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1MRS 751108-MUM
Protection Relay
Technical Reference Manual, General
REX 521
Voltage divider:
4.1.6.3. Calculated analog channels
In case that no measuring devices are applied for measuring neutral current (Io), the
calculated (virtual) channel Ios can be used in some of the configurations. See
section “Select Io” for information about how to take Ios into use. Calculated Uos is
also used in some of the configurations in which no measuring device is available
for the residual voltage (Uo). One configuration also includes calculated main
voltages (U12s, U23s, U31s), calculated from the measured phase voltages (U1, U2,
U3). For detailed information about in which configurations the calculated channels
are used, see Table 2.-1 in REX 521 Technical Reference Manual, Standard
Configurations
(see “Related documents” on page 7).
4.1.6.4. Select Io
If the analog channel Iob will be used for protection and measuring functions in the
configuration it has to be enabled in the relay. Do this by selecting Iob, 0.2/1
A from HMI or the Relay Setting Tool, path Configuration\Analog
scales\Select Io. If the calculated Ios will be used it can be enabled from the
same place by selecting Ios. In some configurations only the default setting Io,
1/5 A is available.
4.1.6.5. Rated frequency
The rated frequency of the protection relay can be set from from HMI or the Relay
Setting Tool, path Configuration\Analog scales\Rated frequency.
It can be set between 50 and 60 Hz, the default value is 50 Hz.
4.1.7. Digital inputs
The digital inputs of the protection relay are voltage-controlled and optically
isolated. For technical data of the digital inputs, see Table 4.2.1-3 on page 44.
4.1.7.1. Filtering of digital inputs
The filter time eliminates debounces and short disturbances on digital inputs. The
filter time may be set individually for each input.
Amplitude error at the whole measuring range
(e = error in per cent)
Amplitude correction factor
= 1/(1+ e/100)
Phase displacement error at the whole
measuring range
(e = error in degrees)
Phase displacement error = - e
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