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 7)
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 8)
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 9)
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 10)
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 11)
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.
Considering the resistances and reactances which are related to the settings (ForwardR, ForwardX) and
(ReverseR, ReverseX):
R
ForwardR
ZBase
FwdR
= × = × =
100
8 19
100
0 9522 0 078
.
. . Ω
EQUATION14048 V1 EN-US (Equation 12)
X
ForwardX
ZBase
FwdX
= × = × =
100
59 33
100
0 9522 0 565
.
. . Ω
EQUATION14049 V1 EN-US (Equation 13)
R
ReverseR
ZBase
RvsR
= × = × =
100
0 29
100
0 9522 0 003
.
. . Ω
EQUATION14050 V1 EN-US (Equation 14)
X
ReverseR
ZBase
RvsX
= × = × =
100
29 6
100
0 9522 0 282
.
. . Ω
EQUATION14051 V1 EN-US (Equation 15)
Section 11 1MRK 504 165-UUS Rev. J
Testing functionality by secondary injection
146 Transformer protection RET670
Commissioning manual
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