Southern California Edison line crews use a new tool to protect workers during a new switch install project
Southern California Edison (Rosemead, California) has been pioneering remote spiking and switching procedures for decades. After an incident back in the late 1970s, the Southern California utility mandated that all underground switching and underground spiking would be performed remotely.
Before that time, lineman/splicers would descend into a vault and verify which position they were about to switch. After they received an “okay” from the foreman, they would grab the handle. They then took the chance that the switch would not violently fail while they were standing directly in front of it. Spiking underground cable was also done while inside an underground structure with the same type of risk to employees.
Since those early days of progress, SCE has continued to find new ways to reduce the risks to workers and has implemented procedures for remote operations of underground switches and spiking cable. A recent switch install on an existing 12-kV underground circuit in the Victorville, California, illustrates just how far the company has come in protecting its line workers.
The Victorville project called for adding new circuit for new commercial and residential load. The complexity of the project required several months of design on the 12-kV 1000MCM jacketed cable north of the substation.
The Salvage substation feeds customers throughout the eastern section of the city of Victorville. In final preparation for the switch install, the field crew cut and spliced in the new equipment in a vault 100 ft north of the substation. The linemen used the remote spiking procedure to prove the cable was de-energized due to the cable's location in the underground vault.
As an initial procedure, two qualified SCE employees positively identified the targeted cable-referencing circuit maps, checked tags, verified switch positions and traced the line from the substation.
In recent years, cable-locating systems for tracing and isolating underground cable have become much more sophisticated. SCE crews also used voltage-detection devices to determine the status of the cable.
Additionally, arc-flash standards have evolved to include distance guidelines and new standards for safety apparel and arc-flash blankets. SCE has integrated all of these safety improvements to lower risks to its line workers.
Once the target cable was verified, the final step was to spike the cable prior to cutting it for the new switch installation. The SCE workers commonly use hydraulic cutters to remotely spike cables targeted to work on to ensure the cable they are about to work on is truly de-energized. As with remote switching, the remote hydraulic spiking procedure is accomplished in the same manner. Two linemen descend the structure, verify the correct cable, install the large scissor-like cutters onto the cable and vacate the underground structure.
Now only the cutters and attached line hoses are exposed to the possible hazard if the de-energized cable is energized through an unforeseen error. Unfortunately, SCE discovered in some cases, especially in vaults, the hydraulic cutters are not the best procedure for spiking cable. This discontentment initiated an industry-wide search for a better way to remotely spike cable. The good news was it was right under the utility's nose.
For the past few years, SCE has been using a new cable-cutting tool developed with Cartridge Activated Cutting Tools (CACT-Co Inc.; Ridgecrest, California) powered by a 38-caliber blank cartridge.
The premise for the cartridge-activated tool is the fact that a small, lightweight cartridge can generate a tremendous amount of energy, cutting large diameter cables quickly and smoothly. A lineman only needs one hand to operate the tool, compared to scissor-type cable cutters or hydraulic-powered tools and cumbersome hosing.
SCE has purchased many of these cartridge-actuated tools for the crews for both safety and ergonomic reasons. SCE line crews are using the tool every day for underground and overhead uses.
SCE contacted Walter Smith, the inventor of the cable-cutting tool, to see if he could design a spiking mechanism similar to the cable cutter that uses a cartridge actuator. Smith and CACT-Co determined it was possible to build a spike tool by building on the cable cutter tool frame and cutter knives. The spiking tool could be actuated the same way the cutter device was actuated, from a remote location using a lanyard attached to the trigger.
Once the spiking tool was proven in the field, CACT-Co and SCE worked together to develop a total of four spiking tool models for a range of cable diameter size from ½ inch to 4 inches. On the Victorville switch installation, the crew working in the vault elected to use the cartridge-actuated spiking tool.
Testing a Tool in the Field
The cartridge-activated cable spiking tool, like the CACT-Co cutter, has been designed to be discharged remotely by a lanyard attached to the trigger mechanism. This makes it possible for workers to stand apart from the cutter and/or outside the vault when the tool is fired.
To begin the spiking procedure, workers attach the tool frame and close it around the cable. Two temporary nylon straps secure the tool on the cable. Making sure the frame lock-pin is in place, the crew inserts the recommended load-size cartridge appropriate to the size of the cable being spiked.
The firing unit and lanyard are then inserted into the tool frame and rotated until it is tight against the cable. Once the firing mechanism is secured, the lanyard is extended in a clear path to a safe position outside the vault.
The final step is to have the last employee remove the safety pin and exit the vault. With all crew members out of the flash zone and line of fire, the foreman can give the go-ahead to spike the cable. An employee then pulls the small lanyard attached to the spiking tool's trigger. A short blast occurs that sounds like a small caliber pistol shot, and the cable is spiked. Following the spike, the crew can confidently proceed with cutting the cable and installing the new switch.
Safe to Splice
SCE line workers have reaped benefits from the ergonomics of using both hydraulic- and battery-operated power hand tools. The cartridge-actuated spiking tool is well accepted, because it is both easier to use and a cleaner way to spike the cable. The tool is also not dependent on batteries or auxiliary power generation. Because the tool involves explosives, additional training is required.
The biggest advantage of cartridge-activated tools, however, is keeping the crew out of the flash zone. If a violent failure should occur on a spike, only the cable and equipment are at risk of being damaged, not the workers.
Don Arnold (Donald.Arnold@sce.com) has been a journeyman lineman, electrical crew foreman, general foreman and now safety supervisor at Southern California Edison for 17 years. He has been with the transmission and distribution safety department for eight years and is based in Victorville, California.