Proper Cable Testing

Cable testing usually is part of construction acceptance testing. Cable acceptance tests give you the "as-built" cable data. Unfortunately, few owners have the important "as-startup-tested" cable test data. Configuration changes, inadvertent physical damage, and misoperation during start-up testing can stress power cables, making cable condition worse than "as-built" tests indicate.

Smart owners test cables during start-up testing, typically on each system after concluding dynamic start-up testing of that system. It’s better to correct cable deficiencies during start-up testing than to go dark in the middle of a critical production run six months later.

Smart owners trend cable test data from day one, with "as-built" data forming the baseline. The data trending curve slopes gradually in a healthy cable. A sudden break in the curve is like the red zone on a gauge.

Without baseline data, you may already be past that break. You may be comparing abnormal data to abnormal data and conclude you don’t have a problem. Trend all cable test data, and conduct baseline testing on any new cables.