IMPACT OF GREEN POWER GENERATION ON DISTRIBUTION SYSTEMS

1. IMPACT OF GREEN POWER GENERATION ON DISTRIBUTION SYSTEMS

2. Not Green Burn conventional fuel Gas Diesel, oil, gasoline Green Use renewable sources to reduce reliance of fossil fuels: Solar Methane (from decomposition) Wind Hydro Biomass (burn it) Tidal

3. Typical Interconnection Protection Disconnects the generator when it is no longer operating in parallel with the utility. Protects the utility system from damage caused by connection of the generator (fault current and overvoltage). Protects the DG generator from damage from the utility system, especially through automatic reclosing.

4. Typical Generator Protection Generator internal short circuits. Abnormal operating conditions (loss of field, reverse power, overexcitation and unbalance currents).

5. Types of Green Power Generators Induction Synchronous Asynchronous

6. Induction 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

7. Synchronous Generator

8. Asynchronous Generator

9. IEEE 1547 SAYSA DG SHALL: Not Cause Overvoltages or Loss of Utility Relay Coordination Disconnect When No Longer Operating in Parallel With the Utility. + Only Discusses 81O/U and 27, 59 Not Energize the Utility when it is De-energized Not Create an Unintentional Islands Use �Utility Grade� Relays Not Cause Objectionable Harmonics Not Cause Loss of Synchronism That Results in Objectionable Flicker

10. Greatly complicates restoration Requires synchronizing at utility substation Inhibits automatic reclosing Power quality issue DG may not be able to maintain voltage, frequency and harmonics within acceptable levels.

11. Feeder deenergizes when utility opens feeder Restoration responsibility on the DG Requires synchronizing to utility Inhibits automatic reclosing

12. OVERVOLTAGE AND LOSS OF COORDINATION Two Sources of Overvoltage +Choice of Delta Interconnection Transformer Primary Winding + Ferroresonance Loss of Coordination +Choice of Grounded Interconnection Transformer Primary Winding.

14. Ungrounded Interconnection Transformers

15. Grounded Primary Interconnection Transformers

16. FERRORESONANCENEW YORK FIELD TESTS �1989FIELD TEST CIRCUIT

17. FERRORESONANCENEW YORK FIELD TESTS -198950KW Synchronous DG, 9KW load, 100KVAR Capacitance and Wye-Delta Interconnection TransformerA=2.74 pu B=2.34 pu C=2.92 pu

18. FERRORESONANCENEW YORK FIELD TESTS -198950KW Synchronous DG, 9KW load, 100KVAR Capacitance and Wye-Delta Interconnection TransformerA=2.74 pu B=2.34 pu C=2.92 puPROTECTION SOLUTION: MEASURE PEAK OVERVOLTAGE NOT RMS (59I)

19. 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

20. PROTECTION FUNCTION BEYOND 81O/U,27 AND 59 Total Interconnect Package Loss of Parallel Fault backfeed removal Damaging conditions Abnormal power flow Restoration

21. TYPICAL INTERCONNECTION PROTECTION FOR WYE-GROUNDED (PRI.) INTERCONNECTION TRANSFORMER

22. TYPICAL INTERCONNECTION PROTECTION FOR UNGROUNDED (PRI.) INTERCONNECTION TRANSFORMER

23. CONCLUSIONS 1. Green Power DGs Interconnected on Distributions Systems Present Significant Technical Problems and Potential Harzards 2. There are No �Standard� Solutions Only Choices with Undersirable Drawbacks 3. IEEE 1547 Provides Limited Real Guidance � Simply Cites Obvious Requirements 4. When Developing DG Interconnection Protection the Technical Issues Raised in this Paper Need to be Addresses

24. THE END