According to Fire Engineering Magazine, there are around ten arc flash incidences per day in the United States. These incidents occur when workers:
Many arc flash incidents are related to racking circuit breakers, chiefly in the power industry. A new robotic device allows a worker to rack circuit breakers from a safe distance of over 75 feet away.
An arc flash is an electrical explosion that results from a low impedance connection to ground or another voltage phase in an electrical system. In other words, an arc flash is an electrical breakdown of the resistance of air resulting in an electric arc. This can occur when there is sufficient voltage in an electrical system and a path to ground or lower voltage.
“An arc flash is a potential disaster,” says Tim Rowland, automation specialist at Industrial Electronic Supply. “A high energy arc flash can cause substantial damage, fire, injury, and/or death.”
The energy released in an arc flash rapidly vaporizes the metal conductors involved, blasting molten metal and expanding plasma outward with incredible force. The result can cause destruction of equipment, fire, and injury—not only to workers working on the equipment, but also to others nearby.
According to CapSchell, Inc., a Chicago-based research firm focused on workplace safety issues, between five and ten arc flash incidents occur on a daily basis in the United States. A good percentage of these are related to racking circuit breakers. Despite provisions in the Electronic Code of Federal Regulations requiring the dissemination and use of proper personal protective equipment, arc flash accidents result in injuries ranging from minor burns to loss of hearing to death.
Move Back!
“Move back” are two words every child hears from a parent when moving towards some danger. inoLECT, a Baton Rouge, La.-based provider of integrated electrical system solutions for the power generation, utility, industrial and electrical engineering fields, has created a remote racking device, the inoRAC™, which greatly reduces the risk of arc flash injuries by allowing operators to remotely rack breakers at distances of over 75 feet from the equipment. A simple idea—move the person away from the potential danger—has been effectively realized in the inoRAC robotic device.
“Standard practice has been for a technician to first don an arc flash suit, essentially a fire suit,” says Rowland. “Then he gets the toolset, goes to the unit, and hand cranks the breaker until it engages. Hopefully, nothing adverse happens, however, statistics show that things do.”
Enter the InoRAC. A small, motorized robotic device, the inoRAC uses Siemens technology and a long communications cable to enable the operator to be out of the area of potential arc flash while doing the breaker service.
Safety for Operators and Equipment
While workplace safety was the driving factor behind the development of the inoRAC, protecting equipment assets is an associated benefit. “In many competitive racking systems, torque wrenches are used,” says Josh Norton, business development manager at inoLECT. “Torque values must be set manually.”
On these units a dial is set to determine the amount of torque put onto each breaker. If a breaker is over-torqued, it can be damaged, making the plant less reliable. “With our unit, the operator never has to do that, because the proper values are already programmed into the PLC and touchscreen,” Norton continues. “When the end user details what breakers they have on their site, we program all the information into the inoRAC. It’s never a question. It’s already set.”
Further, the unit can be programmed to match established racking procedures, important because each customer has specific procedures to rack their breakers. The inoRAC can incorporate these specifics, a huge benefit to customers by ensuring compliance with standard operating procedures, even by inexperienced personnel.
“The new guy is always the one who gets nominated to rack breakers,” says Norton. So even from day one, he can follow the steps. As long as he uses the unit, he will always be doing the correct procedure, which increases his safety.
Norton points to the use of a Siemens variable frequency drive as an important part of ensuring equipment integrity. “We use a variable frequency drive that allows us to speed up and slow down the racking process,” he says. The device slows down the racking process just prior to insertion to protect the equipment.
“We sell remote racking devices to protect the operator, which is priority number one,” says Norton. “But we also want to protect the customer’s equipment, because if we tear up their breakers, our device is not going to be used. We go one step further than everyone else by truly protecting equipment by doing torque monitoring, position monitoring, and revolution profiling.”
By monitoring torque, the linear position of the breaker as it goes on the stabs and the number of revolutions the breaker has turned, the inoRAC provides triple redundancy to protect the equipment.
“We want to see all three in operation at the right level and time,” he says. “If I know a breaker takes 20 revolutions to rack it in, at around 18 revolutions I want to slow it down, to ensure that I’m not tearing anything or hitting it at full speed. I want to slow it down and ease it up to the stop.”
Universal Application, Continuing Development
Norton says that one of the advantages of the Siemens components in inoRAC is the flexibility they provide. “They help this product achieve its goal of being a universal product,” he says. The inoRAC can work across the electrical spectrum from 480 volts to 38 kV and with a wide range of make and model of breakers.
According to Norton, inoLECT’s next generation of remote racking devices will incorporate Siemens’ next generation micro PLC, the Simatic S7-1200. “This PLC will allow us to do wireless operation,” concludes Norton. “That is definitely something customers will want. We see the market wanting remote operation for anything electrical, and we want to be a part of doing remote operation across the entire electrical spectrum within a facility, not just racking breakers. That’s where we are headed.”
To see the inoRAC in action, click here to view a short YouTube video.
To date, emphasis has been placed on incorporating technologies that would facilitate material handling with precision, including tight tolerance control and reduced performance variation. One research project associated with overhead crane use focuses on input shaping, which has been shown to significantly reduce the residual swing that accompanies the hoisting and movement of payload. Even when hoist distances are large, the shaping process reduces residual oscillation amplitude well below the level obtained with time-optimal, rigid-body commands. An integrated control system within the laboratory— Siemens’ contribution to the project—is critical for this and other projects to succeed.