When a tree branch falls onto a power line and then onto the ground, it often blows a fuse and knocks out power. In some cases, the cause for the blown fuse clears itself and no repair is required, but the overhead electricians must replace a fuse to restore electricity.
To eliminate some sustained power outages when the fault clears itself, overhead electricans for Commonwealth Edison Co. (ComEd; Chicago, Illinois) are installing TripSaver Dropout Reclosers, which are manufactured by S&C Electric (Chicago). These devices can detect current surges, interrupt the power flow temporarily and safely restore power if there is no damage to the lines.
A TripSaver has a five-second reclosing time delay, so if the fault clears itself, the TripSaver will reclose and restore power. As a result, the customer only experiences a momentary interruption and then is restored to service. If the TripSaver recloses into a fault, the second operation has a timing curve similar to a comparable fuse link. This design makes the TripSaver backwards compatible with existing circuits.
Overhead electricians are currently installing the reclosers throughout ComEd's service territory as one of several electric service reliability enhancement tools. Field crews can exchange a 100K fuse for a 100K TripSaver, which will coordinate with upstream and downstream fuses.
Before the overhead electricians began installing the TripSavers in the field, the utility looked for a way to make the replacement of the standard fuses with the new device faster and more efficient.
ComEd's distribution standards and engineering team approached the methods group, proposing a 100-A cutout jumper tool, because the device the overhead electricians were using wasn't meeting their needs. They were looking for a way to start the TripSaver replacement and fuse-upgrade project without taking an entire circuit or a portion of a circuit out of service. ComEd also wanted the ability to swap out fuse tubes for TripSavers using a one-person overhead operating crew.
Fortunately, some ComEd employees had already identified a tool that would serve the purpose. At the April 2008 IEEE T&D Expo, they remembered seeing a tool called the JackJumper, manufactured by Utility Solutions (Hickory, North Carolina).
Taking a circuit out of service to install equipment can require a significant amount of time and labor. Multiple crews often need to execute many steps in a switching routine to de-energize the line in question. In some cases, a multiperson crew may install a set of conventional cable jumpers to perform a TripSaver installation.
Now they can accomplish the task with a one-person overhead operating crew. By using the JackJumper, they eliminate the switching necessary to install a TripSaver device or do a fuse upgrade. Instead, they simply attach the JackJumper, remove the fuse tube from the cutout body and install the TripSaver. One lineman working in a bucket truck can now install the TripSaver rather than several crews.
ComEd began investigating the use of the JackJumper in December 2008. A month later, the methods group began testing the TripSavers on de-energized equipment at its training facility. The group ran several tests such as closing the cutout fuse hard to see if it would become disconnected from the cutout. They also tried different ways of installing the jumper.
Before beginning the field testing, the overhead electricians made sure that the pole involved was in good condition, there wasn't a crack in the cutout insulator, and the cutout or conductor weren't damaged. They would then use a shotgun stick to install the JackJumper, remove the fuse tube and install the TripSaver.
During the field trial, the overhead electricians made sure it was safe and secure, and there were not going to be any surprises when they were using it out in the field.
Once all tests had been completed and everything worked well, the JackJumper was referred to the safety and training departments for review. ComEd approved the device for use in February 2009. So far, the company has ordered more than 50 of the devices and has distributed the tools for use across its entire service territory.
ComEd personnel are pleased with the JackJumper as it affords them the ability to install TripSaver units more efficiently with less switching and with no customer power interruptions. These tools help to create a more effective workforce and increased customer satisfaction.
Tom Distasio (Thomas.Distasio@ComEd.com) is a methods specialist with strategic and support services for ComEd in Oak Brook, Illinois. He has been with the company for 26 years.
Thomas Callsen (Thomas.Callsen@ComEd.com) is a principal engineer with the distribution standards department for ComEd in Oakbrook Terrace, Illinois. He has been with the company for 24 years and is a registered professional engineer.
Darryl Mitchell (Darryl.Mitchell@ComEd.com) is the Chicago regional engineering manager in the distribution engineering and design department for ComEd in Chicago, Illinois. He has been with the company for 29 years.