Safety control requirements for grounding and lightning protection of building electrical equipment?

Safety control requirements for grounding and lightning protection of building electrical equipment

1. The grounding mode of the low-voltage power supply system on the construction site shall meet the following requirements:

(1) When the power supply of the construction site is provided by a special transformer, the TNS protection system with the neutral point directly grounded on the low-voltage side of the transformer should be adopted;

(2) When the construction site is powered by a special generator, the neutral point of the generator must be directly grounded, and TNS protection system should be adopted and set independently;

(3) When the construction site is directly powered by an external transformer, its basic grounding and zero connection mode should be consistent with the external power supply system. When the external power supply is TNC system, the power supply should be switched to TNS system after entering the construction site;

(4) In the same power supply system, no part of equipment should be connected with zero protection, and the other part should be grounded.

2. Zero connection and repeated grounding of construction power supply protection shall meet the following requirements:

(1) In the neutral line protection system, the metal shell of electrical equipment must be connected to the protection neutral line (PE line).

(2) The protective neutral wire shall meet the following requirements:

(1) The protective zero line should be led out from the zero line (N line) at the incoming line of the distribution room and the general distribution box.

(2) The unified sign for protecting the zero line is the green/yellow double-color insulated conductor. Under no circumstances shall the green/yellow double-color conductor be used as the load line.

(3) The protective zero line (PE line) on the load side must be isolated from the working zero line (N line), and it is forbidden to mix the protective zero line with the working zero line.

(4) the control switch or fuse should not be installed on the protective zero line.

⑤ The cross section of protective zero line should not be less than that of corresponding working zero line. Multi-stranded insulated copper wire with protective zero line section not less than 2.5mm2 connected with electrical equipment.

(3) The protective zero line of the overhead line terminal and the distribution box more than 50m away from the power transformer shall be repeatedly grounded.

3. The construction electricity grounding resistance shall meet the following requirements:

The working grounding resistance of power transformer or generator should not be greater than 4ω.

(2) In TN neutral point protection system, repeated grounding should be connected to the protection zero line, and the resistance value of each repeated grounding should not be greater than10Ω.

4. The rain period construction lightning protection shall comply with the following provisions:

(1) Independent lightning protection devices shall be installed for transformers and distribution devices located in mountainous areas and lightning-prone areas.

(2) If towering buildings and metal structures (vertical lifting devices, scaffolding, etc. ) is not within the protection range of lightning protection devices for adjacent buildings (structures), and lightning protection devices shall be installed as required.

(3) The impulse grounding resistance of lightning protection device should not be greater than 30Ω.

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