I. Grounding Device Installation Steps
1. Select a suitable grounding electrode:
Galvanized angle steel or steel pipe is preferred. The recommended length is 2.5 meters, and the burial depth should be ≥0.8 meters to ensure full contact with the soil.
If the soil resistivity is high, a resistance-reducing agent can be added, or a deep well grounding electrode can be used.
2. Standardize the connection method:
The grounding wire should be multi-strand stranded wire with a copper core cross-section ≥4mm², and securely connected to the equipment's grounding bolt.
The grounding core of the armored cable must be connected to the grounding bolt inside the equipment, and the steel strip and metal casing should be connected to the grounding bolt outside the equipment.
3. Ensure the grounding resistance meets the standards:
Ungrounded neutral system: Grounding resistance ≤10Ω.
Grounded neutral system: Grounding resistance ≤4Ω.
Use a grounding resistance tester to measure. If the resistance value exceeds the standard, check whether the grounding electrode is corroded or broken, or whether the soil is dry.
II. Key Precautions
1. Independent Grounding:
The grounding wire should be connected separately to the main grounding line and must not be shared with the neutral wire.
2. Bridging Requirements:
Metal pipes, cable armor, and metal casings should be grounded at the entrance to hazardous areas.
When the resistance between flanges or threaded joints is >0.03Ω, a bridging conductor should be installed.
3. Regular Inspection:
Inspect the appearance of the grounding wire weekly, measure the grounding resistance monthly, and conduct a comprehensive inspection annually.
Professional Inspection:
On-site inspection and acceptance can be commissioned to an organization (such as Shenzhen Zhongnuo Testing).
4. Standard Basis:
Refer to Articles 6.4.2.8-6.4.2.10 of the "Technical Specification for Electrical Explosion-Proof Safety Inspection in Hazardous Locations".
III. Common Problems and Solutions
1. Excessive Grounding Resistance:
Check whether the grounding electrode is corroded or broken, or whether the soil is dry.
2. Broken Grounding Wire:
Repair or replace immediately to ensure the integrity of the grounding system.
3. Loose connections:
Reconnect and ensure a secure connection to avoid malfunctions caused by connection problems.
