The 3-Phase Programmable Resettable Sectionalizer (3Ø PRS) is a device which has built-in intelligence to discriminate between temporary (transient) and permanent faults on 3-phase distribution systems. It operates in conjunction with a 3-phase gang operated automatic recloser.
It is specifically designed for the protection of 3-phase lateral lines. When installed at the beginning of the laterals, it virtually eliminates nuisance outages. Its functional concept and design greatly improve system coordination.
Traditionally, the individual laterals are protected by expulsion-type fused cutouts. These cutouts are intended to operate only during a permanent fault on the lateral by carefully coordinating the fuse links with the time current characteristics of the upstream automatic circuit recloser or reclosing circuit breaker.
Unfortunately, coordination between fuse links and upstream automatic circuit reclosers is unachievable above a few thousand amperes. Coordination, if achieved on paper, can easily change as the fault current increases due to larger capacity facilities, addition of larger substations or reconductoring. Errors in re-fusing is another way that system coordination can be lost.
The 3Ø PRS is a protective device designed to automatically sectionalize faults synchronously on all the three phases of a three-phase distribution system. Since the 3Ø PRS doesn’t need time-current characteristics for its operation, the coordination range is extended to the maximum interrupting rating of the three phase upstream protective device.
This difference in functionality makes the 3Ø PRS an ideal device for application on three phase distribution laterals where available fault currents make recloser-fuse coordination unachievable. The synchronous operation of the 3Ø PRS also prevents 3-phase imbalance. As the 3Ø PRS is programmable and resettable, it provides the utility with an economical and easy to retrofit method of enhancing protection of the distribution system.
The 3Ø PRS comprises three cutout mountings and three electronic modules with no mechanical link between the three units. The three electronic modules are integrated with 2.4GHz RF transceivers. The communication range is up to 20 feet (open air). A synchronous drop-out is achieved by all of the three 3Ø PRS units when a permanent fault is seen by any of the three units.
The 3Ø PRS modules fit into the standard mounting of the Chance Type C, S&C (MPS) Type XS and ABB Type ICX cutout. This interchangeability reduces the cost of retrofit installation.