What Are the Grounding Specifications for Explosion-proof Electrical Equipment?

Ⅰ. Understand explosion-proof electrical equipment

Explosion-proof electrical equipment mainly refers to electrical equipment used in dangerous places, flammable and explosive places. Commonly used explosion-proof electrical equipment is mainly divided into explosion-proof motors, explosion-proof transformers, explosion-proof switch equipment and explosion-proof lamps. Explosion-proof electrical equipment is mainly used in places containing flammable and explosive gas and dust such as coal, petroleum and chemical industry. Electrical equipment used in explosion-hazardous atmospheres shall be constructed to prevent sparks, arcs or dangerous temperatures from becoming a source of ignition for explosive mixtures at the installation site.

Ⅱ. Grounding specifications for explosion-proof electrical equipment

1. Non-energized bare metal parts such as metal shell, metal frame, metal wiring pipe and its accessories, cable protection pipe, and metal sheath of cables of explosion proof electrical panel equipment should be grounded.

2. All electrical equipment except the lighting fixtures in Zone 2 in explosion-hazardous places should use special grounding wires; multi-strand flexible stranded wires should be used, and the cross-sectional area of the copper core should not be less than 4mm2. Metal pipelines, metal casings of cables, etc., can be used as auxiliary grounding wires. For the neutral point ungrounded system, the grounding resistance value is not greater than 10Ω; for the neutral point grounding system, the grounding resistance value is not greater than 4Ω.

3. For the lighting fixtures in Zone 2 of the explosive gas hazardous environment, the metal pipeline system with reliable electrical connection can be used as the ground wire, but the pipeline for transporting flammable substances shall not be used.

4. The grounding trunk should be connected to the grounding body at no less than two places in different directions in the explosion-hazardous area.

5. If the power supply of explosion-proof electrical equipment enters the explosion-hazardous place, if the TN-type power supply system is used, it should be the TN-S type (with separate neutral line N and protection line PE) in the dangerous place, that is, in the dangerous place, The neutral wire and the protective wire should not be connected together or combined into a single wire. Any part of the conversion from TN-C to TN-S, the protective wire should be connected to the equipotential bonding system in a non-hazardous place.

6. If a TT-type power supply system is used in Zone 1 (the grounding of the power supply is separated from the grounding of exposed conductor parts), the power supply will be protected by a (residual) leakage current action protection device.

7. If the IT type power system is used (the neutral wire is isolated from the ground or grounded by impedance), an insulation monitoring device should be provided to indicate the first ground fault.

8. When the armored cable is introduced into explosion-proof electrical equipment, its grounding core wire should be connected with the grounding bolt inside the equipment, and its steel tape or metal sheath should be connected with the grounding bolt outside the equipment.

9. In the design and operation of the electrical installation of explosion-proof electrical equipment, the influences caused by static electricity, lightning and electromagnetic radiation should be considered.