There is now a great deal of confidence in the testing being conducted at cable production sites, which has become well-understood, controlled, effective and standardized. That helps explain why many users have an expectation for similar quality control for accessories and systems after installation and assembly. But one of the biggest challenges in testing cable systems is finding the optimal balance between being as effective as possible while presenting the least risk of damage through premature ageing.
These days, accessories and even sub-assemblies are subject to factory tests. This, for example, has culminated in the Dutch TSO, TenneT’s approach to replacing its 110 and 150 kV substations. Bay replacement has been developed based on modularity and being withdrawable. Moreover, it was felt that this challenging program could only succeed if most of the preparatory work was conducted outside the substations, with minimal interruption of operational systems. This resulted in prefab bays, both for AIS and GIS; testing beforehand as much as allowed; installation on-site within a short time span and minimum out-of-service time. There was also restricted finalization of works in the allocated substation with wiring and testing kept to the absolute minimum. Standardization, preparation and testing outside the station were regarded as meaning fewer hours in the substation, which benefitted safety.
Over the last decade, a lot of development has taken place in standards and different on-site testing methods of cables and cable systems in general. In addition, the entire field of testing marine cable has matured rapidly, with funds involved increasing greatly and due to the ‘stormy’ development of wind power projects and their cables. Submarine cable testing methodology has also progressed to allow preventing unexpected power failures.
For polymeric cables in particular it can be stated that testing is all about the system and AC offers more effective testing, even for DC cables. System testing is more relevant for HV/EHV than for MV cables because the interface with accessories in the case of the latter is far less sensitive due to much lower electrical stresses. Important references include CIGRE Guide 841, IEEE 400 series and articles published in INMR.
Plan to attend the 2022 INMR WORLD CONGRESS in Berlin where cable testing expert, Paul Leufkens, will present an overview of what has transpired in recent years when it comes to on-site cable testing. His lecture will be sub-divided into commissioning; MV cable maintenance & diagnostics; HV cable maintenance & diagnostics and developments in condition monitoring.