Power System Protection: 5 Basic Concepts you Should Remember about SF6 Circuit Breaker

SF6 circuit breaker is a popular and modern CB, it is widely used on 250 kV, and 500 kV power systems for protection purposes. Today you’ll learn 5 fundamental concepts about SF6 breakers.

What is SF6 Circuit Breaker and Why it is named so

The breaker tank of such CB contains sulfur hexafluoride gas (SF6)which is used as the arc quenching material. Due to this reason, the name SF6 is given. SF6 CB is widely used for protecting modern power systems.

What are some properties and features of SF6 gas

  1. SF6 is an electronegative gas which has strong tendency to absorb free electrons.
  2. It is non-toxic and can be safely handled.
  3. It is highly dense gas and its density is recorded to be 5 times more than air.
  4. It exhibits excellent insulation features.
  5. It has excellent arc quenching properties.

Name the types of SF6 circuit breakers on the basis of construction

SF6 Circuit breakers are divided into three basic types.

  1. Non-puffer type
  2. Single pressure puffer type
  3. Double pressure puffer type

The video below explains these three types in detail.

What are some Pros associated with SF6

The advantages of using SF6 circuit breakers are:

  1. Unlike oil circuit breakers there are no carbon deposits and by-products which cause pollution.
  2. They have low maintenance cost compare to majority of other breakers.
  3. They inflammable and fire risk is negligible due to which they can be used in places where explosion hazards are expected to happen.
  4. They are fast and have very short arcing span.
  5. Unlike air blast CB the noise problem is little to none since the gas is enclosed.
  6. Compared to air it has a very high dielectric strength and can interrupt much larger currents.

What are some Cons associated with SF6 circuit breaker

Some disadvantages of SF6 CB include:

  1. The gas should be reconditioned after every successful operation.
  2. SF6 is an expensive gas.
  3. Arcing in SF6 CB produces a by-product HF which is extremely dangerous. The crew working with SF6 breakers should take care and keep this fact in mind while dealing with such breakers.

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