What comes to mind when contemplating the strength of a wire? A lot of people only consider what can be seen on the outside. For example, how far the wire can be pulled before it breaks or how high of a temperature it can withstand before it melts. But what about breakdowns in the integrity of a wire that cannot always be detected with the human eye? What about a wire’s “electrical” strength?
As soon as insulation is manufactured it starts to age. Over time its performance deteriorates and its ability to isolate the conductor is decreased. Subjecting the wire to harsh environments and temperature extremes accelerates insulation degradation even further. Damage to a wire’s insulation during manufacturing such as a nick by a wire cutter can also lower the insulation’s integrity.
The simplest of tests used to detect breakdowns in wire insulation is a Megohm (or Megger) Test, also known as an Insulation Resistance (IR) test. During Megohm Testing, the test equipment applies a high direct current (DC) voltage, usually 500 to 1500 VDC, between a conductor and one or several other conductors for a specific time period. Since we are testing for wire insulation integrity we want little or no current to flow between the conductors. Thus, a high resistance value is expected – typically 35 to 100 Megohms.
Here at InterConnect Wiring most of our wiring harnesses and panels are installed in military aircraft. A hazardous situation can exist if a wire insulation failure adversely affects equipment or causes personnel injury – especially while in the air. Therefore, we understand how extremely important it is for us to detect any insulation deterioration quickly in our electrical wiring products during the manufacturing process and take preventive measures. Every electrical test we run on our products includes Megohm Testing. We are very aware that wire insulation breakdown can exist even though they are not easily visible. We have made advancements over the years in testing our products to make sure that our wires are “electrically” strong. When we perform a Megger Test, a high resistance is desired; therefore, if a Borg tells us RESISTANCE IS FUTILE we laugh in their face. We are much tougher than they are and so are our aircraft electrical wiring harnesses!