Hitachi Relion 670 Series Applications Manual page 60

Section 4
Analog inputs
Protected Object
L1
a)
b)
IEC16000139 V1 EN-US
Figure 17:
Where:
1)
2)
3)
4)
4.2.3 Relationships between setting parameter Base Current, CT
rated primary current and minimum pickup of a protection IED
Note that for all line protection applications the parameter Base Current (i.e. IBase setting in the IED)
used by the relevant protection function, shall always be set equal to the largest rated CT 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. 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.
54
L2
1
(+)
INS
(-)
(+)
INS
(-)
Connections for single-phase CT input
shows how to connect single-phase CT input in the IED.
is TRM where these current inputs are located. It shall be noted that for all these current inputs the
following setting values shall be entered.
For connection (a) shown in Figure 17:
CTprim= 600 A
CTsec= 1A
CTStarPoint=ToObject
For connection (b) shown in Figure 17:
CTprim= 600 A
CTsec= 1A
CTStarPoint=FromObject
shows the connection made in SMT tool, which connect this CT input to the fourth input channel of the
preprocessing function block 4).
is a Preprocessing block that has the task to digitally filter the connected analog inputs and calculate
values. The calculated values are then available for all built-in protection and control functions within the
IED, which are connected to this preprocessing function block.
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IED
2
BLOCK
^GRP2L1
(+)
^GRP2L2
^GRP2L1L2
^GRP2N
(-)
3
1MRK506375-UEN Rev. N
4
SMAI2
AI2P
AI1
5
AI2
AI3
AI4
AIN
IEC16000139-1-en.vsdx
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Railway application RER670
Application manual