A Unique Solution to a Refinery’s Power Quality Problems.

PSS retrofits manual switchgear with fault-closing capability in one day.

A Canadian oil refinery had been experiencing excessive power disturbances from their local electric utility, and decided to build a 230-kV substation that would allow the facilities to be served from a coal-fired power plant located a mere mile away. However, the refinery’s consultant determined that a means would be needed for detecting and interrupting low-level ground faults because their system was reactively grounded. The existing 25-year-old S&C switchgear at the refinery was equipped with manually operated feeder bays and thus did not meet this requirement. The power fuses in the gear would properly protect equipment from high-level faults, but relays and power-operated switches would be required to protect against low-level faults.

While it is not uncommon for large facilities to simply replace their old switchgear with new equipment offering this added capability, the refinery was fearful of an extended shutdown and the subsequent loss of production associated with removal of the existing gear, and installation and commissioning of new equipment.

Upon learning of the dilemma through the refinery’s consultant, S&C proposed a turnkey solution wherein the 10 feeder bays of the switchgear would be modified to allow automatic switch operation upon sensing low-level fault currents. It would involve the installation of current transformers, ground fault relays, and motorized switch operators into bays that were not designed to accept them.

Since there was insufficient room on the stile of each feeder bay to incorporate a motorized switch operator, a special design was developed in which the operator would be mounted behind the switch on the outside of the gear.

Well in advance of the agreed-to shutdown date, S&C engineers designed and built a similar feeder bay and prototype operator mounting bracket, to determine the ease with which the procedure could be performed on the actual gear. From this mock-up, it was determined that the concept was sound and, after a few modifications, the design drawings were finalized.

By 6:30 AM on the day of the shutdown, S&C had assembled a crew of 19 skilled factory technicians, low-voltage and medium-voltage electricians, and installers. Luckily, the weather was favorable and after properly grounding the equipment, work commenced at 7:30 AM. With each key team member well aware of the required methods and goals — and with all other members having been assigned a particular responsibility — the procedure went off like clockwork. The refinery was able to reenergize the gear about 5:00 PM, one hour before the scheduled completion time.

Time after time, S&C engineers have proven their resourcefulness in solving unique power delivery problems. Want to find out more? Or have a unique problem of your own? Contact Power Systems Services at (773) 338-1000.