4–280 869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
MONITORING CHAPTER 4: SETPOINTS
With the known value of Z
nn
and phasor value for each current and voltage, all the
parameters of equation (1) are known and hence operating signal can be calculated.
The algorithm for detection of the stator inter-turn fault comprises two sections:
• Learning Phase – this runs only once during commissioning for a given setup of CTs,
PT
s and machine rating. This phase is used for calculation of unbalance impedance
Z
UBbase
of the machine, to be used by the monitoring phase. Local/remote command
based provision is can be used to call for learning phase of the algorithm. Once the
command for learning phase is given from front panel or communication medium, the
monitoring algorithm will break and go to learning algorithm to acquire new set of
Z
UBbase
value. Monitoring phase is disabled until Z
UBbase
is calculated. Once the new
average of Z
UBbase
is calculated and the monitoring phase will be automatically
active.
• Monitoring Phase – Once the learning phase is done
, the monitoring phase is initiated
that checks for the operating signal and alarms whenever it exceeds Pickup Stage 1
and Pickup Stage 2.
Path:
Setpoints > Monitoring > Stator Inter-Turn Fault
Settings
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Configurable
Default: Disabled
This setting enables the Stator Inter-Turn Fault functionality.
NEG SEQ IMP AUTOSET
Range: Manual, Auto
Default: Auto
As a convenient alternative to manually determining the negative sequence impedance
(Z
nn
), the relay can automatically calculate the setting Neg Seq Impedance from the
nameplate information (Horse Power, Poles and Rated Voltage).
NOTE:
• When setpoint NEG SEQ IMP AUTOSET is changed from Auto to Manual, learning
phase is automatically initiated to calculate the new Z
UBbase
.
• When setpoint NEG SEQ IMP AUTOSET is already set to Manual and Z
nn
value is
changed, learning phase is automatically initiated to calculate the new Z.
• When setpoint NEG SEQ IMP AUTOSET is changed from Manual to Auto, a new Z
nn
value is calculated based on the nameplate information (Horse Power, Poles and
Rated Voltage) and learning phase is automatically initiated to calculate the new
Z
UBbase
.
• When setpoint NEG SEQ IMP AUTOSET is set to Auto and any of the nameplate
informat
ion (Horse Power, Poles and Rated Voltage) is changed, a new Z
nn
value is
calculated and learning phase is automatically initiated to calculate the new Z
UBbase
.
NEG SEQ IMPEDANCE:
Range: 0.10 to 100.00 in steps of 0.01
Default: 10.00
This setting is only visible when Neg Seq Imp Autoset is set to Manual. This setting
defines the negative sequence impedance Z
nn
calculated by the user.
PICKUP STAGE 1:
Range: 0.001 to 10.000 in steps of 0.001
Default: 0.100
This setting specifies a first pickup threshold of the ratio between Z
np
and Z
pp
averaged
over 100 msec. There is no unit to this setting
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