ABB RET 541 Product Manual page 54

54
Transformer Terminal
M
MF
RET/1I
Θ
REF/1I
P> Θ
MF
Fig. 9 Protection, control, measurement and supervision functions of YNyn-connected power transform-
ers, implemented with RET 543 transformer terminals, REF 543 feeder terminals and REA 101 arc
protection. The neutral point of the low-voltage network is earthed via a low resistance. The
scheme is also applicable to other types of low-impedance earthed networks, where the neutral
point is earthed effectively or via a low reactance. This sceme can be applied also for parallel con-
nected transformers.
M
3I> 51
50
3I > 68
2f
RET/3I
I > 51N
0
REF/3I
50N
CBFP 62BF
REF 54_
M
3ΔI > 87T
87TN
ΔI >
M
0
HV
ΔI > 87TN
0
RET/RTD
LV
49T
3
3I > 68
2f
HV
RET 54_
REF, REA/3I
3I> 67
RET/3I
I > 51N
0
50N
CBFP 62BF
REF 54_
RET 541, RET 543, RET 545
000
3U> 59
3U< 27
3I I
0
R
3U
TCS
000
000
3I> 51
HV 50
3I> 51
3I I
0
LV 50
I > 51N
0
3I U
HV 50N
R
I
I > 51N 0
0
TCS
LV 50N T T
O w
U
CBFP 62BF
LV
CBFP 62BF
U
90
HV
000
3U> 59
3U< 27
3I I
0
R
3U
pf
f> 81O
TCS
df/dt 81O-R
f
CBCM
E MCS
YNyn transformers impedance earthed LV neutral
1MRS755543
3I>
&
REA 101