ABB RER670 - Example; Examples How to Connect, Configure and Set VT Inputs for most Commonly Used VT Connections; Setting of Voltage Channels

For all other protection applications (e.g. transformer protection) it is typically
desirable to set IBase parameter equal to the rated current of the protected object.
However this is only recommended to do if the rated current of the protected object
is within the range of 40% to 120% of the selected CT rated primary current. If for
any reason (e.g. high maximum short circuit current) the rated current of the
protected object is less than 40% of the rated CT primary current, it is strongly
recommended to set the parameter IBase in the IED to be equal to the largest rated
CT primary current among all CT
s 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 IBase parameter and the rated
CT primary 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.
4.2.4 Setting of voltage channels
SEMOD55055-44 v4
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 VTsec and VTprim for each
voltage channel. The phase-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
SEMOD55055-47 v3
Consider a VT with the following data:
110 100
/
22
kV V
IECEQUATION16054 V1 EN-US (Equation 1)
The following setting should be used: VTprim=110
(value in kV) VTsec=100
(value in V)
4.2.4.2 Examples how to connect, configure and set VT inputs for most
commonly used VT connections
SEMOD55055-60 v6
Figure
16 defines the marking of voltage transformer terminals commonly used
around the world.
1MRK 506 375-UEN A Section 4
Analog inputs
Railway application RER670 2.2 IEC 55
Application manual