VAMP 52 - Inverse delay; More stages (definite time delay only); Setting groups

2.7 Current unbalance stage I2> (46) 2 Protection functions Technical description
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Inverse delay
The inverse delay is based on the following equation.
Equation 2.7-1
2
2
2
2
1
K
I
I
K
T
mot










, where
T = Operation time
K
1
= Delay multiplier
I
2
= Measured and calculated negative sequence phase
current of fundamental frequency.
I
mot
= Nominal current of the motor
K
2
= Pick-up setting I
2
> in pu. The maximum allowed
degree of unbalance.
Example:
K
1
= 15 s
I
2
= 22.9 % = 0.229 xI
mot
K
2
= 5 % = 0.05 xI
mot
4.300
05.0
1
229.0
15
2
2








t
The operation time in this example will be five minutes.
More stages (definite time delay only)
If more than one definite time delay stages are needed for
current unbalance protection, the freely programmable stages
can be used (chapter 2.21).
Setting groups
There are two settings groups available. Switching between
setting groups can be controlled by digital inputs, virtual
inputs (communication, logic) and manually.