Vista® Underground Distribution Switchgear
Overcurrent Control
A unique microprocessor-based overcurrent control provides fault detection, and initiates operation of the resettable vacuum fault interrupters. This full-featured control offers exceptional flexibility and reliability, and includes features unavailable in other manufacturers’ devices — or available only at substantial cost.
Using virtually any personal computer, and with no special software, the overcurrent control can be readily programmed in the shop or in the field.
- Four families of curves. Standard “E” and “K” speed curves plus special, customizable “coordinating-speed” tap and main curves.
- Superior coordination with upstream protective devices and downstream power fuses. Minimum total clearing time, from initiation of a fault to total clearing, is 40 milliseconds (2.5 cycles). Coordinating-speed curves were specifically created for optimal coordination on underground distribution systems.
- Custom curve attributes. Coordinating-speed curves can be easily modified to include instantaneous pickup levels and definite time delays.
- Separate phase and ground curves are standard — allowing better coordination with source-side breaker trip settings.
- No extra “wake-up” time. If closed into a fault, Vista UDS will trip and clear the fault per the selected TCC, with no additional delay.
- Self -powered. Current transformers on fault-interrupter ways provide sensing and power.
- Event recorder captures information on the last twelve operations of each fault interrupter.
- Optional external trip provisions offer additional functionality. Input from external sources such as transformer sudden-pressure relays can also trip the fault interrupters.