4–294 869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
MONITORING CHAPTER 4: SETPOINTS
When “Neg Seq Imp Autoset” is set to Auto, the internal algorithm calculates this value
from the motor nameplate information (kWatts, rated voltage and number of poles) using
the Heuristic method.
With the known value of Z
nn
and the phasor value for each current and voltage, all
parameters of equation (1) are known and hence the operating signal can be calculated.
The algorithm for detection of the stator inter-turn fault is comprised of two phases:
• Learning Phase – this runs only once during commissioning for the given CTs, PTs and
machine rating. This phase is used to calculate the unbalance impedance Z
UBbase
of
the machine that is used by the monitoring phase. The setpoint “Learn Turn Fault
Data” can be used to initiate the learning phase of the algorithm. Once set to Yes from
front panel, the monitoring algorithm pauses and the learning algorithm runs to
acquire a new set of Z
UBbase
values. The monitoring phase is disabled until Z
UBbase
is
calculated; once the new average of Z
UBbase
is calculated, the monitoring phase is
automatically reactivated.
• Monitoring Phase – Once the learning phase is complete and the new average of
Z
UBbase
is available, the monitoring phase runs, checking for the operating signal, and
alarms whenever it exceeds Pickup Stage 1 and Pickup Stage 2.
Both the learning and monitoring phase algorithms calculate the average of Z
UBbase
over a
window size of 100 ms.
Path: Setpoints > Monitoring > Stator Inter-turn Fault
FUNCTION
Range: Disabled, Alarm, Latched Alarm, Configurable
Default: Disabled
This setting enables the Stator Inter-turn Fault function.
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).
• When NEG SEQ IMP AUTOSET is changed from Auto to Manual, the learning phase is
automatically initiated to calculate the new Z
UBbase
.
• When NEG SEQ IMP AUTOSET is already set to Manual and the Z
nn
value is changed,
the learning phase is automatically initiated to calculate the new Z
UBbase
.
• When 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 the learning phase is automatically initiated to calculate the new Z
UBbase
.
• When NEG SEQ IMP AUTOSET is set to Auto and any of the nameplate information
(Horse Power, Poles and Rated Voltage) is changed, a new Z
nn
value is calculated and
the 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.
To Next Page
Loading...
