April 26, 2004

Introducing New TCC Curves for Vista^® Underground Distribution Switchgear.

S&C is pleased to announce the release of two new families of time-current characteristic curves for the Vista Overcurrent Control, “ANSI/U.S.” and “IEC,” joining the familiar E Speed, K Speed, Coordinating Speed Tap, and Coordinating Speed Main curve offerings.

These new curves conform to the requirements of IEEE C37.112-1996, “IEEE Standard Inverse-Time Characteristic Equations for Overcurrent Relays.” They enhance the ability of Vista Underground Distribution Switchgear to coordinate with upstream relays utilizing CO9, CO11, and IAC curves, as well as microprocessor-based relays such as Schweitzer Engineering Laboratories’ Model SEL-351 featuring US and IEC curves. Each new family of curves includes five different inverse time-overcurrent curve shapes, allowing even more flexibility when coordinating with upstream and downstream protective devices.

New “R300” firmware is required to affect the new TCCs, and will be included in S&C Overcurrent Controls manufactured after April 30, 2004. The new firmware will also be available on CD-ROM for downloading into existing controls. Installation is straightforward and takes about ten minutes. There are no hardware compatibility issues; all overcurrent controls shipped since the beginning of Vista UDS production in June 1997 can be upgraded.

To assist in the selection of the new curve families, S&C Instruction Sheet 681-515 has been revised to include an appendix explaining how to select the proper curve family and time-overcurrent settings meeting the user’s requirements. In addition the new curves are included in Coordinade™ — The S&C Protection and Coordination Assistant.

To learn more about the new TCC Curves and to order the new Vista Overcurrent Control firmware CD-ROM, contact your local S&C Sales Office.