Despite the use of modern network equipment, the number and severity of incidents does not decrease as might have been expected. This is due to some components less covered by standardization, i.e. interfaces between equipment. The paper is focused on the problems which can be encountered during the lifetime of the network equipment because of the insufficient attention on the compatibility between them. Such problems could be solved advantageously through a increased consideration of the interfaces in the standardization. It describes some cases for which this lack of standardization can lead to a heavy impact on the network components leading to a decrease of reliability of the network. Normative works should consider the interface between network equipments. Either those topics should be included in the equipment standard, or dedicated standards related to these interfaces should be established. Furthermore, end users should be encouraged to participate more actively in this work.

This paper gives the results of partial discharge measurements in the context of a joint project with the Belgian DNO's. The objective of this project was to gather experience with on-line PD "monitoring" in secondary substations to evaluate its suitability (compared to on-line "spot" PD measurements) for condition assessment of the selected enclosed MV switchgear.