ETAP 5.
0
Transformer MVA Sizing
Copyright 2003 Operation Technology, Inc.
Transformer MVA Sizing
Based on ANSI C57 and IEC 60076 standards Considers multiple cooling stages and transformer types (3-phase & 1-phase) Considers altitude correction factors Considers temperature correction factors Load variation Considers short-circuit impedance requirements Use connected load or operating load to size the transformer
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 2
MVA Sizing Page
Transformer MVA Loading Short-Circuit Impedance limits
Correction Factors & Load Variation
Sizing Results Section Larger Required Smaller Impedance
Consider Growth Factor for Max. MVA
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 3
Temperature Correction
Ambient temperature in degree Celsius For air cooled transformers use the air ambient temperature For water cooled transformers use the water temperature Based on C57.92-1981 and IEC 76-2
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 4
Altitude Correction
Derate the transformer capacity based on altitude of the installation Derating starts above 1000 m or 3300 ft Based on C57.92-1981 and IEC 76-2
800 meter
900 meter
1000 meter
1100 meter
1200 meter
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 5
Load Variation
Growth Factor
Allowance for future load growth
Load Factor
The ratio of the average load to the peak load over a designated period of time Load Factor = 100 x ( kWi x Ti ) / ( kWp x Tt )% Load Factor = 100 x E / ( kWi x Tt )%
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 6
Where: I = interval of time when the load is non-zero kWi = load at interval i Ti = number of hours of interval i kWp = peak load Tt = Ton + Toff Ton = total hours when the load is on Toff = total hours when the load is off E = energy (kWh) consumed by load over the interval
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 7
Short-Circuit Impedance Size Requirement
Use Primary Short-Circuit kA and FLA to Calculate Impedance Primary 3-Phase FLA = MVA / (kVLL *3) Primary 1-Phase FLA= MVA / (kVprimary) Zcalculated =100*(FLAprimary / ISC_primary)
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 8
Connected or Operating Load
Connected Load
Determine the radial load connected to the transformer secondary Can include spare loads for conservative results
Operating Load
PowerStations load flow program determines the power flow through the transformer Automatically updated in the transformer required MVA field (load flow study case info page option) Can determine loading in radial or looped systems
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 9
Sizing Results and Automatic Updating
Sizing results include MVA and % Z for
Required Size (Actual calculated Size) Next Standard Larger Size Next Standard Smaller Size
Automatically Update the calculated rated MVA, Max MVA and % Z into the Rating page of the transformer
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 10
Transformer MVA Sizing Page Update automatically when you press these buttons
Transformer Rating Page
Transformer Rating Page
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 11
ETAP 5.0
Unit Transformer Sizing
Presented by Farrokh Shokooh
Copyright 2003 Operation Technology, Inc.
Unit Transformer Sizing
Based on IEEE C5F-116 Standard Optimize unit transformer turn ratio Consider system voltage variation Consider generation station auxiliary load Automatically detect generator, cable impedance and bus nominal kV Generator reactive vs. capacitive plots Optimization reports
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 13
Transformer Tap Optimization Page
Transformer Impedance Section Primary / Secondary Cable Impedance Generator Information System kV Information
Auxiliary Load Information Optimization Results Section
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 14
Automatic System Parameter Update
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 15
Primary Fixed Tap Editor
Use 0.1% Tap Step to obtain best Optimization results Set the maximum/minimum fixed tap range
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 16
MVAR Delivery Curve
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 17
Unit Transformer Tap Optimization Reports
Input Data Optimal Tap Position Transformer Power Input and output at different system voltage levels (system voltage variation) Generator Power Output at different system voltage levels Generator and System voltage at different system voltage levels
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing Slide 18
Copyright 2003 Operation Technology, Inc. Workshop Notes: Transformer Sizing
Slide 19
