The McDonnell Group

By Peter Manos
Principal Strategy Consultant

Utilities have built the grid smartly enough from the start, to meet the normal fluctuations in demand that are typically seen, and have always placed a high value on anything that can reduce peak demand, and increase what we call “diversity of load,” or the random element that tends to offset different electric customer’s usage patterns. The more diverse the load, the less sharp and high the peaks in demand will be. Tiny Tim’s wedding eliminated the normal diversity, since a lot more people stayed up late to watch the show, and many then shut off their TVs at the same moment.

Delivering the value of making the load more diverse is a key element of a wide range of Smart Grid technologies currently being deployed, including those championed by the various clients of The McDonnell Group that you can read about elsewhere on our website.

We are accustomed to thinking that the main benefit of many of these smart grid technologies is reducing peak demand. Similarly, we are accustomed to thinking of blackouts as being the result of not having enough power to meet peak demand. Yet another consideration in both cases is the need to protect big, base-loaded power plants when there is too much power being generated in a region, and too little electrical demand compared to the supply. Severe overheating and damage can occur to generating equipment when it remains connected to too low of an electrical load.

Our grid has been smart enough over the decades to keep thousands of generator rotors, each weighing as much as a train locomotive, spinning in synchronized fashion at 60 cycles per second, on a 24/365 basis. You cannot slow down a fleet of machines of that size quickly enough to meet an unexpected massive drop in demand or loss of load. As a result, these big generating facilities are designed to “trip” (go off line) in response to very unstable situations.

This factor is involved during cascading blackouts such as the event in August 2003 with the Northeastern Power Grid, something even younger readers will remember. When a section of an interconnected grid is suddenly shut down, it creates instabilities in adjacent sections. There are cases where outages occur because an operating region within the grid that was exporting excess power to neighboring regions is suddenly “islanded” to protect itself from neighboring instabilities during the cascade portion of a blackout sequence. After isolating itself, if the oversupply of power generation in the islanded region cannot be reduced quickly enough, the largest generating unit(s) will trip, and the oversupply in the islanded area may then become an undersupply, leading to the next domino falling in the cascading blackout.

To see the additional potential benefits of these smart grid technologies beyond the obvious peak reduction benefits, now let’s imagine a different “Tiny Tim” event, this time on a hot summer day. Demand suddenly drops due to an outage on part of the grid Adjacent parts of the grid are now under threat due to the instability created by that neighboring outage. But the potential cascading blackout scenario is now playing out on a smart grid.

What happens? The adjacent utilities’ operating areas that were under threat due to the initial blackout in the neighboring area have smart grid devices installed throughout their territory. These devices can help prevent the domino effect because they have the potential to absorb the imbalances that a sudden over-supply creates.

You have electric vehicles that were driven to work and are sitting in the parking lot, plugged in but not charging. During the beginning of a potentially cascading blackout situation at peak load times, these partially-charged electric vehicles, and the home appliances or commercial devices (such as ice-makers for air conditioning) that were waiting to be charged or run during off-peak hours, could become another tool in the System Operator’s tool kit.

Smart-grid enabled devices on the distribution system can play a role similar to the generation control systems and capacitor banks Systems Operators employ in matching supply with demand on the grid. They will help to reduce the likelihood that small outages march on to become bigger ones…the small outages will be more likely to just tiptoe a bit, and then stop.