Industry Webinar Dynamic Load Modeling NERC Load Modeling Task Force (LMTF) December 2016
Industry WebinarDynamic Load Modeling
NERC Load Modeling Task Force (LMTF)December 2016
RELIABILITY | ACCOUNTABILITY2
Introduction
• Goals: Increase industry expertise and focus on dynamic load models and
modeling practices Share latest understanding and advancements in dynamic load
modeling Update industry on efforts underway in the NERC Load Modeling Task
Force (LMTF)
• Webinar Topics Fundamentals of end-use loads Composite load model Benchmarking and implementation Load composition data Distributed energy resource modeling Related LMTF activities
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NERC LMTF
• Kickoff January 2016• LMTF webpage• Key Focus Areas
Industry-wide engagement and participation – utilities, subject matter experts, software vendors, regional load modeling groups, etc.
Consolidate and share load modeling practices across industry Support industry-wide advancement of dynamic load modeling Develop guidelines, technical references, industry webinars, etc. Help ensure robust software implementation Share lessons learned and study approaches
• Chair: Dmitry Kosterev, BPA
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Speakers
• Ryan Quint – NERC (NERC LMTF Coordinator)• Dmitry Kosterev – BPA (NERC LMTF Chair)• Hamody Hindi – BPA (WECC LMTF Chair)• Bernie Lesieutre – Univ. Wisconsin• Jamie Weber – PowerWorld• John Undrill – Consultant
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History & Background
Why is this important?How did we get to where we are today?
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Why Dynamic Load Modeling?
• Validation of power-voltage oscillations WECC: July 2 and August 10 1996, August 4 2000
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Why Dynamic Load Modeling?
• Fault-Induced Delayed Voltage Recovery (FIDVR) Observed as early as 1980s in So. California, Florida, Georgia, mid-West Related to stalling of residential air-conditioners
• Distributed energy resources Emerging need in early 2010s
400
420
440
460
480
500
520
540
560
-10 0 10 20 30 40
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Air Conditioner Testing Round 1
• SCE, EPRI, and BPA tested single-phase residential A/C units Voltage sags, ramps, oscillations,
frequency excursions
• Stall for sudden ΔV to 50-60% of nominal in less than 3 cycles
• Once stalled, they remain stalled Cannot overcome load torque -
coolant pressure must equalize
• Reactive power up to ~ 7x rated• Thermal protection trips in 2-30
seconds
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Air Conditioner Testing Round 1
80 85 90 95 100 105 110 1152.6
2.8
3
3.2
3.4
3.6
Pow
er (k
W)
Ambient Temperature (F)80 85 90 95 100 105 110 115
0.56
0.58
0.6
0.62
0.64
0.66
Sta
ll V
olta
ge (p
er u
nit)
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Development of Initial Performance Model
• Motor stalls when voltage drops below Vstall for duration Tstall Vstall ~ 0.52-0.6 pu Tstall ~ 0.033 sec
0 50 100 150 2000
2000
4000
6000
8000
10000
12000
Voltage [V]
Com
pres
sor R
eal P
ower
[W]
Real Power
RUN
STALL
STALL
115F110F105F100F95F90F85F80F
0 50 100 150 2000
2000
4000
6000
8000
10000
12000
Voltage [V]
Com
pres
sor R
eact
ive
Pow
er [V
AR
]
Reactive Power
RUN
STALL
STALL
115F110F105F100F95F90F85F80F
0 0.2 0.4 0.6 0.8 1 1.20
1
2
3
4
5
6Real Power
Rea
l Pow
er (p
er u
nit)
Voltage (per unit)
RUNSTALL
STALL
Source: BPA
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Electromagnetic Transient Simulations
Negative peak of electrical torque ~8x rated torque
Speed is pulled down very strongly by negative Telec
Current by stalled motor 5x rated current
5 kW 1-ph A/CH = 0.048 sec
Source: J. Undrill
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Electromagnetic Transient Simulations
Negative peak of electrical torque ~1-2x rated torque
Speed minimally pulled down by negative Telec
Current returns to near rated current
100 kVA 3-ph MotorH = 0.3 sec
Source: J. Undrill
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Point-on Wave Simulations
• “Common mode failure” of testing Applied voltage sag at point-on-wave
zero crossing in every test
• Instantaneous voltage drop to 0.62 pu for 3 cycles Voltage zero crossing Voltage peak Voltage 45 deg point
• Worst case – zero crossing
Source: Univ. Wisconsin
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Stall Voltage vs. Point on WaveSimulation
Source: Univ. Wisconsin
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Stall Voltage vs. Point on WaveTesting
Source: Univ. Wisconsin, BPA
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Scroll vs. Reciprocating
Scroll Compressors• Vast majority of new compressors• Better fault ride-through ability• May run backwards after fault
~1-1.25x rated current – not locked rotor – up to tens of minutes
• Estimated to be ~ 50% of A/C fleet today (2015 NERC FIDVR Workshop)
Reciprocating Compressors• Majority of fleet until 2000s• Disappearing due to energy
efficiency requirementsSource: BPA
Reciprocating
Scroll
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Reasonable Stall Voltage and Time
Vstall[pu]
Tstall[cycles]
Conservative 0.49 10.5 20.51 30.53 4
Moderate 0.35 10.37 20.4 30.42 4
Optimistic 0.30 40.35 50.4 6
Vstall[pu]
Tstall[cycles]
Conservative 0.62 30.63 40.64 5
Moderate 0.56 30.57 40.59 5
Optimistic 0.46 30.48 40.52 5
TestingSimulation
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Reasonable Stall Voltage and Time
• Based on latest testing, simulation, and understanding of single-phase air-conditioners...
• Reasonable values of Vstall/TstallVstall: 0.40-0.45 pu Tstall : 2-4 cycles
• Sensitivity studies are key
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Composite Load Model
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Meeting the Needs of TODAYfor Dynamic Load Modeling
Addressing issues and practiceswith the existing dynamic load models
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Technical Reference Document
• Documents current state of dynamic load modeling• Follow-up to the NERC FIDVR Workshop in September 2015• Document approved by NERC PC December 2016
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Load Model Benchmarking
• Initial LMTF member and vendor benchmarking• NERC LMTF default data set tested using standard test events• EPRI testing and supporting this effort• Results being compiled to identify any discrepancies• Fixing any software implementation issues identified
Voltage Flow (Measured at From End)Bus Vmag [pu] From Bus To Bus Flow MW Flow MVar
1 1.020 102 101 165.0 82101 1.020 101 1 165.3 90.1102 0.999
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Load Model Benchmarking
-20 0 20 40 60 80 100 1203.545
3.55
3.555
3.56
3.565
3.57
3.575
3.58
3.585
3.59
P-M1----
MOTOR A P (PU ON SYSTEM MVA BAS
PTIGE
Source: PacifiCorp
Source: PowerWorld
0 2 4 6 8 10 12
Time (s)
-20
0
20
40
60
80
Active power (MW)
Active power at motor terminal bus
PSS/E
PSLF
PW
TSAT
Source: EPRI
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Load Model Benchmarking
4 6 8 10 12 14 16 18 20
Time [s]
159
160
161
162
163
164
165
166
P lo
ad
[MW
]
P load
[MW]
PSLF
PSSE
PowerWorld
TSAT
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Network Boundary Equations & Initialization
Source: PowerWorld
• Standardized procedures for software initialization• Familiarize and standardize practices for dealing with current
sources in dynamics – motor model numerical issues• Overcome “crashing” issues
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Common Initialization & Network Boundary Equations
Source: PowerWorld
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Robust Default Data Sets
• Developed robust default data sets for use across regions as starting point Suitable and reasonable parameters for protection Can be modified with regional data, composition data
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Developing Load Composition Data
Source: WECC
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Developing Load Composition Data
Source: WECC
Source: DOESource: CEC
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Reliability Guideline: Load Composition
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Modeling Distributed Energy Resources in Dynamic Load Models
• Developing Reliability Guideline on modeling DER in dynamic load models and powerflow models
• Coordination with NERC DERTF efforts
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Modeling Distributed Energy Resources in Dynamic Load Models
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Reliability Guideline:DER in Dynamic Load Models
Source: PowerWorld
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Reliability Guideline:DER in Dynamic Load Models
• Utility-Scale Distributed Energy Resources (U-DER): distributed energy resources directly connected to the distribution bus or connected to the distribution bus through a dedicated, non-load serving feeder. These resources are specifically three-phase interconnections, and can range in capacity, for example, from 0.5 to 20 MW although facility ratings can differ.
• Retail-Scale Distributed Energy Resources (R-DER): distributed energy resources that offset customer load. These DER include residential, commercial, and industrial customers. Typically, the residential units are single-phase while the commercial and industrial units can be single- or three-phase facilities.
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Utility Forum: Dynamic Load Modeling
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Meeting the Needs of TOMORROWfor Dynamic Load Modeling
Addressing issues and practiceswith future dynamic load models
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Progressive Stalling and Tripping
Source: PowerWorld
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Progressive Stalling and Tripping
Source: PowerWorld
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Efficient Data Format & Model Management
UVLS
UFLS
Bss
jXxf1:tap
Bfar
Load (far-end) Bus
Low-side Bus
System Bus(230, 115, 69kV)
Feeder Equiv. Model
Pdg
Qdg
Pfar
Qfar
Pnet
Qnet
DER
Transformer Model
Rfdr +jXfdr
1
2
4
3
5
N
...
Load Components
Distribution Equivalent
* DER included as one or more of the N components
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Efficient Data Format & Model Management
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Dynamic Load Modeling in Real-Time Stability Analysis
• Why do we ignore real-time modeling practices?
• Why do we require induction motor load in planning studies but not in real-time studies?
• What are the limitations in moving towards inclusion of induction motor load in real-time models?
• How do we proceed cautiously?
RELIABILITY | ACCOUNTABILITY42
Event Recreation and Model Validation
• Model can be tuned to accurately represent actual system disturbances for event forensics
• Model used for planning studies is not expected to match traces perfectly – should capture the event in principle
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Closing Remarks
• Evolution of end-use loads continuing to evolve• Increasing DER penetrations, need for modeling practices• Composite load modeling
Reference material for understanding model and parameters Default data sets Robust implementation Used for thousands of transient stability studies effectively
• Load composition data• Validation and sensitivity analysis
RELIABILITY | ACCOUNTABILITY44
Wrap Up
• Participation in NERC LMTF Email Ryan Quint ([email protected]) to get added to LMTF Roster Encourage anyone working in this area to participate, particularly utility
planners and modelers
• Thank you for your interest in dynamic load modeling and the NERC LMTF!
RELIABILITY | ACCOUNTABILITY45
CONFIDENTIAL – Limited Distribution
NATF Modeling Practices GroupUpdate
January 24, 2017NERC SAMS Meeting
Ed Ernst- NATF Program Manager
CONFIDENTIAL – Limited Distribution (NERC)Copyright © 2017 North American Transmission Forum. Not for sale or commercial use. Limited Distribution documents are confidential and proprietary. Limited Distribution documents may be used by employees of North American Transmission Forum (“NATF”) member companies who have a need to know the information in the document, by NATF staff, and by entities who have permission to receive Limited Distribution documents pursuant to a written agreement with the NATF, for purposes consistent with the NATF’s mission. All rights reserved.
CONFIDENTIAL – Limited Distribution
Outline
• NATF Practices Groups• NATF Modeling Practices Group Activities• Coordination between NATF and NERC
2
CONFIDENTIAL – Limited Distribution
NATF Practice Groups• Compliance• Human Performance• Modeling• Operator Training• Security• System Operations• System Protection• Transmission-Nuclear Interface• Vegetation Management• Equipment Performance and Maintenance
3
CONFIDENTIAL – Limited Distribution
NATF Modeling Practices Group Current Activities
• Recent Public Posting of NATF Documents• On-going monthly work of Modeling Practices
Group and its various working groups• MOD-033 Reference Document update• June 20-21, 2017 NATF-NERC Modeling
Workshop
4
CONFIDENTIAL – Limited Distribution
Recent Public Posting of NATF Documentsat www.natf.net
CONFIDENTIAL – Limited Distribution
On-going monthly calls of Modeling Practices Group and its various working groups• Dynamic Load Modeling Working Group
– Sharing experiences– Following work of other groups: NERC Load Modeling Task Force, etc.– No documents under development
• Transmission Planning Working Group– Sharing experiences on TPL-001-4, TPL-007, MOD-033 model validation and transmission/sub-
transmission connected renewables– Following work of other groups: NERC GMD Task Force, etc.– Working on MOD-033 Reference Document- target completion date March 2017
• Distributed Energy Resources Working Group– Sharing experiences – Following work of other groups: NERC Distributed Energy Resources Task Force, etc.– Awaiting NERC Distributed Energy Resources Document – Plan to develop a Distributed Energy Resources Reference Document during 2017
• EMS Modeling Working Group– Current focus is on the building of external models– Working on EMS External Model Reference Document – target completion early 2017
CONFIDENTIAL – Limited Distribution
MOD-033 Reference Document
CONFIDENTIAL – Limited Distribution
MOD-033 Reference Document Timeline
• January 30, 31- Team call to review latest draft of document• Late February - Team completes final document • March – NATF Modeling Practices Group Core Team and
NATF Board Approval • March/April - Release Public version of document for
broader industry use• June 20-21 - Present at June 2017 Modeling Practices
Group Workshop• MOD-033 document to be proposed as compliance
implementation guidance for NERC to “endorse” for industry to use as an example of a way to be compliant.
8
CONFIDENTIAL – Limited Distribution
June 20-21, 2017 NATF-NERC Modeling Workshop - hosted by Exelon (Com Ed)
• Tentative Agenda topics– Dynamic Load Modeling– Power Plant Modeling – MOD-033 – Integrating Renewables at the Transmission Level – Modeling DER (renewables at the distribution level)– Catch all session: NERC/FERC update, Node-breaker-
experiences of planners who have transitioned to node-breaker to include EMS perspective, NERC modeling updates, Emerging modeling issues (Beyond Positive Sequence RMS Modeling, Interconnection-wide Assessments), etc.
CONFIDENTIAL – Limited Distribution
Coordination between NATF and NERC
• Document development• Jointly Sponsored June 20-21 Modeling
Workshop hosted by Exelon(Com Ed) in Chicago • Regular NATF-NERC meetings at Gerry
Cauley/Tom Galloway level to coordinate efforts• Ryan Quint of NERC staff has standing slot on
Monthly NATF MPG and its working group calls to cover topics as needed
• Ed Ernst has standing slots on SAMS and MWG calls to cover topics as needed
10
CONFIDENTIAL – Limited Distribution
NATF Modeling Practices Group Update
Questions?
11
HYDRO-QUÉBEC TRANSÉNERGIE’SSHORT-CIRCUIT ANALYSIS METHODS
AND APPLICATIONS
Vito De Luca, eng.With special thanks to Jean-Luc Pépin, eng..
January 24th 2017
Prepared for NERC’s System Analysis and Modeling Subcommittee
OBJECTIVES
Hydro-Québec TransÉnergie2
Share with industry experts HQT’s expertise in the field of short-circuit analysis from a planning point of view.
Provide insight on NERC’s proposal regarding building an interconnection wide short-circuit case based on experience with short-circuit case modeling.
Provide recommendations to utilities and ISO’s to help with short-circuit case building.
INTRODUCTIONSHORT-CIRCUIT ANALYSIS IN PLANNING APPLICATIONS
Hydro-Québec TransÉnergie3
1 Short-circuit Analysis from a Planning Perspective
― Not necessarily a task reserved exclusively for operations and protection engineers!
― Essential for long term transmission system planning― Provides a broad outlook of increasing short-circuit levels and X/R
ratios, indicative of changes and upgrades within the continuously evolving transmission system
Main Applications in System Planning ― Evaluation of high voltage circuit breaker duties― Assessment of system strength and impact on Bulk system reliability
SHORT-CIRCUIT ANALYSIS AT HQTBACKGROUND
Hydro-Québec TransÉnergie4
2 Short-circuit model developed in conjunction with base case model
since early 1990’s Need for short-circuit monitoring due
to unique system characteristics― Majority of power generation situated in the north
― Load centres concentrated in the south
― Vast network composed of long transmission lines at 735 kV
― Series compensation
― System design based on maximum breaker duty of 50 kA
― Regional substations composed of 4+ transformers in parallel
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie5
3
Main components of HQT’s short-circuit analysis method :1. Short-circuit case modeling2. Short-circuit calculation methods3. Breaker data validation
ISC (kA) BD (kA)
Short-circuit Model
Short-circuit Calculations
ISC/BD %
Breaker DutyValidation
BreakerData
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie6
3
1. Short-circuit Case ModelingModeling
DataGO, TO,
LSEData Validation & Mapping
Short-circuit Case Model
Operations Data & Planning CriteriaTSO, TP
Base Case
ModelingDatabase
Modifications for Short-circuit
studies
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie7
3 Short-circuit case model is based on HQT’s main base case model
used for planning studies― Modeled in PSS/E― Best available model with most up-to-date modeling data, including all in
service equipment, recent upgrades and future projects.― Provides a larger scope (0-15 years), necessary for long term planning
HQT’s multidisciplinary approach to case building― Base case consists of steady state, short-circuit and dynamics data― Sequence data always included in load-flow cases― Comprehensive modeling practices in application well before the
implementation of NERC’s MOD-032 standard― Avoids redundancies in modeling data collection process
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie8
3 Mapping the transmission system to a simplified bus-based load-
flow software― Simplified representation of electrical system― Define bus numbers with respect to one-line diagrams used by operators― Bus numbers assigned to line taps, generators and groups of electrical
equipment in substations (i.e. bus bars, breakers, switches)― Mapping is required in the absence of more detailed node-breaker model
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie9
3 Bus mapping example:
Substation One-line Diagram
PSS/E Bus Representation
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie10
3 Bulk system modeled to represent normal operating conditions
during peak load that would produce highest possible short-circuit levels― Winter peak― All available generation in service― All transmission equipment in service
Base cases adapted for short-circuit studies― Saturated generator reactances (xd’’)― Load modeling― Modifications to ring bus configurations at load-serving substations― Comprehensive (“umbrella”) and probabilistic scenarios
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie11
3
2. Short-circuit Calculation Method Calculation of total or asymmetrical fault current
22 )()( dcactot III +=
acI
where,
dcI
totI Total rms fault current
AC symmetrical current component
DC component
-1,5
-1
-0,5
0
0,5
1
1,5
1 16 31 46 61 76 91 106 121 136 151 166 181 196 211 226
IcaIccItot
-1
-0,5
0
0,5
1
1,5
2
2,5
1 16 31 46 61 76 91 106 121 136 151 166 181 196 211 226
ItotIcc
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie12
3 Based on the Fixed impedance decaying short-circuit calculation method
'''' ''
)( IeIII dTt
ac +−=−
RXt
dc eIIπ2
''2−
=
''I Initial sub-transient symmetrical rmsshort-circuit current (A)
where,
'I
t
''dT
RX
Transient symmetrical rms short-circuit current (A)
Time elapsed between fault inception and instant of contact separation of the breaker (ms)
Synchronous machine sub-transient time constant (ms)
Equivalent impedance ratio obtained in transient stage
0,3
0,4
0,5
0,6
0,7
0,8
0,9
Stade sous-transitoire
Stade transitoire
Stade permanent
Réactance d’une machine synchrone en fonction du temps
X’’d
X’d
Xd
5
1
5
0
5
1
5
Stade transitoire(évalué avec les réactance transitoires)
Stade sous-transitoire (évalué avec les réactances sous-transitoires)
Stade permanent(non évalué par PSSE)
1
5
0
5
1
5
2
5
Stade sous-transitoire (évalué avec les réactances sous-transitoires)
Stade transitoire(évalué avec les réactance transitoires)
Stade permanent(non évalué par PSSE)
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie13
3
Short-circuit calculations are automated using in-house python-based program
―Calculates Iac, Idc and Itot at time t using I’’, I’ and X/R values obtained from PSS/E
―Retrieves breaker data in separate sql-based database
―Compares Itot at a given bus to the breaker duties of breakers mapped to that bus
―Breaker location factors are applied as not all breakers are positioned to interrupt the maximum fault current at a given bus
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie14
3 Symmetrical fault currents I’’ and I’, and X/R ratios obtained using
ASCC activity in PSS/E
―Calculates first cycle or instantaneous symmetrical fault currents considering sub-transient and transient machine reactances.
―Three-phase, line-to-ground and line-line-to-ground type of faults
―Function that is easily integrated in automation files for short-circuit analysis at multiple buses
―Requires saved and solved power flow case for pre-fault conditions (i.e. pre-fault voltage at machine terminals)
―Flat conditions used to obtain system X/R ratios (source voltages set at equal unity)
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie15
3
Assumptions―All elements considered in short-circuit calculations―Generators modeled in negative and zero sequence as impedance
connected to ground at generator neutral―Loads represented as constant shunt admittances―Transformer impedances are those defined at nominal tap position―Voltages at machine terminals remain constant during the duration of
the fault―Resistance of arcing fault current is neglected―DC lines and FACTS are considered blocked
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie16
3
Re-examination of short-circuit calculation method― New functions available in PSS/E (ANSI, IEC, BKDY)
― Advantages:• Total fault current obtained directly from PSS/E• Based on internationally accepted standards• Predefined machine impedance correction factors for AC current decay
― Calculation methods benchmarked to results obtained from EMTP software using test model
― Results:• ASCC method produced results that more closely resembled those obtained with EMTP• Method is more conservative than ANSI and more realistic than IEC (realistic voltage levels
as opposed to uniform voltage level applied to system) • New functions require various manual adjustments to produce adequate results for all
system scenarios (i.e. IEC not recommended for certain system topologies)• Closely resembles BKDY, however BKDY incompatible with analytical tools
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie17
3
3. Breaker data validation Not all breakers are created equal!
―Nameplate data presented differently depending on different breaker design standards, which can lead to incorrect breaker duty assessment
―Three main design standards:
• ANSI C37.X – Breakers generally built approximately between 1941 to 1971
• ANSI C37.0X – Breakers constructed between 1964 to present
• IEC 56 – Breakers generally constructed between 1971 to present
―Need for breaker nameplate interpretation guide and data validation
―NERC standards? FAC-008? MOD-032?
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie18
3Standard Nameplate Rating Conventions Breaker Ratings VI Curve
ANSI C37.X
• Rated Interrupting capacity specified in constant power (MVA) or in total current (kA)
• Often 2 rated voltages are given• Important to associate rated voltage
values with correct current rating
ANSI C37.0X
• Rated Interrupting capacity specified in symmetrical MVA or current (kA)
• Usage of K factor• Maximum current obtained at 1/K of rated
maximum voltage
IEC 56
• Rated Interrupting capacity specified in constant symmetrical current (kA)
• Current capacity rated for voltages up to rated voltage
Rated maximum interrupting current
Rated interrupting current at rated voltage
Rated voltageMinimum voltage for rated interrupting current
kA
kV
Rated interrupting MVA
K rated short-circuit current
Rated short-circuit current
Rated maximum voltage 1/K Maximum voltage
kA
kV
Symmetrical interrupting capability MVA
Tension assignée
kA
kV
Pouvoir de coupure assignéen court-circuit (kA)
SHORT-CIRCUIT ANALYSIS AT HQTMETHOD
Hydro-Québec TransÉnergie19
3 Breaker Nameplate Examples
CONCLUSIONLESSONS LEARNED AND RECOMMENDATIONS
Hydro-Québec TransÉnergie20
4 Accurate modeling is key
― Transformer modeling is the primary source of error when computing short-circuit currents
• Cumbersome sequence data modeling in PSS/E• Connection code errors• Replacing three-winding transformers with two-winding transformers is possible if no
load is connected to third winding― Modeling inaccuracies can result in a margin of error of +/- 5-10% when conducting
short-circuit calculations.
Short-circuit calculation methods must be evaluated and chosen according to each system’s specific requirements Room for improvement in regards to tools and software for short-circuit
analysis (i.e. breaker duty evaluation, mapping to ASPEN, etc.) General standard needed for breaker nameplate data validation and reporting
END
Hydro-Québec TransÉnergie21
QUESTIONS?
PCPMTF UPDATE TO SAMS
Mohamed Osman, P.E., Senior Engineer of System AnalysisNERC – SAMS MeetingJanuary 24-25, 2017
RELIABILITY | ACCOUNTABILITY2
PCPMTF Background
• PCPMTF: Plant-Level Controls and Protection Modeling Task Force• Studying effects of plant-level, turbine, and boiler control and protection
systems• Comprehensive look at the short- and mid-term post-disturbance behavior of
plant control and protection systems• Outlining impacts plant control and protection systems have on unit reliability
and system stability during grid disturbances
• PCPMTF Stakeholders:• Turbine Manufacturers; Generators Owners/Operators; North American
Generator Forum (NAGF); experts in power system dynamics and control; stability simulation software vendors
RELIABILITY | ACCOUNTABILITY3
Events Investigated to Quantify Effects of Boiler and Turbine Controlers
Event Event Description Boiler/Turbine Control
1 Turbine hydraulic system pump tripped in part because of the acceleration detection circuit.
Boiler/Turbine controls could be improved to provide smooth transfer
2 Megawatt transduces were improperly scaled. Error in Boiler/Turbine controls scaling
3 Turbine PLU and transmission line protection schemes not tuned properly
Not a Boiler/Turbine control issue. The PLU is a form of over-speed protection.
4 Turbine intercept valve logic in error Error in Boiler/Turbine controls logic
5 Dynamic models overestimate generator governing response Not a Boiler/Turbine control issue
6 Aux bus under voltage setting may not take into account grid disturbance
Not a Boiler/Turbine control issue
7 GT high rate of change cause a “blowout”. Boiler/Turbine controls could be improved to reduce rate of change
8 Turbine tripped due to acceleration detection circuit Doesn’t the acceleration detection work before synchronization and primary frequency response (PFR) control work after synchronization. Logic of OEM requirement and PFR need resolution.
9 Turbine hydraulic system pump tripped due to capacity limits Boiler/Turbine controls should include PFR limits
10 Drum level trip due to lag in starting second BFP. Boiler/Turbine control should include PFR limits
RELIABILITY | ACCOUNTABILITY4
What is the issue?
• If we look at the generator tripping events that the TFhas looked at and could not be duplicated by models,most occurred because of either:• Equipment failure• Expected protection action (correct action)• Protection action that was not properly coordinated• Complex dynamics of combustion/boiler systems
RELIABILITY | ACCOUNTABILITY5
Generator Protection
• Loss of field• Overexcitation protection• Overvoltage protection• Undervoltage protection• V/Hz protection• Over/Under-Frequency protection• Power/Load Unbalance (for STs)• Reverse Power relays• Many others (e.g. Neg. Sequence, Phase Differential Current,
etc.) which cannot be modeled in positive sequence simulation tools
RELIABILITY | ACCOUNTABILITY8
Generator Protection
• WECC has for years used simple models in GE PSLFTM
called gp1/gp2 that model many of these functionsgenerically – WECC uses these only to monitor thebehavior in simulations, not to trip units
• This can be a good starting point, with the next stepsbeing to:– Update those models– Double check to ensure they are applying reasonable default
settings/assumptions– Add missing features (e.g. V/Hz, Power/Load unbalance, etc.)
RELIABILITY | ACCOUNTABILITY9
Available Models
• Existing turbine-governor models (see IEEE PES- TR1report [1]) allow for reasonable modeling of:– Unit ramp rates in power– Deadband– Outer-loop MW controllers– Baseload– Temperature limit of GTs
• The new IEEE Std 421.5 will have documented OEL,UEL and stator current limiter models
RELIABILITY | ACCOUNTABILITY10
Task Force Recommendations
• Adopt a model similar to gp1 (and gp2) in GE PSLFTM that can monitor and provide warnings of potential unit tripping due to the generator encroaching on possible trip-zones of protection systems.
• Inclusion of Volt/Hz, over excitation limiter, under excitation limiter and reverse power dynamic models in future year planning cases.
• NERC SPCS should look closely at the reliability impacts of plant-level controls and protection on applicable NERC Reliability Standards.
RELIABILITY | ACCOUNTABILITY11
References
[1] IEEE Task Force on Turbine-Governor Modeling, Dynamic Models for Turbine-Governors in Power SystemStudies, IEEE Technical Report PES-TR1, January 2013.
RELIABILITY | ACCOUNTABILITY12
Short Circuit Case Coordination Mohamed Osman, Senior Engineer, System AnalysisNERC – SAMS Meeting January 24-25, 2017
RELIABILITY | ACCOUNTABILITY2
• MMWG case verification: The tie lines have greater than +10% difference between the cases for
three phase (3Φ) symmetrical faults. NERC identified the following case modeling discrepancies: o Missing tie-line modeling and/or incorrect impedances (Z= R+jX) (issue); o Retired generators or new generators are missing from either case (issue);o Transformers representation (issues):
– 3-winding transformers are represented as 2-winding transformers;– incorrect/mismatched impedances (Z= R+jX);
o Number of lines between buses varies and their respective impedances differs (possible issue)
Planned, yet not communicated region topology changes since MMWG case creation (issue)
Short Circuit Case Benchmarking:Identified Modeling Errors
RELIABILITY | ACCOUNTABILITY3
• NERC and the EI Regional Staff are discussing options that would encourage coordination between planning and short-circuit cases
• Proposed options: Option 1: Review and use a single interconnection model that includes
sequence data Option 2: Interconnection wide case built parsed from planning
coordinator models Option 3: Require Planning Coordinators to adopt best practices (looking
into neighboring systems) and coordinate boundary areas
• Option 3 was selected
Short Circuit Case Benchmarking:Future Steps
RELIABILITY | ACCOUNTABILITY4
Short Circuit Case Benchmarking:Future Steps
• Request for Short Circuit cases from PC will be sent end of this month by ERAG.
• NERC and the Regional Entities will perform specific data checks.
• Between PC short-circuit cases:• Tie-lines and topology at boundary areas• Compare modeling of all BES elements such as transformer windings
• Between PC short-circuit and MMWG planning cases:• Ensuring generation resources are reasonably matched between the cases• Fault current level at substation buses within an acceptable + 10% difference
margin
RELIABILITY | ACCOUNTABILITY5