To Ground or Not To Ground
Dear Swami,
A portable generator supply company supplied a generator for a show and told me to use the building ground since the generator is not close enough to any earth to pound in a grounding rod. I believe their generator is ungrounded because they only supplied three hot conductors (black, red, and blue) and a neutral conductor (white) with no grounding conductor (green). Does the generator need to be grounded? Do they need to provide a true earth ground that is bonded to a grounding rod? Or can they use the ground from the building to ground the generator?
Signed,
Floating Above Earth
Dear Floating,
The laws of man vary according to location, but the laws of nature are immutable. You should follow the local codes and regulations dealing with driving a grounding rod, but never violate the laws of nature, common sense, and safety.
The reasons for grounding are three-fold: 1. to limit voltages due to lightning, line surges, or unintentional contact with higher voltage lines; 2. to provide a stable 0-volt reference; and 3. to provide a low impedance path for fault current in order to insure the fuse or circuit breaker will trip in the event of a fault to ground.
Regardless of the local codes and regulations, every electrical system that we use in live event production should have a grounding or earthing electrode. When it comes to portable power generators, perhaps the most important reason for this is for lightning protection. In the event of a lightning strike, there needs to be a low impedance path into the earth to shed the electrical energy it generates. Electrodes come in different forms. A grounding rod is only one of them. If you can't drive a grounding rod, then the building grounding electrode can provide that low impedance path to earth for lightning protection. And if there is lightning in the area (within about six miles), the generator should be shut down for 30 minutes after the last lightning strike. I like to use an app called Spark (part of the WeatherBug app) to track lightning.
It's also very important to run a grounding conductor (the green conductor) in addition to the three phase conductors and the neutral conductor. Without it, there is no low impedance path for fault current that would insure that the circuit breaker trips if there is a ground fault. So if, for example, there is a fault to the chassis of a light or junction box, it would stay energized and could potentially hurt some unfortunately soul who wanders close enough to touch it.
Portable power generators can be very safe or very dangerous, depending on how they are set up and operated. Be safe!
Swami Candela of the Third Millennium
A portable generator supply company supplied a generator for a show and told me to use the building ground since the generator is not close enough to any earth to pound in a grounding rod. I believe their generator is ungrounded because they only supplied three hot conductors (black, red, and blue) and a neutral conductor (white) with no grounding conductor (green). Does the generator need to be grounded? Do they need to provide a true earth ground that is bonded to a grounding rod? Or can they use the ground from the building to ground the generator?
Floating Above Earth
Dear Floating,
The laws of man vary according to location, but the laws of nature are immutable. You should follow the local codes and regulations dealing with driving a grounding rod, but never violate the laws of nature, common sense, and safety.
The reasons for grounding are three-fold: 1. to limit voltages due to lightning, line surges, or unintentional contact with higher voltage lines; 2. to provide a stable 0-volt reference; and 3. to provide a low impedance path for fault current in order to insure the fuse or circuit breaker will trip in the event of a fault to ground.
Regardless of the local codes and regulations, every electrical system that we use in live event production should have a grounding or earthing electrode. When it comes to portable power generators, perhaps the most important reason for this is for lightning protection. In the event of a lightning strike, there needs to be a low impedance path into the earth to shed the electrical energy it generates. Electrodes come in different forms. A grounding rod is only one of them. If you can't drive a grounding rod, then the building grounding electrode can provide that low impedance path to earth for lightning protection. And if there is lightning in the area (within about six miles), the generator should be shut down for 30 minutes after the last lightning strike. I like to use an app called Spark (part of the WeatherBug app) to track lightning.
It's also very important to run a grounding conductor (the green conductor) in addition to the three phase conductors and the neutral conductor. Without it, there is no low impedance path for fault current that would insure that the circuit breaker trips if there is a ground fault. So if, for example, there is a fault to the chassis of a light or junction box, it would stay energized and could potentially hurt some unfortunately soul who wanders close enough to touch it.
Portable power generators can be very safe or very dangerous, depending on how they are set up and operated. Be safe!
Swami Candela of the Third Millennium
Yes, regardless of local regulations physics stays the same.
ReplyDeleteI notice most trailer mounted and small portable generators that I have seen and used (in Australia) are not supplied with either a wire or grounding rod by the hire company; they are often operated without one. These are usually one day and relatively small events, not large festivals with a dedicated power / distribution company. Whenever I am involved in generator hire (no matter the size) I insist on installing a ground.
There are countless stall holders using small generators on a regular basis who start them up and plug them in without any grounding considerations. There is room for improvement in respecting and safely using these very handy devices.
I like your post used generator sales & load bank testing
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