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Transfer Constraint Relief

In today's climate of growing environmental pressures, regulatory issues and a need to deliver a Return On Investment, it is clear that it is no longer acceptable for transmission systems to have unduly conservative power transfer levels. Clearly, using existing transmission assets more effectively is an attractive option. 

Constraints are determined from system models, and dynamic modelling is required to identify some of the constraints. There are inherent uncertainties in dynamic modelling, particularly relating to dynamic effects that involve generators and loads connected over a wide area:

  • How do loads contribute to dynamics?
  • Are the generators and their control systems all working as planned?
  • Are there dynamic interactions between plants in particular operating scenarios?

Because of the uncertainties, it is necessary to allow a margin of error between the predicted stability limit and the actual operating constraint. However, more effective use can be made of the transmission system if the constraints can be adapted following accurate measurement of system conditions.

For example, where a transmission corridor constraint can be defined in terms of allowable voltage phase angle difference rather than power transfer, increased secure transfer levels can be achieved. For transmission corridors constrained on the basis of oscillatory stability, these constraints can be relaxed when the oscillations present are shown to be well damped.

The key to adapting these constraints is accurate and reliable real-time knowledge of actual power system conditions. The Psymetrix PhasorPoint system delivers proven solutions for the real-time determination of voltage phase angle difference and power system oscillatory behaviour, including damping.  These applications can be used in two ways:

  1. Raise transfer constraints for normal conditions and restrict in abnormal conditions, identified by measurements of angle or damping
  2. Define transfer limits adaptively, based on measurement of prevailing system dynamics

Psymetrix's PhasorPoint enables higher available transfer capacity and significant financial benefits in avoiding constraint costs.

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