator, a tubular or flat male contact available so when that post insulator rotates this male contact will connect and disconnect the two circuits. Those two circuits are connected to the rest two post insulators with female contacts. Generally, it is designed in such a way that, the rotation of male contact in the opposite direction makes it disconnect or isolate from the female contacts. The rotation of the central post insulator is obtained by lever mechanism or motor or handle.




Pantograph Type Isolator


Pantograph Type Isolator is a single break isolator. It constructed with a vertically placed arrangement on a post insulator and operated by a rod insulator. Pantograph type isolator requires a very small place or area and it is very compact and attractive in design. It provides very higher reliability and great operation than other conventional isolators. In modern switchgear systems in electrical substations, generating stations, pantograph type isolators are using.


According to placement based in power system, there are also three types of Isolator available,

  • Bus Side Isolator
  • Line Side Isolator
  • Transformer Bus Side Isolator
Bus Side Isolators are used for coupling or connecting two Busbars in power systems, substations. All of the power systems are designed with a minimum of two buses- the main busbar and the parallel busbar. During maintenance of the power system, the Bus side isolator helps a lot to isolate the part which requires maintenance.

Line Side Isolator is connected between the busbar and line feeder. It is used to isolate a particular feeder from the supply feeder.

Transformer Bus Side Isolator used in both transformer incoming and outgoing ends. It is used to isolate the transformer from the power system for maintenance or any other reason.




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Electrical Isolator Types, Function, Symbol, Diagram Electrical Isolator Types, Function, Symbol, Diagram Reviewed by Author on 6/08/2021 Rating: 5
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