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Destructive Testing (POTENTIALLY)

Destructive Testing is not encouraged for any test. The only reason it is mentioned here, is to prove a point. IT CAN BE DESTRUCTIVE IF THE PROPER, TRAINED PERSONELL ARE NOT PERFORMING THE CRITICAL TESTS!


There are many tests that have been used throughout our careers, that when proof emerges that there is damage being incurred, the destructive procedure stops. We have code that changes every three years. Of course, the electrical standards, equipment, codes, and practices change frequently as well. We are constantly undergoing plenty of change. The following tests are briefly outlined.

Primary Current Injection Hi Pot Testing

Primary Current Injection Test (Breaker Testing)
Molded Case Circuit Breakers (MCCB) are safety devices that need to be tested in order to prove they will continue to provide safety. A primary current injection test is a series of tests that prove the breaker will interupt within the parameters to prove it is a safe device. Like other devices, they can age and deteriorate. Keeping these devices maintained and serviced are a great concern in our field. Some facilites take this concern lightly, and some facilities adhere to the specifications very strictly.

There is a Canadian Standards Association (CSA) - C22.2 NO. 5-13 document that gives the parameters for the test. This is a guidline. The actual procedure takes a very highly trained individual to expedite the tests. Putting the breakers through high current testing for a length of time can heat the breakers, and if the improper testing equipment is performed, it can prematurely age the breaker. In some cases it can actually destroy the breaker completely.

These parameters are under constant scrutiny. The frequency that these standards are being reviewed has been narrowed considerly in the past few years. The following outline is probably outdated already.

MCCBs are given two interruption tests at "limited" fault current.
10 kilo-amperes (kA) for 101-800 ampere breakers
14kA for 801-1200 ampere breakers
20kA for 1201-1600 ampere breakers
25kA for 1601-2000amp breakers
60kA for 4001-5000amp breakers

MCCBs are given two (2) interruption tests at maximum rated short-circuit current (SSC) at 100kA interrupting current.
#1) The test circuit be closed on the circuit breaker - safely clearing the fault.
#2) The circuit breaker be closed on the maximum fault - safely clearing the fault.

Thermal, IR scans are less destructive, and in many cases more reliable than primary current injection system testing done "in-house." It is the opinion of this site, that only highly trained individuals, coupled with the proper equipment, should be doing primary current injection tests. Just saying.

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High Pot Testing (HiPot)
High Pot Testing is a high voltage test that performs insulation resistance and dielectric breakdown. The tester will first test for mis-wiring, resistance, opens, and shorts. It will then apply the user specified amount of voltage through the unit into the cable or harness. The newer models that connect to the computer for analysis, and recording purposes are extremely accurate and easy to keep within ISO standards because of the software updates. Ramp times, along with progress bars give you a graphical view of your test, and give you piece of mind the test is being completed safely and efficiently.

The manual HiPot testing equipment heavily relies on the user, and depending on the age, can open the margin for error to damage the insulation of the cable. Manual dials without safety interlocks, and pressing inputs to interrupt current/voltage are sketchy set ups and are unfortunately used in some companies. Safety interlocks can be wired to make sure the operator, under no circumstances, can get shocked by the test if the tester exceeds 45 uC. The more "manual" the test is, the more innacurate the results can be and can sometimes overheat the conductor. This can fatigue the cable, and this type of testing is not endorsed.

The new machines will pick up over current, leakage, and dielectric failure (breakdown, withstand, and resistance). This picks up on stray strands, or stray shielding, contaminants on the conductor, nicked insulation, or terminal spacing issues.

Current failures which point to an excess of inrush, are sometiimes caused by shields in the cable. That's why it's beneficial to have a computer based HiPot tester to allow a setting to be used that checks off "high capacitance shield allowed" or something simliar.

Leakage Failures can happen because of solder flux being present. This doesn't mean the cable is bad, it's just a cable preparation error.

Dielectric failure can also self heal if solder slivers vaporize. This is why it's recommended to do two tests. The second time the test is executed, the solder is clear and the cable will pass.

The duration of a hipot test is normally 60 seconds.

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