4
5
4
Installation to TN-S-System
– THF in the transformer star point
2.
Open both the HV- main switch and the LV-main switch.
3.
Care should be taken to ensure that no earth/neutral bond exists on the supply (transformer) side
of the filter. This may result in a by-pass situation causing excessive current to flow via the system
earth, heating of the cables and inactivating the filter.
4.
Measure the isolation resistance between point A and B to ensure that the resistance between
point A and B is high. R
e
needs to be over 50 k
Ω
. Any earthing conductor with lower resistance
by-passing the THF between the star point and B might be subject to high third harmonic current and
heating of the cables, and inactivating THF.
5.
Make the earthing in point B.
The installation shall be done following the local
wiring rules suggesting to work all power off.
Prior to installation of THF in the transformer
star-point between point A and B following
measures must be taken.
1.
Measure the fundamental 50/60Hz current in the
star point connector conductor. Load balancing is
recommended, if the unbalance current exceeds 15%
of the rated primary current of the CT.
Installation to TN-S-System
- THF in the N-conductor
1.
Measure the fundamental 50/60Hz current on the N-conductor.
Phase balancing is recommended,if the unbalance current
exceeds 15% of the rated primary current of the CT.
2.
Open the LV-main switch.
3.
Check that there is no earting bond on the load side between
N-conductor after the point B and the earthing system.
4.
Measure the isolation resistance between point A and B or to
ensure that the resistance between point A and B is high. R
e
needs to be over 50 k
Ω.
5.
Resistance measurements must be carried out between the
downstream (building) earth & neutral to ensure that no
erroneous earth/neutral connection exists other than that intended
to achieve a TN-S-system. Such accidental connection could cause
excessive current to flow in the system earth and heating of the
cables.
The installation of THF in the N-conductor
6.
Before the installation turn the by-pass switch of THF-unit ON.
7.
Connect the OUTPUT-terminal to the load side (B).
8.
Connect the INPUT-terminal to the line side (A).
9.
The N-conductor of TN-S-system shall be earthed on the line
side of THF only. No earthing is allowed between N-terminal
and earthing system on the load side of THF (OUTPUT-terminal).
10.
After the installation turn the by-pass-switch in OFF-position.
11.
Check that the THF connection is right by measuring the
current with THF ON and OFF. In proper installation the filtering
effect should be around 90% and the 150/180 Hz voltage
across THF should be 10...45V.
The installation of THF in the PEN-
conductor
6.
Before the installation turn the by-pass switch of THF-
unit ON.
7.
Connect the OUTPUT-terminal to the load side (B).
8.
Connect the INPUT-terminal to the line side (A).
9.
The PEN-wire shall be earthed after the OUTPUT-
terminal only. No earthing is allowed between the
transformer star point (N-terminal) and the INPUT-
terminal.
10.
After the installation turn the by-pass-switch in OFF-
position.
11.
Check that the THF connection is right by measuring
the current with THF ON and OFF. In proper installation
the filtering effect should be around 90 % and the
150/ 180 Hz voltage across THF should be 10...45V.
Summary of Contents for THF 1BS Series
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