8 Obligatory Checks
The transformer should be powered up only after checking the following items: name plate ratings, parallel operation, connections: cables, busbars, tap change connections, grounding connection, thermal protective device, impurities removal and insulation resistance test.
1st Check (name plate ratings)
Make sure the name plate ratings are in accordance with the ratings foreseen for the place of installation.
2nd Check (parallel operation)
When transformers are to be operated in parallel, make sure they are connected with the right polarity. If there is only one transformer or more of them, but not operated in parallel, just skip to the next check.
Learn more about principles of transformers in parallel connection.
3rd Check (connections: cables, bus bars)
Make sure all connections to cables or bus bars are properly connected and well positioned.
4th Check (tap change connections)
Make sure that all connections at the tap change panel are firmly tightened and at the same position in the three phases.
5th Check (grounding connection)
Make sure the grounding mesh is correctly connected to the bolt provided for this purpose.
In addition, make sure the grounding mesh has been correctly executed at the right place foreseen in the project and shown in the drawing.
6th Check (thermal protective device)
In case of transformers fitted with a thermal protective device, check the connections of the circuit, making sure that the voltage is in accordance and that the alarm and shut-off contacts are connected to their corresponding loops.
7th Check (impurities removal)
Make sure there are no materials, equipment or any other impurities laid on the transformer, between the coils or obstructing the ventilation in the cooling channels.
8th Check (insulation resistance test)
It is always recommendable to check the insulation resistance by making measurements between the LV and HV windings and from the windings to the ground.
ONLY after these checks are made, the transformer can be connected to the system.
Voltage shall be applied while the transformer is set to no load, and such voltage shall be measured at the secondary winding to check for the corresponding output ratings. Operations under voltages other than the rated one can cause saturation significant loss increase, which could lead to over-heating and noise above the standard levels.
The load should be applied progressively until the rated power .
- Schneider Electric – Trihal Catalogue
- Instruction Manual For Dry-type Transformers – WEG