This SAE Aerospace Recommended Practice (ARP) identifies the minimum requirements for the testing of insulated electrical wiring for on-aircraft, aeronautical and aerospace applications. The testing requirements defined herein, ensure that a wire fault can be found safely when using a high potential voltage tester (hipot). This test is intended to aid in finding a breach in the wire insulation, and not for the identification of the resistance of the insulation. The test method defined herein is limited to equipment which ia able to control and limit the DC output to 1500 VDC maximum. This type of wire dielectric tester is typically designed to trip on current leakage and not necessarily on arc detection. This test method is solely designed to identify gross/large wire insulation damage or degradation.
Rationale: Standardization of Electrical Wiring Interconnect Systems (EWIS) insulation breakdown testing for aerospace systems is critical for safety of maintenance personnel and preservation of aircraft systems. Reliable electrical insulation is a critical component of EWIS airworthiness. Wire insulation is constantly stressed over its life. Dirt, moisture, various fluids, corrosion, vibration, electrical spikes and surges, mechanical stresses from pulling and tugging, and many other factors add up to further deteriorate insulation. This can be instantaneous, but is more likely to be a slow and steady decline over time. The remaining life of the insulation could be measured in years, or it could break down at the next startup. Hipot (high potential voltage testing) or insulation breakdown testing can assist in finding wiring faults when electrical systems or components are functioning intermittently due to a wiring faults. This ARP provides guidance in effective and safe ways of performing insulation break down testing (hipot) through the use of a Low-Energy High Voltage (LEHV) signal, which induces a spark at a defect location. As with all wire test methods, adherance to recommended process and understanding the limitations of the test equipment and unit under test is pivotal to personnel safety and test outcome.