How can you perform contact resistance test of HT circuit breaker

CONTACT RESISTANCE MEASUREMENT TEST

How can you perform contact resistance test?

It has a two different test set.

  1.  MOM 600A Micro-Ohmmeter  (MAGGER)
  2. CIBANO 500 (Omicron)

MOM 600A Micron-Ohmmeter (Magger)


The micron ohmmeter `is designed to measure the resistance of any (HT, LV, VCB, OCB, ACB) Circuit breaker (Male, Female) contacts, Bus-Bar Joints, contact elements in Bus-Bar.
 when contact resistance rises because of oxidation, loosened or improperly tightened threaded joints, temperature rises abnormally at the points of contact. This abnormal heating reduces conductivity thereby accelerating the rise in temperature and this often leads to serious trouble.
The micro-ohmmeter can be used to detect such problems early so that they can be remedied long before trouble starts. Checking contact resistance at regular intervals provides a clear indication of the state of your system.

Testing Description

Contact Resistance of Circuit Breaker 


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  1. First, you checked your equipment position his completed isolated with PTG(Portable Temporary Ground).
  2. Your equipment contact it has a closed position.
  3. Connect the Micro-Ohmmeter to Ground Connection.
  4. Connect the Micro-Ohmmeter to the circuit breaker (Fig A).
  5. Set the current limit in 100A.
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  6. Now rotate the current regulator and increase slowly in the limit of current.
  7. Press the resistance pushbutton for the result.
  8. Read the result and noted.

Contact Resistance of Bus-Bar Joints

  1. Connect the micro-ohmmeters current cables to the object being tested. Do not connect the sensing cables since measurements will be taken using an external movable voltmeter.(Fig B)
  2. Set the current limit in 100A.
  3. Connect an external voltmeter to the bus-bar.
  4. Now rotate the current regulator and increase slowly in the limit of current.
  5. Read the voltmeter (0.1 mV = 1 µΩ in this example).

CIBANO-500 
Contact resistance
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