Final Thoughts

Fault Reporting for a Smart Grid

Calculating the location of the fault is just a first step in the process of fault analysis.

The articles in this issue of the magazine discuss in great detail how we can determine the location of a short circuit fault on a transmission line or distribution feeder using many different methods:

  • Impedance based single and multi-ended
  • Travelling waves based
  • Embedded in multifunctional IEDs
  • Applied in off-line software tools
  • Based on communications between current sensors

The impact of many factors on the fault location has also been considered - fault resistance, time synchronization, mutual coupling, series compensation and many others.

One aspect that has not been covered is how the information is made available to the user.  In the past (end of last century) this was done (and in many cases still is) by remotely accessing the IED end retrieving the fault location information in the form of a proprietary event report. This in general is not a problem if we are concerned with a single fault. However, it is a huge problem if we need to analyze a wide area disturbance when hundreds of relays operated, as during the North American Blackout of 2003.

That is why, the industry has made a big effort to standardize the reporting of fault location information.  IEC 61850 led the way introducing a dedicated logical node for fault location - the RFLO. IEC 61850 also developed the XML based substation configuration language - a file format for information exchange between engineering tools.

Based on the IEC TC 57 Working group 10's developments mentioned above, IEEE PES Power Systems Relaying Committee Working group H5b developed an IEEE C37.239 standard, which defines a Common Format for Event Data Exchange (COMFEDE) among power systems, thus helping utilities efficiently integrate and analyze event data from across multi-vendor equipment, contributing to the improvement of the reliability of the system and moving us in the direction of the Smart Grid.

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