Commissioning of high-voltage cable systems in wind farms 36-170 kV
Updated: Sep 30
Before taking over a new wind farm, a comprehensive commissioning program should be performed to verify that the electrical infrastructure is free from defects that could lead to costly failures, reduced reliability, or potentially hazardous incidents during operation. This requirement should also apply to the high-voltage cable system.
In modern wind farms, the cable network often represents a substantial part of the electrical infrastructure, typically consisting of many kilometers of cable connected through hundreds of joints and terminations.
Power cables are factory-tested before delivery, and when an approved sheath test has been successfully completed, defects in the cable itself are relatively rare. In contrast, experience shows that joints and terminations are significantly more vulnerable to installation-related defects that may reduce service life or lead to premature failure.
To identify such weaknesses before energization, it is recommended to perform a complete insulation and Partial Discharge (PD) diagnostic test in accordance with IEC 60840, IEC 60502-2, and IEEE 400.
Why Hipot Testing Alone Is Not Enough
A conventional Hipot test is essentially a Go/No-Go test. The acceptance criterion is simply whether the cable system can withstand the specified test voltage for a defined period.
While valuable, a standalone Hipot test may produce false-positive results, particularly on newly installed cable systems.
Common installation defects such as:
Poor preparation of the XLPE insulation surface
Air voids within accessories
Incomplete removal of the semiconductive layer
Improper shrinkage of cable accessories
Incorrect installation of stress control components
may survive the voltage withstand test despite being potential sources of future failure.
To detect these defects, Hipot testing should be combined with Partial Discharge diagnostics. PD testing is widely recognized as the most effective diagnostic method for assessing the quality and integrity of high-voltage insulation systems. It is also commonly used during Factory Acceptance Testing (FAT) as a quality control requirement before equipment leaves the manufacturer.
Commissioning with DAMPED AC & PD/diagnose (SAT)
Neka HV diagnostics perform commissioning on HV cable systems up to 132 kV:
Damped AC Hipot test (2*U0)
Damped AC PD diagnose (0,2-2*U0)
DAC (Damped AC) technology operates at frequencies between 20 Hz and 300 Hz, enabling testing under conditions that closely resemble normal service operation at 50 Hz. This provides a highly representative assessment of the insulation system while requiring significantly less power than conventional AC test equipment.
During the PD diagnosis, the following information is obtained:
PD Mapping (location of discharge sources)
PDIV – Partial Discharge Inception Voltage
PDEV – Partial Discharge Extinction Voltage
PRPD Pattern Analysis (Phase-Resolved Partial Discharge)
PD Magnitude and Intensity
Assessment of insulation condition and defect severity
Benefits of DAC & PD Commissioning Testing
1. Verification of Insulation Strength
Confirmation that the cable installation can withstand test voltages up to 2 × U₀, in accordance with IEEE 400 recommendations.
2. Verification of PD-Free Operation
Confirmation that the system is free from measurable partial discharge activity. If PD is detected, the source can be identified and evaluated according to IEC 60270.
3. Complete Cable Route Documentation
Generation of an overview of the cable system, including accurate location and verification of all joints and terminations.
4. Identification of Installation Defects
Detection of latent installation-related defects before the system is energized and handed over for operation.
5. Reduced Risk and Lifecycle Cost
Early identification of defects minimizes the risk of unplanned outages, warranty disputes, and costly repairs during the operational lifetime of the wind farm.
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