The protection type and installation method of residual current protection devices must be compatible with the environmental and operational conditions. Residual current protection devices must be installed for the following: Class I portable electrical equipment and handheld power tools with metal casings; electrical equipment installed in harsh environments such as damp or highly corrosive areas; electrical machinery used at construction sites; temporary electrical equipment; socket outlets in hotel guest rooms; socket outlets in residential buildings with a high risk of electric shock; underwater lighting in swimming pools or bathhouses; underwater power supply lines and electrical equipment; and medical electrical equipment that comes into direct contact with the human body (excluding equipment in thoracic surgery rooms).
For power supplies serving passageway lighting and emergency lighting in public areas, fire-fighting elevators, electrical equipment ensuring safety in public areas, power supplies for fire-fighting equipment (such as fire alarm systems, fire pumps, and fire escape lighting), power supplies for anti-theft alarm systems, and power supplies for other locations or electrical installations where an immediate power cutoff due to leakage would result in accidents or significant economic loss, residual current alarm devices that do not cut off the power supply should be installed instead.
From the perspective of preventing electric shock, residual current protection devices need not be installed for the following: electrical equipment powered by safety extra-low voltage; electrical equipment with double or reinforced insulation used in standard environments; electrical equipment powered by isolating transformers; electrical equipment used in areas employing ungrounded local equipotential bonding measures; and other electrical equipment posing no risk of leakage or electric shock.
The installation of residual current protection devices must comply with the manufacturer's product specifications.
The leakage current of electrical circuits and equipment equipped with residual current protection devices must be controlled within permissible limits. The rated non-operating current of the selected residual current protection device must be at least twice the maximum normal leakage current of the electrical circuits and equipment. If the leakage current of the electrical circuits or equipment exceeds the permissible limit, the circuits or equipment must be replaced with ones having adequate insulation. When electrical equipment is equipped with a high-sensitivity residual current protection device, the grounding resistance requirement for the equipment's dedicated grounding system may be relaxed, provided that the prospective touch voltage remains within permissible limits. The insulation resistance of electric motors and other electrical equipment equipped with earth-leakage protection devices should not be less than 0.5 MΩ during normal operation.
Before installation, the earth-leakage protection device must be carefully inspected to ensure that its casing, nameplate, terminals, test button, and certificate of conformity are in good condition.
Earth-leakage protection devices intended to prevent electric shock accidents serve only as supplementary protection; the installation of such a device must not result in the removal or abandonment of existing safety measures.
When installing an earth-leakage circuit breaker with short-circuit protection, sufficient clearance must be maintained in the direction of arc discharge to accommodate arc flashover. Earth-leakage protection devices should not be installed in locations subject to severe mechanical vibration or strong alternating magnetic fields. Installation must take into account hazards such as water and dust, and appropriate protective measures must be implemented.
After installing an earth-leakage protection device, the fundamental electric shock protection measures for low-voltage power supply lines and electrical equipment must not be removed; only appropriate adjustments within a limited scope are permissible.
