ABB RELION REX640 Technical Manual page 689

1MRS759142 C
REX640
Technical Manual
12600 0 26 0 18 ( . .
⋅ +
U
=
s
240
GUID-829B26A6-9EE9-4AF0-94AC-95E37D2F91C6 V1 EN
According to the criterion, the value of U
on if the stability of the scheme is achieved with U
to choose a bigger core of 65 percent with:
R = 0.47 Ω (value given by the manufacturer).
in
U = 81 V (value given by the manufacturer).
k
R = 0.18 Ω
m
12600 0 47 0 18 ( . .
⋅ +
U
=
s
240
GUID-44A7E02C-6845-4A9D-AE19-E9DD1CEE5983 V1 EN
U = 2 · U = 68 V (required value).
k s
As mentioned earlier, I
m
= 0 and I = m · 0.5 · I
rs o
I = n · m · I = 240 · 4 · 0.055 A ≈ 53 A
prim e
I = 4· 0.5 · 0.055 A = 0.11 A
rs
The setting value can be calculated with:
I

rs
Operatevalue
=
 
I
CT _ n 2

GUID-5E1204C3-45B3-45EA-A5FF-F5A7165FC5C8 V1 EN
The resistance of the stabilizing resistor can be calculated:
R = U / I = 34 V / 0.11 A ≈ 309 Ω
s s rs
However, the sensitivity can be calculated more accurately when the actual values of
I and I are known. The stabilizing resistor of the relay is chosen freely in the above
u rs
example and it is assumed that the resistor value is not fixed.
)
V 23 V
≈
should be 2 · U
k
)
V 34 V
≈
= 0.5 · I gives a realistic value for I
e
, the value for the sensitivity is:
0 11 . A

 
2 2 . %
  =  ≈

A
5
 

Section 4
Protection functions
(Equation 136)
= 2 · 23 V = 46 V. It depends
s
= 40 V. Otherwise, it is possible
k
(Equation 137)
in Equation
prim
(Equation 138)
132. If I
u
683