Equipment grounding on Korean substations covers connecting each item — transformers, switchgear, panels — to the earthing system and measuring earth resistance and electrical continuity so the substation runs safely. However good the mesh grid is, a loose or broken connection between equipment and grid leaves dangerous voltage on enclosures during a fault. This work also requires reviewing low-voltage earthing systems and whether earthing is integrated, common or separate. This guide covers three stages: planning, installation and measurement.
Contents
- Common Pre-Work Review
- 1. Planning
- Planning Checklist for Equipment Earthing
- 2. Installation
- 3. Measurement
- FAQ
- Reference Standards
- Summary
Common Pre-Work Review
Review the design (including architectural and mechanical drawings), schedule, building services rules, KEC, standard electrical specifications and design criteria, KESCO inspection criteria, the power supply terms and KOSHA guides on earth conductors, earthing design and equipotential bonding. Prepare an earth resistance tester, continuity tester, cable cutter and hydraulic compression tool, plus bare stranded copper, earth sleeves, lugs, earth terminal boxes and terminals.
1. Planning
- Work out an equipment earthing method suited to site conditions.
- Compare the equipment earthing calculation and drawings against that method.
- Review the low-voltage earthing system (TN, TT, IT) based on how protective and neutral conductors are connected.
- Review whether integrated, common or separate earthing applies.
- Prepare the equipment earthing plan following the method statement guidelines.
Planning Checklist for Equipment Earthing
| Item | Content |
|---|---|
| Earthing system | TN, TT or IT, depending on how protective and neutral conductors connect |
| Earthing arrangement | Integrated, common or separate earthing |
| Equipotential bonding | Secure connections for personal safety and equipment protection |
| Links | Connections to the mesh grid and structural earthing |
| Measurement | Earth resistance and electrical continuity |
Installation and test criteria for each system and arrangement follow the KEC and client design standards.
2. Installation
- Prepare equipment earthing work to suit the site.
- Connect earth conductors, rods, the mesh and steel structures to equipment fully, electrically and mechanically, per the design and standard procedure.
- Remove coating or paint from contact surfaces before connecting.
- Allow for galvanic corrosion when joining dissimilar metals.
- Make equipotential bonding connections secure, since they protect people and equipment.
- Bury conductors below the frost depth at the equipment location.
- Visually inspect that the work follows the specified method.
3. Measurement
- After installation, measure earth resistance and electrical continuity to check for problems.
- Analyze results and keep records.
- If needed, plan reinforcement or improvements to the earthing method.
FAQ
Why measure electrical continuity?
Even with good earth resistance, a broken conductor or poor joint between equipment and grid gives no protection. Continuity testing confirms the connection.
Why review TN, TT and IT systems?
The protective method and earthing requirements depend on how protective and neutral conductors are connected, which sets the installation and test criteria.
How does integrated earthing differ from separate earthing?
Integrated earthing ties power, telecom and lightning protection earths into one system; separate earthing gives each its own. Install to the arrangement in the design.
Reference Standards
- Electricity Business Act (전기사업법) — law.go.kr
- Electrical Safety Management Act (전기안전관리법) — law.go.kr
- Electric Technology Management Act (전력기술관리법) — law.go.kr
- Electrical Construction Business Act (전기공사업법) — law.go.kr
- Occupational Safety and Health Act (산업안전보건법) — law.go.kr
- Korea Electro-technical Code (KEC, 한국전기설비규정) — law.go.kr
- Technical Standards for Electrical Equipment (전기설비기술기준) — law.go.kr
- KEPCO design standards and substation construction practice; Korean Industrial Standards (KS)
- NCS competency unit Substation Equipment Grounding (기기접지공사, 1901070326_22v2; NCS is Korea’s National Competency Standards) — ncs.go.kr
Summary
The most common mistakes are measuring only earth resistance without checking continuity, and connecting over paint. Planning depends on the earthing system and arrangement; installation on full joints, equipotential bonding and dissimilar metals; and measurement on recording resistance and continuity. Related guides: Substation Mesh Grounding, Substation Structural Grounding, Other Substation Equipment Works. A Korean version of this guide is available here.
This article restructures the Korean NCS competency unit ‘Substation Equipment Grounding’ (기기접지공사, code 1901070326_22v2) as a practical reference. Actual work must follow applicable standards and the judgment of qualified professionals; always confirm specific values, deadlines and criteria against the latest regulations and client standards.
Written/reviewed by VOLT · Last updated 2026-10-26