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Instructional Literature
Page
92
Effective: May 2008
Instructions for the FP-6000 Protective Relay
For more information visit: www.eaton.com
IB02602004E
current polarized direction unit. To achieve maximum sensitivity
to a fault a phase shift is applied to each polarizing quantity, see
diagrams below.
The zero sequence voltage polarizing option uses a zero
sequence voltage polarized direction measurement unit. The
negative sequence voltage polarizing option uses a negative
sequence voltage polarized direction measurement unit. The
dual polarizing uses two directional measurement units, one is
the zero sequence voltage polarized direction measurement unit
and the other is the current polarized directional measurement
unit (see Figures 17 and 18).
IX Gnd Dir Cntrl:
This setting allows the user to select the IXGround Polarizing
Method. Ground direction units are used to supervise the relay
elements that are responsible for tripping ground faults. Ground
direction supervision includes zero sequence voltage polarizing,
negative sequence voltage polarizing and dual polariz-ing. This
includes single phase to ground and double phase to ground
faults (see Figures 17 and 18).
Ph Dir Min Voltage:
The Phase Direction Minimum Voltage setting is the threshold
used to determine when memory voltage will be used. The
maximum torque angle determines the maximum sensitive
operating line. A fixed minimum voltage value will be used to
determine when to use memory voltage and a fixed minimum
current will be used to enable the fault direction determination.
When a phase current is lower than the minimum current limit a
reverse direction may be assumed. The memory voltage will be
used no longer than 200 milliseconds (see Figure 16).
Figure 17. Negative, Zero Sequence Voltage Polarized Ground
Directional Characteristic.
Figure 18. Current Polarized Ground Directional Characteristic.
Thermal Replica Model
The FP-6000 provides the thermal replica model to approximate
the hot spot temperature. The algorithm of the model is
essentially adopted from the field proven Eaton Corporation's
MP-3000 motor relay with some minor changes to adapt other
applications.
In the FP-6000, the effective heat current can be the phase RMS
current or a combination of the positive and negative sequence
currents (I1+K*I2). If the RMS is selected, the setting Therm
Model Type will be ignored. If the sequence current combination
is selected, the effective heat current will depend on the Therm
Model Type setting that allows the user to select their own K or a
fixed value that the MP-3000 motor relay uses. The thermal
model itself is completely defined with a few parameters that can
be obtained from the motor nameplate. If some RTD channels
are configured to sense the motor windings temperature and the
corresponding RTD trips are enabled, the thermal model will be
adjusted with the maximum stator temperature. With the stator
direct temperature measurements, the thermal model includes
the estimated heat loss between stator and rotor; as a result,
motor can tolerate more heat generated from overload condition.
In other words, with stator temperature measured, the adjusted
thermal model allows motor to run longer or higher overload
conditions. Cooling is modeled by a gradual emptying of the
thermal memory.
V
0
(
V
2
)
MTA (Maximum
Torque Angle)
I
0
(
I
2
)
υ
Rev
erse
Fo
rw
ard
MTA (Maximum
Torque Angle)
I
pol
I
0
Forward
Reverse