7.9 Trip Circuit Supervision
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P = 2*0.003^2x22000 = 0.40 W
Select the next bigger standard size, for example 0.5 W.
When the trip contacts are still closed and the CB is already
open, the resistor has to withstand much higher power
(Equation 7.9.1-3) for this short time.
Equation 7.9.1-3
P = 121^2/22000 = 0.67 W
A 0.5 W resistor will be enough for this short time peak power,
too. However, if the trip relay is closed for longer time than a
few seconds, a 1 W resistor should be used.
Using any of the non-dry digital inputs DI1...DI6
In this scheme an auxiliary relay is needed to connect the wet
digital input to the trip circuit (Figure 7.9.1-5). The rated coil
voltage of the auxiliary relay is selected according the rated
auxiliary voltage used in the trip circuit. The operating voltage
range of the relay should be as wide as possible to cover the
tolerance of the auxiliary voltage.
In this application using the other wet inputs for other
purposes is not limited unlike, when using the dry inputs.
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