VAMP 265 - Page 83

Technical description
2 Protection functions
2.13 Inverse time operation
VM265.EN011
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83
Example of limitation
CT = 750/5
I
N
= 577 A
CT
0
= 100/1 (a cable CT for I
0
)
Secondary scaled I
GNsec
is now 3.85 A
For 5 A CT secondaries and 1 A residual current inputs VAMP
relay VAMP 265-5D7AAA is used. It has 5 A phase current
inputs and 1 A residual inputs.
For overcurrent stage I> the table below gives 12.5 A. Thus the
maximum setting for I> stage giving full inverse delay range is
12.5 A / 3.85 A = 3.25 xI
gn
.
For earth fault stage I
0
> and input I
01
the table below gives
0.25 A. Thus the maximum setting for I
0
> stage giving full
inverse delay range is 0.25 A / 1 A = 0.25 pu. This equals a 25 A
primary earth fault current.
When using input signal I
0Calc
the corresponding setting is 12.5
A / 1 A = 12.5 pu. This equals a 9375 A of primary earth fault
current.
RATED INPUT
Maximum secondary scaled setting
enabling inverse delay times up to
20x setting
Order code
I
L
I’
L
I
01
I
02
I
L1
, I
L2
,
I
L3
&
I
0Calc
I’
L1
, I’
L2
,
I’
L3
&
I’
0Calc
I
01
I
02
VAMP 265-1_
1
1
2.5 A
2.5 A
VAMP 265-3_
1
5
2.5 A
12.5 A
VAMP 265-4_
5
1
12.5 A
2.5 A
VAMP 265-5_
5
5
12.5 A
12.5 A
VAMP 265-_A
5
5
1.25 A
1.25 A
VAMP 265-_B
5
1
1.25 A
0.25 A
VAMP 265-_C
1
5
0.25 A
1.25 A
VAMP 265-_D
1
1
0.25 A
0.25 A