High frequency modeling of a shielded four-core low voltage underground power cable

摘要

Underground low voltage (LV) power cables have a long life span, and so far minimum effort was put in methods for condition assessment. However, a slow but steady increase in the amount of faults is being observed and future de-central power generation may further put pressure on the reliability of the LV grid. Therefore, condition monitoring for LV cable systems is under investigation. With the occurrence of intermittent faults, fast transients from discharges may be observed before an outage occurs. To estimate if such signals are measurable, a model of the cable valid up to 50 MHz was derived. Numerical simulations have been used to obtain the parameters of the multi-conductor transmission line model, with special consideration of the copper screen configuration. Measurements on a 60 m cable segment have been performed to verify the model, showing good agreement. This model will be used to investigate signal propagation through a LV grid with focus on the feasibility to base LV condition monitoring on signals which may originate from upcoming cable faults.