EPIC 2019 Dominion Energy’s Usage of RTDS HIL Technology to Strengthen Their Grid Joseph Petti 10/28/2019
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November 1, 2019
Grid Transformation • New technologies have disrupted the grid • Distributed Generation • FACTS Devices
• Dominion must create new solutions to maintain reliability • Solutions must be tested thoroughly prior to field installation • RTDS Hardware in the Loop testing 2
November 1, 2019
Real Time Digital Simulator • Real time simulation is too demanding for a regular PC • IBM multicore processors
• Analog and digital inputs/outputs • +/- 10V • +5 to +24V
• Connects to Doble amplifier to create secondary values of current and voltage 3
November 1, 2019
Hardware-in-the-Loop
Doble Amplifier
Relay Outputs
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November 1, 2019
Commercial Relay Customizable Logic
Dominion Test Cases • DG Transfer Trip • •
Power Line Carrier communication is common in the Dominion system but is not as reliable as it once was Back up settings allow DG to stay online during communication outages
• Bidirectional Power Flow • • •
System was built for a radial grid DG installation leads to bidirectional power flow Feeder protection needs to be modified for present and future system usage
• Series Compensated Lines • • •
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Increase real power transfer capability Improve stability Transmission protection schemes are impedance based
November 1, 2019
Local Protection for DG Sites • Incorporate various elements into the existing recloser at the PCC • Voltage, frequency, phase, rate of change of frequency
• Recloser constantly checks for communication signal
• When none is detected the back up protection is active for 4 minutes • Allows time for communication to be reestablished
• 4 minute limit has potential to be extended if pilot performs well
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November 1, 2019
Test Bench Setup 34.5 KV / 13.8 KV 230 KV /34.5 KV
F3
PCC CT
R Utility Source
F1 S
PT
DER1 5 MW
Relay
F2 Load 1
DER2 5 MW
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November 1, 2019
Results • Various scenarios and simulations were executed: • • •
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Various operating conditions - Heavy/light local load & with/without DER2 Faults at various locations - 3 phase/single phase (High Z/Low Z) 58 total test cases
Operating Condition
Number of Test Cases
Successful Test Cases
With DER2
17
16
Without DER2
31
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November 1, 2019
PG Fault on Adjacent Circuit 34.5 KV / 13.8 KV
PCC
230 KV /34.5 KV
CT
R Utility Source
S
PT
DER1 5 MW
Relay
F2 Load 1
DER2 5 MW
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November 1, 2019
PG Fault on Adjacent Circuit
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November 1, 2019
Island with 10% Excess Load 34.5 KV / 13.8 KV
PCC
230 KV /34.5 KV
CT
R Utility Source
S
PT
DER1 5 MW
Relay
Load 1
DER2 5 MW
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November 1, 2019
Island with 10% Excess Load
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November 1, 2019
Findings • Voltage, current, frequency, phase, and rate of change of frequency are excellent indicators of a grid event • No one element can detect all disturbances
• A perfect island will not cause the algorithm to trip the site offline • No active sites with spinning generation and inverter based generation for now
• Pilot installation occurred early October 2019
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November 1, 2019
Bidirectional Power Flow • Directional Overcurrent •
The DOC element, 67, combines directionality with the standard overcurrent element
•
The directional element uses phase angle displacement between the current phasor of a particular phase and the reference variable to determine the directionality (forward or reverse)
•
Usually single phase elements
• Reverse Power
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•
The RP element, 32R, is also a directional protection element that relies upon both voltage and current values to determine reverse power
•
Measures 3 phase active or reactive power to detect reversal
•
Normally, not used for single phases for fault detection due to availability of OC elements
•
Detects reversal of power for a non-exporting DER at the PCC during sudden loss of generation at the utility side or Loss of Mains (LOM) situation November 1, 2019
Test Bench Setup Feeder1
230 KV /34.5 KV
F3
F2
PCC
34.5 KV / 13.8 KV CT
R
Utility Source
F1
S
S Relay
Load 3
Feeder2
Load 2
DER2 5 MW
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November 1, 2019
Load 1
DER1 5 MW
PT Local Load
Results • Various scenarios and simulations were executed: • • •
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Various operating conditions - Heavy/light local load & with/without DER2 Faults at various locations - 3 phase/single phase (High Z/Low Z) 12 scenarios in total in each case(with and without DER2)
Operating Condition
Successful indication by DOC
Successful indication by RP
Without DER2
12
3
With DER2
12
3
November 1, 2019
Scenario 1: High Z Three phase fault at F1
PCC
Feeder1
34.5 KV / 13.8 KV CT
F1
R
S
Utility 230 KV /34.5 KV Source
S Relay
Load 3
Feeder2
Load 2
DER2 5 MW
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November 1, 2019
Load 1
DER1 5 MW
PT
Local Load
Scenario 1
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November 1, 2019
Scenario 2: Bolted 3 phase fault at F1
PCC
Feeder1
34.5 KV / 13.8 KV CT
F1
R
S
Utility 230 KV /34.5 KV Source
S Relay
Load 3
Feeder2
Load 2
DER2 5 MW
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November 1, 2019
Load 1
DER1 5 MW
PT Local Load
Scenario 2
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Scenario 3: High Z single phase to Ground fault at F2
Feeder1 230 KV /34.5 KV
PCC
F2
34.5 KV / 13.8 KV CT
R
S
Utility Source
S Relay
Load 3
Feeder2
Load 2
DER2 5 MW
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November 1, 2019
Load 1
DER1 5 MW
PT
Local Load
Scenario 3
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November 1, 2019
Findings • Low fault impedance causes the voltage to collapse, which leads to a negligible power magnitude • During phase to ground faults power in one phase might reverse direction, however the three phase power is not considered in the reverse direction as the other two phases increase power to compensate
• Reverse power is not a reliable indicator of fault identification, and the DOC element should be considered instead for feeder protection
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November 1, 2019
Series Compensated Lines • Provide numerous benefits •
Increase real power transfer capability
•
Improve stability
• Create several line protection challenges •
Schemes are typically impedance based
•
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Directionality issues
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đ?‘‰1 đ?‘‰2 đ?‘ƒ= sin đ?›ż đ?‘‹đ??ż Power Transfer Equation
đ?‘‰1 đ?‘‰2 đ?‘ƒ= sin đ?›ż đ?‘‹đ??ż − đ?‘‹đ??ś Power Transfer Equation with Series Compensation
Transmission Line Protection • Directional comparison blocking (DCB) •
Zone 1 covers 80% of line with no delay
•
Zone 2 covers 150% with delay
•
Zone 3 senses reverse fault and blocks
Zone 1
Fault on Line
B Steady State
Zone 3 A
A
B Zone 1 Zone 2 R-X Plane for DCB
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Project Basis • Two series capacitors on Dominion Energy system • The lines are critical for system stability
Bath County Pumped Storage Facility 26
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Series Capacitors in ASPEN OneLiner Software
Test Cases • Five single line to ground (SLG) fault cases • Cases 1-4 assume 0 fault impedance • Case 5 assumes 20 Ohm fault impedance
Test Cases for Hardware-In-The-Loop Simulation
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Case 1&2: Bath County Terminal • Expected zone 2 to assert • 10.417 ms delay
Blocking Bit Zone 2 Blocked
Bits in Relay
MOV Bypass
Zone 2 Asserts
Steady State
Fault
Zone 2 Fault Case 28
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R-X Plane Seen by Bath County Relay
Case 1&2: Lexington Terminal • Expected zone 3 to assert • Blocking signal sent Bits in Relay
Reverse Element Asserts
Zone 3 and Blocking Signal Asserts
Zone 3 Fault Case 29
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R-X Plane Seen by Lexington Relay
Findings • All faults within zone of protection detected • All outside zone faults blocked as intended
• Zone 1 operation on compensated lines requires further analysis
Summary of Simulation Results
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Conclusion • RTDS allows Dominion to study new technology and ideas to strengthen the grid • Various generation, impedance, and communication strategies can be explored
• Allows us to discover weaknesses in the scheme and engineer a better solution • Fun fact: Part of my Master’s Thesis is a RTDS project I completed at Dominion
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1 November 2019