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T&D Reliability: The Next Battleground in Re-Regulation

Fortnightly Magazine - March 1 1999

data. For the typical outage, a customer calls in and says his lights are out. The duration clock starts at that time. If no other customer nearby calls in the next few minutes, then a truck is dispatched to that customer to fix what is probably a blown fuse on his transformer. If that is the case, then when the fuse is replaced and service restored, the duration clock stops for that interruption. If any other customers are served by that transformer, they are counted, too, even though they may not have called. If the troubleman who restored the service can guess the cause (a "fried" squirrel at the base of the pole, a broken tree branch or lightning in the area), he will note it on his trouble report, along with his estimates of the number of customers and the time of restoration. If three customers are interrupted for 30 minutes, then the system will record one outage, three customer interruptions and 90 customer interruption minutes.

Where the possibility for error enters is that the actual outage may have started some time before the customer called, especially if it is in the middle of the night. So utilities that install automatic detectors that seize the customer's phone line and call in for him will find their measured performance deteriorates even though their actual service restoration time has improved. The next cause of error is the estimate of how many customers are interrupted. If the utility uses an automated system with accurate customer counts for each potential interrupting device (fuse, recloser, switch), then the count can be fairly accurate, but if the lineman makes an estimate based on his knowledge of the system, possibly checked by the dispatcher, it could be quite wrong. One auditor's test: Have the system print the number of customers interrupted for each device that has been interrupted more than once. If the numbers vary widely, the company's only defense is to see if the errors are due to switching changes.

Moreover, these are just the easy cases. With such complications as calls not getting into the call center, partial restoration of circuits through temporary switching and the possibility of additional problems downstream of what was thought to be the offending device, counting customer interruptions and minutes gets tricky. There is a general sense among those of us who have worked with these data that utilities' manual systems tend to understate the actual number of overall minutes. There also is a general understanding that in a major storm with hundreds or thousands of outages, the systems are sorely taxed, and with accuracy of reporting being secondary to restoration of service, the numbers suffer.

Nevertheless, look for PUCs and their reliability auditors to ask for improvements in outage reporting systems, in part to improve their ability to monitor performance but also on the theory that in order to manage the problem, the utilities themselves need good information. At the very least, PUCS are requiring annual reporting of outages, customer interruptions, customer minutes and the various ratios, with and without