Transient Fault Detection in Distribution Networks

Powerline Technologies is part of the Fundamentals Ltd Group. Their CEO, Brian Lasslett, gives his thoughts and solution on transient fault detection.

Distribution networks are traditionally designed to detect permanent faults and protect network assets by the use of devices such as fuses, circuit breakers, reclosers and Fault Passage Indicators (FPI).

The evolution of these devices is focused on improvement of operating parameters such as detection time.  Whilst protection against permanent faults is clearly necessary, it is increasingly insufficient as networks transition to the new smart grid.  Traditional protection devices give no visibility of early transient faults, which do not trigger them, but which are nevertheless important as an early sign of developing failure.

When permanent faults suddenly occur, customers experience power outages which are measured by the regulator as customer interruptions (CI) and customer minutes lost (CML).  The result is significant cost as penalties are levied by the regulator on the DNO and the DNO has to react to reconnect power.

As new requirements for more accurate, multi-purpose, real-time monitoring become necessary, DNOs are realising traditional fault monitoring equipment is falling short of meeting their needs because it:

  • is not accurate enough
  • cannot predict transient pre-faults (line disturbance/momentary/pecking fault)
  • is a single-purpose point product
  • has many hidden costs that add up over the life of the investment

New technologies now present an opportunity to improve on this approach by facilitating transient fault (pre-fault) detection in distribution networks. This approach uses waveform analysis to detect early indications (small anomalies) in the waveform to build up a cable health model which records potential fault ‘hot spots’ and predicts their time to failure.  These early indications can take the form of transients, momentary interruptions or line disturbances, all of which are indications of future permanent faults. Waveform analysis can detect these anomalies before they present any visibility to customers or DNOs.

Powerline Technologies (part of the Fundamentals Ltd group) and its partner Aclara Technologies are developing solutions that will detect pre-faults on low voltage (LV) underground cable and overhead Line (OHL) networks up to 69kV.

The Powerline Technologies’ VoltNetTM solution places smart grid sensors at the LV substation and in the LV network that accurately detect, classify and locate transient faults (including pre-faults) before they become permanent faults. VoltNetTM waveform analysis algorithms detect changes in the waveform as anomalies and statistically compare the captured waveform with a library of generic waveforms to classify and accurately locate faults. The waveform analysis algorithms use innovative machine learning to continually improve the accuracy of the algorithms to classify and locate faults.

Sophisticated management software analyses the information from the sensor network, which continually monitors the LV feeder cables, providing cable health information on load parameters, faults and power quality.

VoltNetTM enables rapid early detection and accurate location of faults and network anomalies, including incipient and early transient “pre-faults”.  This will enable DNOs to transition from reactive to proactive maintenance operations resulting in dramatically reduced CML/CI, whilst accurate location of faults will mean the excavation and replacement policy can be improved delivering reduced civil works costs.

For overhead MV lines, Aclara’s Grid Monitoring Platform, comprising analytics software and smart grid sensors, detects all events and faults on an OHL circuit (even if a circuit breaker or recloser did not trip). It provides this information automatically both to the SCADA system and to the Aclara Sensor Management System (SMS) software. Using powerful waveform analysis software, events are automatically categorised and recorded in SMS dashboard reports.

These categories include momentary line disturbances, permanent faults and high current alarms. Power quality events such as voltage sag/surges and harmonic events are also recorded. This allows utilities to determine worst performing circuits by not only looking at the fault events captured within the Aclara system, but also by analysing voltage sag/swells, load, etc.

While an in-depth analysis of each event can be performed in the system, the Aclara SMS software offers a summary event report which provides a concise view of all of the activity on each circuit. The worst performing circuits for momentary outages can be determined by filtering on this type of event to produce a customised report.

The results can also be sorted so the circuits with largest number of momentary will appear at the top of the report. DNO engineers can drill-down on a specific timeframe to look at each event and possible root causes.

Aclara SMS continually monitors and reports the performance of circuits. This information can be easily shared with engineers and operators to proactively identify problematic circuits and to track trends in circuit performance as well as seasonal variations.

The Powerline Technologies VoltNetTM and Aclara Grid Monitoring solutions will enable faults to be detected much more quickly. They will also enable preventative maintenance to detect faults before a hard failure, leading to lower costs for DNOs and more reliable networks for consumers. In addition, the solutions will provide better asset management, contributing to lower energy costs and better network resilience and security.

For more information you can visit www.powerline-technologies.com.