I heard an entertaining story at the Finepoint circuit breaker conference in Pittsburgh about a flying cow sinking a fishing boat. Apparently, some Russian soldiers herded several cows grazing near their airfield into the back of their transport plane. While over the Sea of Japan, the cows got loose and went crazy. Worried about losing the plane, the soldiers opened the back door and pushed the cows out.
The story went on to say that a Japanese fishing boat was in the path of one of these Kamikaze cows, which went straight through the hull of the boat, sinking it. When rescued by the authorities, the fishermen were promptly thrown into jail; no one believed that cows fell from the sky. Later, the Russian Embassy grudgingly admitted the story was true.
While a very entertaining story, googling Russians, Cows and Japanese Fishing Boats exposes this as yet another bogus fish story that never happened.
However, a true story was that of a flying shark dropping on a California golf course. I recently heard a CBC interview with the groundskeeper who found the 2-foot shark. He said there were many claw marks on the side of the fish, so he figured a large bird of prey snagged the shark in shallow water. Somehow, the shark twisted free, and landed on the golf course. The groundskeeper put it into a bucket of water, took it several miles back to the ocean, where it swam away.
I always engage my students in the concept: Can all accidents be prevented? If you happened to be on that golf course, a 10-lb shark falling from the sky may very well break your neck. How on earth could you have prevented that accident!
Although you couldn't imagine being hit by a flying shark, there are certain instances in electrical systems where an inappropriate action can have dire consequences.
A significant example is with switches, which are rated as either load break or non-load break. A load break switch is designed to be opened under load and interrupt the current flow with no dire consequence. A non-load break switch is not!
Designed to interrupt current, non-load break switches are intended as isolators, providing an additional lockout point, generally close to the load. Before they are operated, it is critical the load be de-energized.
Look inside a non-load break switch and you will find no arc chutes or spring to assist during operation. With no spring assistance, the arc that is created over the centre snap action during opening will not be quickly extinguished. With slow opening, no arc extinguishment and no arc chutes, it is easy to draw an arc that goes phase-to-phase then phase-to-ground when opened under load.
Rarely does it indicate on the front cover the switch is not to be opened under load. Often, the only way to tell externally is by the initial movement of the operating handle. You should be able to tell within 10 or 15 degrees of handle movement whether the mechanism is spring assisted. When you don't feel spring resistance, then it's highly likely you are dealing with a non-load break switch, and you need to move the switch back into the closed position and make sure your load is de-energized.
Discuss this important difference during your electrical safety meetings. We suggest non-load break switches be identified with a distinctive paint colour. What matters is that someone can tell from 50 feet away the switch must not be operated under load.
I have been fortunate to never have a switch blow up on me, but remember the ancient adage: A smart person learns from their mistakes; a wise person learns from the mistakes of others.
I have had many people describe switches exploding, so please learn from the mistakes of others. Switches can fly apart and, if you get hit, you will be hurt.
Until next time, be ready, be careful and be safe.