Offline testing provides many benefits over online cable partial discharge testing, including:

• Testing can be conducted on any cable circuit with any termination configuration.
• Partial discharge activity from along the cable route can be measured and located, which is often difficult with on-line techniques. 
• Offline testing gives us the ability to measure partial discharge and tan delta simultaneously.
• We can apply test voltages greater than normal working voltages.
• Testing above normal working voltage is recommended by the IEEE 400.2 – 2013 ‘Guide for Field Testing of Shielded Power Cable Systems Using Very Low Frequency (VLF)’.

Comparison: Offline vs. Online Partial Discharge Testing

Multiple applications
The service is effective on all types of HV/MV cable up to 66kV. Paper insulated cables can be tested to approximately 5km in length and polymeric insulated cables up to
approximately 8km in length.

Typical uses include:

Valuable Business Benefits of Cable Mapping

• Safe, non-destructive testing with 20+ years of proven success worldwide
• Fast and accurate site service
• Works with both paper and polymer insulated cables
• Reduces costly excavation work
• Minimises risk of unplanned outages
• Complies with IEEE 400.2 international standards

• Our system is safe, non-destructive and has a 20 year track record of success, from the UK to the Far East.
• Fast and accurate site service.
• Works with paper and polymer insulated cables.
• Reduces the need for expensive excavation work.
• Ideal for pre-commissioning and post-repair tests
• Locates partial discharge activity in cables before it leads to failures.
• TD testing can detect water treeing of cable.
• Reduces the risk of unplanned, expensive outages.
• Non-destructive VLF and Tan Delta testing.

Tan Delta (TD) testing is a complementary offline test that assesses the bulk insulation quality of cables. It is especially effective in detecting water treeing in XLPE insulation, which reduces cable life expectancy.

The IEEE 400.2 – 2013 standard defines acceptable TD testing parameters, ensuring accurate and reliable results.

Frequently Asked Questions (FAQs)

Q: How does offline PD cable mapping improve reliability?
A: By detecting insulation weaknesses early, offline PD mapping prevents unexpected failures, reduces unplanned outages, and extends cable life.

Q: What’s the difference between Tan Delta testing and PD mapping?
A: PD mapping locates specific defects (partial discharge sites), while Tan Delta provides a bulk insulation assessment. Used together, they deliver a complete view of cable health.

Q: How long does a test typically take?
A: Most tests can be completed within a few hours per circuit, depending on cable length and site access.

Why Partner with EA Technology?

• Global expertise in cable condition assessment and diagnostics
• Trusted by utilities, industrial sites, and infrastructure providers
• Comprehensive reporting with actionable insights
  
  

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Ensure the long-term reliability of your high-voltage cables.

Contact EA Technology today to schedule an Offline Partial Discharge Cable Mapping assessment.