Siemens Reyrolle 7SR45 Argus Device Manual page 93

[dw_burden-of-relay-for-diff-currents_5A, 1, en_US]
Figure 5-3
Sample Calculation
CT ratio: 100/1
Rated CT burden (R
CT winding resistance (R
Rated secondary current (I
Case 1
In the absence/loss of auxiliary power, the minimum phase current required for the relay operation in single
phase = 0.2 I
rated
[fo_ALF_V3, 1, --_--]
R = 28.5 at 0.2 A (Refer to impedance graphs for current > 1 A (rated current, I
b
ALF ≥ 1.933
Reyrolle, 7SR45, Device Manual
C53000-G7040-C101-2, Edition 09.2020
Burden of the Relay for Different Currents
): 2.5 VA (R = 2.5 Ω for 1 A secondary current)
bn bn
): 0.5 Ω
ct
): 1 A
sr
(I = 0.2 A for rated current of 1 A).
s
5.2 Current-Transformer Requirements and Sample Calculations
rated
Applications
= 1 A))
93