Industry Webinar - NERC Agendas Highlights Minutes/… · Industry Webinar. Dynamic Load Modeling. NERC Load Modeling Task Force (LMTF) December 2016. 2. RELIABILITY | ACCOUNTABILITY

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


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

http://www.nerc.com/comm/PC/Pages/Load%20Modeling%20Task%20Force%20(LMTF)/Load-Modeling-Task-Force.aspx


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


History & Background

Why is this important?How did we get to where we are today?


Why Dynamic Load Modeling?

• Validation of power-voltage oscillations WECC: July 2 and August 10 1996, August 4 2000


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


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


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)


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


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


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


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


Stall Voltage vs. Point on WaveSimulation

Source: Univ. Wisconsin


Stall Voltage vs. Point on WaveTesting

Source: Univ. Wisconsin, BPA


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


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


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


Composite Load Model


Meeting the Needs of TODAYfor Dynamic Load Modeling

Addressing issues and practiceswith the existing dynamic load models


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


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



-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



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


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


Common Initialization & Network Boundary Equations

Source: PowerWorld


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


Developing Load Composition Data

Source: WECC


Developing Load Composition Data

Source: WECC

Source: DOESource: CEC


Reliability Guideline: Load Composition


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


Modeling Distributed Energy Resources in Dynamic Load Models


Reliability Guideline:DER in Dynamic Load Models

Source: PowerWorld


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.


Utility Forum: Dynamic Load Modeling


Meeting the Needs of TOMORROWfor Dynamic Load Modeling

Addressing issues and practiceswith future dynamic load models


Progressive Stalling and Tripping

Source: PowerWorld


Progressive Stalling and Tripping

Source: PowerWorld


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


Efficient Data Format & Model Management


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?


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


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


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!

mailto:[email protected]


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.


Outline

• NATF Practices Groups• NATF Modeling Practices Group Activities• Coordination between NATF and NERC

2


NATF Practice Groups• Compliance• Human Performance• Modeling• Operator Training• Security• System Operations• System Protection• Transmission-Nuclear Interface• Vegetation Management• Equipment Performance and Maintenance

3


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


Recent Public Posting of NATF Documentsat www.natf.net


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


MOD-033 Reference Document


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


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.


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


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


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


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


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



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



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



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



3 Bus mapping example:

Substation One-line Diagram

PSS/E Bus Representation



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



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



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)



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



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)



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



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



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?



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)



3 Breaker Nameplate Examples

CONCLUSIONLESSONS LEARNED AND RECOMMENDATIONS


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


QUESTIONS?

PCPMTF UPDATE TO SAMS

Mohamed Osman, P.E., Senior Engineer of System AnalysisNERC – SAMS MeetingJanuary 24-25, 2017


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


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


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


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


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.)


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


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.


References

[1] IEEE Task Force on Turbine-Governor Modeling, Dynamic Models for Turbine-Governors in Power SystemStudies, IEEE Technical Report PES-TR1, January 2013.


Short Circuit Case Coordination Mohamed Osman, Senior Engineer, System AnalysisNERC – SAMS Meeting January 24-25, 2017


• 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


• 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


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
