Overview
IEC 61557-2:2019 defines requirements for insulation resistance measurement equipment used on low-voltage distribution systems (up to 1 000 V AC and 1 500 V DC) when the installation or equipment is de-energized. It is Part 2 of the IEC 61557 series (protective measures testing, measuring and monitoring) and is intended to be used together with IEC 61557-1:2019 (general requirements). The 2019 edition is a technical revision that adds measurement category requirements, expanded operating instructions, and aligns the document structure with the rest of the IEC 61557 series.
Key topics and technical requirements
- Scope: Equipment for measuring insulation resistance of de-energized equipment and installations.
- Output voltage: DC output; open-circuit voltage shall not exceed 1.25 × rated output voltage.
- Rated current: Minimum 1 mA.
- Measuring current: Peak current shall not exceed 15 mA; any AC component ≤ 1.5 mA peak.
- Influence of capacitance: Operating uncertainty within the marked measurement range must not exceed ±30% under rated conditions. A measured resistance of 1 MΩ (±1%) shall not vary by more than 10% when a 2 µF capacitor is connected in parallel (or a manufacturer-specified capacitance).
- Overvoltage tolerance: User safety must be maintained when extraneous DC or AC voltages up to 120% of the highest rated output voltage are applied for at least 10 s. Where specific marking is used, AC overvoltage can be reduced to 1.1 × phase-to-phase voltage with appropriate pictogram or wording.
- Measurement category markings: Equipment for distribution systems must be at least Measurement Category III; for electrical equipment at least Category II.
- Marking & operating instructions: Machine marking must include rated output voltage/current, measurement range, rated voltage to earth, and measurement category. Instructions must warn that measurements are only on de-energized parts, cover operation with hand-driven generators, and (for battery-powered instruments) state the number of possible measurements.
- Safety and accessories: Insulation testers must comply with IEC 61010-2-034; test leads and probes must comply with IEC 61010-031.
Applications and users
- Practical for manufacturers of insulation resistance testers, handheld insulation meters, and factory test equipment.
- Used by electrical contractors, maintenance technicians, commissioning engineers, and safety inspectors performing insulation testing on motors, switchgear, cables and installations in industrial and commercial buildings.
- Relevant for procurement teams specifying test equipment to meet safety and measurement-category requirements.
Related standards
- IEC 61557-1:2019 - General requirements for testing/monitoring equipment
- IEC 61010-2-034 - Safety requirements for insulation and dielectric test equipment
- IEC 61010-031 - Safety requirements for hand-held probe assemblies
Keywords: IEC 61557-2, insulation resistance, insulation testing, low voltage distribution systems, measurement category, insulation tester, protective measures, IEC 61557 series.
Open preview (PDF)Electrical safety in low voltage distribution systems up to 1 000 V AC and 1 500 V DC - Equipment for testing, measuring or monitoring of protective measures - Part 2: Insulation resistance
