What Is Contact Resistance Test & How It Is Performed

The term “contact resistance test” refers to the resistance to current flow produced by the device’s surface conditions and other variables while it is closed. This can occur when the following individuals cross paths:

  • Breakers
  • Contactors
  • Retransmissions
  • A set of switches
  • Connectors 

The contact resistance test determines the resistance of electrical connections such as terminations, joints, connectors, busbar sections, and cable connections. These can be any two conductor connections, such as cable or busbar segments. The ohmmeter is the device used to perform the ductor test, and as such, it is sometimes referred to as a ductor tester.

Why Do You Need a Contact Resistance Test? 

To maintain a circuit breaker’s health and functionality, the contacts must be inspected regularly. Because of improperly maintained or broken connections, arcing, phase loss and even fire can occur.

Increased contact resistance can result in decreased current carrying capacity and increased losses in high-current connections. Typically, ductor testing is performed using a micro/milli-ohmmeter or a low ohmmeter.

Contact resistance testing assists in detecting fretting corrosion of contacts and diagnosing and preventing contact corrosion. A system with a significant voltage drop can be created by increasing contact resistance, which must be regulated.

What Is The Procedure Of  Contact Resistance Testing? 

Visual inspection and contact resistance testing are the two most often conducted tests on a circuit breaker’s contacts.

Examining the circuit breaker’s contacts for pitting caused by arcing, as well as damaged or deformed contacts, is included in the visual inspection check.

The second inspection is the contact resistance test. This is accomplished by applying a constant current to the contacts and monitoring the voltage drop across them. It is necessary to compare the resistance value to the manufacturer’s standard. Additionally, it is prudent to compare the current value to historical records.

These tests must be conducted concurrently since contacts can have a high contact resistance yet be damaged. A connection must exhibit adequate contact resistance and pass a visual inspection test to be recognized as healthy.

Typical Method for Contact Resistance Test

Micro-ohmmeters commonly measure contact resistance using the four-wire (Kelvin) DC voltage drop, which assures readings that are more accurate by removing the contact resistance and point set resistance.

The contact resistance test is conducted using two current injection connections and two potential leads for voltage drop measurement; the voltage cables must be connected as near to the connection to be tested as feasible and must always be included inside the linked circuit produced by the interlocked current leads.

The contact resistance is determined by comparing the voltage drop recorded by the microprocessor-controlled micro ohmmeters to the contact resistance. Simultaneously, potential inaccuracies caused by thermal EMF effects in the connections are added to the recorded overall voltage drop. When the Voltage is intact in the measurement by a variety of different means. They will induce inaccuracies in the contact resistance test in this situation.

Contact resistance influences thermal conductivity measures, mainly when transporting heat via the granular medium. When fluid flow changes channels, a decrease in hydrostatic pressure occurs.