Insulation Resistance Reasons for a Short Circuit

Circuit Flow

• A basic circuit generates electrical currents by conducting electrons along a controlled pathway. A controlled pathway uses resistors to regulate and redirect electrical currents along a wire or series of wires. For example, a light bulb filament acts as a resistor element by converting electrical current into light. In effect, the electrons heat the filament to the point where it begins to glow, while other electrons travel past the filament to complete the circuit. Short circuits occur when a resistor element weakens or fails to absorb the current. These conditions allow electrical currents to overload a circuit’s wiring.

Insulation Breakdown

• Circuit wires sit inside insulation materials that help to keep the electrical current contained inside the circuit pathway. Insulation breakdown occurs whenever the materials used to insulate a circuit begin to deteriorate. Since different types of insulation materials perform differently, a circuit may require rubber, plastic or glass materials depending on the type of circuit and the amount of current moving through the wires. In some cases, a poorly wired circuit can cause resistor and/or wire materials to overheat. When this happens, insulation materials become stressed beyond their capacity. Other factors that contribute to insulation breakdown include frequent vibration, high humidity levels and high voltage levels.

Effects

• Insulation materials carry different threshold levels that determine the amount of voltage a material can withstand before it begins to break down. Once voltage amounts exceed this threshold, a material’s resistance level decreases, meaning electrical currents can eventually seep through the material. Circuits that exceed this threshold on a frequent basis may cause insulation materials to weaken. When this happens, the material’s threshold level continues to drop. These conditions leave materials susceptible to even weaker or lower voltage amounts, which can cause further insulation breakdown to occur.

Arc Tracking

• When a circuit shorts out, the electrons or electrical current form an arc across a circuit’s wires. Circuit wires typically include a hot wire and a ground wire. Arc tracking occurs when electrical arcs form along these primary circuit wires. Deteriorated insulation materials can expose wire surfaces to one another and cause arc tracking to occur. When this happens, electrical arcs can form sparks that further deteriorate insulation materials and in some cases cause fires to develop. Arc tracking can also occur whenever a conductive liquid makes contact with insulating materials. In this situation, electrical current is drawn through the insulation material. These conditions contribute to insulation breakdown and lower the material’s resistance threshold.