In my March editorial, I discussed how public utility commissions craft reliability-based rates. I mentioned that several utilities are now rewarded if they keep their outage numbers and times down, but they are penalized if their numbers creep up. I thought I did my homework, calling regulators and reliability gurus, but maybe I should have made a few more calls.

George Blomeley, vice president of Georgia Transmission, called about my editorial and went so far as to congratulate me for addressing such a timely issue. He suggested I might go a step further and check into transmission-reliability issues, and he posed these questions:

• Should retail customer-related outage numbers apply to transmission?

• Should the reliability of bulk transmission be measured differently than sub-transmission?

• Should radial transmission lines in rural areas be held to higher reliability limits than loop-feed lines in urban areas?

Darn, I'd rather Blomeley just straighten me out, but he'd rather torment me by making me rethink everything I'd written. Because he is so much fun to talk to, I forgive him. Blomeley is one of those refreshing old-style guys who says what he thinks when he thinks it. He is working with 20 to 30 utilities to develop transmission-outage data standards. The standards would provide Blomeley with tools to help him define levels of service provided to his customers, the suburban and rural cooperatives in Georgia.

Although most utilities consider raw outage data confidential, an outage standard would provide our industry a means to exchange information and benchmark using common definition. Utilities also could better interact with the North American Reliability Council, national and state regulatory bodies, and technical organizations.

SGS Statistical Services is coordinating the development of these standards. SGS President Gregg Spindler states, “Having an outage data standard insures that whatever performance measures are used, the underlying data will be there to support it.” Spindler warned me that outage data does not have a “bell-shaped” normal distribution but instead is highly asymmetrical. He provided me with a graph of circuit outages from 3209 circuits collected from 14 utilities in 1999 that shows 75% of all circuits have fewer outages than the average circuit. I really had to think about that for a while, but it makes sense that unruly circuits would skew data.

Let's assume we manage to get on the same page with reliable outage data. How will we use this data to ensure we are maintaining a reliable infrastructure? It looks like the oversight responsibility for transmission facilities might be migrating over to independent system operators (ISOs) and regional transmission organizations (RTOs).

In March, I had dinner with Phil Pettingill, manager of Policy Development for the Cal ISO, during which we discussed both reliability and the development of maintenance standards. Pettingill actually comes by his opinions firsthand. He worked at PG&E in both maintenance and operations at staff headquarters. He was even on the process team helping to craft ISO rules before the ISO was officially in existence. When the ISO came into being, Pettingill decided he'd rather switch than fight, or maybe he decided he would rather make the rules than follow them.

Whatever the reason, Pettingill has quite a passion for what he does, working with utilities to develop the practices and rules that will assure that utility infrastructure is adequately maintained.

Pettingill challenged my understanding of what constitutes transmission. I've always thought of transmission in terms of voltage class, say as 115 kV or higher. Pettingill said I should consider function when determining whether a circuit is classified as distribution or transmission (see sidebar on page 4). He also suggested that I consider lines used primarily for bulk-power transfer to be transmission and lines dedicated to delivery of electricity to retail customers to be distribution.

Because the ISO focuses only on service to wholesale customers, Pettingill believes transmission maintenance standards that rely on reliability indices should focus on circuit outages, not customer retail outages.

To develop a common statistical language that would apply to all of California, Cal ISO brought in Andy Steward of EDM International and Tom Boardman, a statistician from Colorado State University, to help Cal ISO get a grasp on how to handle outage data. This duo looked for ways to handle the significantly asymmetrical data, but they were unable to find a common statistical model to properly model outage data. They suggested the ISO consider using a “bootstrap” technique, in which the data itself is used to develop the model.

The Cal ISO asks that each utility provide the appropriate availability data collected by both structure type and voltage class. The data evaluation from California utilities provided valuable insights. For example, lines constructed on steel towers and steel poles generally do not fall down under windy conditions. Thus, the steel-towered 500- and 230-kV lines have higher reliabilities than the 115- and 69-kV lines. For similar designs, voltage class was an effective way to group data and minimize variability.

When discussing statistics, Pettingill offered a hypothetical case in which 200 circuits are tracked over a 10-year period with an average of four outages per circuit per year. Because of the asymmetrical nature of the data and a standard deviation of three, a worst-case limit might be eight outages per year and a best-case limit might be 0.2.

“We expect the utility to maintain the system so that the outages stay between these limits,” states Pettingill. “With the 10 years of historical data, we have a 99.5% confidence that the number of outages per circuit will remain between 8.0 and 0.2 if circumstances don't change.”

The ISO is also looking for longer-term shifts and trends in the performance of a voltage class. If the outage numbers for the last five years were above the 10-year mean, or consistently increased, then the system reliability has shifted to the negative, even if the outage numbers remain within specified limits.

Pettingill would like to see our industry develop national reliability standards. I agree. Instead of fighting with regulators, let's get on board and work with regulators to define standards that will define acceptable transmission service.

FERC Order 888

Defining Distribution

1. Local distribution facilities are normally in close proximity to retail customers.
2. Local distribution facilities are primarily radial in character.
3. Power flows into local distribution systems; it rarely, if ever, flows out.
4. When power enters a local distribution system, it is not re-consigned or transported to some other market.
5. Power entering a local distribution system is consumed in a comparatively restricted geographical area.
6. Meters are based at the transmission/local distribution interface to measure flows into the local distribution system.
7. Local distribution systems will be of reduced voltage.