5 kV insulation testers for MV cables & motors
Insulation resistance testers up to 5 kV are the workhorse of medium-voltage diagnostics. A 5000 V DC source drives meaningful test stress into MV cables, larger motors and generators, transformers and switchgear, while advanced methods such as the dielectric discharge (DD) and step-voltage tests locate ageing deep inside the insulation. The Amperis range for the electrical sector includes 5 kV instruments for substation and industrial maintenance.
What it measures and how it works
With output up to 5 kV the tester reaches the TΩ range needed for sound MV insulation. Alongside PI and DAR, two methods stand out: the step-voltage test raises the voltage in stages to expose insulation that weakens under stress, and the dielectric discharge (DD) test analyses the reabsorption current after discharge to find ageing and voids that a single spot reading hides. Strong guard circuitry keeps surface leakage out of the result.
How to choose the right tester
- Size the voltage to the asset: 5 kV covers MV cables and machines rated to roughly 6.6 kV.
- Require step-voltage and DD test modes for true diagnostics, not just a resistance number.
- Check the top of the measuring range — healthy MV insulation can exceed 1 TΩ.
- Demand effective noise rejection for testing near energised plant.
- Favour data logging, automatic ramp profiles and report export for asset records.
Need help matching range to your network? Ask our engineers.
Applications
The 5 kV range suits medium-voltage distribution and rotating plant:
- MV power cables and terminations
- Medium-voltage motors and generators
- Distribution transformers and bushings
- MV switchgear and circuit breakers
- Acceptance and condition-based maintenance
Applicable standards
Amperis instruments are referenced to IEC/EN standards, not national PN/PL designations:
- IEC/EN 61010-1 — instrument safety
- IEC/EN 61326-1 — electromagnetic compatibility (EMC)
- IEEE 43 — insulation resistance and PI for rotating machines
- IEC 60034-27-4 — off-line winding insulation resistance
- IEC 60502 — MV power cable insulation; ANSI/NETA ATS/MTS for field values
Frequently asked questions
When do I need 5 kV instead of 2.5 kV?
Once assets are rated above about 1 kV — MV cables and larger machines — a 5 kV source applies representative stress and reaches the TΩ values where healthy MV insulation actually sits. Lower voltages under-test these assets.
What does the dielectric discharge (DD) test add?
DD measures the dielectric reabsorption current one minute after a timed charge, normalised to capacitance. It is sensitive to ageing and multi-layer insulation problems, making it valuable on cables and machine windings where PI alone can be inconclusive.
Can it test transformers and bushings?
Yes. A 5 kV tester checks winding-to-winding and winding-to-earth insulation and bushing integrity, complementing ratio and winding-resistance measurements during transformer maintenance.
Technical resources
Step up to 10 kV for HV substation work or back to 2.5 kV for LV machines; combine with transformer testing, switch testing or our dielectric test sets. Request a quote for the r