I've been recently involved with power conditioning installations in several "older" (buildings circa +/- 1940's)industrial situations. Various uncommon voltages are common, along with out-dated(?) grounding practices. Most recent was a 580v ungrounded delta system where I was told the plant had a "floating" ground. The building steel, water, and all usual electrodes were in place. Does this "floating" ground refer to the ungrounded delta system, or is there more to it? I keep finding that 20yrs+ in this trade only keeps showing me how much I don't know (keeps one humble AND careful!). Thanx for any help.
Floating Ground
- Thread starter photon
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Re: Floating Ground
I have always thought of a floating ground as a fault condition. A circuit cannot be floating and grounded as the two conditions are mutually exclusive.
A floating secondary on the other hand is a normal condition in 240 volt delta systems and any other system were the system is kept free of grounding connections for the sake of continuity of operation. Such systems are usually fitted with ground detectors of some kind so that any accidental ground fault can be cleared before a complimentary fault establishes a dead short via ground. Remember that the US NEC permits the system to be ungrounded if it is not wye connected, does not have a center tapped phase, and cannot be grounded in such a way as to keep the voltage under 150 volts relative to earth.
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Tom H
I have always thought of a floating ground as a fault condition. A circuit cannot be floating and grounded as the two conditions are mutually exclusive.
A floating secondary on the other hand is a normal condition in 240 volt delta systems and any other system were the system is kept free of grounding connections for the sake of continuity of operation. Such systems are usually fitted with ground detectors of some kind so that any accidental ground fault can be cleared before a complimentary fault establishes a dead short via ground. Remember that the US NEC permits the system to be ungrounded if it is not wye connected, does not have a center tapped phase, and cannot be grounded in such a way as to keep the voltage under 150 volts relative to earth.
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Tom H
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