DISTRIBUTION NETWORK RELIABILITY

Now many utilities have been making great strides in improving reliability in the last 20 years and even in a conversation I had with a Regulator a couple of years back there was a sense that the need for incentives was now being questioned. Job Done!  I disagree, those who know me may not be surprised, but I will attempt to justify my concerns.

All are agreed that removal of fossil fuels will increase the load on electricity networks.  With increased load comes increased customer dependency, it has been a feature of recent blackouts that other societal effects occur when electricity supplies are lost, for instance electric train disruption during major faults. The August 2019 outage in England affected over 1 million customers electricity supply for 25 to 45 minutes, but it affected train passengers for hours as they were stranded until the signalling system and train systems could be restarted. As we move to electric vehicles we could wake up to a partially charged car battery and cold houses. Working from home also increases the expectations and dependency on supply reliability (and decent bandwidths).

Electricity used to be a luxury, then it became a convenience, then it became essential and now it is becoming a basic need in our lives as precious as drinking water, shelter, security and food.  This expectation for the “ever presence” of electricity will drive further CI and CML improvement.

Suburban and rural customers bear the brunt of the current levels of unreliability, and their experience is masked by being averaged inside the CI and CML figures with reliable urban parts of the network.

The next CI/CML improvement drive could focus on those suburban and rural networks and this may not just be more undergrounding and interconnection, but could include a role for local generation to provide local resilience during outages.  For this to be possible we need full fault isolation to be achieved from all possible directions, even for radial networks. Radial networks could be redefined into areas of microgrid operation each with a normally closed microgrid isolation point from the main radial supply.

On loss of supply, the intelligent feeder automation would fully isolate the fault, restore supplies as it does at present, but now it has options to restore ”downstream” radial networks as well, by opening the microgrid isolators and invoking the ”downstream “ microgrids to restore within their zone of influence.

These microgrid isolators would be more complicate devices with power electronics capable of re-synchronisation prior to reclosure after the fault repair.  Each microgrid would require a controller, demand response options, storage, and local reactive power and could spawn rural high tech jobs installing maintaining and monitoring those microgrids .

Currently a lot of people are concerned about safe operation of networks with embedded microgrids, but this methodology recognises and manages these risks and this strategy could enable bidding “Restore “ and “Dynamic” products into the flexibility market and cause a step change improvement in rural network reliability.

Derek Macfarlane is interested in your responses….

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