ABB Relion 670 Series Applications Manual page 80

Section 4
Analog inputs
to set the parameter
among all CTs involved in the protection scheme and installed on the same voltage level. This
will effectively make the protection scheme less sensitive; however, such measures are
necessary in order to avoid possible problems with loss of the measurement accuracy in the
IED.
Regardless of the applied relationship between the
current, the corresponding minimum pickup of the function on the CT secondary side must
always be verified. It is strongly recommended that the minimum pickup of any instantaneous
protection function (e.g. differential, restricted earth fault, distance, instantaneous
overcurrent, etc.) shall under no circumstances be less than 4% of the used IED CT input rating
(i.e. 1A or 5A). This corresponds to 40mA secondary for IED 1A rated inputs and to 200mA
secondary for IED 5A rated inputs used by the function. This shall be individually verified for all
current inputs involved in the protection scheme.
Note that exceptions from the above 4% rule may be acceptable for very special applications
(e.g. when Multipurpose filter SMAIHPAC is involved in the protection scheme).
4.2.4 Setting of voltage channels
As the IED uses primary system quantities, the main VT ratios must be known to the IED. This
is done by setting the two parameters
to-phase value can be used even if each channel is connected to a phase-to-earth voltage from
the VT.
4.2.4.1 Example
Consider a VT with the following data:
132 kV
3
EQUATION2016 V1 EN-US
The following setting should be used:
4.2.4.2 Examples how to connect, configure and set VT inputs for most
commonly used VT connections
Figure 19
world.
+
U
Pri
IEC06000591 V1 EN-US
Figure 19: Commonly used markings of VT terminals
74
IBase in the IED to be equal to the largest rated CT primary current
110 V
3
defines the marking of voltage transformer terminals commonly used around the
+
A
(H1)
U
Sec
N
(H2)
a) b)
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IBase parameter and the rated CT primary
VTsec and VTprim for each voltage channel. The phase-
VTprim=132 (value in kV) VTsec=110 (value in V)
a da
A
(X1) (H1) (X1)
dn
n N
(X2) (H2) (X2)
c)
1MRK 511 401-UEN Rev. K
SEMOD55055-44 v4
SEMOD55055-47 v3
(Equation 1)
SEMOD55055-60 v6
a
A
(X1)
(H1)
B b
(H2) (X2)
d)
en06000591.vsd
Bay control REC670
Application manual