Grounding requirements for electrical equipment enclosures protected by earth leakage protectors

1. The outer casing of the electrical equipment protected by the leakage protector must be grounded, and the grounding generally has the following requirements:

(1) The metal casing of the protected electrical equipment shall be grounded separately.

(2) The grounding of the metal casing of the electrical single-girder crane electrical equipment is preferably separated from the grounding of the neutral point of the power supply.

2. When the above requirements are not met and a common grounding method must be adopted, the following requirements shall be met:

(1) When the electric single-beam crane adopts the electromagnetic leakage protector, the outer casing of the protected electrical equipment can be connected to the protective ground wire (PE line) or protection.

Zero line (PFN line). In this case, the automatic switch may not be checked, but the dynamic stability and thermal stability of the leakage protector (zero sequence transformer) must be checked.

(2) When an electronic leakage protector is used, the metal casing of the protected electrical equipment can also be connected to the protective ground. In this case, in addition to checking the dynamic stability and thermal stability of the zero-sequence transformer, it should also check whether the auxiliary power supply voltage of the leakage protector is within the allowable voltage range when single-phase grounding occurs. Ensure that the leakage protector can operate reliably.

(3) The grounding resistance should be able to ensure the reliable operation of the leakage protector.

(4) When the electric single-girder crane power distribution system adopts the leakage protector for hierarchical protection, in order to make the protectors of all levels selectively act, the breaking time of each level should be different.