Now a days almost all electricity boards are encouraging the use of bust duct above 1000 Amp  between Transformer and main panel instead of connections through cables. This is designed in IP 32 or IP 65 indoor or outdoor based as per the transformer's location. Air insulated bus duct is dust and vermin proof  with Aluminium or Copper conductor. it comes in segregated or non-segregated versions.  Flexible copper connection is required at transformer or DG section because bus duct is static equipment .