Number of MV/LV transformers

Main characteristics to consider to determine the number of transformers:

• Surface of building or site
• Total power of the installed loads
• Sensitivity of circuits to power interruptions
• Sensitivity of circuits to disturbances
• Installation scalability

The basic preferred configuration comprises a single transformer supplying the total power of the installed loads. Certain factors contribute to increasing the number of transformers (> 1), preferably of equal power:

• A high total installed power (> 1250kVA): practical limit of unit power (standardization, ease of replacement, space requirement, etc),
• A large surface area (> 5000m²): the setting up of several transformers as close as possible to the distributed loads allows the length of LV trunking to be reduced
• A need for partial redundancy (down-graded operation possible in the case of a transformer failure) or total redundancy (normal operation ensured in the case a transformer failure)
• Separating of sensitive and disturbing loads (e.g.: IT, motors)