Understanding Leakage Current

Leakage current refers to the unintentional flow of current from electrical conductors to unintended paths. It can occur due to insulation breakdown, contamination, or other faults in power system assets, such as transformers, cables, or distribution equipment. Leakage currents can potentially lead to equipment damage, electrical fires, or pose safety hazards.

Leakage current may indicate:

Imperfections in Insulation: Insulation materials may have microscopic imperfections, voids, or impurities. These imperfections can provide unintended paths for electric current to flow through the insulation, leading to leakage current. The quality and purity of the insulation material play a significant role in minimizing imperfections.

Surface Contamination: Dust, moisture, dirt, and other contaminants on the surface of the insulation can create conducting paths that allow current to bypass the insulating material. Surface contamination can be a significant contributor to leakage current.

Temperature and Humidity Effects: Temperature and humidity levels can impact the conductivity of insulating materials. High temperatures and humidity levels can lead to an increase in leakage current as the insulation's resistance decreases. This is especially relevant in high voltage and high-power applications.

Electromechanical Stress:  Mechanical stress, such as vibration, bending, or flexing, can cause localized changes in the insulation material, leading to increased leakage current. This is particularly important in situations where cables or wires are subject to mechanical stress.

Voltage Stress: Applying a high voltage to insulating materials can cause electrical breakdown, resulting in increased leakage current. The electric field strength within the insulation material can cause ionization or partial discharges, leading to current flow.

Material Degradation: Over time, insulation materials may degrade due to factors like UV exposure, chemical reactions, or aging. Degraded insulation materials can develop cracks, voids, or other defects that contribute to leakage current.

Corona Discharge: In high voltage systems, especially in areas of sharp curvature or irregularities, the electric field strength can become concentrated, leading to corona discharge. Corona discharges can create localized ionization and leakage current.

Environmental Factors: Environmental factors, such as pollution, salt, or chemical exposure, can lead to surface contamination and chemical changes in insulating materials, which can exacerbate leakage current.