GE 869 Instruction Manual page 426

MONITORING
4–294
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
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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
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
calculated; once the new average of Z
automatically reactivated.
• Monitoring Phase – Once the learning phase is complete and the new average of
Z is available, the monitoring phase runs, checking for the operating signal, and
UBbase
alarms whenever it exceeds Pickup Stage 1 and Pickup Stage 2.
Both the learning and monitoring phase algorithms calculate the average of Z
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 ), the relay can automatically calculate the setting Neg Seq Impedance from the
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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
• When NEG SEQ IMP AUTOSET is already set to Manual and the Z
the learning phase is automatically initiated to calculate the new Z
• When NEG SEQ IMP AUTOSET is changed from Manual to Auto, a new Z
calculated based on the nameplate information (Horse Power, Poles and Rated
Voltage) and the learning phase is automatically initiated to calculate the new Z
• 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
the learning phase is automatically initiated to calculate the new Z
NEG SEQ IMPEDANCE:
Range: 0.10 to 100.00 Ω in steps of 0.01 Ω
Default: 10.00 Ω
This setting is only visible when Neg Seq Imp Autoset is set to Manual. This setting
defines the negative sequence impedance Z
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
over 100 msec.
and the phasor value for each current and voltage, all
values. The monitoring phase is disabled until Z
UBbase
is calculated, the monitoring phase is
UBbase
UBbase
calculated by the user.
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869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 4: SETPOINTS
UBbase
UBbase
UBbase
.
value is changed,
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.
UBbase
value is
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value is calculated and
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.
UBbase
and Z averaged
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of
is
over a
.
UBbase