Increase the capacity of a 12 kV/4.16 kV secondary selective substation at a large refinery, design, implementation and commissioning

This paper will detail the processes in the design, revamp and commissioning of an existing 12 kV-4.16 kV 15 MVA secondary-selective substation for a major refinery with its N-1 capacity already exceeded due to load creep. The project installs a third 15 MVA transformer with associated switchgear, bus ducts, protection and transfer control system. The paper will briefly outline the conceptual plan and engineering for the project. The primary focus of the paper will be to detail the effort in modification of the existing power system configuration, developing a startup and commissioning plan, factory acceptance testing, and the actual startup and commissioning. The management directive was to complete a “flawless” startup and commissioning of the substation within a compressed refinery turnaround window. A flawless startup was important to management because a functional failure in a main electrical substation was unacceptable. The business cost of such a failure could easily exceed the capital cost of the substation. It was deemed as cost effective by management and engineering personnel to insure that the design, construction and testing of the substation was as thorough as possible. The design was completed by one team and reviewed by the fresh eyes of a completely independent team. The paper will review important tests performed during the startup and commissioning, along with the benefits and usefulness it provided. The complicated system was checked by the vendor, checked again by the startup team, and then completely checked for functionality at the end user´s facility. The testing included the normal functional and secondary injection testing, but additionally used primary injection to test relays and CTs and test certain relay functions. The paper will conclude with a discussion of the lessons learned during the testing.