southern company interconnection process -...

Southern CompanyInterconnection Process

Dexter LewisResearch EngineerResearch and Technology ManagementSouthern Company

Outline

• Southern Company• GPC Solar • Interconnection Process

–Application requirements–Distribution impact study–Witness Testing

Southern Company

Southern Company

• 45,502 MW of generating capacity– 41% natural gas, 37% coal, 16% nuclear, 6% hydro– PV – 60 MW with 115MW in application process– Hydro – 2,785 MW of generating capacity with 16MW of new capacity planned for next 5 years

– Biomass – 128 MW– Landfill Gas – 3.2 MW landfill gas generator in Gulf Power Service Territory

Georgia Power Solar• Georgia Public Service Commission adopted a motion that 

requires Georgia Power Company to bring online 260MW of solar capacity by 2015 and 265MW by 2017 (525MW total).– 100MW of distributed small‐scale generation– 425MW of utility‐scale solar

• Small generators ( 100 ) are eligible to sell their electricity under the Renewable & Non‐renewable Tariff (RNR‐7) and the Solar Purchase Tariff (SP‐1).  Larger customers ( 80 ) may sell their electricity as a Qualifying Facility– RNR‐7 – Company will pay avoided cost– SP‐1 – Company will purchase at 17.00 cents/kWh

GPC Number of Interconnection Requests

1 to 65 Inter

GPC kW Installed/Proposed/Anticipated

1 to 5000kW

GPC Average kW per Interconnection

1 to 1000kw/Inter

GPC Interconnection Process

Customer Submits Application Package

GPC Processes & Reviews Application 

Package

GPC and Customer Site Visits

GPC Conducts Distribution System 

Studies

GPC Conducts Interconnection Equipment Study

GPC Offers Customer Interconnection 

Proposal

Distributed Generation 

Interconnection Agreement Executed

Customer pays GPC Interconnection Cost 

Upfront

GPC Installs GPC Interconnection Equipment

GPC Conducts Facility Acceptance Testing

GPC Authorizes Parallel Operation 

Facility

10 Days +10 Days +10 Days

+45 Days +45 Days +5 Days/+90 Days +10 Days/+30 Days

+10 Days +Construction

+7 Days +3 Days

Up to 155 Days + Construction

Customer Submits Application Package• Facility One‐Line Electrical Diagram• Facility Relay and Metering One‐

Line• Proof of site control in the form of a 

property tax bill, a lease agreement or other legally binding contract

• Application for Distributed Interconnection

• Required Technical Data

GPC Interconnection Process

Customer Submits Application Package

GPC Processes & Reviews Application 

Package

GPC and Customer Site Visits

GPC Conducts Distribution System 

Studies

GPC Conducts Interconnection Equipment Study

GPC Offers Customer Interconnection 

Proposal

Distributed Generation 

Interconnection Agreement Executed

Customer pays GPC Interconnection Cost 

Upfront

GPC Installs GPC Interconnection Equipment

GPC Conducts Facility Acceptance Testing

GPC Authorizes Parallel Operation 

Facility

GPC Conducts Distribution Equipment Study

• 15 to 30 Business Days for GPC to conduct and complete DSS of Facilities less than or equal to 2MW after Facility is conceptually finalized by both GPC and Customer.

• 25 to 45 Business Days for GPC to complete DSS of Facilities 2MW to 10 MW after Facility design is conceptually finalized by both GPC and Customer.

Distribution Study Practices (Inverter Based)

• Less than 25kW – Stamp and Go Procedure– Inverter must be UL Standard 1741 

• Less than 1MW – Stiffness Factor Procedure– Engineering Guide for Integration of Distributed Storage and 

Generation EPRI ID: 1024354– Stiffness Factor = Isc/Idsg

DPV Hosting CapacityCategory Criteria Basis FlagVoltage Overvoltage Normal Voltage (ANSI C84.1) ≥ 1.05 Vpu

Voltage Voltage Deviation

Maximum difference in node voltage from no PV to full PV

≥ 3% at primary≥ 5% at secondary≥ ½ band at regulators

Voltage Unbalance Phase voltage deviation (ANSI C84.1) ≥ 3%

Loading Thermal Element loading ≥ 100% normal rating

Protection Total Fault Contribution

Total fault current contribution at each sectionalizing device ≥ 10% increase

ProtectionForward Flow Fault Contribution

Forward flow fault current contribution at each sectionalizing device

≥ 10% increase

ProtectionSympathetic Breaker Tripping

Breaker zero sequence current due to an upstream fault ≥ 150A

Protection Reduction of Breaker Reach

Deviation in breaker fault current for feeder faults ≥ 10% decrease

Protection Breaker/Fuse Coordination

Fault current increase at fuse relative to breaker current increase ≥ 100A increase

Protection Anti-Islanding Minimum load at each sectionalizing device ≥ 50%

Power Quality

Individual Harmonics

Individual harmonic voltage magnitude ≥ 3%

Power Quality

Total Harmonics Total harmonic voltage distortion ≥ 5%

Control Regulator Increased duty > basecase+1

Control Capacitor Increased duty > basecase+1

CYME Analysis (Inverter Based)

• Voltage Violations – 97% to 105% ANSI C84.1 Primary – 3% Voltage Imbalance

• Overload Conditions• Neutral current

– Total current less than 33% of trip setting

• Simulations– Summer peak load without DG– Summer peak load with DG – Valley at 10:00AM – 2:00PM  without DG – Valley at 10:00AM – 2:00PM  with DG– Locked automation setting testing

CYME Analysis Assumptions

• Connected Transformer kVA Load Allocation Model– Use historical peak and valley substation loading information

– Locked customer loading for customers > 2MVA– 60% constant impedance & 40% constant power loads

• Electronically Coupled Generator– Kw, pf, Fault Contribution (140% of nameplate)

GPC Interconnection Process

Customer Submits Application Package

GPC Processes & Reviews Application 

Package

GPC and Customer Site Visits

GPC Conducts Distribution System 

Studies

GPC Conducts Interconnection Equipment Study

GPC Offers Customer Interconnection 

Proposal

Distributed Generation 

Interconnection Agreement Executed

Customer pays GPC Interconnection Cost 

Upfront

GPC Installs GPC Interconnection Equipment

GPC Conducts Facility Acceptance Testing

GPC Authorizes Parallel Operation 

Facility

Facility Acceptance Testing• Inverters >250kW• Witness Test

– GPC Witness Test Personnel• Required to record and witness test

– GPC Switching Personnel• Required to operate the disconnecting of the high side fuse or switch

– Customer Setting Engineer• Required to make adjustments to interconnection protection equipment

– Customer Test Engineer• Required to perform secondary injection testing on interconnection protection 

equipment

– Customer Systems Operator• Required to perform the customer switching of DC and AC systems

– Inverter Control Engineer• Required to make adjustments to set points of the inverter if needed

– Customer Representative• Required to sign witness test report upon completion

Facility Acceptance Testing• Transient Overvoltage Test

• Single Phase Disconnect Test– Shut down timing – 2 sec disconnect, 5 min reconnect

• Inverter Control Mode Test– Control power factor to 

predetermined set point– 30 min

Site Testing Pictures

Normal Peak Voltage = 400 Volt = 1 PU

Maximum Peak reached = 702 Volt = 1.76 PU PASS

Normal Peak Voltage = 400 Volt = 1 PU

Maximum Peak reached = 1100 Volt = 2.75 PU

FAIL

Normal Peak Voltage = 400 Volt = 1 PU

Maximum Peak reached = 1171 Volt = 2.93 PU

Transient Over Voltages last 24 ms

FAIL

Notice the voltage peaks barely goes above 800 Volts or 2 PU

PASS

By Comparison, look at the same inverter installed at another location

Notice the voltage peaks barely goes above 800 Volts or 2 PU

PASS

By Comparison, look at the same inverter installed at another location

Single phase opened here

Single phase closed here

Approximately 7 seconds of open phase

Single Phase Open Voltage Test

After settings on the inverter were changed

The inverter takes 2 seconds before shutting down.

Next Steps

• Interconnection study with multiple connected DG• Winter peak interconnection study?• Need better estimate of time series impact• Need CBA of constant PF inverter control• Need to share learnings from utility experiences• Southern Company needs to develop a DERMS

• Develop strategic plans at all business units for the integration of DER

Questions?

Dexter LewisResearch EngineerResearch and Technology ManagementSouthern Company