416
6
F
2
S
0
8
3
4
Factor “k” is calculated as follows:
K = (CT ratio)/(VT ratio) = (600/5A)/((150kV/ 3 )/(110V)/ 3 )) = 0.088
<Z1S, Z1XS, Z2S, Z3S, Z4S, Z1G, Z1XG, Z2G element>
Z1S, Z1XS, Z2S, Z3S, Z4S, Z1G, Z1XG, Z2G element settings are calculated as shown in the
following table.
<Z3G, Z4G element>
Zero sequence current compensation is not applied to Z3 or Z4. Z3G and Z4G
settings should be larger than the calculated values because of the underreaching effect without
zero sequence current compensation.
a. Setting condition of Z3G element:
The Z3G element must operate on all faults for which the Z2G element operates.
(lower setting limit: Z3G > Z2G)
The Z3G element must not operate on load current. (upper setting limit), so:
X3G setting = [Zline
×
130%](Z2G setting)
×
2.6(operating margin for no zero phase
sequence current compensation)
×
1.5(operating margin)
= 500% of Zline
b. Setting condition of Z4G element
The operation zone of the Z4G element includes the operating zone of the Z3G element
remote terminal relay.
Element Actual
impedance
(ohms)
k factor
Relay impedance
(ohms)
Z1S 3.692
0.32
Z1XS 5.999
0.53
Z2S 5.999
0.53
Z3S 13.84
1.22
Z4S 16.61
1.46
Z1G 3.461
0.088
0.30
Z1XG 5.999
0.53
Z2G 5.999
0.53
Z3G 23.07
2.03
Z4G 27.68
2.44
PSBSZ ----- 2.00
PSBGZ ----- 2.00
3.5 Blinder
setting
Zero sequence compensation is not applied to the blinder elements.
Recommended setting: 5.00 ohms
These elements should not operate under maximum load current:
Rset < load impedance/margin
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Summary of Contents for GRZ100-211B
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