ABB UniGear Series, Engineering Manual

Page: 39 / 112

ENGINEERING S ENS O RS
1VLG5 00007 E 27
Primary current
Setting example
In this example, an 80 A / 0.150 V at 50 Hz sensor is used and the application has a 1 000 A
nominal current (I
n
).
Figure 31: Single line diagram
When defining another primary value for the sensor, also the nominal voltage should be rede-
fined to maintain the same transformation ratio. However, the setting in the protection relay
(
Rated Secondary Value
) is not in V but in mV / Hz, which makes the same setting value valid
for both 50 Hz and 60 Hz nominal frequency.
𝑅𝑆𝑉 =
𝐼𝑛 𝐼𝑝𝑟
⁄
× 𝐾𝑟
𝑓𝑛
RSV Rated secondary value in mV / Hz
I
n
Application nominal current
I
pr
Sensor-rated nominal current
K
r
Sensor-rated voltage at the rated current in mV
f
n
Network nominal frequency
In this example, the value is as calculated using the equation.
𝑅𝑆𝑉 =
1000 𝐴 80 𝐴
⁄
× 150 𝑚𝑉
50 𝐻𝑧
= 37.5
𝑚𝑉
𝐻𝑧