Toshiba GRL100-701B Instruction Manual page 407

Table K-7 CT Requirement defined by V
Td [ms]
35
50
75
100
150
V : Knee point voltage [V]
k
R : Secondary CT resistance [ohms]
ct
R : Actual secondary burden [ohms]
2
I : Maximum secondary fault current
fmax
I : Maximum secondary load current
Lmax
Max{I + I
LMAX fmin
I : Minimum fault current
fmin
I : Maximum out-flowing fault current for the special condition
fmaxout
<Accuracy limit factor of CTs is given>
Td [ms]
35
50
75
100
150
R
=
VA
n '
R
n' : Equivalent accuracy limit factor defined by the equation above.
I : Secondary rated current
n
R : Rated secondary burden [VA]
VA
R : Secondary CT resistance [ohms]
ct
R : Actual secondary burden [ohms]
2
n : Rated accuracy limit factor
I : Maximum secondary fault current
fmax
I : Maximum secondary load current
Lmax
Max{I + I
LMAX fmin
I : Minimum fault current
fmin
I : Maximum out-flowing fault current for the special condition
fmaxout
Y is determined by the ratio of the impedance between node D to Terminal C and node D to
Terminal B. If their impedance is assumed to be p and q respectively, Y can be obtained using the
following equation.
q
= ⋅
Y X
2 +
p 2 q
For example, Y = X/4, if p=q and Y=X/2, if p=0.
Requirement 1
V ≧ I (R + R )×3
k fmax ct 2
V ≧ I (R + R )×3
k fmax ct 2
V ≧ I (R + R )×4
k fmax ct 2
V ≧ I (R + R )×4
k fmax ct 2
V ≧ I (R + R )×8
k fmax ct 2
/2, I }: The larger of (I
fmaxout
Table K-8 CT Requirement defined by n'
Requirement 1
n' I ≧ 3.75 × I
n fmax
n' I ≧ 3.75 × I
n fmax
n' I 5 × I
≧
n fmax
n' I 5 × I
≧
n fmax
n' I ≧ 10 × I
n fmax
+
2
/ I R
⋅
n ct
n
+
R
2 ct
/2, I }: The larger of (I
fmaxout
(K-3)
 406 
(Special case)
k
Requirement 2
V >
Max{I + I /2, I } ×(R
k LMAX fmin fmaxout
V > × (R
Max{I + I /2, I }
k LMAX fmin fmaxout
V > × (R
Max{I + I /2, I }
k
LMAX fmin fmaxout
V > × (R
Max{I + I /2, I }
k
LMAX fmin fmaxout
V >
Max{I + I /2, I } ×(R
k
LMAX fmin fmaxout
+ I /2) and I
LMAX fmin fmaxout
Requirement 2
n' I >
Max{I + I /2, I }
n
LMAX fmin fmaxout
n' I >
Max{I + I /2, I }
n
LMAX fmin fmaxout
n' I >
Max{I + I /2, I }
n
LMAX fmin fmaxout
n' I >
Max{I + I /2, I }
n
LMAX fmin fmaxout
n' I >
Max{I + I /2, I }
n
LMAX fmin fmaxout
(K-1)
+ I /2) and I
LMAX fmin fmaxout
6 F 2 S 0 8 5 0
+ R )×14.4
ct 2
+ R )×20
ct 2
+ R )×28.8
ct 2
+ R )×36.8
ct 2
+ R )×50.4
ct 2
×18
×25
×36
×46
×63