ADM
A/
D
co
nv
er
si
on
sc
al
in
g
w
ith
C
T
ra
tio
A/
D
co
nv
er
si
on
sc
al
in
g
w
ith
C
T
ra
tio
Ph
as
or
ca
lc
ul
at
io
n
of
in
di
vi
du
al
ph
as
e
cu
rr
en
t
Ph
as
or
ca
lc
ul
at
io
n
of
in
di
vi
du
al
ph
as
e
cu
rr
en
t
Differential function
D
er
iv
e
eq
ua
tio
n
to
ca
lc
ul
at
e
di
ffe
re
nt
ia
lc
ur
re
nt
s
Trafo
Data
Ph
as
or
s
&
sa
m
pl
es
Ph
as
or
s
&
sa
m
pl
es
Instantaneous (sample based)
Differential current, phase A
Instantaneous (sample based)
Differential current, phase B
Instantaneous (sample based)
Differential current, phase C
Fundamental frequency (phasor
based) Diff current, phase A &
phase current contributions from
individual windings
Fundamental frequency (phasor
based) Diff current, phase B &
phase current contributions from
individual windings
Fundamental frequency (phasor
based) Diff current, phase C &
phase current contributions from
individual windings
Negative sequence diff current
& NS current contribution from
individual windings
ANSI09000162_1_en.vsd
MAX
Settings for Zer. Seq.
Current Reduction
IDMAG_A
IDMAG_B
IDMAG_C
IDMAG_NS
ID_B
ID_A
ID_C
IBIAS
52
152
ANSI09000162 V1 EN
Figure 37:
Treatment of measured currents within IED for transformer differential function
shows how internal treatment of measured currents is done in case of a two-
winding transformer.
The following currents are inputs to the power transformer differential protection
function. They must all be expressed in power system (primary) A.
Section 6
1MRK 502 048-UUS A
Differential protection
112
Technical manual
