The main reasons why an appliance's casing becomes electrically charged include the following:
Electrical leakage
Issues such as damaged insulation or aging wiring inside the appliance can cause current to leak onto the casing. In this case, it is necessary to check whether the earth leakage circuit breaker is functioning correctly and to inspect the internal insulation to ensure safe operation.
Grounding wire issues
Excessive grounding wire resistance: If the grounding connection is poor or the resistance is too high, the charge on the appliance casing may not be effectively diverted to the ground, causing the casing to become charged. You should check that the grounding connection is secure and that the resistance meets safety standards.
Broken grounding wire: The grounding wire may break during use for various reasons, causing the appliance to lose its grounding protection and the casing to become charged. Inspect the appliance plug and grounding wire for any signs of damage or breakage.
Damp appliance casing
If the appliance casing remains in a humid environment for an extended period, insulation performance may deteriorate, causing the casing to become charged. Check whether the appliance is located in a damp environment and take appropriate moisture-proofing measures.
Proximity between the appliance and power cables
When an appliance is positioned too close to power cables, current may be induced (e.g., via electromagnetic induction), causing the appliance casing to become charged. To resolve this, move the power cables a suitable distance away from the appliance to minimize mutual interference.
In summary, there are various reasons why an appliance casing might become electrically charged; specific causes must be investigated and addressed to ensure electrical safety.