VAMP 257 - Unbalance Protection (46)

VAMP 257 Feeder and motor manager
Technical description
VAMP Ltd
34
VAMP 24h support phone : +358 (0)20 753 3264
VM257.EN002
Parameter Value Unit Default Description
T_Off
Enabled;
Disabled
- Enabled Trip off event
Measured and recorded values of unbalanced load
function:
I
2
/I
1
> (46)
Parameter Value Unit Description
Measured
value
I2/I1 %
Relative negative sequence
component
SCntr Cumulative start counter
TCntr Cumulative start counter
Flt % Maximum I
2
/I
1
fault component
Recorded
values
EDly %
Elapsed time as compared to
the set operating time, 100% =
tripping
2.3.6. Unbalance protection (46)
NOTE! This function is available only in motor protection mode.
The unbalance stage protects the motor against unbalanced
phase currents and single phasing. The protection is based on
the negative sequence current.
Both definite time and inverse time characteristics are
available. The inverse delay is based on Equation 2.3.6-1. Only
the base frequency components of the phase currents are used
to calculate the negative sequence value I
o
.
Equation 2.3.6-1
2
2
2
2
1
)( K
I
I
K
T
MOT
−
=
where,
T = Operation time
K
1
= Thermal time constant of the rotor (I
2
2
t value)
I
2
= Negative sequence phase current, base frequency
component
I
MOT
= Nominal current of the motor
K
2
= The maximum allowed degree of unbalance