Setting Of Voltage Channels - ABB REG670 Applications Manual

1MRK 502 071-UEN -
4.2.4
4.2.4.1
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual
primary current among all CTs involved in the protection scheme. The rated CT
primary current value is set as parameter CTPrim under the IED TRM settings.
For all other protection applications (e.g. generator, shunt reactor, shunt capacitor and
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 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 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.
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).

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 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.
Example
Consider a VT with the following data:
132 kV 110 V
3 3
EQUATION2016 V1 EN
The following setting should be used: VTprim=132 (value in kV) VTsec=110 (value
in V)
Section 4
Analog inputs
(Equation 1)
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