To augment reliability indices, SRP now monitors sag energy to represent the "pain" of customers who are sensitive to voltage sags. LIGHTNING STRIKES A TRANSMISSION LINE. A BREAKER OPENS. The fault clears within a few cycles. The line is re-energized. No customers lose power. Repeat this series of events 25 times in a month normally void of anything but sunshine. It is certainly not a typical month for the Salt River Project (SRP, Phoenix, Arizona, US). But, the atypical happens, and this would constitute a really bad month in terms of power quality, especially for certain voltage-sag-sensitive customers.
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