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• Current Transformer Ratio:
RC = 1200/5 = 240
• Voltage Transformer Ratio:
RV = 600/1 = 600
Relay secondary ohmic impedances are:
Z
= Z
pri
Z1L
= Z2L = 15∠77˚
Z
= 50∠73° x 240/600 = 20∠73° ohms
0L
3.2.1
Ratio of Zero and Positive Sequence Impedances (ZR)
Z
/Z
= 20/6 = 3.33
0L
1L
Then REL 301/302 will automatically calculate the zero sequence current compensation factor
(k
) by using the value of "Z 0L /Z 1L ", "Ang Pos.", "Ang Zero" and reference to equation 1 in
0
Section 2.2.1 i.e.,
NOTE:
3.2.2
Zone-1 Distance Settings
A setting of 80% of the line impedance for Zone-1 reach is recommended, thus the Zone-1
phase and ground reach should be
"Zone-1 Ø" = 6 x 0.8 = "4.8 OHMS" and
"Zone-1 G" = 6 x 0.8 = "4.8 OHMS"
NOTE:
As stated above, start with a setting of 80% of the line impedance for the Zone-1 reach setting.
Adjustment of the Zone-1 reach (line percentage) should be considered if any of the following
are true:
x R
/R
C
V
(
)/Z
(
k
= Z
–
Z
=
Z
0
0L
1L
1L
OL
The setting range of ZOL/ZIL has been expanded 0.1 - 7.0 to 0.1 - 10. Also the
setting ranges of Ang Pos. (Positive sequence line impedance angle) and Ang
Zero (Zero sequence line impedance angle) have been expanded from 40 -90 to
10 -90 as well. These changes were made to accommodate a wide variety of
system components and configurations. However, the selection of each set-
ting has to be carefully considered if the maximum fault current is 200 Amperes
(secondary or above).
If the maximum fault current is 200 Amperes (secondary) the following restric-
tions must be observed:
ZOL/ZIL less than or equal to 7.5
The setting difference of |Ang Pos| - |Ang Zero| = 50 or less
If the maximum fault current is less than 200 Amperes (secondary) these re-
strictions do not apply.
"Zone-1 Ø" and "Zone-1 G" can be set for different values if the application
requires.
⁄
)
∠
(
(
Z
AngZero AngPos
–
1L
I.L. 40-386.4
) 1
)
–
3-3
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