EE544 Distribution 1

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EE544 Distribution 1

• Distribution Feeder Analysis
• Regulation of Voltages

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Feeder Analysis

• Feeder Analysis
• Voltage Regulation
• Load Tap Changers
• Regulators
• Line Drop Compensators

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Transformer Modeling
Transformer taps for voltage regulation Basic
Single Phase Transformer and model Modeling
transformer to integrate into distribution power
flow - Admittance Matrix - ABCD matrix for
ladder method
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Single Phase Transformer- Model
1
3
z1/y
V3-V4 -
a(V3-V4) -
V1-V2 -
I3
More general Admittance Matrix I1 y
-ay -y ay V1 I2 -y
ay y -ay V2 I3
-ay a2y ay -a2y V3 I4
ay -a2y -ay a2y
V4
V1
I1-I3/a
4
2
I4
I2
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Single Phase Transformer- Model
z1/y
V2 -
aV2 -
V1 -
I2
Basic equations V1 aV2 z I1 V1 aV2
z I2/a I2 a I1 I1 I2/a Kersting
generalized matrix ( p 187-189 2nd Ed. Note
ntN2/N11/a And Zt is refered to secondary,
i.e., Zt z/a2 nt z V1 a z/a
V2 ABCD form I1 0
1/a I2 V2 1/a -z/a V1
Inverse ABCD form I2 0
a I1
I1I2/a
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye-wye grounded transformer
Is1
Is2
Is3
Zs
Zs
Zs
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye-wye grounded transformer
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Wye- ungrounded Delta transformer
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Wye- ungrounded Delta transformer
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Wye- ungrounded Delta transformer
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Wye- ungrounded Delta transformer
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Wye- grounded Delta transformer
Modify Y for source impedance and set up current
vector Then solve
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Wye- grounded Delta transformer
Modify Y for source impedance and set up current
vector Then solve
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Wye- grounded transformer
VLGABC At VLGabc Bt Iabc
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Wye- grounded transformer
VLGabc at VLGabc bt Iabc
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Autotransformer
V2 V1 Vx V1 (N2/N1) V1 Vx (N2/N1)
V1 V1/V2 N1/ (N1N2) a Ic I2 (N2/N1) I1
I2 Ic I2 I2 N2/N1 I1/I2 (N1N2) / N1
1/a
X1
V2 -
Vx -
I2
N2
H1
V1 -
X2
I1
N1
Ic
Same properties as a two winding transformer No
electrical isolation
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Autotransformer
S2 V2 I2 Delivered VA Sx Vx
I2 rating of x coil Sc V1 Ic
rating of c coil
X1
V2 -
Vx -
I2
N2
H1
V1 -
X2
I1
N1
Sc Sx V1 / (I2 N2/N1) V2I2 N2 /(N1
N2) V2I2 (N2/N1)(N1 /(N1 N2) Sc Sx
S2 (1-a) ltlt S2 a 1 ( note alt 1 for
configuration shown)
Ic

• Much smaller than equivalent two winding
  transformer
• EHV substation/switching transformers
• Voltage Regulator

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Autotransformer
S2 V2 I2 Delivered VA Sx Vx
I2 rating of x coil Sc V1 Ic
rating of c coil
X1
V2 -
Vx -
I2
N2
H1
V1 -
X2
I1
N1
Sc Sx V1 / (I2 N2/N1) V2I2 N2 /(N1
N2) V2I2 (N2/N1)(N1 /(N1 N2) Sc Sx
S2 (1-a) ltlt S2 a 1 ( note alt 1 for
configuration shown)
Ic

• Much smaller than equivalent two winding
  transformer
• EHV substation/switching transformers
• Voltage Regulator

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Type B Voltage Regulator
16 5/8 taps /- 10 a .9 1.1
Sc 0.1 S2
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Effect of Voltage Regulator
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Effect of Voltage Regulator
287 KVA 0.0.87 pf lag
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C3 b
Sub
C1 5000 C1 5000
3
4
1
2
C3 a
618 KVA 0.874 pf lag
13800 kV
732 KVA 0.82 pf lag
Source impedance j0.005 pu
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221 KVA 0.9 pf lag
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Effect of Voltage Regulator
S,H
L,X
a
A
1
1 2 3
Sub
4 5 6
3
4
2
1
2
B
b
13800 kV
C
c
Source impedance j0.005 pu
1
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Effect of Voltage Regulator
Phase a 3 Phase b 3 Phase c 2
Raise LTC Tap 8
Initial Loading
Peak Loading(2X)
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Voltage Regulator Automatic Control
The Line Drop Compensator - Controller that
drives the tap-changing mechanism
Microprocessor
-Vlevel
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Voltage Regulator Automatic Control
The Line Drop Compensator - Controller that
drives the tap-changing mechanism
Vlevel Desired Voltage at Load
Center BW Bandwidth (V)
Microprocessor
Delay Motor 30Sec
VR Vreg-Icomp Z VRltVlelvelBW/2gtRaise VR
gtVlelvelBW/2gtLower
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Voltage Regulator Automatic Control
For our feeder ( Peak Load) Load Center bus
3 Desired voltage Vlevel 122 V Feeder
peak current 180 A 200 A gt CT rating 200-5
A Ratio Nct 40 CTp/CTs Ratings CTp 200
Cts5 A Substation nominal l-n voltage 7967 V
gt PT rating 7967 120 V Ratio NPT
7967/120 Impedance to load center (Positive
Sequence) (Ohm)
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Voltage Regulator Automatic Control
We want VR Vreg-Icomp Z to mimic Load
center voltage VLC VLC Vsub I Z VR
(Vsub/Npt) (I /Nct) Z Let Z (Nct/Npt) Z
ohms VLC Npt Vr Z is calibrated in volts
i.e. in terms of rated secondary CT
current Multiplied by Z Z CTs (Nct/Npt) Z
CTp Z / Npt
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Voltage Regulator Automatic Control
Initially regulator tap is normal and a 1
Actuals
0.98 0.986 0.991
Regulator does not Know about laterals
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Voltage Regulator Automatic Control
Using Power Flow Program for Settings
Distribution power flow programs have a
setting Computation feature Model the LDC
computation Determine Tap needed Calculate Z by
phase
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Voltage Regulator Automatic Control
Other Regulator Connections
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Voltage Regulator Automatic Control
Other Regulator Connections
Regulator sees Ia In balanced case Ia
(Ia/v3)/30deg
Changing Tap in one Phase affects all phases
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Voltage Regulator Automatic Control
Other Regulator Connections