CLEMSON UNIVERSITY DG CONFERENCE UPDATE ON THE CURRENT STATUS OF DG INTERCONNECTION PROTECTION WHAT IEEE 1547 DOESN’T TELL YOU ABOUT INTERCONNECTION PROTECTION Chuck Mozina Consultant Beckwith Electric Co., Inc.

CLEMSON UNIVERSITY DG CONFERENCE OUTLINE Update the Current Status of DG Interconnection Protection Tell You What IEEE 1547 Doesn’t Discuss New DG Method and Practices + Calf. Rule 21

CLEMSON UNIVERSITY DG CONFERENCE Types of DG Generators Induction Synchronous Asynchronous

CLEMSON UNIVERSITY DG CONFERENCE 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. Point of common coupling

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

CLEMSON UNIVERSITY DG CONFERENCE IEEE 1547 Addresses Generators 10 MVA or Less Started Work in 1997 Has Over 300 Participants Met Every Other Month Referred Most Issues of Substance to 3 New Standards Groups

CLEMSON UNIVERSITY DG CONFERENCE What 1547 SAYS A 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

CLEMSON UNIVERSITY DG CONFERENCE What 1547 SAYS A 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

CLEMSON UNIVERSITY DG CONFERENCE 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.

CLEMSON UNIVERSITY DG CONFERENCE Typical 4-Wire Distribution Feeder Circuit Pole-top transformer rated for line-to-neutral voltages example: 13.2 KV  3  7.6 KV DG

CLEMSON UNIVERSITY DG CONFERENCE Ungrounded Interconnection Transformers Problems Advantages Can supply the feeder circuit from an underground source after substation breaker A trips causing overvoltage Provide no ground fault backfeed for fault at F 1 & F 2. No ground current from breaker A for a fault at F 3. Low Voltage (SEC.) High Voltage (PRI.) DG

CLEMSON UNIVERSITY DG CONFERENCE Grounded Primary Interconnection Transformers Problems Advantages No ground current from breaker A for faults at F 3 ( ). No overvoltage for ground fault at F 1. No overvoltage for ground fault at F 1. Low Voltage (SEC.) High Voltage (PRI.) Provides an unwanted ground current for supply circuit faults at F 1 and F 2. Allows source feeder relaying at A to respond to a secondary ground fault at F 3 ( ). DG 2 3

CLEMSON UNIVERSITY DG CONFERENCE FERRORESONANCE NEW YORK FIELD TESTS –1989 FIELD TEST CIRCUIT

CLEMSON UNIVERSITY DG CONFERENCE FERRORESONANCE NEW YORK FIELD TESTS KW Synchronous DG, 9KW load, 100KVAR Capacitance and Wye-Delta Interconnection Transformer A=2.74 pu B=2.34 pu C=2.92 pu

CLEMSON UNIVERSITY DG CONFERENCE FERRORESONANCE NEW YORK FIELD TESTS KW Synchronous 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)

CLEMSON UNIVERSITY DG CONFERENCE CONDITIONS FOR FERRORESONANCE 1.DG Must be Separated From the Utility System (islanded condition) 2.KW Load in the Island Must be Less than 3 Times DG Rating 3.Capacitance Must be Greater Than 25 and Less Than 500 Percent of DG Rating 4.There Must be a Transformer in the Circuit to Provide Nonlinearity

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

CLEMSON UNIVERSITY DG CONFERENCE TYPICAL INTERCONNECTION PROTECTION FOR WYE- GROUNDED (PRI.) INTERCONNECTION TRANSFORMER

CLEMSON UNIVERSITY DG CONFERENCE TYPICAL INTERCONNECTION PROTECTION FOR UNGROUNDED (PRI.) INTERCONNECTION TRANSFORMER

CLEMSON UNIVERSITY DG CONFERENCE RECIPROCATING ENGINE OUT OF SYNCHRONISM CONDITION

CLEMSON UNIVERSITY DG CONFERENCE Power Angle Analysis of Out-of-Synchronism Condition If A 1 >A 2 DG goes unstable and slips a pole, results in high levels of transient shaft torque

CLEMSON UNIVERSITY DG CONFERENCE CONCLUSIONS 1. DGs Interconnected on Distributions Systems Present Significant Technical Problems 2. There are No “Standard” Solutions Only Choices with Undersirable Drawbacks 3. IEEE 1547 Provides Limited Real Guidance – Simply Cites Obvious Requirements 4. Hopefully, the Three Newly Formed IEEE Standards Groups Will Address the Technical Issues Raised in this Paper

CLEMSON UNIVERSITY DG CONFERENCE THE END UPDATE ON THE CURRENT STATUS OF DG INTERCONNECTION PROTECTION QUESTIONS