Electrical cable that tripped Synfuels Plant replaced

A 15-kilovolt cable experienced a ground fault event at the Great Plains Synfuels Plant on July 26 resulting in loss of power to multiple areas of the plant.

“Maintenance technicians identified and isolated the failed cable run before performing the necessary electrical switching, allowing process operations technician to restart the systems that had tripped,” said Dan Pillar, Dakota Gas electrical and instrumentation (E&I) superintendent. “Unfortunately, the substation fed by the failed cable is one of the few areas of the plant that has a single power feed.”

As a result of the failure, both trains of the oxygen plant went down, as well as all 14 gasifiers. Aaron Marquardt, Dakota Gas process operations shift superintendent, said, “An upset like this affects every control room onsite, and can significantly affect production; however, production losses were minimized because of the quick action taken by field technicians in every area of the plant.”

Some of the gasifiers were quickly restarted, which allowed the gas path to continue running, as well as the front end of the ammonia plant. The utilities group was able to keep all the utilities, like steam and oxygen feeds, available for plant use. Process operations field technicians in the urea area immediately switched to the carbon dioxide backup systems to be able to continue producing urea.

Coordination began immediately to locate and acquire three 1,300-foot lengths of high-voltage power cable. Over the course of the next two-and-a-half weeks, while waiting for the new cable shipment, confined space entry permits were issued, faulty cables were removed from the underground duct banks, and then the new cables were pulled in with help from nearly every E&I maintenance technician on site.

Permanent power was restored on Aug. 20.