ABB RELION REX640 Technical Manual page 158

Basic functions
sensor setting
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 (
which makes the same setting
60 Hz nominal frequency.
RSV
RSV
I
n
I
pr
f
n
K
r
In this example, the value is as calculated using the equation.
150
80
With this information, the protection relay's current (Rogowski) sensor
settings can be set.
Table 92: Example setting values for current (Rogowski) sensor
Setting
Primary current
Rated secondary value
When considering setting values for current sensor interfaces and for
protection functions utilizing these measurements, it should be noted
that the sensor measurement inputs in the relay have limits for linear
behavior. When this limit is exceeded, the input starts to saturate. The
saturation is reflected to the protection functions connected to the
sensor inputs. To ensure that the related protection functions operate
correctly, the start value setting for protection functions utilizing either
instantaneous or definite minimum time characteristics must not exceed
the linear measurement range. Furthermore, the effect on protection
functions utilizing inverse time characteristics should be considered. The
upper limit of the linear measurement range depends on the selected
application nominal current and the type of the current sensor used.
93
shows the limits for an 80A/150mV 50Hz sensor.
158
Primary current . Taken from the sensor's technical data, this
Rated Secondary Value ) is not in V but in mV/Hz,
I
n
K
×
r
I
pr
=
f
n
Rated Secondary Value in mV/Hz
Application nominal current
Sensor-rated primary current
Network nominal frequency
Sensor-rated voltage at the rated current in mV
A
150 mV
×
mV
A
= . 5 625
50 Hz Hz
Rated Secondary Value valid for both 50 and
Value
150 A
5.625 mV/Hz
1MRS759142 F
(Equation 1)
(Equation 2)
Table
REX640
Technical Manual