Zustandsbewertung von Kabeln
Dan Keller studierte Elektrotechnik an der BA Bautzen und Wirtschaftsingenieurwesen an der WHZ Zwickau. Er arbeitete in verschiedenen Positionen im Engineering und im technischen Vertrieb. In seinen Tätigkeiten beschäftigte er sich unter anderem mit Steuerungen und Safety-Konzepten für Hochspannungsprüfanlagen sowie der strategischen Analyse und Entwicklung von Märkten. Seit 2021 leitet er bei HIGHVOLT ein Vertriebsteam mit dem Schwerpunkt Monitoring für HS-Kabelsysteme. Er ist Mitglied in der CIRED Working Group 2021-3, die sich mit dem Risikomanagement für den Lebenszyklus von Kabeln und Freileitungen beschäftigt.
Innovative quality measurements for long HV cables
Ensuring quality throughout the lifecycle of a cable system is the basis to manage the availability and reliability of the network and to reduce related maintenance and failure costs. Quality assurance of cable systems starts with type and pre-qualification tests during development and routine tests after manufacturing. Transportation, laying and installation of joints and terminations will generate the highest stress levels of the cable system’s lifecycle. This is evident by the highest probability of failure occurring at the joints and terminations for the entire cable system. Therefore, a commissioning test on-site is strongly recommended, but this is only a snapshot in time and cannot guarantee years of service. To test the integrity during the cable’s lifetime, maintenance or diagnostic measurements are key. In the event of a failure, it is important to identify the type of failure and its location to allow for a post mortem analysis of the root cause to be achieved. Therefore, failure location systems are key to help reduce outage times and to direct repair teams and necessary equipment to the correct location quickly. In the case of longer cables (> 10 km), a more accurate method to identify the failures is required. Another advantage would be an immediate evaluation of the failure location, seconds after a critical incident occurs. A solution will be proposed coping with these requirements. The next level of cable surveillance would be a monitoring system. For other components, such as GIS, transformers and bushings, partial discharge (PD) monitoring systems are known. With these systems the evolution of failures might be indicated by PDs and so the measurement of the effective discharge and the localization of discharges will be of increased importance. Unfortunately, conventional PD measurement and monitoring systems will not be able to replicate this capability for cables as they do not anticipate the signal attenuation along the cable. In addition, with an integrative measurement of an equivalent charge an evaluation of the effective discharge energy of a real failure is not possible. As a solution a wide band gap measurement over a large frequency range with a high resolution is the proposed alternative. It is based on an “Event Trigger” using the statistical dependency of samples to extract full time signals and enables advanced signal processing to estimate the effective charge at the location of a PD. Due to the nature of the impulses, even signals buried under noise can be evaluated. To do so, a wide band gap HFCT was especially developed to cope with the cable dimensions and the operational behaviour under AC and DC voltage.