SRP given OK to upgrade ratings for major Phoenix-area power lines

Salt River Project (SRP) has been given approval to upgrade the total transfer capacity (TTC) ratings for two major transmission pathways in the metropolitan Phoenix area.

The performance category upgrade approved by the Western Electricity Coordinating Council’s (WECC) board of directors at its June 27 meeting in Portland, Ore., changes the categories of the lines and allows SRP to upgrade the amount of power that can be transmitted along two parallel 500-kV pathways.

Currently, parallel lines run from Hassayampa to Jojoba and from Hassayampa to Pinal West. A line that currently runs from Jojoba to Kyrene is also included in the category upgrade, which changes the category from C to D, and changes the performance requirements the utility has to meet.

“With the approved change, we will look at the loss of each line separately in a normal contingency analysis,” Rob Kondziolka, SRP’s director of transmission and generation operations, told TransmissionHub on June 27. Without the change, the utility’s analysis would have to consider the two lines as though they were a single line.

The change in performance requirements will also allow the utility to upgrade the lines’ ratings, though Kondziolka says that won’t be done until a fourth 500-kV line, from Pinal West to Coolidge, is completed in 2014.

At that time, the changes approved will allow SRP to upgrade the lines’ ratings from approximately 8,010 MW to 9,875 MW, Brian Keel, manager of transmission planning for SRP, told the WECC board.

In fact, Keel said, the new line is the reason SRP requested the rating upgrade. “Because of that additional transmission, you have the potential for the [area’s] TTC to really increase,” he said.

Without the higher rating, “what you’re really doing is building a transmission line and getting very little benefit out of it,” Keel said.

This is not the first time SRP has requested a change in a line’s performance category for “common corridor” or parallel lines, Kondziolka said. “We have done this twice already for lines that emanate out of the Palo Verde hub, so this is really the third time going to the WECC board for an approval of a change from category C to category D,” he said.

“It allows us to look at the losses of two [parallel] lines separately, and doesn’t require us to meet a performance criteria for the simultaneous loss of the two lines,” Kondziolka said.

WECC board member Paul Feldman expressed concern that SRP’s request for an exemption to a WECC criterion seemed to imply that the utility and WECC were increasing their collective reliability risk.

“If we did this and there’s an outage a week later, would we be sorry we did it?” Feldman asked.

“There is a criterion with WECC that says, if [a utility is granted an exemption] and then actually has an outage, you have to bring it back to [WECC] and explain how that happened and how you mitigate that, or you may lose that exemption,” Keel said.

“Just because you get [an exemption] doesn’t mean you get one for life,” he added.