A single partial discharge sensor tells you that discharge activity exists. It does not tell you where, along a cable or inside a busbar, the source is. When an operator has to act – decide whether to take a bay out of service, plan a jointing job, or replace a section of cable – the location of the defect is the decisive information. A multi-channel partial discharge diagnosis system answers this question by measuring many points at the same time and comparing the signals. This article explains the HUWOR multi-channel PD diagnosis system (model HMJ9041).
From single sensors to a synchronised picture
The HMJ9041 acquires several detection channels simultaneously. Each channel is connected to a sensor on the equipment – TEV sensors on switchgear panels, ultrasonic sensors for airborne acoustic signals, HFCT sensors on cable screens and UHF sensors in GIS. Because the channels are acquired at the same instant, the system can compare the arrival time and the amplitude of each discharge pulse between sensors.
This synchronised measurement is what makes location possible. A discharge pulse travels through the equipment at a known velocity; by measuring the difference in arrival time between two or more sensors, the system estimates where along the circuit the source is. This time-difference-of-arrival (TDOA) approach is the same principle used in cable fault location, applied continuously during operation.
What the HMJ9041 is used for
The system is deployed where a fleet of equipment is monitored as a whole rather than panel by panel:
- Substation switchgear rooms, where one multi-channel unit covers many panels with TEV and ultrasonic sensors
- Long cable circuits, where sensors at both ends and at intermediate joints locate the discharge along the route
- GIS bays, where UHF sensors on several compartments locate the discharge inside the enclosure
- Industrial plants with distributed HV switchgear and motor circuits
Multi-channel diagnosis in practice
In a switchgear room with, say, twenty panels, a multi-channel system with one sensor per panel gives the operator a live map: each panel shows its discharge level, and a rising trend on one panel is immediately visible. When a reading rises, the TDOA analysis and the phase-resolved patterns narrow the search to a specific phase or compartment, and the maintenance team goes to the right location with the right tool.
The system also supports periodic diagnosis: a patrol with the portable detector can be combined with the online multi-channel unit, using the online trend to guide the portable inspection to the panels that need attention.
Choosing a multi-channel system
A multi-channel diagnosis system is the right investment when:
- The equipment is concentrated (switchrooms, substations) so many sensors can share one unit
- Fault location matters – cable routes or long GIS where the source must be found, not just detected
- The monitoring programme covers multiple technologies (TEV, ultrasonic, HFCT, UHF) under one platform
- The site needs to scale gradually, adding channels as sensors are installed
The HMJ9041 feeds the same HUWOR monitoring platform as the single-channel sensors, so a site can start with a few channels and expand without changing the software.
Summary
Detection says a discharge exists; diagnosis says where it is and how serious it is. The HMJ9041 multi-channel PD diagnosis system acquires TEV, ultrasonic, HFCT and UHF channels synchronously, locates discharge sources by comparing arrival times between sensors, and gives the operator a live condition map of the whole fleet. For substations and cable networks where location is as important as detection, it is the practical step beyond single-point monitoring. Contact the HUWOR sales team for a channel plan and system configuration.