Automatic Location of Arc-faults through Remote Monitoring (ALARM)

Objective(s)

1. Test the feasibility of a technical alternative and lower cost fault locating device.
2. Derive insight into the potential to more widely and cost-effectively deploy such monitoring equipment to feeders showing early indications damage (e.g. transient fuse operations).

Problem(s)

It is widely understood that underground LV networks regularly experience pecking faults – short duration arc faults typically caused by water ingress at partially damaged cable sections or connection/transition points in the network. Such events progressively damage the cable system, and can lead to the development of fuse-operating transitory faults (with customers off for the time required to change fuses). This can then develop to permanent faults with longer customer outages occurring for reactive fault location and repair to be completed.

Fault data from the last four regulatory years shows there have been 331 LV feeders with four or more transient fuse incidents in the East Midlands region of WPD. In total, 526 fuse incidents occurred after there had already been four incidents.

Method(s)

The project proposes to test the feasibility of a technical alternative and lower cost fault locating device. This will be achieved by WPD providing a real-world testing opportunity, and by the manufacturer using this opportunity to demonstrate (and tune at their cost) the fault locating device’s operation.

The project proposes to install substation monitors capable of identifying and locating distance to cable arc-faults. Each monitor consists of Rogowski Coil based phase-current sensors (for up to five LV feeders) together with voltage taps, connected to a Metrology and Communications Unit (MCU) which processes the sensor data and generates and logs substation loading and condition parameters.

Each monitor will capture and retain voltage and current waveforms from the monitored LV feeders when pre-set triggers are activated (e.g. rate of change of voltage or phase current). The captured waveforms will be forwarded via a GPRS/mobile data connection to a processing data centre where inductance and resistance values for the faulting network will be estimated. The estimated value of inductance will then be used to establish a distance to fault estimate.

• Scope

  The project will follow a two phase approach.

  In Phase One, monitors with the supplier’s existing fault location capability will be installed, and data will be analysed by the supplier. This Phase One data will primarily be used to confirm operating parameters for improved data capture hardware that the supplier has also already designed. This improved fault location hardware and capability will then be deployed and tested in Phase Two of the project.

  Phase Two will then seek to demonstrate optimised fault location data for monitored feeders to the distribution business.

• Success Criteria

  Overall success will be:

  • Identification of pecking faults within monitoring data, reliably distinguishing them from other network transients and disturbances
  • Capture of sufficient pecking fault data to estimate confidence in DtF indications for transient arc-faults;
  • Quality of captured auxiliary data (e.g. upstream and downstream network impedance indications) is sufficient to support reliable distance to fault calculations
  • Quantitative understanding of the frequency and magnitude of transient arc-faults on monitored feeders
  • Automatic generation and notification of distance to fault indications; and

  DtF indications are successfully used by local teams to guide repairs ahead of permanent faults developing.

• Potential for New Learning

  It is expected that the parties involved will learn to what degree the utilised relatively low cost hardware and associated software algorithms can accurately predict:

  • The distance to fault for fuse operating faults; and
  • The distance to damage for transient non-fuse-operating pecking events that frequently are the precursors to transitory faults/fuse operations and permanent faults

  Given the technically alternative impedance measurement basis of the system, the project will also be testing this approach

• Documents and links

  NIA Project Registration and PEA Document

  Phase One - Learning Report Executive Summary 

  Phase One - Results and Learning from the Phase One Monitoring Period Slides 

  Phase Two - Further Findings - Project Deliverables 7 and 8 Combined 

  Annual Progress Report 

  Closedown Report 

• Monthly updates

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