ABB PQFA, Instruction Manual

Page: 36 / 98

PQFA Instructions Manual
Asea Brown Boveri Jumet S.A.
36
6.4.2. CT’s connection topology: cases
The location of the CT’s is critical to ensure the proper operation of the active
filter. The CT’s are the “eyes” of the filter and it will react in accordance with
the information supplied by them.
The location of the CT’s must always be in closed loop configuration. This
means that the CT’s must see the load current and the filter current.
In some cases, summation CT’s might be needed to fulfil the closed loop
requirement.
Typical circuit topologies and adequate CT’s location are described hereafter
in the following order:
Case 1: Global compensation – one feeding transformer.
Case 2: Individual compensation – one feeding transformer.
Case 3: Global compensation – transformer busbar not accessible.
Case 4: Two independent feeding transformers.
Case 5: Back up generator.
Please bear in mind that the active filter always needs 3 CT’s: one per phase.
6
6
.
.
4
4
.
.
2
2
.
.
1
1
.
.
C
C
a
a
s
s
e
e
1
1
:
:
G
G
l
l
o
o
b
b
a
a
l
l
c
c
o
o
m
m
p
p
e
e
n
n
s
s
a
a
t
t
i
i
o
o
n
n
–
–
o
o
n
n
e
e
f
f
e
e
e
e
d
d
i
i
n
n
g
g
t
t
r
r
a
a
n
n
s
s
f
f
o
o
r
r
m
m
e
e
r
r
This is the most frequent configuration: one transformer feeds several non-
linear loads. The active filter is installed in central position and filters the
combined harmonic currents.
This configuration and the proper location of the CT’s is represented
hereafter.
Figure 6.1. Global compensation – one feeding transformer.
PQF
LOAD LOAD LOAD