It is important to regularly check the condition of circuit breakers. They may look fine and are operating well. However, some might be at the brink of failure. Failure could cause serious problems in your electrical system. If one of the circuit breakers fails and a power fault occurs, the electrical system and the equipment attached may be seriously damaged. This may result in high repair costs and interruption of electrical service.
The ANSI/NETA MTS-2011 or the Standard for Maintenance Testing Specifications for Electrical Power Distribution Equipment and Systems guides technicians on what testing method to conduct and the expected values during a test. Below are the recommended DC electrical tests by the InterNational Electrical Testing Association (NETA).
1. Contact Resistance Test
This diagnostic method measures the circuit breaker’s contact resistance. There are times that circuit breaker contacts develop carbon deposits, pitting or corrosion. This may introduce serial resistance which reduces the current flowing through the contacts. This may result in localized Ohmic heating and eventual failure. Also, one of the reasons to conduct a contact resistance test is to determine the condition of the pivot point between the stationary and moving contacts.
The insulation resistance helps technicians find gross defects on the circuit breaker’s insulation system. However, pinpoint problems like tracking, moisture buildup and insulation degradation, an overpotential test is needed.
3. DC Overpotential Testing
The overpotential test is one of the diagnostic methods recommended by the ANSI/NETA MTS-2011. This test is conducted by applying a high DC voltage across the insulation system of the circuit breaker being tested. This helps determine if the insulation is still within the manufacturer’s specifications.
Circuit Breaker Insulation Systems
Below are the two main insulating components of circuit breakers.
Vacuum Bottles or Arc Chutes
The arc chute is one of the important components in a circuit breaker. The arc chute extinguishes the arc during in case of a power fault. Arc chutes must stretch and contain the arc. If the arc chute is faulty, a restrike may occur where the arc reestablishes itself. When this happens, the circuit breaker may not be able to clear the fault and the next upstream component has to clear the fault.
Backboard Assembly for Low Voltage Breakers and Pole Units for Medium Voltage Breakers
These components are used as support for the arc chutes and the power carrying components of the circuit breakers. The insulation of these components degrade and form carbon tracking due to arc interruption.
Protec Equipment Resources offers various options for you to acquire the needed electrical test equipment for maintenance and troubleshooting. Choose to rent, lease or purchase an insulation tester, circuit breaker test set or other testers you need. We have offices strategically located across the United States to ensure you get the equipment you need on time. Please call a representative today at 1-866-352-5550 for assistance.