Sel 411L - Page 259

P.3.151
Date Code 20151029 Protection Manual SEL-411L Relay
Protection Functions
Ground Directional Element
Ground Directional
Element Equations
For legibility, these equations use vector quantities, defined in Tabl e 3.79. The
analog quantities are listed in Section 17: Analog Quantities.
32QG
Directional Calculation
Equation 3.75
Forward Threshold
If Z2F is less than or equal to 0:
Equation 3.76
Z2F is greater than 0:
Equation 3.77
Reverse Threshold
If Z2R is greater than or equal to 0:
Equation 3.78
If Z2R is less than 0:
Equation 3.79
32V
Directional Calculation
Equation 3.80
Table 3.79 Vector Definitions for Equation 3.49–Equation 3.61
Vector Analog Quantities Description
V
2
1/3 [3V2FIM] 3V2FIA Negative-sequence voltage
V
0
1/3 [3V0FIM] 3V0FIA Zero-sequence voltage
I
2
1/3 [L3I2FIM] L3I2FIA Negative-sequence current
IG LIGFIM LIGFIA Zero-sequence current
IP IPFIM IPFIA
a
a
The polarizing current angle quantity, IPFIA, is an internal quantity only and is not available
as an analog quantity.
Polarizing current
z2
Re V
2
I
2
1Z1ANG• 
*
• 
I
2
2
-------------------------------------------------------------------------=
Z2FTH 0.75 Z2F 0.25
V
2
I
2
------
• –• =
Z2FTH 1.25 Z2F 0.25
V
2
I
2
------
• –• =
Z2RTH 0.75 Z2R 0.25
V
2
I
2
------
• +• =
Z2RTH 1.25 Z2R 0.25
V
2
I
2
------
• +• =
z0
Re 3V
0
I
G
1Z0ANG• 
*
• 
I
G
2
-----------------------------------------------------------------------------=