ABB Relion 620 Series - Page 109

Figure 33: Example of ABB Rogowski current sensor KECA 80 D85 rating plate
Current (Rogowski) sensor setting example
In this example, an 80 A/0.150 V at 50 Hz (0.180 V at 60 Hz) sensor, such as
the example shown in Figure 33 , is used in a 50 Hz electrical network. The
application has a 150 A nominal current (In) corresponding to the protected
object’s nominal current. The application nominal current is set to Rogowski
sensor setting Primary current . Taken from the sensor’s technical data, this
example sensor can be used with up to 4000 A application nominal current.
As the Rogowski sensor is linear and does not saturate, the 80 A/0.150 V
at 50 Hz sensor also works as a 150 A/0.28125 V at 50 Hz sensor. When
defining another primary value for the sensor, also the nominal voltage has
to be redefined 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 Rated Secondary Value valid for both
50 and 60 Hz nominal frequency.
RSV
I
I
K
f
n
pr
r
n
=
×
(Equation 1)
RSV Rated Secondary Value in mV/Hz
I
n
Application nominal current
I
pr
Sensor-rated primary current
f
n
Network nominal frequency
K
r
Sensor-rated voltage at the rated current in mV
In this example, the value is as calculated using the equation.
150
80
150
50
5 625
A
A
mV
Hz
mV
Hz
×
= .
(Equation 2)
With this information, the protection relay's current (Rogowski) sensor
settings can be set.
1MRS757644 H
Basic functions
620 series
Technical Manual
109