Grid Reliability and Resilience

Grid Reliability and Resilience

Reliability is well defined and understood.

Basically, it measures how often, and how long electricity is unavailable for users.

(This assumes that the quality of electricity meets established criteria, e.g., Voltage that is within prescribed limits and at a prescribed frequency.)

But how is resiliency defined?

“Resiliency is the ability for the electric power system to withstand and recover from extreme, damaging conditions.”

Reliability can be measured, resiliency cannot.

It’s possible to improve reliability, but resiliency is a squishy, unmeasurable concept that diverts attention from reliability for political reasons.

Those who have recently proposed the need for resiliency have said that resiliency requires diversity in supply, microgrids and distributed generation.

  • Diversity in supply refers to having wind and solar on the grid. But wind and solar can’t be relied on to supply electricity if baseload power becomes unavailable: Diversity doesn’t improve resiliency … or reliability.
  • Microgrids and distributed generation also don’t achieve resiliency or reliability. See Understanding Microgrids for an examination of microgrids and distributed generation at

The vast majority of failures of the grid to supply electricity is from downed or failed power lines which account for more than 80% of outages. Occasionally, it’s from the failure of a substation or a piece of gear, such as switching equipment.

But, rarely, actually almost never, does the failure of a baseload power plant cause the grid to go down.

Components of the grid: Tramsission lines, substations, pad-mounted and pole-mounted distribution transformers. Not shown are cut-outs, regulators, reclosers, etc., and power genertaion equipment.

Based on these facts, the only way to significantly improve this aspect of resiliency, i.e., withstanding failure, is to bury all the transmission and distribution lines throughout the country.

Ignoring whether this is technically possible, it’s a question of cost.

  • Greater resiliency and reliability can be achieved, not with wind and solar, but by spending huge sums of money to bury all the transmission and distribution lines throughout the United States. But even that can’t achieve perfect reliability because of flooding, whether it’s from springtime flooding along the Mississippi or Super Storm Sandy, can also cause buried transmission and distribution lines to fail.

Resiliency has become a buzzword used to support wind and solar.


A recent event has demonstrated the confusion surrounding the term resiliency.

The Secretary of the Department of Energy (DOE) proposed a “Grid Resiliency Pricing Rule” and directed FERC to require RTO/ISOs to “establish just and reasonable rates for wholesale electricity sales” for power plants to ensure reliability and resiliency.

This proposal was made in response to coal-fired and nuclear power plants being forced from the grid by the auction system used by RTO/ISOs. The term resiliency was used because the suggested fix was to require a 90-day fuel supply stored on-site at power plants. See The Market for Electrify is Rigged at

The proposed rule was targeting reliability since the removal of nuclear and coal-fired power plants from the grid could result in an inadequate supply of electricity and blackouts.


Resiliency also refers to the ability to recover from a grid failure.

”Diversity in power generation, microgrids, and distributed generation don’t increase the grid’s ability to recover from an outage. Especially where the outage is caused by failed transmission and distribution lines.

Recovery depends on what is damaged.

  • For downed transmission and distribution lines, recovery requires trained people with supplies quickly available to make the necessary repairs.
  • For highly specialized equipment, it means having replacements readily available.

For example, if a large solar storm, such as a Carrington event, destroyed power transformers, it could take several months, or even a year to build replacements. See Preparing For A Carrington Event at


Diversity in supply, i.e., wind and solar, can’t improve resiliency … or reliability. Neither can microgrids and distributed generation.

Restoring power after a failure relies on having the right equipment and trained people ready to make repairs … and not on installing wind and solar, or using microgrids, and distributed generation.

In the final analysis, resiliency is a political football meant to encourage the development of wind and solar.

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