ABB THF 1BS Series, Installation And Operation Instruction Manual

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44
Installation to TN-S-System
- THF in the N-conductor
The installation shall be done following the local
wiring rules suggesting to work all power off. Prior
to installation of THF on N –conductor between
point A and B following measures must be taken.
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.