Insulation Resistance Test
An insulation resistance test applies a controlled direct-current voltage to assess the resistance of electrical insulation.
What this term means in maintenance
An insulation resistance test applies a controlled direct-current voltage to assess the resistance of electrical insulation.
What the test evaluates
It may be used on:
- Motors
- Cables
- Transformers
- Generators
- Switchgear
- Windings
- Electrical equipment
Practical example
A motor winding is tested phase-to-phase and phase-to-earth before return to service.
Factors affecting results
Results depend on temperature, humidity, test voltage, equipment condition, contamination, and test duration.
Trending
Comparable readings over time are often more useful than one isolated result.
Safety
Equipment must be isolated, discharged, and handled by competent personnel.
Common mistake
Comparing readings taken at different temperatures without correction can lead to incorrect conclusions.
Related concepts
Related maintenance terms
Keep exploring connected CMMS, reliability, and maintenance planning terms.
Polarization Index
Polarization Index is the ratio of insulation resistance measured after ten minutes to the resistance measured after one minute during a timed insulation test.
Motor Current Signature Analysis
Motor Current Signature Analysis evaluates motor electrical-current patterns to identify possible electrical, mechanical, and driven-equipment faults.
Electrical Isolation
Electrical isolation is the controlled disconnection and securing of electrical energy so equipment cannot become energized during work.
Insulation Resistance Test FAQs
- What is an insulation resistance test?
A DC test assessing resistance of electrical insulation.
- What equipment can be tested?
Motors, cables, transformers, generators, switchgear, and windings.
- What affects the result?
Temperature, humidity, test voltage, duration, contamination, and equipment condition.