Example of standard MV/LV network structure

Network structure:

Example network above consists of:

• MV consumer substation;
• Two MV ratings: 20 kV and 6 kV;
• The main MV switchboard fed at 20 kV can be backed up by a set of four generators. It feeds:
  • An MV 20 kV network in a loop system comprising three secondary switchboards MV4, MV5 and MV6;
  • Two 20 kV/6kV transformers in a single line supply system;
• The MV main switchboard is made up two bus sections fed at 6 kV by two sources with coupler;
• It feeds three MV secondary switchboards and two 6 kV/LV transformers in a single line supply system;
• the secondary switchboard MV2 is fed by two sources with coupler and is made up of two bus sections. It feeds two 6 kV motors and two 6 kV/LV transformers in a single line supply system;
• the secondary switchboards MV1 and MV3 are fed by a single source. Each feeds a 6 kV/LV transformer and a 6 kV motor;
• the main low voltage switchboard MLVS1 can be backed up by a generator;
• the main low voltage switchboard MLVS2 is fed by two sources with coupler;
• the main low voltage switchboard MLVS3 is fed by a single source;
• the motor control centers 1 and 3 are fed by a single source; the motor control center 2 is fed by 2 sources with no coupler.

Reference: Protection of Electrical Networks – Christophe Prévé