Maintaining Long Rural Feeders
with Large Interconnected
Distributed Generation
Keary R. Dosier, P.E.
UC Synergetic
The Proliferation of DG / IPPs
• Solar Photovoltaic • Wind
• Landfill Gas
• Hydroelectric
• Biomass
• Other
The Proliferation of DG / IPPs
Economic
Political
Social
The Proliferation of DG / IPPs
• Resource Availability •
– Sunlight
•
– Wind
•
– Landfills
•
Energy Cost
Land Cost
Interconnection Cost
Generation Cost
The Interconnection Request
•
•
•
•
•
Large Rural Land Fill
Methane Gas
9 MW of Synchronous Generators
Plan for 24 x 365 Operation
Around 50 Years of Planned Operation
Interconnection Options
• Existing 115 kV Transmission Line
– Utility Performance Risk Low
– Cost Of Building a New Substation
– Significant Time Required for Planning and
Coordination
• Existing 23 kV Distribution Feeder
– Utility Performance Risk High
– Cost of upgrading distribution facilities
– Less Time Required
The Rural Distribution Feeder
0.5 MW
0.2 MVAr
10.0 MW
7 mi
Station
1.5mi
5 mi
2.0 MW
0.9 MVAr
2.0 MW
0.9 MVAr
3 mi
2.5 MW
0.9 MVAr
- 1.2 MVAr
3.0 MW
1.1 MVAr
- 1.2 MVAr
19 mi
The Rural Distribution Feeder
•
•
•
•
•
•
10 MW Peek Demand
3 MW Valley Demand
1500 Customers
96 Line Miles
20 Miles to the Last Customer
7 Miles to the Land Fill
Peak Load – No Generation
Valley Load – No Generation
Accommodating the Interconnection
• Interconnection Study Objective
– Determine the lowest cost method of supporting
the interconnection why adhering to the utility
requirements:
•
•
•
•
Capacity
Reliability
Flicker
Service Voltage Requirements
Accommodating the Interconnection
• For Reliability
– Install Electronic (2) Electronic Reclosers
• For Voltage Performance
– Convert 2 miles of #2 ACSR to 477 AAC
– Require Generators to be run at 96% PF Leading
Common Mode of Operation
• Non-Voltage Regulating
• Constant Power Target
• Constant Power Factor Target
Low Voltage
Station
Watts
VARs
High Voltage
G
Customer Proceeds with Installation
• Utility constructs infrastructure upgrades paid
for by the landfill customer
• Customer Proceeds with construction and
commissioning of the 9 MW generator set
Landfill Generator Added
-9.0 MW
2.4 MVAr
1 MW
Station
0.5 MW
0.2 MVAr
7 mi
G
3 MW
1.5mi
5 mi
2.0 MW
0.9 MVAr
2.0 MW
0.9 MVAr
3 mi
2.5 MW
0.9 MVAr
-1.2 MVAr
3.0 MW
1.1 MVAr
-1.2 MVAr
19 mi
Peak Load – Gen 9MW @ -96%PF
Valley Load – Gen 9MW @ -96%pf
Valley Load – Gen 9MW @ -96%pf
2-1200 kVAr Caps Closed
Customer Complains of Nuisance Trips
• Generator Protection Tripping
– Power Factor limits
– Overvoltage limits
• Contributing Factors
– 9 MW Gen Set Consumes around 2.4 MVAr to
operate at 96% PF leading
– Voltage fluctuation from distribution capacitor
operations
Corrective Action
•
•
•
•
Change generator power factor target to unity
Remove 2-1200 kVAR Capacitor Banks
Install 4-600 kVAR Capacitor Banks
Install 300A Voltage Regulator
– At midpoint between Generator and Substation
– Co-Generation Mode
– Line Drop Compensation (LDC)
Mitigation Applied
-9.0 MW
0.0 MVAr
1.0 MW
Station
0.5 MW
0.2 MVAr
7 mi
G
LDC
1.5mi
5 mi
2.0 MW
0.9 MVAr
- 0.6 MVAr
2.0 MW
0.9 MVAr
- 0.6 MVAr
3 mi
2.5 MW
0.9 MVAr
- 0.6 MVAr
3.0 MW
1.1 MVAr
- 0.6 MVAr
19 mi
Peak Load – Gen 9MW @ Unity
LDC Reg & 2-600 kVAr Caps
Valley Load – Gen 9MW @ Unity
LDC Reg & 2-600 kVAr Caps
The solution works
• No More Nuisance Tripping Complaints
• No Customer Voltage Complaints
• Utility Losses Reduced by 30 KW
A New Customer is Cause for
Reevaluation
• Developer Plans Shopping Center & Residential
• Beyond New Voltage Regulator 1 Mile
New Customer
-9.0 MW
0.0 MVAr
3.0 MW
Station
0.5 MW
0.2 MVAr
7 mi
G
2.0 MW
LDC
1.5mi
5 mi
2.0 MW
0.9 MVAr
- 0.6 MVAr
2.0 MW
0.9 MVAr
- 0.6 MVAr
3 mi
2.5 MW
0.9 MVAr
- 0.6 MVAr
3.0 MW
1.1 MVAr
- 0.6 MVAr
19 mi
Solution to Serve New Customer
• Bypass regulator with a double circuit line
• Build 1 wire mile of #1/0 ACSR under the
existing 477 AAC feeder starting at the midpoint
voltage regulator.
Added Infrastructure
-9.0 MW
0.0 MVAr
3.0 MW
Station
0.5 MW
0.2 MVAr
7 mi
G
2.0 MW
LDC
1.5mi
5 mi
2.0 MW
0.9 MVAr
- 0.6 MVAr
2.0 MW
0.9 MVAr
- 0.6 MVAr
3 mi
2.5 MW
0.9 MVAr
- 0.6 MVAr
3.0 MW
1.1 MVAr
- 0.6 MVAr
19 mi
Complication with IVVC Systems
• IVVC – Integrated Volt-Var Control
• CVR – Conservation Voltage Reduction
• DSDR – Distribution System Demand Response
Added Infrastructure
-9.0 MW
0.0 MVAr
3.0 MW
Station
0.5 MW
0.2 MVAr
7 mi
G
2.0 MW
LDC
1.5mi
5 mi
2.0 MW
0.9 MVAr
- 0.6 MVAr
2.0 MW
0.9 MVAr
- 0.6 MVAr
3 mi
- 0.6 MVAr
- 0.6 MVAr
19 mi
5.5 MW
2.0 MVAr
Complication with IVVC Systems
Peak
Complication with IVVC Systems
Valley
Questions?