Settings Example
[dw_7SR5_function87GHApplicationAndSettingNotes3, 1, en_US]
Figure 5-46 Example System – Restricted Earth Fault
Plant Data
See Figure 5-46
Settings Requirements
[fo_function87TExample7, 1, en_US]
Assigned through fault current (rated stability limit) = 16 ⋅ load current = 8.4 kA, or, as specified by the user
Required Fault Setting (Primary Operate Current)
10 to 25 % of protected winding rated current, or as specified by the user
Required P.O.C. = 53 - 131 A. Say 60 A.
Line CT (LCT) and Connection Details
Turns ratio (T)
1 to 600
Voltage knee point (V
K
) 350 V
Magnetising current (Imag) @ V
K
40 mA
CT secondary resistance (R
CT
) 7.5 Ω
CT lead loop resistance (R
L
) 0.15 Ω max.
Neutral CT (NCT) and Connection Details
Turns ratio (T)
1 to 600
Voltage knee point (V
K
) 350 V
Magnetising current (Imag) @ V
K
50 mA
CT secondary resistance (R
CT
) 6 Ω
CT lead loop resistance (R
L
) 0.15 Ω max.
Protection and Automation Functions
5.21 87GH Restricted Earth-Fault Protection – High-Impedance
Reyrolle 7SR5, Transformer Protection Device, Device Manual 301
C53000-G7040-C015-1, Edition 11.2019
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