Transformer Protection

Many smaller substations have no control house and do not need one since the power transformer is protected by power fuses; eliminating the need for relays, a battery bank and charger, and communications equipment. Typically these small substations have been located in remote rural areas which have very light loads; however, rural isn't quite as rural as it once was, and these substations are now being loaded at much higher levels. With these increased loads due to the increased number of customers served by the substations, the utility may find it desirable and/or necessary to upgrade the power transformer's protection from a set of power fuses to a circuit switcher. The utility would understandably like to accomplish this upgrade at the lowest possible cost without sacrificing reliability, and if it was not necessary to add a control house to the substation a significant cost savings would be realized. This paper provides full information on a circuit switcher solution which can provide current sensing, fault interruption, an uninterruptible power supply, a capacitor trip device, a digital protection relay, and an RTU--all integrated into a single product package to produce full functionality at a fraction of the cost of adding a substation control house. This solution, its full capabilities, and its advantages to the utility (financial, functional, and otherwise) will be covered in this paper.
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