Detroit Edison Co., (DECo) had been using three-recloser schemes for improving system reliability since 1992; since that time the original solution had become out-dated due to improvements in equipment designs and capabilities. The challenge was to integrate the new equipment, with its many different protocols, with the existing legacy system. DECo posed this challenge to their major suppliers: Develop equipment that will integrate seamlessly into the existing system without any additional proprietary interfaces or hardware. Cooper Power Systems formed a team with DECo to meet this goal. Along the way, this partnership expanded into a strategic alliance that saved DECo as much as $1 million per year on recloser scheme costs. Their concentration focused not just on recloser scheme compatibility, but expanded to include life cycle cost, inventory management and process improvement.
By changing the focus from first cost to life cycle cost, DECo was able to assess all of the costs associated with procuring and operating a piece of equipment throughout its life. Several design features and process improvements resulted in life cycle cost savings as well as enhanced capability.
Control/RTU Integration
Cooper's new recloser control and automation platform, the Kyle® Form 5, has an integral loop scheme and imbedded communications functionality that uses S-COMM protocol. (DECo uses System Northwest's S-COMM protocol for their pole-mounted devices.) A second independent communications port gives DECo the capability of upgrading in the future to DNP 3 protocol. Since RTU function is built into the control, there is no need for a separate RTU cabinet and its associated wiring and installation. Elimination of the separate RTU is estimated to save DECo $8,500 per installation (DECo installs more than 40 reclosers per year). The Form 5 and recloser integrates seamlessly into DECo's existing system with no discernable difference to the distribution management system or the substation submaster.
All existing loop sectionalizing, midline and tie controls are integrated into the Form 5 control, so DECo can install the same control in any functions. The new control takes the place of five differently configured controls that DECo previously had to stock and a total of 21 line items from its stock shelves.
Installation
The new NOVA recloser, a vacuum recloser using completely solid-state insulation, is 600lbs less than the previous recloser and 30% smaller. It is much easier to handle, and can be installed much faster than the old one. Because of its reduced weight, it can be installed on most existing poles, saving the cost of replacing the pole with a heavier version. Since the NOVA recloser contains no oil, there is no chance of leaks or spills and in addition, the recloser is more sensitive to ground fault trip settings, improving hot line work safety for crews.
Reduced Maintenance
Studies show that the true costs of removing, transporting and maintaining a recloser every 12 years is as much as installing a completely new recloser. The NOVA recloser does not need maintenance throughout its life, translating to a $15,000 savings per unit to amortize over 24 years. Another advantage of the recloser is its cypoxy insulators, in contrast to the traditional porcelain insulators. The new insulators are more resistant to damage and cracking from flashover or physical abuse, which also helps reduce maintenance costs and improve reliability.
This strategic alliance was able to reduce inventory and delivery costs by "drop ship" deliveries directly to service centers, with no additional testing needed on the units, cutting the transportation costs by 19%. As a result of the demonstrated success in three-phase reclosers, DECo and Cooper plan to expand the alliance to single-phase reclosers for greater reliability gains and cost savings.
"For us, distribution automation helps limit customers affected by outages. Cooper's state-of-the-art recloser and recloser controls easily integrated into our existing system - and reduced the cost of a three recloser loop scheme by $40,000," says Jim Evans, DECo Principal Engineer, Relay Engineering DAS/SCADA.