siemens' a monitoring relay is said to not dedect the phase failure since the voltage which appears at the load terminals due to coupling between phases will make it impossible to dedect that. So what do u think about this voltage (what is exactly this phenomenea?)and so how the other model insulation relays of the siemens are capable of dedecting in spite of this voltage ?
monitoring relay
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There are many ways to sense phase loss on a 3 phase system. One of them is by sensing voltage only. If you use that, and you have a spinning motor down stream of the meter when the phase drops off from up stream, it can "fool" a simple phase loss detector because the motor will act like a "rotary phase converter" (Do a search on that term for more information) and couple a voltage to the lost phase. Better relays will pick up a voltage IMBALANCE and trip on that, cheaper ones do not. A better method, when motors are involved, it so use current detection and current imbalance.
By the way, Siemens has many different types of phase monitor relays, you were looking at one of the cheaper ones.
By the way, Siemens has many different types of phase monitor relays, you were looking at one of the cheaper ones.
ptonsparky
Tom
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