GENERATOR CIRCUIT BREAKERS BASIC INFORMATION AND PARTS OF GENERATOR CIRCUIT BREAKERS TUTORIALS



What Are Generator Circuit Breakers?

Generator circuit breakers represent another class rated for very high continuous currents and short circuit currents, typically at generator voltages. Generator breakers are incorporated into generator bus ducts and can include other switchgear components for measuring current, detecting faults, and grounding.

Generator breakers are available up to 50 kA nominal current and up to 220 kA interrupting current. Two technologies are employed—air blast at the higher ratings and SF6 self blast at the lower and medium power levels (up to 120 kA). For nominal currents above 20 kA, the generator breaker is usually equipped with a forced cooling system, using water, for example. Generator breakers have been available since the 1960s.

Advantages of using generator breakers include the following:
Reduced station cost by eliminating station transformers and increasing station layout flexibility.

Simplification of operation, especially during commissioning and recommissioning; this is because the generator can be handled as a separate unit, isolated from the main and unit transformers.

Fault protection between the generator and transformer. Two zones of protection are created and generator faults are cleared by the opening of the generator breaker alone.

Unbalanced load protection of the generator.

Protection of the generator from transformer faults.

Reliability/availability increase.

Historically, generator circuit breakers have been of air-blast design with pneumatic operators. This is the technology still used today for large nuclear and fossil fuel power plants (up to 1500 MW), and large pumped storage installations.

The design has a tubular housing and is horizontal. Newer designs utilize SF6 self-blast technology and hydraulic operators. These are rated for application to smaller power plants (gas turbine/cogen, for example) from 60 to 400 MW and smaller pumped storage installations.


PARTS OF GENERATOR CIRCUIT BREAKERS

Outline and interrupter details of a generator air-blast circuit breaker-type DR, 36 Kv, up to 50 kA with forced cooling, 200 kA.

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