Utilizing the ring operation mode of MV distribution feeders

1
Utilizing the ring operation mode of MV
distribution feeders

• MV networks in Finland
• Neutral isolated and compensated systems
• Networks are traditionally used radially but
  constructed partly meshed
• Open-points of the network are often at the
  remote controlled disconnector stations
• The perspective of the study
• Ring connection of two feeders fed from the same
  primary substation
• When the ring-connection is advantageous and what
  the preconditions are?

2
Utilizing the ring operation mode of MV
distribution feeders- improved preconditions

• Increased breaking capacity and reduced operation
  times of SF6-insulated switch-disconnectors
• Modern feeder terminals
• Economic voltage and current sensors available
• Measurements and state estimation of loads

3
Conclusions

• Benefits
• Optimal power flow between looped feeders
• Reduced maximum voltage drop
• Reduced power losses
• Possibility to determine the distance to earth
  faults
• neutral isolated and compensated systems
• Option for dynamic use of ring connection
  according to seasonal load variations
• Option to increase the integration capacity of
  distributed generation at existing network

4
Conclusions

• Major drawbacks
• More complicated feeder protection
• Such as autoreclosures of overhead line feeders
• Severity of voltage sags are increased compared
  to radial operation mode
• Especially systems including mainly overhead
  lines