Setting Of Voltage Channels; Example; Examples How To Connect, Configure And Set Vt Inputs For Most Commonly Used Vt Connections - Hitachi Relion 670 Series Applications Manual

Section 4
Analog inputs
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).
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 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-ground voltage from the VT.
4.2.4.1

Example

Consider a VT with the following data:
132kV
3
EQUATION1937 V1 EN-US
The following setting should be used: VTprim=132 (value in kV) VTsec=120 (value in V)
4.2.4.2 Examples how to connect, configure and set VT inputs for most commonly
used VT connections
Figure 18
+
V
Pri
ANSI11000175 V1 EN-US
Figure 18:
56
120V
3
defines the marking of voltage transformer terminals commonly used around the world.
+
A
(H1)
V
Sec
N
(H2)
a) b)
Commonly used markings of VT terminals
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a da
A
(X1) (X1)
(H1)
dn
n N
(X2) (H2)
(X2)
c)
1MRK511407-UUS Rev. N
(Equation 1)
a
A
(X1)
(H1)
B b
(H2) (X2)
d)
ANSI11000175_1_en.vsd
Phasor measurement unit RES670
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