For long cable circuits – urban feeders running kilometres through tunnels, industrial supply lines and connections to distributed generation – the cost of failure is high and the fault location effort is painful. These circuits are also the best candidates for continuous partial discharge (PD) monitoring: the investment in sensors and a monitoring unit pays off where periodic testing leaves months-long gaps.
Why long circuits need online monitoring
Periodic testing leaves gaps
A cable tested once a year is unprotected for the other 364 days. On a long circuit serving critical load, a defect that develops between tests goes unseen until it fails.
Fast-developing defects
Some failure mechanisms – especially at joints and terminations – can progress rapidly once started. Continuous monitoring catches the trend in hours, not months.
Localisation in long circuits
Online monitoring with multiple sensor points along a route supports section-level localisation, narrowing the search when an alarm fires.
Configuring an online cable monitoring system
1. Sensor placement
- HFCT clamps at cable terminations, grounding points and cable links – the standard online coupling for cable PD.
- Section monitoring – sensors at both ends and at intermediate link boxes split a long route into monitored sections.
2. Monitoring unit
- Multi-channel acquisition for synchronised measurement across sensor points
- PD amplitude, rate and pattern recording with baseline trending
- Alarm output to the control room or asset platform
3. Communication
- IoT gateway with LoRa, RS485 or Ethernet uplink to the monitoring platform
- Remote access for engineers, so alarms reach the right desk
Interpreting online cable PD data
- Baseline first – establish the circuit’s normal PD level; alarm on deviation.
- Trends over thresholds – rising activity at a joint position is the actionable signal, not a single reading.
- Patterns – phase-resolved patterns help distinguish genuine PD from noise and identify the defect family.
- Coordinate with load – correlate activity with load cycles where possible.
Online monitoring and periodic testing together
The two approaches complement each other: periodic oscillating wave testing provides a high-sensitivity condition map at intervals, while online monitoring watches continuously between tests. A circuit flagged by either is investigated – often with a confirmatory offline test before excavation or joint replacement.
About HUWOR
Zhuhai Huawang Technology Co., Ltd. (HUWOR) supplies HFCT clamps, multi-channel PD monitors and IoT gateways for online cable monitoring, plus oscillating wave test sets for periodic diagnosis, supporting utilities and industry worldwide with OEM/ODM options and application guidance. Contact the HUWOR sales team for a long-circuit monitoring configuration.