©1996-2009 Operation Technology, Inc. – Workshop Notes: Short-Circuit IEC

Studi Aliran Daya

©1996-2009 Operation Technology, Inc. – Workshop Notes: Short-Circuit IEC

LEADING & LAGGING

POWER FACTORS

jQP

IV

SS

IVS

LL

LN

*

13

*1

3

3

Power in Balanced 3-Phase Systems

Lagging Power Factor Leading Power Factor

Inductive loads have lagging Power Factors. Capacitive loads have leading Power Factors.

Current and Voltage

Power in Balanced 3-Phase Systems

Leading Power Factor

Lagging Power Factor

ETAP displays lagging Power Factors as positive and leading Power Factors as negative. The Power Factor is displayed in percent.

jQ P

Leading & Lagging Power Factors

P - jQ P + jQ

©1996-2009 Operation Technology, Inc. – Workshop Notes: Short-Circuit IEC

PER - UNIT

Jika telah memiliki dua parameter dasar

Maka dua parameter lain dapat dihitung menggunakan rumusan dalam kurung.

The different bases are:

•IB (Base Current)

•ZB (Base Impedance)

•VB (Base Voltage)

•SB (Base Power)

3-Phase Per Unit System

B

actualpu

B

actualpu

Z

ZZ

I

II

B

actualpu

B

actualpu

S

SS

V

VV

ETAP selects for LF:

100 MVA untuk SB adalah fixed untuk seluruh sistem.

Rating kV menggunakan titik acuan dari ratio belitan transformator digunakan untuk menentukan tegangan dasar (basis) untuk bagian sistem yang berbeda.

3-Phase Per Unit System

Example 1: The diagram shows a simple radial system. ETAP akan mengkonversi nilai impedansi cabang sesuai dengan basis yang tepat untuk perhitungan Load Flow .

The LF reports show the branch impedance values in percent. The transformer turn ratio (N1/N2) is 3.31 and the X/R = 12.14

2B

1B kV

2N

1NkV

Transformer Turn Ratio: Rasio belitan trafo digunakan ETAP untuk menentukan tegangan basis pada bagian yang berbeda dari sistem. Different turn ratios are applied starting from the utility kV rating.

Untuk menentukan tegangan basis

1BkV

2BkV

2

pu

pu

RX

1

RX

ZX

Transformer T7:

Persamaan untuk mencari impedansi transformer T7 adalah 100 MVA base.

06478.0)14.12(1

)14.12(065.0X

2pu

Transformer T7:

Persamaan untuk mencari impedansi transformer T7 adalah 100 MVA base.

RX

xR pu

pu

005336.014.12

06478.0R pu

06478.0)14.12(1

)14.12(065.0X

2pu

005336.014.12

06478.0R pu

The transformer impedance must be converted to 100 MVA base and therefore the following relation must be used, where “n” stands for new and “o” stands for old.

)3538.1j1115.0(5

100

5.13

8.13)06478.0j1033.5(

S

S

V

VZZ

23

oB

nB

2

nB

oBo

punpu

38.135j15.11Z100Z% pu

Impedance Z1: Tegangan basis ditentukan menggunakan rasio belitan trafo. Impedansi basis untuk Z1 ditentukan menggunakan tegangan basis pada Bus5 dan MVA basis.

0695.431.3

5.13

2N1N

kVV utility

B

165608.0100

)0695.4(

MVA

VZ

22B

B

N1/N2 =13,8/4,16 = 3,31

8.60338.60100% jZZ pu

)0382.6j6038.0(1656.0

)1j1.0(

Z

ZZ

B

actualpu

Nilai per-unit dari impedansi dapat ditentukan secara cepat setelah impedansi basis diketahui. Nilai ini dapat dilihat secara langsung dengan mengali dengan seratus persen.

This value will be the value displayed on the LF report.

The LF report generated by ETAP displays the following percent impedance values in 100 MVA base

Load Flow Analysis

Load Flow Problem• Given

– Load Power Consumption at all buses– Configuration– Power Production at each generator

• Basic Requirement– Power Flow in each line and transformer– Voltage Magnitude and Phase Angle at each bus

Lingkup Kajian Studi Aliran Daya(Determine Steady State Operating Conditions)

– Voltage Profile– Power Flows– Current Flows– Power Factors– Transformer LTC Settings– Voltage Drops– Generator’s Mvar Demand (Qmax & Qmin)– Total Generation & Power Demand– Steady State Stability Limits– MW & Mvar Losses

Mendapatkan Ukuran dan Parameter

• Cable / Feeder Capacity• Capacitor Size• Transformer MVA & kV Ratings (Turn Ratios)• Transformer Impedance & Tap Setting• Current Limiting Reactor Rating & Imp.• MCC & Switchgear Current Ratings• Generator Operating Mode (Isochronous / Droop)• Generator’s Mvar Demand• Transmission, Distribution & Utilization kV

Optimize Operating Conditions• Tegangan bus sesuai batas yang dapat diterima/

Bus Voltages are Within Acceptable Limits

• Tegangan dan rating isolasi peralatan/ Voltages are Within Rated Insulation Limits of Equipment

• Aliran daya dan arus tanpa melampaui batas rating maksimum/ Power & Current Flows Do Not Exceed the Maximum Ratings

• Menentukan losis MW dan MVAR/ System MW & Mvar Losses are Determined

• Menghilangkan sirkulasi aliran MVAR/ Circulating Mvar Flows are Eliminated

Assume VR

Calc: I = Sload / VR

Calc: Vd = I * Z

Re-Calc VR = Vs - Vd

Proses Perhitungan

• Non-Linear• Secara iteratif

– Asumsi Tegangan Beban/LoadVoltage (Initial Conditions)

– Menghitung arus I– Menghitung Voltage Drop Vd

berdasarkan Arus.– Hitung ulang tegangan VR– Gunakan lagi Tegangan Beban/Load

Voltage sebagai kondisi initial sampai diperoleh hasil sesuai tingkat presisi yang dispesifikasi .

1. Accelerated Gauss-Seidel Method

• Low Requirements on initial values, but slow in speed.

2. Newton-Raphson Method

• Fast in speed, but high requirement on initial values.

• First order derivative is used to speed up calculation.

3. Fast-Decoupled Method

• Two sets of iteration equations: real power – voltage angle, reactive power – voltage magnitude.

• Fast in speed, but low in solution precision.

• Better for radial systems and systems with long lines.

Metode Perhitungan

kV

kVAFLA

kV

kVAFLA

EffPF

HP

EffPF

kWkVA

Rated

Rated

RatedRated

1

33

7457.0

PF dan Efisiensi pada saat kondisi pembebanan 100 %

kV

kVA1000I

)kV3(

kVA1000I

kVA

kWPF

)kVar()kW(kVA

1

3

22

NAME PLATE BEBAN

kV

kVAFLA

kV

kVAFLA

EffPF

HP

EffPF

kWkVA

Rated

Rated

RatedRated

1

33

7457.0

Where PF and Efficiency are taken at 100 % loading conditions

kV

kVA1000I

)kV3(

kVA1000I

kVA

kWPF

)kVar()kW(kVA

1

3

22

Load Nameplate Data

Constant Power Loads• In Load Flow calculations induction,

synchronous and lump loads are treated as constant power loads.

• The power output remains constant even if the input voltage changes (constant kVA).

• The lump load power output behaves like a constant power load for the specified % motor load.

• In Load Flow calculations Static Loads, Lump Loads (% static), Capacitors and Harmonic Filters and Motor Operated Valves are treated as Constant Impedance Loads.

• The Input Power increases proportionally to the square of the Input Voltage.

• In Load Flow Harmonic Filters may be used as capacitive loads for Power Factor Correction.

• MOVs are modeled as constant impedance loads because of their operating characteristics.

Constant Impedance Loads

© 1996-2008 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis Slide 28

• The current remains constant even if the voltage changes.

• DC Constant current loads are used to test Battery discharge capacity.

• AC constant current loads may be used to test UPS systems performance.

• DC Constant Current Loads may be defined in ETAP by defining Load Duty Cycles used for Battery Sizing & Discharge purposes.

Constant Current Loads

Constant Current Loads

Exponential Load

Polynomial Load

Comprehensive Load

Generic Loads

Feedback Voltage •AVR: Automatic Voltage Regulation•Fixed: Fixed Excitation (no AVR action)

Generator Operation Modes

Governor Operating Modes• Isochronous: This governor setting allows the

generator’s power output to be adjusted based on the system demand.

• Droop: This governor setting allows the generator to be Base Loaded, meaning that the MW output is fixed.

Isochronous Mode

Droop Mode

Droop Mode

Droop Mode

Adjusting Steam Flow

Adjusting Excitation

Swing Mode•Governor is operating in Isochronous mode•Automatic Voltage Regulator

Voltage Control•Governor is operating in Droop Mode•Automatic Voltage Regulator

Mvar Control•Governor is operating in Droop Mode•Fixed Field Excitation (no AVR action)

PF Control•Governor is operating in Droop Mode•AVR Adjusts to Power Factor Setting

In ETAP Generators and Power Grids have four operating modes that are used in Load Flow calculations.

• If in Voltage Control Mode, the limits of P & Q are reached, the model is changed to a Load Model (P & Q are kept fixed)

• In the Swing Mode, the voltage is kept fixed. P & Q can vary based on the Power Demand

• In the Voltage Control Mode, P & V are kept fixed while Q & are varied

• In the Mvar Control Mode, P and Q are kept fixed while V & are varied

Generator Capability Curve

Generator Capability Curve

Generator Capability Curve

Field Winding Heating Limit

Armature Winding Heating Limit

Machine Rating (Power Factor Point)

Steady State Stability Curve

Maximum & Minimum Reactive Power

Field Winding Heating Limit Machine Rating

(Power Factor Point)

Steady State Stability Curve

Generator Capability Curve

Load Flow Loading Page

Generator/Power Grid Rating Page

10 Different Generation Categories for Every Generator or Power Grid in the System

Generation Categories

X

V)*COS(

X

*VVQ

)(*SINX

*VVP

X

V)(*COS

X

*VVj)(*SIN

X

*VV

jQPI*VS

22

2121

2121

22

2121

2121

222

111

VV

VV

Power Flow

Example: Two voltage sources designated as V1 and V2 are connected as shown. If V1= 100 /0° , V2 = 100 /30° and X = 0 +j5 determine the power flow in the system.

I

var536535.10X|I|

268j1000)68.2j10)(50j6.86(IV

268j1000)68.2j10(100IV

68.2j10I

5j

)50j6.86(0j100

X

VVI

22

*2

*1

21

2

1

0

1

Real Power FlowReactive Power Flow

Power Flow1

2

V E( )

Xsin

V E( )

Xcos

V2

X

0

The following graph shows the power flow from Machine M2. This machine behaves as a generator supplying real power and absorbing reactive power from machine M1.

S

ETAP displays bus voltage values in two ways

•kV value

•Percent of Nominal Bus kV

%83.97100%

5.13

min

alNo

Calculated

Calculated

kV

kVV

kV 8.13min alNokV

%85.96100%

03.4

min

alNo

Calculated

Calculated

kV

kVV

kV 16.4min alNokV

For Bus4:

For Bus5:

Bus Voltage

Lump Load Negative Loading

Load Flow Adjustments• Transformer Impedance

– Adjust transformer impedance based on possible length variation tolerance

• Reactor Impedance– Adjust reactor impedance based on specified tolerance

• Overload Heater– Adjust Overload Heater resistance based on specified tolerance

• Transmission Line Length– Adjust Transmission Line Impedance based on possible length variation

tolerance

• Cable Length– Adjust Cable Impedance based on possible length variation tolerance

Adjustments applied

•Individual

•Global

Temperature Correction

• Cable Resistance

• Transmission LineResistance

Load Flow Study Case Adjustment Page

Allowable Voltage DropNEC and ANSI C84.1

Load Flow Example 1 Part 1

© 1996-2009 Operation Technology, Inc. - Workshop Notes: Load Flow AnalysisSlide 57

Load Flow Example 1 Part 2

Load Flow Alerts

Bus Alerts Monitor Continuous Amps

Cable Monitor Continuous Amps

Reactor Monitor Continuous Amps

Line Monitor Line Ampacity

Transformer Monitor Maximum MVA Output

UPS/Panel Monitor Panel Continuous Amps

Generator Monitor Generator Rated MW

Equipment Overload Alerts

Protective Devices Monitored parameters % Condition reported

Low Voltage Circuit Breaker Continuous rated Current OverLoad

High Voltage Circuit Breaker Continuous rated Current OverLoad

Fuses Rated Current OverLoad

Contactors Continuous rated Current OverLoad

SPDT / SPST switches Continuous rated Current OverLoad

Protective Device Alerts

If the Auto Display feature is active, the Alert View Window will appear as soon as the Load Flow calculation has finished.

© 1996-2009 Operation Technology, Inc. – Workshop Notes: Load Flow Analysis Slide 62