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DISTRIBUTED GENERATION ISLANDING - IMPLICATIONS ON POWER SYSTEM DYNAMIC PERFORMANCE

DISTRIBUTED GENERATION ISLANDING - IMPLICATIONS ON POWER SYSTEM DYNAMIC PERFORMANCE. Sandhya P Prabhu April 19, 2006. What is islanding ?. Figure 1 Typical distributed system with DG’s [2] . Figure 1 Typical distributed system with DG’s [2] .

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DISTRIBUTED GENERATION ISLANDING - IMPLICATIONS ON POWER SYSTEM DYNAMIC PERFORMANCE

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  1. DISTRIBUTED GENERATION ISLANDING - IMPLICATIONS ON POWER SYSTEM DYNAMIC PERFORMANCE Sandhya P Prabhu April 19, 2006

  2. What is islanding ? Figure 1 Typical distributed system with DG’s [2] Figure 1 Typical distributed system with DG’s [2]

  3. Implications of unintentional islanding • Hazard to utility line workers and public • Damage to customer equipment if the voltage and frequency provided by the DG is not regulated • Damage to the DG’s in the island when island is reconnected to the grid

  4. Out - Phase – Reclosing • What is reclosing / out – of – phase reclosing? • Produces transients which are potentially damaging to utility & customer equipments Figure 2 Phase voltages on source and DG side for a simulation of 180º out-of-phase reclosing [1] • Unusually high inrush currents in transformers

  5. Active Anti - Islanding 1)Communication based schemes 2)Local detection schemes 1a) Transfer Trip Scheme

  6. 1b) Power Line Signaling Scheme [2]

  7. 2a) Method of impedance measurement [2]

  8. Dynamic Impact of Anti-Islanding Measures Under voltage trip sensitivity • Undervoltages due to faults can lead to unnecessary DG tripping • With extensive DG penetration, simultaneous DG tripping due a fault can cause voltage collapse in the local system (voltage regulation equipment takes time to react)

  9. Positive sequence voltage magnitude for simulations of a system with 45% DG penetration, comparing results for sensitive DG undervoltage tripping to results with less sensitive tripping and no tripping. [1]

  10. Active Anti-Islanding Impact • Degradation of power quality and system stability as DG penetration becomes higher • Currently the local islanding detection methods virtually guarantee that the DG will be unable to provide grid support or improve grid stability when the grid is stressed anti-islanding protection disconnects the DG when it detects voltage and frequency excursions on the grid. • Because of the reclosing practice, anti-islanding techniques must trip DG’s within about 200 milliseconds before the breaker is reclosed. Failure to do so will lead to out-of-phase re-energization of the DG.

  11. Conclusion • DG penetration levels are not sufficient to cause the problems discussed above. • With the growth of DG, these system issues will be confronted in the future. • The dynamic performance impact needs to be addressed. • Inadvertent islanding detection schemes not having an undesirable impact on interconnected system performance would be a highly desirable development.

  12. References [1] Distributed Generation Islanding – Implications on Power System Dynamic Performance. R. A. Walling, Senior Member, IEEE, and N. W. Miller, Fellow, IEEE [2] An Assessment of DG Islanding Detection Methods and Issues for Canada July, 2004 CETC-Varennes 2004-074 (TR) 411-INVERT [3] Islanding Detection Method of Distributed Generation Units Connected To Power Distribution System. J.E.Kim, Member IEEE, J.S.Hwang

  13. Questions / Comments ?

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