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Demystifying grounding: continuous ground

lectricit Qubec - Michel Chartier, ing. ATD

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Actually, by ensuring the current of all electrical devices is connected to the ground, continuous ground first and foremost protects people. For example, when electric devices (such as anything with a motor, cook stoves or other appliances) become defective and are no longer firmly connected to the ground, the current will have no path to follow. The device will appear to be working normally even though users are not protected from stray electricity.

If someone simultaneously touches the frame of a defective appliance and another device with proper grounding (a sink, for example), he or she will become a path for the current and receive an electric shock that could even be lethal.

The following figure explains what occurs: 

 

 

 

No path for the current

Electric cook stoves are a familiar example since most of us have one at home. And this device is often placed close to other appliances or the kitchen sink.

Twenty-some years ago, I received a small electric shock between my cook stove and my dishwasher. After a few tests, I realized the stove was the problem. To demonstrate how dangerous the situation was, I installed a switch and a lightbulb between the two appliances. The switch was flicked to OFF, but the 100W bulb continued to shine brightly. Needless to say, I replaced the cook stove the very next day!

Poor continuous ground can easily endanger unsuspecting people’s lives. This is why it is crucial to make sure the continuous ground is done properly and the unsheathed copper (or green) wire is connected properly.

The following figure explains what occurs:

 

 

 

Path for the current

Stray electricity can also move between two devices frequently found in electrical rooms. To protect people’s safety, European manufacturers make equipment with plastic or PVC casing, as these materials reduce the risk of electric shock. In North America, commonly used power tools have a similar plastic casing. Moreover, they are not equipped with a continuous ground connection (the round hole in the outlet) and therefore are sold with the label “double isolated.”

The importance of continuous ground should never be minimized. Electric devices must always be properly grounded.