by Jen Neville
Delivering reliable power every moment of the day to thousands of Americans in the Southwest requires coordination with customers, as well as foresight, planning and preparedness. Having backup plans and replacement equipment is vital to providing resiliency.
“Mead Substation is an important facility for Western and many of our customers,” said Desert Southwest Electrical Engineer Gerry Hartill. “Having a dependable 345/230 transformer at this location is essential to meet contractual power flow requirements on the 345-kV [kilovolt] line.”
Weighing in at 373 tons, the existing Mead 345/230 transformer, identified as KU2A, performs its part in Western’s interconnected system. This massive unit is used to “transform” the voltage of power from 345-kV to 230-kV or vice versa depending on system demands and power flows.
Although the system is reliable, this particular 50-year-old transformer is close to the end of its useful life and presents a risk to the system, Western and customers. A new transformer has been ordered and delivered, and will be installed by mid-year 2016. However, the installation of this new unit requires numerous substation upgrades and will take several months to complete.
Western, along with its DSW customers, decided last summer that the risk of failure of the unit was too great, and a backup unit should be prepared in the interim. “Since this piece of equipment is so important, Western’s managers decided that a similar transformer, stored as a spare at Liberty Substation, should be moved to Mead Substation to minimize the outage time if the Mead transformer were to fail,” explained Hartill.
Hartill worked with DSW Construction, Maintenance and Procurement personnel to prepare specifications and get a contract in place to have the transformer disassembled at Liberty Substation, transported, and then reassembled at Mead Substation.
The small business contractor that was awarded the project hired a specialized subcontractor to perform the disassembly and reassembly of the transformer. The contractor also hired a subcontractor that specializes in heavy hauling and moving large transformers to transport the disassembled transformer between substations. The disassembled transformer still weighed about 213 tons when it was ready for transport by the heavy transport vehicle. The heavy hauling company carefully planned the route taking into account size and weight restrictions of roads and bridges.
The trip required two days and included police escorts in Arizona, California and Nevada. The removed parts were transported to Mead Substation by several flatbed trucks and the 31,000 gallons of insulating oil was transported in tanker trucks.
Now fully assembled, the backup transformer is stored near the existing KU2A transformer, which continues to transform power to support the Desert Southwest grid. If KU2A were to fail before the new transformer is ready for service, the backup transformer could quickly be moved into position to minimize the outage time on our 345-kV transmission line.
“Our customers rely on the system’s strength and resiliency to serve power to millions of Americans. Taking this step was a proactive response to a very real concern,” said Western’s Administrator and CEO Mark Gabriel during a recent visit to the substation.