Transcript clemson university dg conference

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.
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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
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Types of DG Generators
• Induction
• Synchronous
• Asynchronous
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To Utility System
Typical
Interconnection
Protection
Interconnection
Transformer
Interconnection
Relay
Utility System
IPP System
Point of common coupling
Local Loads
•
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.
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Typical Generator Protection
• Generator internal short
circuits.
• Abnormal operating
conditions (loss of field,
reverse power,
overexcitation and
unbalance currents).
Local Loads
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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
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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
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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
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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.
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Typical 4-Wire Distribution Feeder Circuit
DG
Pole-top transformer rated for line-to-neutral voltages
example: 13.2 KV 3  7.6 KV
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Ungrounded Interconnection Transformers
Advantages
Provide no ground fault
backfeed for fault at F1 &
F2. No ground current from
breaker A for a fault at F3.
Problems
Low
Voltage
(SEC.)
DG
High
Voltage
(PRI.)
Can supply the feeder
circuit from an
underground source
after substation breaker A
trips causing overvoltage
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Grounded Primary Interconnection
Transformers
Advantages
No ground current from
breaker A for faults at
F3(
). No overvoltage
for ground fault at F1.
No overvoltage for
ground fault at F1.
2
Problems
Provides
an unwanted
ground current for supply
circuit faults
at F1 and F2.
Low
Voltage
(SEC.)
DG
3
High
Voltage
(PRI.)
Allows source feeder
relaying at A to respond to
a secondary
ground fault at F3(
).
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FERRORESONANCE
NEW YORK FIELD TESTS –1989
FIELD TEST CIRCUIT
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FERRORESONANCE
NEW YORK FIELD TESTS -1989
50KW Synchronous DG, 9KW load, 100KVAR Capacitance
and
Wye-Delta Interconnection Transformer
A=2.74 pu B=2.34 pu C=2.92 pu
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FERRORESONANCE
NEW YORK FIELD TESTS -1989
50KW 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)
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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
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PROTECTION FUNCTION BEYOND
81O/U,27 AND 59
Total Interconnect Package
Loss of Parallel
Fault backfeed removal
Damaging conditions
Abnormal power flow
Restoration
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TYPICAL INTERCONNECTION PROTECTION FOR WYEGROUNDED (PRI.) INTERCONNECTION TRANSFORMER
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TYPICAL INTERCONNECTION PROTECTION FOR
UNGROUNDED (PRI.) INTERCONNECTION
TRANSFORMER
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RECIPROCATING ENGINE OUT OF
SYNCHRONISM CONDITION
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Power Angle Analysis of
Out-of-Synchronism Condition
Power
P = |Eg| |ES|
Max
X
STABLE
A2
120
UNSTABLE
Pm=Pe
If A1>A2 DG goes
unstable and slips a
pole, results in high
levels of transient shaft
torque
XFAULT
Line
Recloser
A1
Line
Recloser
Trips
PFAULT
Angle
Utility
Substation
180
Q -Q
g s
DG
Local
Load
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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
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THE END
UPDATE ON THE CURRENT STATUS OF DG
INTERCONNECTION PROTECTION
QUESTIONS