Transformers Fittings
In order to install a medium voltage transformer below is the list of necessary fittings:
- Plain bi-directional rollers with blocking facilities.
- Skid base, lifting and jacking lugs
- Neutral and earthing terminals
- Rating and terminal marking plates
Transformer Thermal Protection
- Temperature protection shall be incorporated to prevent thermal overloading of the power transformers.
- BMS monitoring shall be provided for each signal accordingly.
- A dial type thermometer shall be provided on the housing of each transformer for measurement of the winding temperature.
- Two thermal sensors of the resistor type shall be molded into each phase of the low voltage section of the spool, these sensors together with appropriate relays and timer shall be provided for each transformer.
- Temperature alarm and tripping signals to the switch-gear from the transformers.
MV Terminals : MV Terminals shall be provided to as per the local regulatory & project specification requirement.
Secondary Termination: Secondary termination shall be provided as per the local regulatory & project specification requirement.
Earthing And Neutral Earthing
All metal parts of the distribution transformer shall be earthed. The method of earthing bar sizes shall be in accordance with BS CP 1013 and BS7430. The neutral conductor of the LV winding shall be provided with a terminal which is brought out of the LV termination box for the main earth lead to be connected. The value of the earth resistance shall comply with the requirement of the BS7430 and authorities and shall not be higher than 1 ohm.
Clearances of live parts of transformers to earth and between phases shall not be less than those specified in the British Standard. The clearances for the terminals in the cable boxes shall note be less than those specified in the requirements for Air, unless the cable boxes are compound filled. The clearances for the heat shrink type of termination shall be similar to that of air. Earthing system must be inspected and repaired during the routine maintenance of transformers.
Vibration Isolation
Where the transformer is subject to vibration during operation, isolation pad should be provided at the skid base. Calculation and criteria of selection of isolation pads should be submitted for technical approval prior to carrying out any installation works of the MV Transformers. All areas having vibration due to other running equipment must be having the suitable vibration isolators for all equipment’s including the transformers