Nihar S Raj, Business Head – Power Consulting (Asia ... · ... Business Head – Power Consulting (Asia) , Presentation, Intercontinental, 22nd Sep 2016 © ABB ... Power System

© 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

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September 21, 2016

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Load Flow StudiesAgenda

1. What is Load Flow Studies2. Basic Equations3. When do I need it ? Is it advantageous4. Case Studies


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.


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…


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.


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



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,




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


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


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


Load Flow Studies – NEPLAN®Result Visualization

1. .


Load Flow Studies – NEPLAN®Result Visualization

1. .

Load flow results


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.


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


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.


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.



.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.


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



.

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%


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


Load Flow StudiesCase Study – 03 : Optimal Separation Points (Distribution n/w)

NEPLAN®


- 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


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


Load Flow StudiesCase Study – 04 : Increase in generation Capacity.

NEPLAN®


- 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


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


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


Short CircuitSpeaker Introduction


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Nihar S Raj, Business Head – Power Consulting (Asia ... · ... Business Head – Power Consulting (Asia) , Presentation, Intercontinental, 22nd Sep 2016 © ABB ... Power System