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Testing of Circuit Breaker

Type tests are conducted on circuit breakers to prove their capabilities and confirm their rated characteristics. These tests include mechanical, thermal, dielectric, and short circuit tests. Mechanical tests check the breaker's opening and closing operation. Thermal tests check temperature rises during rated current flow. Dielectric tests check withstand capacity to power frequency and impulse voltages. Short circuit tests use oscillograms to observe breaker behavior during short circuits. Routine tests also check proper breaker functioning and include power frequency voltage, millivolt drop, and operational tests.

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Osama Salem
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296 views2 pages

Testing of Circuit Breaker

Type tests are conducted on circuit breakers to prove their capabilities and confirm their rated characteristics. These tests include mechanical, thermal, dielectric, and short circuit tests. Mechanical tests check the breaker's opening and closing operation. Thermal tests check temperature rises during rated current flow. Dielectric tests check withstand capacity to power frequency and impulse voltages. Short circuit tests use oscillograms to observe breaker behavior during short circuits. Routine tests also check proper breaker functioning and include power frequency voltage, millivolt drop, and operational tests.

Uploaded by

Osama Salem
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Testing of Circuit Breaker

Testing of circuit breakers is more difficult as compared to other electrical


equipment like transformer or machine because the short circuit current is
very large. Testing of the transformer is mainly divided into two groups,
type tests, and routine tests.

Type Tests of Circuit Breaker

Type tests are conducted for the purpose of proving the capabilities and
confirming the rated characteristic of the circuit breaker. Such tests are
conducted in the specially built testing laboratory.Type tests can be
broadly classified as the mechanical performance test, thermal test,
dielectric or insulating test, short circuit test for checking the making
capacity, breaking capacity, short time rating current and operating duty.

Mechanical Test – It is mechanical ability type test involving the repeated


opening and closing of the breaker. A circuit breaker must open and close
at the correct speed and perform its designated duty and operation
without mechanical failure.

Thermal Test – Thermal tests are carried out to check the thermal
behavior of the circuit breakers. The breaker under test deal with the
steady-state temperature rises due to the flow of its rated current through
its pole in a rated condition. The temperature rise for rated current should
not exceed 40° for current less than 800A normal current and 50° for
normal value of current 800A and above.

Dielectric Test – These tests are performed to check power frequency and
impulse voltage withstand capacity. Power frequency tests are kept on a
new circuit breaker; the test voltage changes with a circuit breaker rated
voltage.
The test voltage with a frequency between 15-100Hz is applied as
follows. (1) between poles with circuit breaker closed (2) between pole
and earth with circuit breaker open, and (3) across terminals with circuit
breaker open.

In impulse tests impulse voltage of specified magnitude is applied to the


breaker. For outdoor circuit dry and wet tests are conducted.

Short -Circuit Test – Circuit breakers are subjected to sudden short-


circuits in short-circuit test laboratories, and oscillograms are taken to
know the behavior of the circuit breakers at the time of switching in, during
contact breaking and after the arc extinction.

The oscillograms are studied with particular reference to the making and
breaking currents, both symmetrical and asymmetrical restriking voltages,
and switchgear is sometimes tested at rated conditions.

Routine Tests of a Circuit Breaker

Routine tests are also performed as per recommendations of the


standards of Indian Engineering Service and Indian Standards. These tests
are performed on the manufacturers’ premises. Routine tests confirm the
proper functioning of the circuit breaker. The routine tests confirm the
proper functioning of the circuit breaker.

Power frequency voltage test being the same as mentioned under the
heading of type tests, the millivolt drop test is performed to determine the
voltage drop within the current path of the breaker mechanism.
Operational test is performed on the breaker by simulating its tripping by
artificially closing the contacts of the relays.

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