Incorporates three OLPD sensors – Transient Earth Voltage (TEV), Airborne Acoustic (AA) sensors (for testing switchgear) and a split-core High Frequency Current Transformer (HFCT) sensor (for testing cable circuits); optional accessories include – indoor acoustic search probe, outdoor parabolic receiver, and PPE Hard Hat Headphones; The unit has three easy-to-understand, 7-level colour-coded PD displays; and includes a digital TEV-dB numerical display. Benefits: can be used as a safety and security device to ensure that it is safe to work near to MV switchgear; rapid (5 seconds per plant item) OLPD 'screening' for large numbers of MV assets; identifies the source(s) of PD within indoor switchgear to guide further diagnostic OLPD testing and/or monitoring; capable of OLPD surveying of outdoor switchyards (for corona and surface discharges) using the outdoor parabolic receiver; and lightweight, portable and easy-to-use.