Congestion Management, Curtailment and Interruption for Distributed Generation

Unison’s network is primarily designed and established for electricity flows in one direction. Increasing number of distributed generation could introduce bi-directional electricity flow on the network. This may lead to congestion of its low voltage and high voltage networks.

Network congestion occurs if an additional unit of electricity injected into the network would cause a component in the network (for example,. a circuit or a transformer) to operate beyond its rated maximum capacity or give rise to an unacceptably high level of voltage at the point of connection to the network. 

Unison manages its network congestion by:

  • ensuring distributed generation connection is in unconstrained areas or accompanied by appropriate network upgrade, and
  • implementing real-time operational curtailment rules and arrangement on case-by-case basis.

The network congestion measure will be dependent on the extent of congestion, technical and operational characteristics, and connection terms and conditions. In some cases, distributed generation may add to an existing network congestion that requires network reinforcement in the near future. Unison will assess the incremental cost to relieve this constraint and allocate a pro-rata share of the network reinforcement cost consistent with its capital contribution policy. 

Interruption

In the event of any fault on a distribution network, any distribution generator must through their own protection systems be automatically disconnected from the network.  The customer has sole responsibility for the safety of their generating plant and equipment under such conditions.