Keeping wires isolated means having good insulation. But sometimes the insulation can be the reason for a cable failing. If the insulation is damaged or insufficient, it can cause errors in the cable.
The most common error is a short, which is an unintended connection between two points. The insulation is not keeping the wires isolated and current is leaking. A low voltage test will find the short.
Sometimes the insulation is not weak enough to be found in a low voltage test. The insufficient insulation will only manifest later when the situation could be potentially dangerous. Running a high voltage test can alert you to the weak insulation so it can be fixed before ever becoming a problem.
Understanding the causes of weak insulation can help you fix them and prevent the problem from reoccurring. The bad insulation can be caused by anything from loose metal particles to solder bridges. The image shows insulation being compressed by a plastic tie wrap. Cirris wrote an article in our Learning Center showing common causes of bad insulation. If you are experiencing issues with insulation, check out the table by clicking the link below.