Download IEEE Rural Electric Power Conference

IEEE Rural Electric Power Conference
Distributed Generation System Impact
Analysis with Computer Modeling
Tools
Sean A. Kufel, P.E.
Power System Engineering, Inc.
www.powersystem.org
April 20, 2015
Session Summary
Goal: Developing a reliable, efficient process for
performing DG system impact studies.
• Data Requirements
• Modeling Generation
– Types of generator models & adding generation
– Types of analysis
– Common modeling errors
• Focus on steps where errors or confusion are common
• NOT: Instructions on using any modeling program
• DISCLAIMER(S): I am not a programmer. I am not
endorsing any particular modeling application.
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System Impact Analysis Goals
Common impacts of DG that can be identified with
computer modeling:
• Voltage rise
• Conductor/equipment overload
• Inadequate device interrupt rating
• Reverse power flow
• Potential for islanding
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Data Requirements
• Utility side:
– Electrical model of distribution system area where DG is
proposed, including:
• Source impedance, including substation power transformer
• System conductors
• Major system equipment – transformers, regulators, capacitors &
protective devices
• Substation area/feeder peak demand
– Historical minimum load in area/on feeder
• Often estimated at around 25% of peak if historical hourly data is not
available
– Protective device settings
– Regulator/LTC settings
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Data Requirements
• Applicant/Developer/Generation side:
– Number of generators to be installed and total aggregate
capacity
– Proposed facility one-line/three-line diagram
– Expected peak generator output & how the generation will be
used (back-up only, intermittent operation, on-site load service,
power export, etc.)
– Location of proposed interconnection (preferably in reference to
distribution system)
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Data Requirements
• Applicant/Developer/Generation side:
– Generator data:
• Operating voltage
• Ratings: kW, kVA, power factor
• Fault information
– Steady-state, transient & subtransient reactance values or generator
equivalent circuit for rotating machines
– For PV with inverter(s), fault current is typically a multiple of rated output
(150% is often used)
– Other equipment data:
• Inverter ratings, solar panel data for PV installations
• Ratings & impedances of any generator step-up transformer units (GSU)
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Generator Fault Information
Impedance Data
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Equivalent Circuit
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Modeling Programs
Milsoft WindMil®
Eaton CYME
• SynerGEE, eTap, Dapper, etc.
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Types of Generator Models
• Generic Generator
• Two operating modes:
– Negative load (constant
kW output)
– Swing kVAR (hold
desired voltage by
adjusting kVAR output)
• Fault output based on
generator impedances
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Types of Generator Models
• Specific Generators
• Common types:
– Synchronous & Induction
– Wind turbine
– Solar array
– Others
• Operating modes &
fault contributions
dependent upon type of
generation
• Mostly the same as
generic for synchronous
machines
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Generic Generator Pros/Cons
• Con:
– Sometimes need to perform impedance calculations when only
fault duty is available
• Pro:
– Conversion utilities are often built in
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Specific Generator Pros/Cons
Pro:
• Possible to create extremely
detailed generator models
with LOTS of specific data
Con:
• Hyper-specific data
generally not needed for
snapshot analysis
• Possible (?) to run highly
specific analysis depending
upon program modules &
capabilities
• Lots of specific data can be
overwhelming
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Information Overload?
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Add Generation to the Model
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Voltage Drop/Load Flow Analysis
Peak Load
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Minimum Load
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Voltage Drop/Load Flow Analysis
Common Error: Generators not included in analysis
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Collecting Results
• From on-screen result boxes:
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Collecting Results
• Via custom reports:
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Voltage Drop/Load Flow Analysis
• Other things to check:
– Substation/source power factor, before & after generation is
added
– Native loads in all protective zones upline of the generation
(with generation offline)
• Aid in determining if islanding is possible
– Current flow through equipment with generation online
– Reverse power flow through equipment and/or substations when
generation is operating (more likely and higher at minimum
load)
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Checking Protective Zone Loads
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Turning on Power Flow Arrows (If Available)
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Short-Circuit Analysis
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Short-Circuit Analysis: General
Gen Z: Steady-state or
“None”
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Gen Z: Subtransient
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Coordination Analysis
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Device-Device Coordination Setup
CYME TCC Settings 
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Device Coordination Check
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Short-Circuit Analysis: Fault Flow
Generator
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End of Protective
Zone 1
Feeder Recloser
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Short-Circuit: Reverse Fault Flow
Initiate fault
immediately upline
of protective device
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Short-Circuit: Fault Flow
• Locations to check during fault flow:
– End of protective device zones
• Especially in direct path between generation and source
• Especially for electronically-controlled reclosers
– Check ground pickup setting versus minimum fault flowing through device
with generation contributing
– Source side of devices in direct path between generation and
source
– Other feeders on substation
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System Impact Study Model Use Keys
• Develop a process and stick to it
• Double-check entered data
• Document analysis results clearly
• Keep track of model changes made to improve system
conditions
– Probably not a good idea to alter the working model of your
existing system if you are a utility, especially if it is an
enterprise or shared model
• Step back and sanity-check results
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QUESTIONS &
DISCUSSION
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Thank You:
IEEE 2015 REPC
Attendees!
Power System Engineering, Inc.
Name: Sean A. Kufel, P.E.
Title: Electrical Engineer
Direct: (740) 568-9220 x11
Mobile: (216) 544-8614
Email: [email protected]
www.powersystem.org
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