In this article, we will see how to conduct routine tests of circuit breakers.
Circuit breakers are an essential part of an electrical circuit. It is a
device that is used as a protective switch for passing electrical current with
tripping conditions checked.
When it detects a trip condition, the breaker opens its contact and
isolates the input and output voltage from contacting each other.
🛠️ Visual Checks
🛠️ Mechanical Test
🛠️ Routine Tests of Circuit Breakers
🛠️ Dielectric Test
🛠️ Tightness Test
🛠️ Resistance Measurement Test
🛠️ Thermal Test
Practically speaking, when a circuit breaker is installed in the panel,
it can sometimes remain idle too for a long duration of time.
This means, there will be cases where that circuit breaker has not been
turned on for many days and suddenly, it is turned on for use.
Visual Checks
Visual
checking is also a very basic testing method to verify the quality of the
breaker.
The
parameters checked are – identification of any auxiliary equipment, corrosion
on the metallic surface, quality, and color of paint, and language and data on
the templates
Mechanical Test
Here,
the circuit breaker is repeatedly opened and closed at a high frequency (which means
more number of times in a short duration).
The
objective is to see that such frequent mechanical switching does not
hamper the desired duty and operation of the breaker.
Also,
the breaker must not go into a failure mode due to such high mechanical
switching rates. Normally, it is operated at least 5 times with a minimum and
maximum voltage limit (85 to 110% of control voltage respectively).
The
breaker must be able to handle such pressure with ease and not fail in such
conditions.
Routine Tests of Circuit Breakers
In any case, whether used or unused, the circuit breaker should
be ready to perform its function, without failing.
So, before dispatching the breaker from a manufacturer’s premises, it is
subjected to various routine tests to see its functionality and whether it is
able to survive in abnormal conditions or not.
You can simply relate it to a quality test. If the quality of a product
is not properly before dispatch, then it will be rejected and not allowed to be
sold in the market.
Likewise, every product that we use undergoes its respective tests in
the factory and a circuit breaker is one of them.
In
this post, we will discuss some standard routine tests that are performed on a
circuit breaker before it is dispatched from a manufacturer’s factory.
Dielectric Test
The
dielectric constant is related to insulation property. Basically, the
dielectric test is performed to check the insulation properties of a
circuit breaker.
In
the field, there will be conditions where an abnormal overvoltage will occur
and hamper the internal circuitry of the breaker (main circuit, auxiliary
circuit, and control circuit).
So,
these circuits are gone through short-duration power frequency tests. In this,
the circuit breaker is subjected to a very high voltage (typically around
2000V) for a short duration of time (maybe 1 minute).
There
are cases where the insulation is not proper and when it is stressed with
such high voltages, then it may start to leak and begin to discharge leakage
currents.
So,
the motive of this test is to see whether the insulation is able to withstand
such high voltages, and also, that there should not be any harmful discharge
from it.
Standard
input frequency will be used – 50 or 60 Hz.
Tightness Test
There
are gas-insulated circuit breakers available in the market. The objective of
the tightness test is to check the tightness of gas-insulated breakers.
For
your information, it is to be noted that the gas used inside these breakers is SF6 (Sulphur Hexafluoride).
Basically,
you can compare this test to a leakage test. All the joint points (which
contain gas) are covered airtight with thin sheets of polythene, for more than
8 hours.
As
the joints are now covered, the gas density inside them is measured by inserting
a gas-detecting port of a detector through these covers.
If
the density received is more, then it means that the breaker is not tight and
gas is leaking through it.
The
unit used in measuring the density is ppm.
Resistance Measurement Test
The
resistance is measured between the switching contacts of the breaker so that we
can identify the power losses that it will cause during the running condition. The less the resistance, the lower will be the losses that occurred.
A
circuit analyzer test kit is used to inject DC voltage between the
contacts, and too in closed conditions. The current will be measured when the
voltage is inducted.
So,
as R= V/I; suppose the resistance is more. Then, as P (Power Loss) =I²R,
more resistance will cause more power loss.
Thermal Test
When
a high current flows through the breaker, the temperature of the pole
increases. This test is done to check whether the temperature of the
pole is under-rated degrees and not exceeding it.
Routine
tests are a must for a circuit breaker to be sold in the market, as it verifies
the proper functionality of the breaker.
Thank You...!!!