VALLEY FORGE, Pa. — A military blimp that broke free from the Aberdeen Proving Ground in Maryland on Oct. 28 and dragged a steel tether some 125 miles before deflating in Montour County, Pa., caused surprisingly little damage to power lines, PJM’s Chris Pilong told the Operating Committee last week.

“We actually didn’t see any impact until it got to PPL territory,” he said.

There, around 2 p.m., it knocked out one 500-kV line, and the two 230-kV lines, in the Sunbury-Susquehanna and Montour area.

In addition, three 69-kV sub-transmission lines were felled by the runaway airship’s several-thousand-foot-long tether, causing a blackout for as many as 35,000 customers.

“Despite the odd cause … there was no permanent, lasting damage,” he said. “Just an unusual afternoon.”

William Skumanich of PPL said those in the company’s control room at the time were flummoxed.

“We in the control center did not know what was going on, and all of a sudden we get this string of outages,” he said. “It was really a mystery. We really thought it was a tornado.”

PPL spokesman Paul Wirth said power was restored to affected customers by midnight, and all damage was repaired later the next day.

ComEd Open-Loop Interface Created

PJM has introduced a change to the ComEd reactive transfer interface. The closed-loop interface, implemented in June 2013, is composed of all ComEd tie lines and is used to control reactive issues during summer peaks, when the zone is importing power.

The interface is being changed to an open loop of six of the ComEd extra-high voltage lines on the zone’s eastern border. Dubbed CE-EAST, it will go into effect March 1.

The change is being made so that certain generators in MISO can help with voltage issues in the Chicago area.

Operational impact will be minimal, PJM said, and the change will be reflected in Manuals 03 and 37.

Winter Reserve Target Same as Last Year

The committee endorsed a 27% winter reserve target, the same value as last year.

The target is based on unit summer ratings and expressed as a percentage of the forecasted weekly peak load. It is derived from simulations of the 13-week winter period.

PJM operations will seek to maintain the 27% margin in scheduling generator maintenance outages.

Concept of ‘Soak Time’ Parameter Introduced

PJM initiated discussion with stakeholders over a proposed new parameter for Capacity Performance units called “soak time,” with the goal of having a concept in place by June 1.

PJM’s Tom Hauske introduced the proposed definition as “the minimum number of hours a unit must run, in real-time operations, from the time the unit is put online (breaker closure) to the time the unit is at its economic minimum or dispatchable.”

Units with a soak time greater than their minimum run time would be able to petition for a unit specific parameter adjustment.

Committee Chair Mike Bryson said the concept primarily would apply to fossil-fired steam units and would not affect penalty assessment hours under the new Capacity Performance product.

ComEd SPS Changes in the Works

Alan Engelmann of Commonwealth Edison gave the following updates regarding special protection systems (SPS):

• Byron Unit: A new 345-kV line between Station 6 Byron and TSS 144 Wayne, expected to be in service by June 2017, will resolve the stability issues for which the Byron SPS was designed. On completion of the line, the Byron Unit Stability Trip Scheme will be removed. As part of the project, a new breaker was installed in October.
• Powerton 345-kV bus and Powerton Unit: In a project targeted for completion in 2017, a reconfiguration of the Powerton 345-kV bus and breaker replacements will allow the removal of the Powerton SPS when the station is in normal configuration.
• Northbrook/Highland Park Transfer Trip: This SPS prevents thermal overloads and low voltage. A normally closed bus tie line will be installed at Highland Park by December, and the SPS no longer will be needed.

— Suzanne Herel