Innovative and safe cable connection in medium voltage switchgear with integrated earthing and testing facilities

In networks operating at 24kV, fully enclosed and earthed cable connectors described in EN 50181 are widely used for connecting medium voltage cables to compact switchgear. During installation, and sometimes during the service life, it is necessary to remove, change or repair those connectors. Of course safety procedures are followed prior to cable access to avoid any dangerous situation. However, the full insulation combined with an earthed layer is a complicating factor for transparent access procedures. In The Netherlands where traditionally the majority of the MV networks operate at 12kV, cable connections with more easy access are in use since many years, enabling more obvious earthing and access procedures. This is of vital importance for field personnel, whose safety depends on it. In this paper we propose a new innovative cable connection that offers the unambiguous safety functionality up to and including 24kV, whereas this was only possible for 12kV until now. We describe the new insulated, non-earthed cable connection with integrated earthing and test facility, and the design process including laboratory testing up to first introduction. Furthermore, we provide a complete modern approach for interconnecting Ring Main Units (RMU's). This includes 3-phase network cables to minimize magnetic fields, special joints from 1-to 3-phase cables to connect to the RMU, an earthing method preventing significant induction currents and the innovative, crystal clear safety procedures.