This paper describes the development and deployment of new portable on-line partial discharge (PD) monitoring devices for the condition monitoring of medium voltage (MV) cables and switchgear. In order to provide a complete MV network monitoring solution, devices for monitoring of PD at both primary and secondary substations are necessary. The authors describe the technologies and methodologies which have been developed to enable complete network monitoring to be achieved in both small and large MV distribution networks. With such technologies in place it is possible for the PD activity on a particular item of plant to be measured over a short periods of time (days/weeks/months) with advanced diagnosis and PD location carried out as a follow up, if and when required. The distributed monitoring devices which are used at secondary substations can assist in testing longer circuits (>1.5 km in length) which cannot be solely monitored at primary substations due to the effects of PD signal attenuation on the cables. Precedence-based data capture with multiple PD sensors has also been applied for use at secondary substations which is of particular use in determining which circuit the PD is on and which direction the PD activity is coming from. Whilst to date the majority ofPD monitoring has involved the use of permanent devices (which requires a large capital expenditure when put across an entire network), the portable PD monitoring technology allows for more flexible operation with units moved between different parts of the network to observe short-term trends in PD activity. In this way the technology can be focused on problem areas in a network, with significantly reduced investment required when compared to installing permanent systems. (4 pages)