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© ABB| Slide 1September 21, 2016
Load FlowTechnical Colloquium Indonesia PLN - ABB
Nihar S Raj, Business Head – Power Consulting (Asia) , Presentation, Intercontinental, 22nd Sep 2016
© ABB| Slide 2
Important notices
September 21, 2016
1. Please be aware of Safety requirements & Emergency Exit2. Kindly keep your mobile phones in “SILENT MODE”.3. More discussions / interactions on the topic.
Power ConsultingGlobal network of industry recognized subject matter experts…
Sri P.Trans. Planning& Operations
John D.Subsynch.Phenomenon
Dave D.HVDC/FACTS
Rodolfo K.System Stability& Dynamics
Albert K.System Studies
Sal G.Digital Grid /Distr. Planning
Lan T.Gen./Renewables Planning
Jin Z.PowerEconomics
Carlos H.SubstationAutomation
Ricardo G.Power SystemAnalysis
Bandaru KFailure AnalysisPower Products
Manoj KArc FlashMitigation
Julia S.Industrial PowerSystems
Arefeh S.InsulationCoordination
Andreas U.Distribution Sys.Modeling
Fahd H.WAMS
Ramana B.AC/DCInteraction
Alireza M.HarmonicsAnalysis
Ines RomeroRenewables /Supergrids
Joaquin M.Microgrids
Paula F.ProtectionCoordination
Nihar R.RenewablesIntegration
© ABBAugust 3, 2016
Ron WilloughbyT&D PlanningOptimization
Khoi V.Energy Storage
A team of 125 technical experts with deep know-how, located worldwide to support you on extensive mattersrelated to electrical power systems
© ABB| Slide 4September 21, 2016
Load Flow StudiesAgenda
1. What is Load Flow Studies2. Basic Equations3. When do I need it ? Is it advantageous4. Case Studies
© ABB| Slide 5September 21, 2016
Load Flow StudiesBasics
* = Required to define the Pd and Qd at PQ bus as at the load bus voltage is allowed to vary within permissible limits.
1. Load flow is the steady state calculationwhose aim is to determine
• Voltage,
• current,
• real & reactive power,
• angle,
• power factor,
• network loss
Define PV Bus
1. Pi and Vi defined, Qi and di to be defined.
2. Generator is always connected to it.
3. It is generally 10 – 15% of the total buses.
PQ Bus *
1. Pi and Qi defined, Vi and di to be defined
2. It is load bus with no generator.
3. It comprises nearly 85- 90% of total buses.
as “1” for convenience.
Swing Bus / Slack Bus/ Reference Bus
1. V & d usually defined V= 1 & d = 0 deg, P &Q to be defined.
2. Only one bus in power system it is numberedas “1” for convenience.
© ABB| Slide 6September 21, 2016
Load Flow StudiesApplication
1. Optimal Transformer Tap settings
2. Generator exciter/regulator voltage set points
3. Size and Location of capacitors
4. Serves as initial conditions for several other types of power system studies such asstability, economics, short-circuit analysis and harmonic studies
5. Other Advantages are…
© ABB| Slide 7September 21, 2016
Load Flow StudiesWhen to do Load Flow….. Advantages
1. Planning of new network.
2. Augmentation of network with new generators, meeting increased load demands and transmissionlines.
3. Helpful to determine the optimization capacity of proposed generating station, substation or newlines.
4. Determining voltages of the buses. Some load bus may be kept within certain tolerances.
5. Minimizing system transmission losses.
6. Checking the loading of important lines, tie –lines. These lines should not be operated close tothermal limits of to their stability limits.
7. Load flow solution gives nodal voltage and phase angles and hence the power injection at all thebuses and power flow through interconnecting tie lines / bus.
8. Connectivity with Utility (Check reactive power specifically during import)
9. To check the viability of new system operating conditions
10. Becomes a base study to do any other study in Power System.
© ABB| Slide 8September 21, 2016
Load Flow StudiesPower Flow Equations
The basic equation for power-flow analysis is derived from the nodal analysis equations forthe power system. For example, for a 4-bus system
where Yij are the elements of the bus admittance matrix,Vi are the bus voltagesIi are the currents injected at each node.
•The node equation at bus i can be written as
© ABB| Slide 9September 21, 2016
Load Flow StudiesPower Flow Equations
Relationship between per-unit real and reactive power supplied to the system at bus i andthe per-unit current injected into the system at that bus:
where Vi is the per-unit voltage at the bus;Ii* - complex conjugate of the per-unit current injected at the bus;Pi and Qi are per-unit real and reactive powers.
Therefore,
© ABB| Slide 10September 21, 2016
Load Flow StudiesPower Flow Equations
© ABB| Slide 11September 21, 2016
Load Flow StudiesProgrames
• Computer programs to solve load flow are divided into two types
• Static (Offline)• Most load flow studies for system analysis are based on static network models
• Dynamic (Real-Time)• Real time load flows that incorporate data input from the actual networks are
typically used by utilities in automatic SCADA systems.• Such systems are used primarily as operating tools for optimization of
generation, VAR control, dispatch, losses, and tie-line control
© ABB| Slide 12September 21, 2016
Load Flow StudiesGIS Based Studies – New Methodology
1. GIS will be the leading tool
2. GIS MMI to be used for
1. Network data entry & management
2. Network and result visualization
3. Web based functionalities
3. Network data will be stored in GISdatabase
4. NEPLAN will be used as calculationengine.
GIS Based Load Flow Studies
First level§ Second level
- Third level
Real Time working on Load flow studiesReal Time working on Load flow studies
© ABB| Slide 13September 21, 2016
Load Flow Studies – NEPLAN®Client Server Interface
1. .
SQL-DBSQL-Server, Oracle inIntranet or Cloud
Application-Server
Client Client Client Client XML
LocalIntranet
Desktop User
© ABB| Slide 14September 21, 2016
Load Flow Studies – NEPLAN®Result Visualization
1. .
© ABB| Slide 15September 21, 2016
Load Flow Studies – NEPLAN®Result Visualization
1. .
Load flow results
© ABB| Slide 16September 21, 2016
Load Flow StudiesCase Study – 01 : Voltage issues in Network
.
TRAIN-1Refinery Area
STG – 1 & 2(38.5MW)STG – 3 & 4(105MW)STG – 5 (92.8MW)GTG – 1 & 2(110MW)
Base Refinery:SS-10, 20, 30, 40, 34, 60, 70, 61-1, 61-2, 77, 22,53, 84, 89-01 & 89-02Train-1 Refinery:SS-03, 05-01, 05-02, 11, 14, 19-01, 19-02, 21,01, 02, 15, 16, 17, 25
220kV Theba SS
GIS 1 GIS 2-2 GIS 2-1
VPCL PH-2 Aux.
© ABB| Slide 17September 21, 2016
Load Flow StudiesCase Study – 01: Selection of Different Operating Modes
. Case Name /OperatingCondition
STG1 STG2 STG3 STG4 STG5 GTG1 GTG2 Plant Load(MW)
Exchange(+ export / -
import)Remarks
CASE-1 ON(25.6MW)
ON(26.6MW) OFF ON
(89.4MW)ON
(72.7MW) OFF OFF 159.53 54.77Base Case i.e. Normaloperating condition
CASE-2 OFF OFF OFF OFF ON(50MW) OFF OFF 159.54 -109.54Min Generation Max
Load
CASE-3 ON(25MW)
ON(25MW) OFF ON
(75MW)ON
(70MW) OFF OFF 159.27 35.73Same as Case-1
CASE-4 ON(25MW)
ON(25MW)
ON(70MW)
ON(75MW)
ON(70MW) OFF OFF 160.48 104.52 Max Generation Max
Load
CASE-5 ON(25MW)
ON(25MW)
ON(70MW)
ON(75MW)
ON(70MW) OFF OFF 122.91 142.10 Max Generation Min
Load
CASE-6 OFF OFF OFF OFF OFF ON(85MW) OFF 142.94 -57.94Only ONE GTG feeding
load
CASE-7 OFF OFF OFF OFF OFF ON(65MW)
ON(65MW) 130.24 0.00Floating Condition (with
only 2 GTG's)
CASE-8 ON(20MW)
ON(25MW) OFF ON
(50MW)ON
(64MW) OFF OFF 158.89 0.00Floating Condition
CASE-9 ON(25MW)
ON(25MW) OFF ON
(50MW)ON
(45MW) OFF OFF 141.07 3.93Min Export Condition
© ABB| Slide 18September 21, 2016
Load Flow StudiesCase Study – 01: Selection of Different Operating Modes
.
85
90
95
100
105
110
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33
Voltage Profile Upper limit +/-5%
Initial Condition New Proposal
85
90
95
100
105
110
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33
Voltage Profile Upper limit +/-5%
Initial Condition New Proposal
1. Base Case scenario
2. Over voltages observed…
1. Case with Min Generation & Max Loadcondition
2. Over voltages observed…
Over voltages observed in both cases. New transformer tap positions indicated tomitigate the challenges.
Possibility of having common tap positions to that easy for operating staff.
© ABB| Slide 19September 21, 2016
Load Flow StudiesCase Study – 01 : Impact of Closing Tie Lines
.
TRAIN-1Refinery Area
STG – 1 & 2(38.5MW)STG – 3 & 4(105MW)STG – 5 (92.8MW)GTG – 1 & 2(110MW)
Base Refinery:SS-10, 20, 30, 40, 34, 60, 70, 61-1, 61-2, 77, 22,53, 84, 89-01 & 89-02Train-1 Refinery:SS-03, 05-01, 05-02, 11, 14, 19-01, 19-02, 21,01, 02, 15, 16, 17, 25
220kV Theba SS
GIS 1 GIS 2-2 GIS 2-1
VPCL PH-2 Aux.
© ABB| Slide 20September 21, 2016
Load Flow StudiesCase Study – 01 : Impact of Closing Tie Lines
.1. Special load flow case was designed
to have increased reliability level.
2. Checked the capacity of existing tielines under normal conditions
3. Capacity found within limits.
4. Margins available were known fornormal operating mode.
5. Voltage variation wrt cable lead lengthwere also within permissible limits.
© ABB| Slide 21September 21, 2016
Load Flow StudiesCase Study – 01 : Summary
Customer’s Need§ Need to Review the existing system§ Ensure high availability§ Avoid under voltage and over voltage.§ Evaluate system under different loading conditions
ABB’s Response§ A complete detail load flow study§ Suggestion of uniform taps within transformers to have voltage profile
within limits§ Analyzing special cases with Tie line closed to evaluate the margin
available and voltage variation.
Customer Benefits§ Reliable power system network§ Voltage profile in tolerable margins§ No over loading of equipments / cables under normal loading conditions
© ABB| Slide 23September 21, 2016
Load Flow StudiesCase Study – 01 : Impact of Closing Tie Lines
.
1. During Peak load conditions, no over voltage condition found at any voltage level till 400kV
2. Under voltage condition found on 132kV and 220kV system.
3. Challenges identified and solutions proposed.
120
122
124
126
128
130
132
1 2 3 4 5 6 7 8 9 10 11 12 13
Voltage at 132kV System
121.5kV,92.11%
202204206208210212214216218220
1 2 3 4 5 6 7 8 9 10
Voltage at 220kV System
202.8kV,92.18%
208.9kV,94.97%125.1kV,
94.78%
© ABB| Slide 27September 21, 2016
Load Flow StudiesCase Study – 03 : Optimal Separation Points (Distribution n/w)
. Before After
Typical Cost saving IllustrationkWh Cost:0.10 $/kWh, Losses saving:160 kW : 160 kW * 8760 h * 0.10 $/kWh = $ 140,160
If the prototype represents 5% of the overall system, the total savings amount is $2,803,200
Network fed by two Substations
Reference : NEPLAN
© ABB| Slide 28September 21, 2016
Load Flow StudiesCase Study – 03 : Optimal Separation Points (Distribution n/w)
NEPLAN®
First level§ Second level
- Third level
• Optimal topology is found with appropriatesoftware packages through the closing ofa jumper that links two feeders and theopening of another so as to maintain theradial condition of the feeders
• The procedure is carried out in order tohave a better operation condition of thenetwork and specifically to reduce thelosses due to the Joule effect
Utilizing Smart Tools Title
© ABB| Slide 29September 21, 2016
Load Flow StudiesCase Study :04 Increase Generation Capacity
1. . 220kV GRID
33kV Board-1
G1 (39MVA) G2 (39MVA) G3 (39MVA) G4 (39MVA) G5 (39MVA) G6 (39MVA) G7 (39MVA) G8 (39MVA) G9 (39MVA)
TIE-1 TIE-233kV Board-2 33kV Board-3TIE -3
Grid Transformers53MVA, 220/34.5kV
Generator Transformers53MVA, 11kV/34.5kV
© ABB| Slide 30September 21, 2016
Load Flow StudiesCase Study – 04 : Increase in generation Capacity.
NEPLAN®
First level§ Second level
- Third level
• System studies for world’s largestpetrochemical refinery.
• Value creation by utilizing existing assetsand optimizing investment.
• Generator curves referred to see theextent improvement possible.
• Coordination with customer and Generatormanufacturer by ABB team.
Load Flow Studies Title
© ABB| Slide 31September 21, 2016
Load Flow StudiesCase Study – 04 : Increase in Generation Capacity.
Total 89 MVAR of Capacitors Proposed at 6.6kV BoardsTotal 89 MVAR of Capacitors Proposed at 6.6kV Boards
Margin of Active power (P) availability from capability curve
GTG
Before reactive power compensation After reactive power compensation Increasein ratedmargin
afterRPC
P(MW)
operatingP (MW) p.f
Rated P(MW) fromPQ curve
Marginavailable
w.r.t rated P(MW)
operatingP (MW) p.f
Rated P(MW) fromPQ curve
Marginavailable
w.r.t ratedP (MW)
1 26 0.8 31.17 5.17 26 0.9 35.07 9.07 3.902 26 0.8 31.17 5.17 26 0.9 35.07 9.07 3.903 26 0.8 31.17 5.17 26 0.9 35.07 9.07 3.904 26 0.8 37.94 11.94 26 0.9 42.52 16.52 4.595 26 0.8 31.17 5.17 26 0.9 35.07 9.07 3.906 26 0.8 37.94 11.94 26 0.9 42.52 16.52 4.597 26 0.8 37.94 11.94 26 0.9 42.52 16.52 4.598 26 0.8 31.17 5.17 26 0.9 35.07 9.07 3.909 26 0.8 38.00 12.00 26 0.9 42.00 16.00 4.00
Total increase in Generation(MW) after reactive power compensation 37.24
© ABB| Slide 32September 21, 2016
Load Flow StudiesCase Study – 04 : Summary
Customer’s Need§ Need to Review the existing system§ Ensure high availability§ Optimize cost by increasing Active Power Generation
ABB’s Response§ A complete detail load flow study§ Identification of the active and reactive power at the generator bus.§ Load flow study followed by Reactive Power study§ Reactive power compensation proposed at the Generator bus
Customer Benefits§ Higher Active Power Availability§ Low Investment§ Huge Optimization in cost§ Solution implemented at site.
© ABB| Slide 33
1. It forms the fundamental base for different studies in Power System
2. It gives many useful parameters which also helps to optimize the overall system
3. It can find the system elements which are getting loaded maximum
4. Need of Voltage compensating device can also be found out
5. System losses can be estimated & minimized.
6. Helps to improve the system economy
7. Different methods are utilized and different software's are also utilized to do this study.
8. Online Load flow analysis is very important tool for Power Engineers. It can be integrated withGIS system and can fetch input from SCADA.
September 21, 2016
Load Flow StudySummary
A very useful tool for all the Power System Engineers and PlannersA very useful tool for all the Power System Engineers and Planners
© ABB| Slide 34September 21, 2016
Short CircuitSpeaker Introduction
© ABB| Slide 35September 21, 2016