Optimising the normal opened points of its MV feeders allows ERDF, the main French distribution network operator, to reduce its losses to approximately 2%, while adopting a summer/winter scheme for its (V)HV/MV substations should allow another rapid reduction of 2% but at the cost of a degradation in supply quality whose acceptability remains to be discussed. The adoption of new MV/LV transformers will also allow new and significant savings whose effects will appear progressively. The experiments and complimentary studies to come will allow ERDF to judge if it is opportune to modify the voltage system to operate the MV network at the lowest possible voltage level with the prospect of gains in the order of 1%. The connection of decentralised generation is shown to be unfavourable overall in terms of losses, except in the case of a connection very close to a (V)HV/MV substation.

The development of MV underground networks has led ERDF, a subsidiary of the EDF group and the main French distribution network operator, to upgrade its MV neutral point system to a compensated neutral one. The indicators of the occurrence of an MV fault (FPI for Fault Passage Indicator) in the network have had to be modified to take this change into account. The first generation of detectors for overhead and underground networks has shown its limits, which has prompted ERDF to develop new ones exclusively for underground networks. Their performance, reliability and maintenance have been widely improved due to the development of new specifications and qualification tests on a reduced scale test bed that is very easy to use and was developed for the occasion. The experience feedback from the new generation experimental indicators placed on the network has confirmed the positive results obtained on the test bed.