He was married, had a very upbeat personality, a good position at the company, and was pleasant to be around. One day, Henry was trying to track down a low voltage problem and was conducting voltage measurements on a 4,160V to 480V dry type transformer on an upper level mezzanine. He took off the transformer cover, knelt down in front of it with a meter to test the 480V side and got the 4,160V side by mistake. The resulting arc flash explosion sent a fireball blasting out of the cabinet catching him in the torso and groin before rolling up his face. With his clothes burning, Henry managed to make it down the ladder. Coworkers put out the fire and rushed him to hospital where he was diagnosed with third degree burns over a large portion of his body. He lingered in the hospital for an agonizing seven days and then died.
{MoSimage}“从那一刻起，我认为电力的方式永远改变，”吉姆菲利普斯说，吉姆菲利普斯在第二天召开进行法医调查。如今，吉姆是美国最重要的专家之一，通过他的T2G技术培训小组教授众多关于电气安全研讨会，并在秋季发表的主题书写了一本书。“如果你足够长的这项业务，你要么了解一个弧闪存的受害者，要么你知道一个了解受害者的人。”
Capelli-Schellpf编纂的一份报告显示effer, Inc., five to 10 arc flash explosions happen in the USA every day, resulting in 1 to 2 deaths. Moreover, over the course of a seven-year study tracking electrical accidents conducted by the U.S. Department of Labor’s Bureau of Labor Statistics, 2,576 U.S. workers died and another 32,807 were injured -- losing an average of 13 days away from work -- due to electrical shock or burn injuries. A second study involving more than 120,000 employees determined arc flash injuries accounted for 77% of all recorded electrical injuries.
What is Arc Flash?
As defined by IEEE and the National Fire Prevention Association (NFPA), an Arc Flash is a strong electric current – and often a full-blown explosion – that passes through air when insulation between electrified conductors is no longer sufficient to contain the voltage within them. This creates a "short cut" that allows electricity to race from conductor-to-conductor… to the extreme detriment of any worker standing nearby.
Arc Flash resembles a lightning bolt-like charge, emitting extreme heat – up to 35,000 degrees Fahrenheit or four times the surface temperature of the sun. Anyone exposed to the blast or heat without sufficient personal protective equipment (PPE) would be severely -- and often fatally -- injured.
电弧闪存事件导致几种伤害。像亨利一样，受害者可能会被烧毁。它们也可以通过爆炸的爆炸伤害等脑震荡和骨折，和/或爆震聋的力抛出，这可以达到160分贝 - 胜于喷气发动机。爆炸的极端热量也可以融化和破碎金属布线和设备，并将其喷洒在房间上作为射弹，导致弹片伤口，烧伤和点燃衣服。
根据大多数的研究中,最常见的原因f these accidents is human error. Henry’s tragic mistake in measuring the wrong side of the cabinet is a case in point. But many other factors may trigger an incident. In some cases just coming too close to a high-current source with a conductive object can cause the electricity to flash over. Other causal factors include equipment failure due to use of substandard parts, improper installation, or even normal wear and tear, breaks or gaps in insulation or dust, corrosion or other impurities on the surface of the conductor.
"It’s practically impossible to completely eliminate arc flash incidents," says Greg Richards, an automation consultant with Siemens Energy & Automation. “The best way to avoid an Arc Flash incident is to avoid working on energized equipment, but that’s not always realistic,” adds Richards. “If you are in a continuous process environment or a facility like an Air Traffic Control tower then you may just have to deal with it.”
“However, there are a number of ways you can significantly reduce the risk, starting with understanding how dangerous these incidents can be, performing all the proper groundwork as outlined by IEEE and NFPA regulations (see NFPA 70E “Standard for Electrical Safety in the Workplace” and IEEE 1584 "IEEE Guide for Performing Arc Flash Calculations") and making sure that when you do work on live equipment you have the appropriate PPE on at all times.”
Using TIA to reduce Arc Flash risk
理查兹有自己的弧形闪光故事。在加入西门子之前，他在一个工厂工作的植物中，一名工人严重伤害了检查电路上的电压，以确保它有足够的电源来驱动另一件设备。“他有第二和三度从腰部燃烧。他在医院近一年，需要多个皮肤移植物。“
这一事件导致公司为公司五个北美植物创建了Arc Flash任务力量。“我们开始了确保我们有正确的PPE，但随后我们寻找消除弧形完全闪烁的方法。”
Eventually Richards realized that reducing the need to open the cabinet in the first place was one of the best ways to accomplish that goal. "People open the cabinet for many reasons, but chief amongst them is that, typically, they don’t know what’s going on inside," he says. "They know there’s a problem; they are getting an alarm or a circuit has tripped or something. But they don’t know exactly what. What if we can get that information without opening the cabinet?"
By integrating all the relevant equipment, such as the motors, drives and switchgear, with the communications network in what Siemens calls a Totally Integrated Automation (TIA) architecture, operators are able to monitor and pull diagnostic information, perform trend and root cause analysis and generally better see what the problems are before sending an electrician into the plant to deal with a problem. Over time Richards found that workers were going into the electrical cabinet less and less often.
“As we used it more, the guys learned to trust the information they were getting,” Richards said. “If a breaker tripped, they knew it. But, before the TIA system, there was nothing to do but reset the breaker. The TIA diagnostics allowed engineers to go back and trend the data—to perform and process the diagnostics externally. For example, if I wanted to know what the drive current was, I could just look that up. As a result, we found that, over time, people were going into the cabinet less and less.”
Phillips agrees that the TIA approach is solid. “If there are ways to monitor and control things that keep people from opening the cabinet then that’s a much better way. The best option is always to avoid the hazard. Doing this through automation and control is a great approach.”
“Having access to this data does not stop arc flash,” cautions Richards. “The number one thing you can do to avoid that is to coordinate your power system and reduce your exposure to a potential incident. And the more you integrate, the less likely you are to have to open the cabinet in the first place.”
Arc Flash Resources:
www.safetybase.com.
Many free articles and downloads - www.brainfiller.com
A global community about arc flash and electrical safety - www.ArcFlashForum.com
Siemens Arc Flash brochure
Siemens Arc Flash studies
Video of Arc Flash accident
