Schweitzer Engineering SEL-387-0 - Figure 3.27 51 PC2 and 51 NC2 Combined Inverse-Time O;C Elements

3.59
Date Code 20170601 Instruction Manual SEL-387-0, -5, -6 Relay
Differential, Restricted Earth Fault, Thermal, and Overcurrent Elements
Overcurrent Element
Curve time-out causes the Relay Word bit 51NC1T to assert. When the current
drops below pickup, 51NC1 deasserts and the element resets according to the
setting 51NC1RS. At the completion of the reset, Relay Word bit 51NC1R
asserts. This bit normally will be at logic state 1, when the element is at rest
during normal system operation. You can verify the state of the bit using the
TAR command via a serial port or the front panel. You can force this bit to 1
during element testing using the Level 2 serial port command RES or the
front-panel RESET51 function under the {OTHER} pushbutton.
51PC2 and 51NC2 Element
Figure 3.27 shows the logic for the inverse-time combined overcurrent
elements 51PC2 and 51NC2.
Figure 3.27 51PC2 and 51NC2 Combined Inverse-Time O/C Elements
The relay determines whether 51PC2 and 51NC2 assert by performing
calculations similar to those for determination of 51PC1 and 51NC1 assertion.
Setting Descriptions
This subsection contains setting names, setting ranges, and labels for the
overcurrent elements associated with Winding 1. Windings 2, 3, and 4
overcurrent element settings have similar names and labels. All windings have
identical setting ranges.
NOTE: These two overcurrent
elements should not be used if the
REF function is enabled. Neutral CT
input to Winding 4 may lead to false
operation of 51PC2 or 51NC2. Set
51PC2P and 51NC2P to OFF for this
situation.
_
+
51PC2
Pickup
Curve Type
Time Dial
51PC2 Wdg 3 and Wdg 4
Phase Inverse-Time
Overcurrent Element Curve
Timing and Reset Timing
Settings:
51PC2P
51PC2C
51PC2TD
51PC2RS
E/M Reset? (Y/N)
Pickup
Curve Type
Time Dial
51NC2 Wdg 3 and Wdg 4
Residual Inverse-Time
Overcurrent Element Curve
Timing and Reset Timing
Settings:
51NC2P
51NC2C
51NC2TD
51NC2RS
E/M Reset? (Y/N)
51PC2T
51PC2R
IAW3
+
51PC2P
_
+
51NC2
51NC2T
51NC2R
_
+
51NC2P
IAW4
IBW3
IBW4
ICW3
ICW4
IRW3
IRW4
Scalar
Multiply
∑
MAG
∑
MAG
∑
MAG
∑
MAG
Scalar
Multiply
Scalar
Multiply
Scalar
Multiply
Scalar
Multiply
Scalar
Multiply
Scalar
Multiply
Scalar
Multiply
MAX
NOTE: All negative-sequence
element pickup settings are in terms
of 3I
2
.