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IMPACT OF WIND POWER GENERATION ON DISTRIBUTION SYSTEMS

Until Public Utility Regulatory Policies Act (PURPA) in 1978, U.S. utilities were not required to interconnect with small generators. - Started DG - Beckwith gets into the interconnection protection business - Hot until late 1980's when tax incentive terminated

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IMPACT OF WIND POWER GENERATION ON DISTRIBUTION SYSTEMS

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    1. IMPACT OF WIND POWER GENERATION ON DISTRIBUTION SYSTEMS

    2. Until Public Utility Regulatory Policies Act (PURPA) in 1978, U.S. utilities were not required to interconnect with small generators. - Started DG - Beckwith gets into the interconnection protection business - Hot until late 1980’s when tax incentive terminated Late 1990’s DG again hot - Driven by high utility rates and de-regulation - DGs can generator cheaper at source of consumption + Peak Shaving and Load Following - Hot until early 2000’s when natural gas prices increased Late 2000’s Green Power drives resurgence of DGs - Regulates require utilities to generator a portion of their power from green sources. - Set high buy back rate – key driver for Distribution Wind Installations Brief DG History

    3. Types of Wind Power Generators Induction Asynchronous Four Types of Wind Generator Design

    4. Induction Wind Generator Induction Excitation provided externally Start up like a motor (no sync. equipment needed) Less costly than synchronous machines Limited in size to 500 KVA

    5. DG Interconnection Protection

    6. DG Interconnection Protection

    9. Ferroresonance can take place between an induction machine and pole top capacitors after utility disconnection from feeder. Ferroresonance can also occur on Synchronous Generators! Generator is excited by pole top capacitors if the reactive components of the generator and aggregate capacitors are close. This interplay produces non-sinusoidal waveforms with high voltage peaks. This causes transformers to saturate, the non-linearities exacerbate the detection problem

    10. FERRORESONANCE NEW YORK FIELD TESTS –1989 FIELD TEST CIRCUIT

    11. FERRORESONANCE NEW YORK FIELD TESTS -1989 50KW Induction DG, 9KW load, 100KVAR Capacitance and Wye-Delta Interconnection Transformer A=2.74 pu B=2.34 pu C=2.92 pu

    12. CONDITIONS FOR FERRORESONANCE DG Must be Separated From the Utility System (islanded condition) KW Load in the Island Must be Less than 3 Times DG Rating Capacitance Must be Greater Than 25 and Less Than 500 Percent of DG Rating There Must be a Transformer in the Circuit to Provide Nonlinearity

    13. FERRORESONANCE NEW YORK FIELD TESTS -1989 50KW Induction DG, 9KW load, 100KVAR Capacitance and Wye-Delta Interconnection Transformer A=2.74 pu B=2.34 pu C=2.92 pu PROTECTION SOLUTION: MEASURE PEAK OVERVOLTAGE NOT RMS (59I)

    14. Asynchronous Generator

    16. DG Interconnection Protection

    17. DG Interconnection Protection

    18. DG Interconnection Protection

    19. Ungrounded Primary Transformer Winding Overvoltage may be caused by Wind Generator when ungrounded primary transformer windings are applied (no ground source) and the Wind Generator backfeeds once utility disconnects Grounded Primary Transformer Winding Ground fault current contribution caused by Wind Generator grounded primary transformer windings during utility faults Source feeder relaying and reclosers responding to secondary ground faults within the Wind Generator facility

    20. Ungrounded Interconnection Transformers

    21. Grounded Primary Interconnection Transformers

    25. CONCLUSIONS 1. Wind Power Generation Interconnected on Distributions Systems Present Significant Technical Problems and Potential Harzards 2. There are No “Standard” Solutions Only Choices with Undersirable Drawbacks. 3. Over-Voltage 59I is Key Element to Detect Ferroresonance 4. When Developing Wind Interconnection Protection the Technical Issues Raised in this Paper Need to be Addresses

    26. THE END

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