October 15, 2001

Trans-Rupter II^® Provides Enhanced Coordination with Downstream Protective Devices

A large utility had experienced two consecutive power fuse operations on a 69-kV transformer at one of their substations. The power fuses had operated in response to a surge arrestor problem at an industrial plant served by the substation. The problem with the utility customer’s equipment was not discovered until the fuses were replaced after the first incident. In both cases, it took the fuses nearly four seconds to clear the fault.

Concerned that another arcing secondary-side fault might cause significant damage to the transformer, the utility decided to upgrade the primary-side protection. They needed a device that would better coordinate with downstream protective equipment. S&C Trans-Rupter II Transformer Protector Model EX, a cost-effective choice for providing enhanced transformer-protection capabilities, met their requirements. Trans-Rupter II is activated by relays, providing more flexible coordination with secondary-side devices, and it’s resettable — advantages not offered by the power fuses. Trans-Rupter II also provides three-phase tripping, a high 31.5-kA fault-interrupting rating, and a 3-cycle interrupting time. Installation of the Trans-Rupter II, which utilizes S&C Mounting Pedestals in this installation, went smoothly and quickly.

In a testimony to the Trans-Rupter II, the utility recently reported that the device successfully cleared a secondary fault caused by another problem with the industrial plant’s equipment.