Strong partnership with onsiteHV delivers innovative DAC technology

On-site Testing of Underground Transmission & Distribution Power Cables

Onsite HV

On-site testing of newly installed MV, HV and EHV cable systems is fundamental to the reliable operation of underground T&D power cable systems for:

  • quality control of cable and accessories installation during after-laying testing 
  • quality maintenance testing during operation or in conjunction with repair work after a failure
  • condition assessment of service aged cable circuits

Damped AC (DAC) is a state-of-the-art testing technology developed specifically for after-laying, maintenance and diagnostic testing which provides a comprehensive and accurate condition assessment capability for all types of underground cable systems up to 400kV.

Advanced DAC technology utilises voltage testing in combination with non-destructive diagnostic methods, such as partial discharge (PD) detection and dissipation factor (tan δ) measurement of the cable system and associated accessories. This modern approach provides information about the actual condition of the insulation, which supports intelligent and informed decisions about maintenance, operation and replacement.


Offshore Wind Farm Testing of Array Cables 33-66kV with compliant IEC 60840 ‘after installation HV AC Testing’

 Onsite HV 2

Submarine or subsea cables play a vital role in bringing the generated power from the wind turbine to the offshore substation and eventually to shore. But repairing any damages to such critical infrastructure can be challenging and costly. Subsea cable incidents and failures account for the majority of losses within the global offshore wind farm industry. Faults in cable connections, terminations and joints can cause a number of issues including project delays and cost overruns during development. Systematic testing and diagnosis during manufacturing, transportation, installation and operation can address the issues of cabling costs and losses, reducing the possible risks of failure during operation. 

EMT offer an effective post laying technology for offshore wind farm testing of 33-66kV  inter-array cabling, which demonstrates the service capabilities and benefits of cable acceptance, maintenance, diagnostic testing and partial discharge diagnosis of all types of newly installed and service aged cables by the application of damped AC (DAC) voltages.

Cable and infrastructure condition based maintenance using this method with PD and Dissipation Factor tan δ, provides operators with a lightweight, portable and simple way to apply technology, and with low energy consumption on site, it offers a small footprint for test equipment. Application takes just a few hours with results available the same day, so cable shut-down time and personnel are minimal during testing.


Testing of Export Cables 132-400kV with compliant IEC 60840 ‘after installation HV AC Testing’

OnsiteHV 3

An effective after-laying testing technology has to:

  • provide adequate information - voltage testing and finger printing (e.g. PD, tan δ) during the entire installation and operation process
  • provide a condition assessment baseline which can be used for future reference and comparison
  • ensure reliable operation of the inter-array cables
  • provide contractors the basis for lowering the risks during the warranty period
  • enable service providers during operation a good basis for condition based maintenance


Technical benefits of using advanced damped AC technology:

  • compact test systems to generate on-site DAC high voltages with low input power and reduced energy consumption
  • integrated sensitive PD detection and PD site localisation compliant to IEC standards
  • integrated with dissipation factor (tan δ) measurements at HV conditions
  • complete cable condition assessment


Economical benefits of using advanced damped AC technology:

  • low costs for transportation
  • high voltage and PD localisation and dissipation factor estimation in one single system
  • simple, lightweight, cost effective equipment with very low input power requirements and able to stress long cable lengths
  • efficient system design enables shorter set-up times versus competing testing technologies


Contract Cable Testing Services

OnsiteHV 4

Alongside our cable testing technology solutions, we offer contract cable testing services providing additional resource to your asset management team. EMT’s range of cable testing services makes us the ideal partner for your cable management programs. We employ a number of highly skilled authorised personnel to carry out on-site cable testing services of newly installed MV, HV and EHV, transmission and distribution power cable systems. EMT provides a national, full cable testing service which includes:

✓ inspection and complete post installation cable condition assessment

✓ high voltage, PD localisation and dissipation factor estimation in one service

✓ fault identification and location of any defects in the insulation of the cable system and accessories

✓ ancillary testing services including cable leak detection and partial discharge

✓ flexible service schedules to accommodate changing installation programs



Speak to a member of the team Email