Continuity testing confirms that protective connections are present and have low resistance under the chosen method. It does not reproduce short-circuit current and cannot alone prove the rated thermal or mechanical withstand of the earth circuit.
Learning objectives
Define test points, method and acceptance and combine measured continuity with design and type-test evidence.
Core engineering principles
The tested path must be specified
Main earth bar, compartments, doors, gland plates, shutters and removable devices may use different bonds.
Measurement current and lead method affect results
Four-wire or suitable low-resistance methods reduce lead error for main bonds; simple continuity may be appropriate only for secondary accessible parts.
Surface condition changes contact resistance
Paint, oxidation and bolted interfaces can create unstable readings. As-found conditions should be recorded before correction.
Continuity is not withstand
A thin braid can show low resistance yet fail under fault current. Conductor size and short-time evidence remain necessary.
Removable parts need position checks
Earth contact should engage and remain effective in required breaker positions.
Engineering application method
- Step 1: Create a test-point matrix from earth-path drawings.
- Step 2: Select instrument and connection method.
- Step 3: Measure main and auxiliary protective bonds.
- Step 4: Check removable-part earth sequence.
- Step 5: Record values, limits and corrections.
Practical example
A door braid can pass a beep test but is not the main fault-current path. The test report should distinguish equipotential door bonding from the rated main earth circuit.
Common mistakes
- Using one arbitrary point for the whole lineup.
- Grinding paint before recording as-found condition.
- Claiming fault withstand from continuity.
- Ignoring racking earth contact.
- Omitting instrument zero compensation.
Design and review checklist
- Are all protective parts included?
- Is the method suitable for expected resistance?
- Are removable positions tested?
- Is continuity separated from withstand evidence?
- Are repairs and as-left values recorded?
Standards basis and official sources
- IEC 62271-200:2021 + AMD1:2024 — AC metal-enclosed switchgear assemblies above 1 kV and up to 52 kV.
- IEC 61439-1:2020 — General rules for low-voltage switchgear and controlgear assemblies where applicable.
- IEC 62271 series — High-voltage switchgear and controlgear framework.
Engineering note: Verify the contracted standard edition, amendments, manufacturer evidence and project-specific studies before applying these principles to a supplied assembly.