ComEd and S&C worked together to build a typical ComEd LS circuit in S&C’s high-power test lab. They used actual ComEd LS settings in the types of devices ComEd has deployed over the years. IntelliRupters were inserted into the scheme in the manner expected to be deployed in the field. They then tested each fault and loss-of-voltage scenario at typical ComEd primary voltage levels and fault magnitude levels. As predicted, they were able to maintain coordination for each scenario. Additionally, the scheme reconfigured properly in each instance.

One of the issues ComEd had to overcome to successfully deploy the scheme was getting a traditional normally closed LS recloser to close back in toward the source after it initially opened as a result of loss of voltage. ComEd’s traditional normally closed LS reclosers do not have built-in logic available that would allow them to reclose after voltage is restored as the scheme works to automatically restore load. To enable this functionality would have required creating custom logic.

Because of concerns with developing, fully testing and maintaining custom logic, ComEd wanted to avoid creating customized complex logic within its existing recloser controls. The solution to the problem was to bring in another source to the scheme just upstream of the normally closed traditional recloser. This would typically be required anyway since large feeders rarely have the available capacity at peak load to fully restore another large feeder.

An actual existing ComEd loop scheme

As a result of research and successful lab testing, ComEd is proceeding with field deployment of this advanced technology within existing loop schemes. The two feeders currently have an existing LS comprised of R1 midpoint, R2 loop tie and R3 midpoint. The feeder fed by Source 2 will need to be segmented further to improve its reliability. Two additional normally closed IntelliRupters will be installed in the existing LS (IR1 and IR2). Two new normally open IntelliRupters also will be installed (IR3 and IR4). IR4 is required because of the capacity constraints of Source 2. This will result in breaking the Source 1 feeder into four sections, further improving its overall reliability without creating miscoordination issues and without requiring additional recloses associated with traditional reclosers and sectionalizers.

The Goal in Sight

ComEd will be able to achieve its goal of improving the performance of its distribution system through economical and effective use of advanced reclosing technology. Along the way, ComEd further expects to avoid wholesale replacement of existing LS reclosers, thus allowing these existing DA assets to continue providing an even greater return on investment. Finally, the utility expects to move toward using the advanced technology to minimize damage to other distribution system components.

Based on these benefits and along with documented history of excellent results to date, ComEd fully expects to continue using DA as one of its most cost-effective tools for achieving excellent distribution system reliability.


The author expresses sincerest appreciation to Angie Schuler, assistant manager of automation and communication services, and Dave Kearns, application director of smart grid technologies automated systems division, both at S&C Electric Co., for their significant contributions in preparing this article.

Jeff Gates ( is a senior engineer in Commonwealth Edison’s distribution automation department, which monitors the performance of the ComEd distribution automation system, establishes settings and coordinates the installation of new distribution automation equipment. He has been with ComEd for 22 years, working in the utility’s construction and maintenance department and distribution testing department prior to joining the distribution automation department. He holds a BSEE degree from the University of Illinois Urbana-Champaign.

Companies mentioned:

Commonwealth Edison|


S&C Electric|