7/24/2019 Impact of Voltage Reduction on Load, Line Loss and Generation
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Impact of Voltage Reduction on
Load, Line Loss and generation
Sushanta Paul
Prof. Ward Jewell
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Introduction
Numerous voltage reduction program for
conservation or peak-load reduction are in use
in the USA and around the world
Design of this program has been based on
experimental evidence
This work presents technical analysis on the
impact of voltage reduction on load, line loss
and generation
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Impact of load type on line loss and load
demand
Constant Power Load: , current
will Increase, as a result line loss will increase
Constant Current load: , since current
remains constant, no change in line loss
Constant Impedance Load: , again
, finally current will decrease, as a result line loss
will decrease
*)tan( IVtconsjQP
*
)tan(
VjQPtconsI
jQP
VtconsZ
2
)tan(
V
jQPI
*
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Impact of Voltage Reduction on Line
Loss for Composite Load ModelConst. PQ load dominant:
Increasing effect of line loss for const. PQ loadswill dominate the decreasing effect of line loss forconst. Z loads resulting in the increase in line loss
Const. Z load dominant: Decreasing effect of lineloss for const. z loads will dominate the increasingeffect of line loss for const. PQ loads resulting inthe decrease in line loss
Const. I load dominant: Line loss will increase if% const. PQ load > % const. Z load or loss willdecrease if % const. Z load > % const. PQ load
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Impact of Load Model on Load, Line LossLoad Model Power Consumption Line Loss
Constant Power Constant Increase
Constant Current Decrease Constant
Constant Impedance Decrease Decrease
Composite Load
(i) Constant Power load
dominant
(ii) Constant Current
load dominant
(iii) Constant impedance
load dominant
Decrease
Decrease
Decrease
Increase
Increase if % of const.
power load > % of const.
impedance load
or
Decrease if % of const.
impedance load > % ofconst. power load
Decrease
PLoad
P
ZP ILoad
I
Load PP ,
ZP ILoad
I
Load
P
Load PPP
ZLoad
P
ZLoad
I
Load
I
Load
P
Load PPPP ZP
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Variation in Active power Generation: Pgen = PLoad + PLoss
Impact of Reduced Voltage on Active Power Generation
Decrement positive, Increment negative
Therefore, PLoad + PLoss > 0
PGen > 0 i.e. active power generation will decrease
Again,
By (1) and (2),
(2)
(3)
(1)
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Variation in reactive power generation:
Due to voltage reduction, reactive power will decrease if,
(4)
Or increase if,(5)
Now at reduced voltage,
System with dominant constant P,Q load:and
Equ. (5), i.e. reactive power generation will increase
System with dominant constant Z load:
Equ. (4), i.e. reactive power generation will decrease
Since;
Equ. (5), i.e. reactive power generation will increase
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System with dominant constant I load:
Equ. (4), i.e. reactive power generation will decrease
Equ. (5), i.e. reactive power generation will increase
Impact of Voltage Reduction on Power Consumption
Composite Load ModelActive Power
Generation
Reactive Power
Generation
Const. PQ Load
Dominant Decrease IncreaseConst. Z Load
DominantDecrease
Decrease, if
Increase, if
Const. I Load
DominantDecrease
Decrease, if
Increase, if
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800
806 808 812 814
810
802 850
818
824 826
816
820
822
828 830 854 856
852
832
888 890
838
862
840
836860834
842
844
846
848
864
858
Const. PQ load
dominant
Const. Z load
dominant
IEEE 34-bus System
Load under regulator 814:
Const. PQ: 195 kW, 97 kVAr
Const. Z: 34 kW, 17 kVArConst. I: 45 kW, 22 kVAr
Capacitors under regulator 852: 750 kVAr
Sub-
station
Voltage
(V)
Total LoadTotal Line
Loss
Power
Supplied
from
Substation
(kW)( kVAr) (kW) (kVAr)(kW) (kVAr)
122 1772 1053 278 197 2050 451
121 1772 1053 278 197 2050 451
120 1770 1052 279 198 2048 452
119 1767 1050 280 199 2047 452
118 1764 1049 282 199 2046 453
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Load under regulator 852: Const. Z Load Dominant
Const. Z: 566 kW, 395 kVAr, Const. I: 517 kW, 266 kVAr Const. PQ: 341 kW, 210 kVAr
Sub-
station
Voltage
(V)
Total Load Total Line Loss Power Generation
(kW) ( kVAr) (kW) ( kVAr)(kW) (kVAr) (kW) (kVAr) (kW) (kVAr) (kW) (kVAr)
124 1772 1053 1771 1052 278 197 310 219 2050 452 2081 873
123 1772 1053 1771 1052 278 197 310 219 2050 452 2081 873
122 1762 1046 1761 1046 275 196 307 217 2037 453 2068 869
121 1745 1036 1748 1038 270 193 303 214 2016 455 2051 864
120 1732 1027 1733 1028 266 190 297 211 1999 456 2030 858
Load under regulator 852: Const. I Load Dominant
Const. I: 566 kW, 395 kVAr, Const. Z: 517 kW, 266 kVAr, Const. PQ: 341 kW, 210 kVAr
Sub-
station
Voltage(V)
Total Load Total Line Loss Power Generation
(kW) ( kVAr) (kW) ( kVAr) (kW) (kVAr) (kW) (kVAr) (kW) (kVAr)(kW) (kVAr)
124 1730 1028 1728 1027 256 181 287 201 1986 412 2014 831
123 1730 1028 1728 1027 256 181 287 201 1986 412 2014 831
122 1721 1023 1719 1022 253 179 283 199 1974 414 2002 828
121 1709 1016 1708 1015 249 176 279 196 1958 417 1987 825
120 1695 1008 1694 1007 245 173 274 192 1936 421 1968 820
Increase inreactive power
Decrease inreactive power
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0.920.940.96
0.981
1.021.04
0.965 0.9736 0.9822 0.9908 0.9994 1.008 1.0166
Gen. (Const. PQ load dominant) Gen. (Const. Z load dominant
Gen. (Const. I load dominant) Load (Const. PQ load dominant)
Load (Const. Z load dominant) Load (Const. I load dominant)
Voltage (V)
Gener
ation
(pu)
Load
(pu)
Active Load and Generation vs. Voltage
Const. PQ load
Const. Z load
Reactive Load and Generation vs. Voltage
Const. PQ load
0.750.785
0.820.855
0.890.925
0.960.995
0.965 0.9735 0.982 0.9905 0.999 1.0075 1.016
Gen.(Const. PQ load dominant) Gen. (Const. Z load dominant)
Gen. (Const.I load dominant) Load (Const.PQ dominant)
Load (Const.Z load dominant) Load (Const. I load dominant)
Ge
neration
(pu)
Load
(pu)
Voltage
Const. Z loadConst. PQ load
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0.0298
0.0313
0.0328
0.0343
0.965 0.9736 0.9822 0.9908 0.9994 1.008 1.0166Loss (Const. PQ load dominant) Loss (Const.Z load dominant)
Loss (Const. I load dominant)
Voltage(V)
Line
Loss(pu) Const. PQ load
Const. I load
Const. Z load
-0.00028
0.00772
0.01572
0.02372
0.03172
0.03972
0.04772
0.055720.06372
0.07172
0.07972
0.965 0.9736 0.9822 0.9908 0.9994 1.008 1.0166
Gen. decr. (Const.PQ load dominant) Gen. decr. (Const. Z load dominant)
Gen. decr. (Const. I load dominant) Load decr. (Const. PQ load dominant)
Load decr. (Const.Z load dominant) Load decr. (Const. I load dominant)
Loss incr. (Const. PQ load dominant) Loss decr. (Const.Z load dominant)
Loss incre. (Const. I load dominant)
Generation
decrease
(pu)
Load
decrease
(pu)
Lossdecrease/increa
se(pu)
Voltage
Line Loss vs. Voltage
Decrease/Increase in Load, Line Loss and Generation vs. Voltage
Const. Z load
Const. I load
Const. PQ load
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ConclusionDue to voltage Reduction:
A decrease in both active and reactive load for all composite
load model
Line Loss increases for dominant const. PQ load, decreases for
dominant const. Z load and for dominant const. I load line loss
will increase if % const. PQ load > % const. Z load or decrease
if % const. PQ load < % const. Z load
Active power generation decreases for all composite load
model
Reactive power generation increases for const. PQ load. For
const. Z and I load, reactive power generation decreases if
or increases if