Capacitance & Tan Delta Test Kit for Power Equipment Insulation does not fail all at once. It deteriorates gradually, over months or years, until the point where it can no longer do its job. The problem is that gradual deterioration is invisible during a routine inspection. You cannot see it, and a standard voltage test will not catch it early enough to be useful. A capacitance & tan delta test kit is the instrument that closes that gap. It measures two things that together tell you exactly what condition the insulation is in, long before it becomes a failure event. What Capacitance and Tan Delta Actually Mean Capacitance is the ability of an insulation system to store electrical charge. Every piece of high voltage insulation, whether it is a transformer bushing, a cable, or a current transformer, has a capacitance value. That value changes as the insulation ages or absorbs moisture. Tracking it over time reveals whether the insulation is behaving the way it should. Tan ...