If the rated secondary current I
rs
of the analog channel is 1 A, then the maximum
current test I
ts
is
I I I A
ts ovrl rs
≤ = × =4 4
EQUATION14041 V1 EN-US (Equation 4)
If the CT of the generator has ratio 9000/1 A, then in primary values
I I I
I
I
A
t ovrl p ovrl
rp
rs
≤ = × = × =
,
4
9000
1
36000
EQUATION14042 V1 EN-US (Equation 5)
Reference is made to the numerical values of the example, explained in the
“Setting guidelines” of the Application Manual. A test current equal to 2.5 time the
base current of the generator is chosen; this choice is related to the selected test
voltage that is applied while testing the point SE and RE.
I I A
t Base
= × = × =2 5 2 5 8367 20918. .
EQUATION14043 V1 EN-US (Equation 6)
The parameter ReachZ1 defines the boundary between zone 1 and zone 2; it is
expressed in percent of the parameter ForwardX
. If the setting of ReachZ1 = 12%,
then corresponding primary value of the reactance is
X
ReachZ ForwardX
ZBase
RZ 1
1
100 100
12
100
59 33
100
0 9522 0= × × = × × =
.
. .0068Ω
EQUATION14044 V1 EN-US (Equation 7)
The calculation of the test voltage, that is related to ReachZ1, is based on the
impedance Z
RZ1
that has imaginary part X
RZ1
and real part R
RZ1
:
RRZ
achZ ForwardR
ZBase1
1
100 100
12
100
8 19
100
0 9522 0 0= × × = × × =
Re .
. . 009Ω
EQUATION14045 V1 EN-US (Equation 8)
The magnitude of the impedance Z
RZ1
is:
2 2 2 2
1 1 1
0.009 0.068 0.069
RZ RZ RZ
Z R X= + = + = W
EQUATION14046 V1 EN-US (Equation 9)
Hence the reference voltage of the test of the boundary between zone 1 and zone 2
is
V Z I V
t RZ RZ t,
.
1 1
0 069 20918 1435= × = × =
EQUATION14047 V1 EN-US (Equation 10)
If the test voltage is lower than V
t,RZ1
(or in opposition), then the test is related to
the zone 1; if the test voltage is higher than V
t,RZ1
, then the test is related to the
zone 2.
1MRK 505 378-UEN A Section 11
Testing functionality by secondary injection
Line differential protection RED670 2.2 IEC 151
Commissioning manual
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