Toshiba GRL100-101A, Инструкция по эксплуатации

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6 F 2 S 0 8 3 5
particular application is satisfactory, it is not necessary to know
β
and DIFI2 at this stage.
Instead, the CT requirement can be obtained by following the procedure in the next section.
From the point of view of hardware limitation, secondary maximum through fault current must be
smaller than full scale of measurement which is 65 times rated current.
2. CT requirement
<Step 1> Check the maximum through fault current I
fmaxth
I
fmaxth
< 65 X I
n
where,
I
fmaxth
: Secondary maximum through fault current
I
n
:Rated secondary current
<Step 2> Check the CT satisfies the condition given by table K-2.1 or K-2.2 depending on CT
types. Each table has two requirements. Both must be satisfied.
<Knee point voltage of CTs is given>
Table K-2.1 CT Requirement defined by V
k
Td [ms] Requirement 1 Requirement 2
35 V
k
≧
I
fmax
(R
ct
+ R
2
)
×
3 V
k
≧
I
Lmax
(R
ct
+ R
2
)
×
14.4
50 V
k
≧
I
fmax
(R
ct
+ R
2
)
×
3 V
k
≧
I
Lmax
(R
ct
+ R
2
)
×
20
75 V
k
≧
I
fmax
(R
ct
+ R
2
)
×
4 V
k
≧
I
Lmax
(R
ct
+ R
2
)
×
28.8
100
V
k
≧
I
fmax
(R
ct
+ R
2
)
×
4 V
k
≧
I
Lmax
(R
ct
+ R
2
)
×
36.8
150 V
k
≧
I
fmax
(R
ct
+ R
2
)
×
8 V
k
≧
I
Lmax
(R
ct
+ R
2
)
×
50.4
V
k
: knee point voltage [V]
I
LMAX
: Maximum secondary load current
R
ct
: secondary CT resistance [ohms]
R
2
: Actual secondary burden [ohms]
I
fmax
:maximum secondary fault current
<Accuracy limit factor of CTs is given>
Table K-2.2 CT Requirement defined by n’
Td [ms] Requirement 1 Requirement 2
35 n’ In
≧
3.75
×
Ifmax n’ In
≧
ILmax
×
18
50
n’ In
≧
3.75
×
Ifmax n’ In
≧
ILmax
×
25
75 n’ In
≧
5
×
Ifmax n’ In
≧
ILmax
×
36
100 n’ In
≧
5
×
Ifmax n’ In
≧
ILmax
×
46
150 n’ In
≧
10
×
Ifmax n’ In
≧
ILmax
×
63
n
R R
R I R
n
ct
ct n VA
⋅
+
+
=
2
2
/
'
(K-1.1)
n’ : equivalent accuracy limit factor defined by the equation above.
I
n
: secondary rated current