IMPACT OF VOLTAGE REDUCTION ON
ENERGY AND DEMAND
A Thesis Presented to the Faculty of
The College of Engineering and Technology
Ohio University
In Partial Fulfillment
of the Requirements for the Degree
Master of Science
by
Khalil Matar
November 1990
ACKNOWLEDGEMENTS
I would like to express my sincere thanks to Dr. Hill for his kind advice
and good guidance through the course of my work in this thesis. I also wish to
thank my parents, brothers and sisters for their support and encouragement
during my study.
iii
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS
iii
LIST OF TABLES.
. • . .
vii
LIST OF FIGURES
ix
CHAPTER 1 -
INTRODUCTION
1
CHAPTER 2 -
ENERGY CONSERVATION PRACTICES BY
VOLTAGE REDUCTION
.
2.1
Definition of Voltage Reduction .
2.2
History of Voltage Reduction
2.3
Types of Voltage Reduction. .
2.4
Energy Sources and Uses . . • .
CHAPTER 3 -
VOLTAGE STANDARDS
3.1
Voltage Standards. . . . . . .
3.2
Service and Utilization Voltages . .
3.3
Explanation of Voltage Ranges
12
3.3.1 Voltage Spread . . . • •
12
3.3.2 Service Voltage Range A
12
Service Voltage Range B
. . . . 12
3.4
Voltage Regulations . . . . .
14
3.5
Primary and Secondary Voltage Spread. .
3.3.3
CHAPTER 4 -
. • . .
15
RESULTS OF FIELD TEST PERFORMED BY
UTILITIES . . .
17
4.1
Introduction
17
4.2
American Electric Power (Test I)
17
iv
Page
.·
.....·
4.3
American Electric Power (Test II)
4.4
Pacific Gas and Electric Test
4.5
Southern California Edison Test
· 24
4.6
San Diego Gas and Electric Test
· 27
CHAPTER 5 -
.
19
24
VOLTAGE REDUCTION STUDY AND STUDY
. . . 30
RESULTS . . . . . .
5.1
Introduction
• 30
5.2
Circuit Characteristics
· 30
5.2.1
Circuit No.1
· 30
5.2.2
Circuit No.2
• 33
5.2.3
Circuit No.3
· · • 34
5.3
Study Conditions
· 34
5.4
Distribution Circuit Analysis
· 35
5.4.1
5.5
Voltage Drop Calculation
Study Results . . .
· · • 35
· 36
5.5.1
Introduction
5.5.2
Study Results Corresponding to AEP Data
· · 36
(T es t II) . . . . . . . . . . . . . . . . . . . . 36
5.5.3
Study Results Corresponding to SDG&E
Data
5.5.4
. . . . . . . . . . . . . .
Study Results Corresponding to SCE
Data
CHAPTER 6 6.1
. . . . · 42
· · 47
CONCLUSION
Conclusion
• • 54
• 54
· · · ·
v
Page
CHAPTER 7 -
DISCUSSION AND RECOMMENDATIONS . . 56
7.1
Discussion
.···
7.2
Recommendations .
··..
56
57
7.2.1 Energy Conservation Experimental
Studies
···.....
7.2.2 Cost-Benefit Analysis
7.2.3 Energy Use.
REFERENCES
....
.
....
....···
vi
..··..
58
58
..··
58
60
LIST OF TABLES
Table
2.1
Characteristics and Examples of Voltage Reduction
Programs . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1
Standard Nominal System Voltages and Voltage
Ranges
4.1
· · · · · · · · · · . . . · · · · .
Energy Savings Due to Voltage Reduction-AEP System
(Test I) · · · · · · · · · · · · · · . · . · · ·
4.2
• • • 18
Demand Change During and After Voltage Reduction
Period-AEP System (Test I)
4.3
· · · 11
. . . . . . . . ..
. . . 20
Energy Savings Due to Voltage Reduction-AEP System
(Tes tIl). . . . . . . . . . . . . • . . . . . . . . . . . 21
4.4
Demand Reduction Due to Voltage Reduction-AEP System
(T est II)
4.5
Energy Consumption and Average Peak Demand-PG&E
System
4.6
23
. . . . . . . . . . . . . . . . . . .
• • • 25
Summary of Voltage Reduction Test Results-SCE
System
· · · · · · · · · · · · · · · · · · · · · · · · · 26
4.7
Voltage Reduction Test Results-SDG&E System
28
4.8
Load Response to Voltage on SDG&E System . .
• 29
4.9
Calculated Response of Various Loads-SDG&E
System
5.1
. . . . . . . . . . . . . . . . . .
• • • . 29
Energy Consumptions and Power Demands for the Three
Distribution Circuits
31
vii
Table
5.2
Utilities and Their Test Results Used in the Study of
the Three Distribution Circuits . . . . . . . . . .
5.3
Energy Savings and Demand Reductions Corresponding to
AEP Data (Circuit No.1)
5.4
• . . . . . . . . . . . . . . . . 37
Energy Savings and Demand Reductions Corresponding to
AEP Data (Circuit No.2)
5.5
. . . 32
. . . . . • . . . . . . . . . . . 40
Energy Savings and Demand Reductions Corresponding to
AEP Data (Circuit No.3)
• . . . . . . . . .
5.6
Summary of Cost-Benefit Analysis
5.7
Energy Savings and Demand Reductions Corresponding to
. • . 41
• • 43
SDG&E Data (Circuit No.2) . . . . . . . . . . . . . . . . 45
5.8
Energy Savings and Demand Reductions Corresponding to
SDG&E Data (Circuit No.3) . . • .
. . • .
5.9
Summary of Cost-Benefit Analysis
5.10
Energy Savings and Demand Reductions Corresponding to
SCE Data (Circuit No.2)
5.11
· • 48
. . . . . • . . . . . • . . . . . 50
Energy Savings and Demand Reductions Corresponding to
SCE Data (Circuit No.3)
5.12
· • 46
. . . .
Summary of Cost-Benefit Analysis
viii
· . 51
. 53
LIST OF FIGURES
Figure
2.1
Relationships between voltage reduction
programs . . . . . . . . . • .
7
2.2
Energy sources and uses in the U.S.
9
3.1
Distribution characteristic of system voltages. .
3.2
Comparison of ANSI with some AEP utilities voltage
spread
• . . . . . . . • . . . . . . • . . . .
ix
13
16
Chapter One
INTRODUCTION
Since the 1973 oil embargo, energy has become a national concern.
Oil
companies have been asked to find new resources, utilities have been asked to
produce and deliver at higher efficiency levels, and consumers have been asked to
conserve energy. As a result of the social, political and economical problems of
this energy crisis, many state regulatory agencies have requested or required that
utilities study or perform voltage reduction experiments to see if it is possible to
conserve energy by this means.
In response, utilities affected by this order
reduced their distribution voltage for energy conservation purposes. Others took
the agencies' request into consideration and performed experimental studies to
determine the impact of voltage reduction on energy consumption and on power
demand level as well. The results of these experiments varied between seasons,
circuits and utilities [1,2,3,5].
The subject of this thesis is the effect of voltage reduction on energy
consumption and power demand level.
The objective is to determine and
examine the impact of a 5% voltage reduction on energy and demand on three
distribution circuits serving approximately 2200 consumers in Ohio. Results of
this study will be used to determine if it is desirable for the Public Utility
Commission of Ohio (PUCO) to institute a new permanent service voltage range
of 120-Volt maximum and 114-Volt minimum, on a 120-Volt base, for energy
conservation. The new service voltage range would be a 6-Volt reduction in the
present range of 126-114 Volts.
Chapter One of this thesis is an introduction to voltage reduction.
Chapter Two presents a historical background on this subject.
Chapter Three
2
discusses voltage standards in use in the U.S. Chapter Four presents the results
of several experimental studies, conducted by utilities, involving the impact of
voltage reduction on energy and demand on distribution circuits. Chapter Five
covers a study on the effect of 5% voltage reduction on energy and demand on
the three distribution circuits previously mentioned. This chapter also presents
the result of this study.
Chapter Six presents the conclusion of this thesis.
Finally, Chapter Seven presents a discussion on voltage reduction as well as
recommendations for further investigation.
Throughout this thesis, voltage and percent voltage always refer to a
120-Volt base unless specified otherwise.
3
Chapter Two
ENERGY CONSERVATION PRACTICES BY VOLTAGE REDUCTION
2.1
DEFINITION OF VOLTAGE REDUCTION
Voltage reduction is a practice that has been routinely employed by many
electric utilities as an aid to energy conservation and as a method of reducing
system peak demand during emergency conditions or, in some cases, during daily
peak load periods. Generally, voltage reduction is employed for a relatively short
duration after which voltage is returned to normal [1,2,6].
2.2
HISTORY OF VOLTAGE REDUCTION
Voltage reduction for peak load shaving is not a new idea. It was used in
California in the spring of 1948 when, due to very dry weather, lack of hydrogeneration and capacity shortages, both voltage and frequency were reduced by
Pacific Gas and Electric Company (PG&E) in order to reduce system load during
peak load periods [11].
In 1973, during the Arab oil embargo, the Public Service Commission of
the state of New 'York directed all electric utilities subject to its authority to
reduce their distribution voltage as a means of reducing energy consumption.
Systems affected by this order were Consolidated Edison, Niagara Mohawk, New
York State Electric and Gas, Rochester Gas and Electric, Orange and Rockland,
Central Hudson, and Long Island Lighting [4,6,11]. Voltage reduction ranged
from three percent to five percent. Apparently, these utilities neither attempted
to quantify energy savings resulting from the voltage reduction nor to maintain a
114-volt lower voltage limit at all service delivery points. With the lifting of the
4
oil embargo, New York utilities were permitted to return to prior electric service
voltage level.
With the advent of the 1973 oil embargo and subsequent media coverage
of the oil shortage and its rising prices, the concept of voltage reduction as a
means of reducing energy consumption was conceived.
The media equated the
reduction in demand due to reduced voltage with a reduction in energy consumption.
In response to this misconception, American Electric Power (AEP)
conducted a one-year study to determine and examine the impact of voltage
reduction on energy use and demand level within their system.
Results of this
study, in which voltage was reduced by five percent for a four-hour period every
other weekday, indicated a total minimal reduction in energy use, approximately
six tenths of one percent, and a reduction in demand by three to four percent.
AEP concluded that voltage reduction as a means of reducing energy use was not
a viable approach for their system, due to the extensive capital investment
required to implement the program and the minimum savings in energy [2,6,11).
In September of 1979, AEP initiated a second test to assess the impact of
a twenty-four hour voltage reduction on energy use and demand level.
In this
test, during which voltage was reduced by five percent for twenty-four hour
period every other day, AEP utilized the same distribution circuits and followed
the same procedure of the first study in 1973. The test results showed that the
energy savings afforded by voltage reduction averaged 3.55 percent for a
twenty-four hour reduction period.
Also, the test showed that a reduction in
demand of approximately 4.0 percent was realized for a twenty-four hour voltage
reduction period [4].
In 1976 the California Public Utilities Commission (CPUC) directed the
electric utility companies subject to its regulation to institute a program of
5
customer voltage reduction for the purpose of reducing system peak loads. Fuel
shortages, with its rising prices and severe restrictions on the construction of new
generating plants, indicated that vigorous conservation efforts were required to
avoid energy capacity shortages. The Commission .based its action on the tactic
which had been used previously in the East and Midwest to alleviate capacity
shortages in the 1950's and 1960's. While these emergency voltage reductions
were intended mainly to reduce system peak loads, the Commission believed that
long-term energy conservation could be obtained by maintaining lower average
service voltage.
As a result, the Commission ordered the regulated electric
companies to reduce the service voltage from 126 volts to 122 volts wherever this
reduction could be implemented without any extensive capital expenditure. The
minimum service voltage remained at 114 volts [1,3]. For San Diego Gas and
Electric Company, it was possible to make reductions on 60 percent of the
distribution circuits. According to San Diego Gas and Electric Company, "These
reductions were made off peak, since the 114-volt minimum already existed
under peak-load conditions" [3].
In 1979 a new service voltage range was instituted by the CPUC, calling
for a maximum service voltage of 120 volts. This was a six-volt or five percent
reduction in the former voltage range of 114-126 volts. Utilities affected by this
order analyzed their distribution circuits and made cost-effective changes where
this would bring them into compliance [3].
The heat wave of the summer of 1988, coupled with drought and steady
economic growth, pushed total U.S. electric output to new records, beginning in
June and persisting into late August.
During this period, a number of power
pools and utilities managed the high demand by encouraging voluntary conservation measures and slight voltage reductions.
In addition, the high degree of
6
transmission integration between utility systems helped in purchased-power
arrangements between neighboring utility systems [10].
2.3
TYPES OF VOLTAGE REDUCTION PROGRAMS
Three types of voltage reduction programs have been employed by public
utilities. These programs are conservation voltage reduction, emergency voltage
reduction and routine voltage reduction [6]. The relationship between these three
programs is shown in Fig. 2.1 and their main characteristics are summarized in
Table 2.1 [6].
Voltage standards used in the United States are presented and
discussed in Chapter Three.
2.4
ENERGY SOURCES AND USES
Energy comes from five different sources and is used by four different
groups of consumers.
Fig. 2.2 presents these sources and groups [12].
As
indicated in this figure, utilities consume one-fourth of the total energy supply
for power generation. The remaining three-fourths of the total energy supply is
consumed by transportation systems, manufacturing, household and commercial
sectors [12].
7
127V
126V
~
c
Z
<
~
122 V
120V
~
e
<
E~
0
;>
114 V
110 V
~
~
~
~
....==
en
en
~
~
cz::
-~
~
E~
;::J
0
~0 "0cz::
Z
~
Z
0
~
E-e
;>
cz::
~
rJ'J
Z
0
U
U
~
c
Z
~
~
~
~
~
~
~
~
~
Fig. 2.1 Relationships between voltage reduction programs.
Purpose
Reduce
Demand
on Bulk
Power
System
Reduce
Peak
Demand for
Revenue
Billing
Reduce
Overall
Energy
Consumption
Experiment
x
x
x
x
x
_---- -..-.-----
x
x
x
x
x
x
x
------ ----_ ....
.....
x
x
x
---------- -------
Dmdil
Typical
Freguene!
Typical
Duration
American Electric Power
Duke Power
Pacific Gas and Electric
Southern California Edison
~-------------~--
City of Galgari Electric System
Cobb Electric Membership
North York Hydro
Scarborough Public Utility
Commission
I Operational I 0-10 per year
I 1-3 bourl
I 1-5 montbJ
~~
1 per year
Seasonal
[------r-----
Permanent
I o-s per month
-------r---------------
I Financial
-----------------r-------r--------r------
Consolidated Edison of New York
Louisiana Power and Light
Maritime Electric
New England Power Pool
Nova Scotia Power
Ontario Hydro
-----------------1-----------------------
OrCanizaUon
Primary
.--.----_.-...- .... ------ ------ ------ ----------------- ------- -------- ------
Energy
Conservation
------r------
Routine
Demand
Reduction
------r------
Emergency
Demand
Reduction
------r------
~
Standard
Procedure
Table 2.1
Characteristics and Examples of Voltage
Reduction Programs
00
9
Gas
Oil
(M
Coal
U1
~
::
33%
43%
20%
a
~
<=
u-.
~
z
i.,
=
~
TOTAL ENERGY
100%
Electric
Utilities
Transportation
Manufactures
Household
&
Commercial
25%
24.4%
27.5%
Fig. 2.2 Energy Sources and Uses in the U.S.
23.1%
10
Chapter Three
VOLTAGE STANDARDS
3.1
VOLTAGE STANDARDS
Standard voltages for use in the United States are specified by the
American National Standards Institute (ANSI) in standard ANSI C84.1 (1977).
The standard is called "Voltage Ratings for Electric Power Systems and Equipment (60 HZ)". The standard nominal system voltages and voltage ranges table
taken from this standard is shown in Table 3.1.
The table shows nominal
voltages and the permissible range of utilization and service voltages for normal
conditions.
The standard establishes voltage ratings for 60 HZ electric power
supply and utilization systems that operate from 100 volts through 230 KV,
together with operating tolerance from nominal voltages. It also makes recommendations to standardizing groups and committees with respect to voltage
ratings for equipment used on power systems and for utilization devices supplied
therefrom [6,7,9].
3.2
SERVICE AND UTILIZATION VOLTAGES
According to the ANSI standard, "service voltage" is measured at the
delivery point where the electric systems of the supplier and the user are
connected.
"Utilization voltage" is measured at the line terminals of the
utilization equipment, which should operate satisfactorily throughout voltage
Range A [7].
120
T.o·w'",
(I
126
S04Y/291
504
4S6Y/263 .
456
3~500
23000
13800
24940Y/14400
34S00Y/19920
20780Y/12000
22860Y/13200
13800Y/7970
12470Y/7200
13200Y/7620
21820Y/12600
2.4000V/13860
2.4150
20260Y/11700
22290Y/12870
22.430
~/
3J6~O
36230
7',\
~/
14490
13460
7'8\
11880
1.4.490Y/8370
13~60Y/n70
12420
24320Y/14040 26190Y/15120
33640Y/19420 36230Y/20920
l'~
12160Y/7020 13090Y/7560
l2870Y/7430 13860Y/8000
""'/
/'8\
""'/
8730Y.'50.40
12600Y/7270
8110Y!.4680
, 1700Y/6760
8320Y/.4800
12000Y/6930
59~0
41160
50.40
72.40
~680
6130
3600
4370
4050
.. 320
6210
2080
3600Y/2080
530
424Y/245
424
212
212/106
(Note d)
184Y/106
3740
2520
~370Y/2520
23.40
~050Y/23.40
(Note f)
106
106/212
tI."
UtllI ••
V.tt • .,.
(No •• e]
..800
6900
37~OY/2160
2160
550
440Y/254
440
630
252
228
570
252/126
228/114
220
Three-phase Systems
126/252
220/110
240/120
~160Y/2.400
11~
114/228
218Y/126
191Y/l10
480Y/277
(No •• e)
S.,.lu v.It•••
Single-Phase Sy,'ems
S.,.lc.
Velt. . .
U,lIh.tI.n .n4
197Y/114
110/220
110
(No ••
208Y/120
'our·.I,..
tI."
UIIIl ••
V.I....
41
25~0
BBOOY/50BO
12700Y/7330
5080
7260
4400
...400Y/25.40
22000Y/12700
2..200Y/13970
197..0Y/ll.400
21720Y/125..0
2J850
32780
36510
23690Y/13680 26400Y/15240
32780Y/18930 36510Y/21080
2~J~O
14520
1.4520Y/8380
13110
13110Y/7570
1l8S0Y /6840 13200Y!7620
12S40Y/7240 13970Y/8070
7900Y/.4560
11..00Y/6S80
41560
6560
3950
2280
3950Y/2280
635
(Note 1)
508
550
508Y/293
25~
254/127
220Y/127
127/254
127
Ser.'ce VeU. . .
Utili..... " ."4
Maximum
440
440Y/254
220
220/110
(No'.
191Y/110
110/220
110
s.r.'~
V.Ue. .
Minimum
(No'. bJ
Maximum
(No'. b)
Minimum
VOLTAGE RANGE 8
VOLTAGE RANGE A
4160
2~OO
(Note 1)
600
480
2~0
120/240
'h,...·.I,..
NOMINAL SYSTEM VOLTAGE
(Not. oJ
STANDARD NOMINAL SYSTEM VOLTAGES AND VOLTAGE RANGES
Table 3.1
~
~
12
3.3
EXPLANATION OF VOLTAGE RANGES
3.3.1 Voltage Spread
For any specific nominal voltage, the voltages actually existing at various
times on any power systems, group of systems or in the industry as a whole are
distributed by percentage in a manner such as that indicated by Fig. 3.1. This
distribution is characteristic of voltage at any point on the distribution system
[9] .
The operation of power systems and the design of equipment to be
supplied from such a system should be coordinated with respect to these voltage
variations so that the equipment will perform adequately and efficiently
throughout the range of actual utilization voltages encountered on the systems.
In order to further this objective, ANSI C84.1 establishes two ranges for service
and utilization voltage variations for each nominal system voltage, designated as
Range A and Range B, the limits of which are given in Table 3.1.
3.3.2 Service Voltage Range A
This range contains the majority of the existing operating voltages.
As
illustrated in Table 3.1, on a 120/240-volt nominal voltage system, the minimum
service voltage would be 114/228 volts and the maximum service voltage would
be 126/252 volts [7].
3.3.3 Service Voltage Range B
This range, which is also called the tolerable zone, includes operating
voltages slightly above and below service voltage Range A. This range is necessary because from practical field or operating conditions voltages slightly outside
of the limits of Range A often results, and they are considered as normal
13
(
(
110 V
114 V
)
Voltage
126 V
Fig. 3.1 Distribution Characteristic of System Voltages
127 V
14
operation, although not entirely desirable [7,9].
On a 120/240-Volt nominal
voltage system, voltage Range B would be 110/220 Volts minimum and 127/254
Volts maximum.
The limits of Range A and Range B apply to sustained voltage levels and
not to momentary voltage excursions that may result from such causes as
switching operations, locked rotor conditions, faults, etc. Voltage incursions into
Range B should be limited in extent, frequency and duration [7,9]. Conditions
causing such excursions require immediate attention and should be corrected
promptly.
3.4
VOLTAGE REGULATIONS
The voltage on a distribution line changes with load current.
During
off-peak periods, when load current is low, the difference in service voltage
between the customer closest to the voltage regulator and the customer at the
end of the regulator zone is small. As load current increases, the voltage to the
customer closest to the regulator is relatively unaffected, but the end-of-line
customer experiences a noticeable drop in voltage.
One common way to ensure that the end-of-line customer service voltage
does not drop below 114 volts is to set the regulator at the maximum permissible
voltage of 126 volts.
The closest customer will then have a constant service
voltage of 126 volts. The end-of-line customer will have a service voltage of 125
or 126 volts off-peak and, depending on the length of the distribution circuits, a
voltage that is less than that on-peak.
Another method of ensuring that no customer experiences a service
voltage less than 114 volts is to set the voltage regulator to supply 114 volts to
the end-of-line customers at minimum load.
This might result in a basic
IS
regulator setting of 115 volts. The regulator line drop compensator is then set to
automatically increase the line voltage as load current increases so that the
end-of-line customer will have a con.stant service voltage of 114 volts. The first
customer will then have a service voltage of 114 volts off-peak and again,
depending on the length of the distribution circuits and the amount of compensation required, a voltage that is more than that on-peak. Of the two methods,
the first method is most common, but the second method results in lower average
service voltages and is highly recommended for circuits that have zero load
growth rate and balanced load.
3.5
PRIMARY AND SECONDARY VOLTAGE SPREAD
Under normal conditions, utilities design their distribution voltage in
compliance with ANSI C84.1 (1977) voltage Range A.
Based on a 120-volt
system, this voltage range spreads from 126 volts to 114 volts at the service
delivery point [7].
However, the ANSI voltage spread differs from that of some electric
utilities.
Fig. 3.2 is a comparison of ANSI voltage spread with some AEP
utilities' voltage spread.
The power industry has determined that it would be
more economical to limit the primary voltage drop to 5 volts and the secondary
voltage drop to 7 volts. This would require additional voltage regulators, but the
distribution transformers and the secondary service facilities would not have to
be oversized for voltage drop requirements.
16
A. N. S. I.
9V DROP
(
) (
3V DROP
SECONDARY
PRIMARY
SERVICE
---------------------t--------------- t1
114V
126V
5V DROP
(
PRIMARY
126V
)
) (
7V DROP
)
SECONDARY
SERVICE
---------------------t---------------
t1
114V
Fig. 3.2 Comparison of ANSI with some AEP utilities voltage spread.
17
Chapter Four
RESULTS OF FIELD TESTS PERFORMED BY UTILITIES
4.1
INTRODUCTION
The most recent reports presented on the subject of voltage reduction
have been prepared by American Electric Power Service Corporation, Pacific Gas
and Electric Company, Southern California Edison Company, and San Diego Gas
and Electric Company.
The studies of these organizations are worthwhile for
review because their results are some of the most comprehensive available and
they are the basis for many current studies.
4.2
AMERICAN ELECTRIC POWER (AEP) TEST I
In 1974 AEP conducted a one-year study on fifteen distribution circuits
during which voltage was reduced, at the distribution station bus, by 5% from
9:00 am to 1:00 pm every other weekday.
Every feeder was equipped with a
metering package that provided power, apparent power and voltage as a function
of time.
The result of this study demonstrated a composite energy saving of
0.54% on the fifteen distribution circuits monitored. Because the composition of
load varies considerably among the AEP operating companies and circuits, this
result cannot be taken as universally applicable. However, these fifteen distribution circuits are considered fairly typical of the AEP system.
Table 4.1
summarizes the energy savings resulting from this test. The test also indicated
that a significant reduction in demand can be realized [2,6].
On the residential circuit, AEP experienced a four percent drop in
demand, diminishing to three percent drop at the end of the four-hour voltage
reduction period. When the voltage was returned to normal, AEP experienced a
18
Table 4.1
Energy Savings Due to Voltage Reduction
AEP System (Test I)
Energy Savings (%)
Company
Year
Spring
Summer
Fall
.73
.31
.57
1.24
.62
.98
1.42
1.38
.35
-.31
.23
.33
1.83
Indiana & Michigan Electric Co.
.35
Residential
.53
Residential
.55
Residential
.34
.58
.48
-.20
.07
.17
1.17
.65
1.38
.39
.02
-.35
-1.03
-1.02
-1.11
.84
-.44
.88
.35
-.49
1.39
1.05
1.22
0.12
0.52
0.47
0.75
Appalachian Power Co.
Residential
Residential
Residential
Ohio Power Co.
Residential
Residential
Residential
.35
.10
.14
Appalachian Power Co.
Commercial
.71
.90
Winter
.89
Indiana & Michigan Electric Co.
.52
Commercial
Ohio Power Co.
Commercial
Appalachian Power Co.
Industrial
.89
1.00
Indiana & Michigan Electric Co.
-.03
Industrial
Ohio Power Co.
Industrial
.55
AEP System
Residential
Commercial
Industrial
Composite
0.40
0.71
0.51
0.54
19
one percent overshoot in demand, tapering to the base level in approximately two
hours [2,6].
On the commercial and industrial circuits, AEP experienced an immediate
drop in demand which remained at that level until voltage was returned to
normal. Table 4.2 presents the change in demand during and after the voltage
reduction period [2].
4.3
AEP TEST II
The reduction period of the first AEP study was four hours.
However,
AEP felt that if voltage reduction was to be employed on a permanent basis as a
method to reduce energy use, a twenty-four hour reduction period should be
utilized. Therefore, in 1979 AEP conducted a second study to assess the impact
of twenty-four hour reduction on energy and demand. In this test AEP utilized
the same circuits and followed the same procedure that was employed in the first
test [4].
The energy savings resulted from this test are presented in Table 4.3. The
numeric values presented in this table are per-unit values on a base of one
percent voltage reduction.
AEP indicated that it was necessary to reduce the
actual values of energy savings to per-unit values because the percent reduction
of circuit voltage with respect to non-voltage reduction days was never 5% at all
times, on all distribution circuits. This means that these values should not be
considered as incremental changes based on a one percent change in voltage, but
rather as a composite average change due to a voltage reduction of approximately
five percent [4].
Energy savings on the residential circuits varied considerably between
circuits and by season. The most consistent energy savings occurred during the
20
Table 4.2
Demand (kW) Change During and After Voltage Reduction Period
AEP System (Test I)
Demand Change (%)
Time of Day
Residential
Commercial
Industrial
Begin volta~e
Reduction V.R.)
-4.07
-3.26
-2.77
0930
0.5 hr after V.R.
-3.99
-3.89
-2.90
1000
1 hr after V.R.
-3.75
-3.80
-2.80
1100
2 hrs after V.R.
-3.15
-3.78
-3.03
1300
4 hrs after V.R.
-2.78
-3.90
-2.69
-3.55%
-3.73%
-2.84%
0900
Average Demand Reduction
1315
1330
1400
1500
1700
2400
Voltage returned
to normal
0.98
-0.26
-1.25
0.5 hr after
normal voltage
1.01
-0.36
-0.08
1 hr after
normal voltage
0.74
-0.61
0.43
2 hrs after
normal voltage
0.13
-0.88
-0.15
4 hrs after
normal voltage
-0.40
-0.65
-1.07
11 hrs after
normal voltage
-0.05
-0.07
-0.54
Voltage Drop (5%) @ 0900 hrs
Voltage returned to normal @ 1300 hrs
Yearly Basis
Minus sign indicated reduction
21
Table 4.3
Energy Savings Due to Voltage Reduction
AEP System (Test II)
Energy Savings (p.u.)
Circuit
Company
~
Circuit
Number
AP Co.
R
R
R
I&ME
OP Co.
Yr.
Fall
Winter
Spring
Summer
1
2
4
0.50
0.50
0.35
1.54
0.88
1.30
0.22
0.75
0.92
1.41
0.90
0.54
R
R
R
7
8
10
1.24
1.32
1.57
0.22
0.61
0.59
1.03
1.17
1.30
0.67
0.87
0.69
R
R
R
11
12
14
0.17
0.36
0.64
0.74
1.23
1.07
0.22
0.85
0.73
0.69
AEP
R
Average
0.45
0.87
0.79
0.79
AP Co.
C
3
0.04
0.93
0.73
I&ME
C
9
1.38
0.59
1.35
0.69
OP Co.
C
15
0.45
0.94
0.66
1.26
AEP
C
Average
0.64
0.82
0.91
1.01
AP Co.
I
5
0.90
1.74
1.42
I&ME
I
6
0.47
0.45
0.33
OP Co.
I
13
0.73
0.54
0.79
AEP
I
Average
0.49
0.33
0.53
0.89
0.83
AEP
R,C,I
Average
0.71
0.27
0.86
0.83
0.84
0.73
0.84
0.53
1.28
22
summer and the winter seasons; these are also the peak loading periods of the
year in the AEP system. The AEP average energy savings was consistent for the
year.
Commercial circuits gave results similar to those of the residential circuits
in that consistent energy savings was realized and the greater savings occurred
during the summer and winter seasons.
Energy savings on the industrial circuits were not as great as either the
commercial or residential circuits. However, AEP indicated that due to several
technical problems and customer voltage complaints, data collected for circuits
No.5 and No. 13 were not sufficient to analyze. Therefore, AEP indicated the
energy saving results for industrial circuits may be biased due to the lack of
complete data.
The year-end composite energy savings due to the voltage
reduction for all fifteen circuits was 0.71 P.U.
AEP obtained the reduction in demand by comparing the average circuit
demand during non-reduction days with the average circuit demand during
reduction days.
The demand of the non-reduction days was used as a base in
order to calculate the percentage difference in demand.
Table 4.4 presents a
summary of the resulting reduction in demand due to voltage reduction [4].
AEP indicated that residential and commercial loads had similar
responses to voltage reduction.
The reduction in demand varied considerably
from one circuit to another but was consistent from season to season. According
to AEP the highest reductions in demand appeared to take place during the offpeak periods when service voltages were at their highest.
The demand reduction for the industrial circuits was lower than for the
residential and commercial circuits. AEP believed that the majority of industrial
customers regulated their utilization voltages internally in their plants during the
Table 4.4
Demand Reduction Due to Volta~e Reduction
AEP System (Test II)
Demand Reduction (p.u.)
Circui t
Company
Im
Cireui t
Number
AP Co.
R
R
R
I&ME
R
R
Fall
Winter
Spring
Summer
1
2
4
2.13
1.00
1.70
1.33
0.79
1.69
0.65
1.04
0.12
1.71
0.78
1.80
R
7
8
10
0.73
0.55
0.86
0.34
0.34
0.67
0.92
1.19
1.08
1.10
0.80
1.00
R
R
R
11
12
14
0.00
1.07
1.33
0.62
1.25
0.92
0.11
0.73
0.75
0.60
AEP
R
Average
1.07
0.84
0.68
1.01
AP Co.
C
3
1.09
0.88
1.13
I&ME
C
9
0.59
0.54
0.85
0.90
OP Co.
C
15
1.04
0.94
0.87
0.78
AEP
c
Average
0.91
0.78
0.94
0.83
AP Co.
I
5
0.70
0.52
0.57
I&ME
I
6
0.36
0.38
0.50
OP Co.
I
13
1.35
0.67
0.77
AEP
I
Average
0.53
0.49
0.40
0.52
0.60
AEP
R,C,I
Average
0.80
0.89
0.78
0.68
0.86
OP Co.
Yr.
0.90
0.86
0.40
0.59
24
voltage reduction period.
This action resulted in rendering the demand
unaffected by changing the utilization voltages.
4.4
PACIFIC GAS AND ELECTRIC (PG&E) COMP ANY TEST
In July of 1976 PG&E began a seven-month voltage reduction test on one
of its substations in the San Francisco division.
During this test the feeder
voltage was lowered at the distribution station bus by three volts on a 120-volt
base every other day.
PG&E indicated that a 2.5% drop in supply voltage
produced approximately 2% reduction in demand during the summer and winter
peak load and 2.5% savings in energy consumption.
Table 4.5 presents a
summary of the PG&E voltage reduction test results [6].
4.5
SOUTHERN CALIFORNIA EDISON (SeE) COMPANY TEST
In April of 1977 SCE initiated a voltage reduction test on four of its
substations.
During this test all types of loads were covered (residential,
commercial, industrial and agricultural). The test was run over a long period of
time to cover all load conditions and climates. The average voltage reduction
varied between 2% and 2.8%. Voltage reductions were implemented on a cyclic
basis of either (a) 24-hour normal, 24-hour reduced or (b) seven-day normal,
seven-day reduced.
SCE indicated that there was a measurable reduction of
demand and energy resulting from voltage reduction.
The composite energy
savings and demand reduction were 4.06% and 4.16%, respectively.
Table 4.6
presents a summary of the energy savings and demand reductions resulting from
this test [1].
46186
1165
2.46
Reduced
Voltage
Difference
% Reduct.
July
47351
August
2.07
% Reduct.
Normal
Voltage
3.49
152100
Difference
4.52
2091
44156
46247
256175
7079728
7201221
Reduced
Voltage
7335853
7353321
August
Normal
Voltage
July
1.95
81346
4088471
4169817
October
3.34
169483
4898556
5068552
Nov.
1.91
1001
51289
52290
Sept.
1.09
575
52355
52930
October
3.40
1953
55465
57418
Nov.
KW Demand-Seven Months
2.28
134688
5774029
5908717
Sept.
kWh Usage-Seven Months
2.82
1627
56163
57790
Dec.
2.33
158617
6649935
6808552
Dec.
Energy Consumption and Average Peak Demand
PG&E System
Table 4.5
2.02
1040
50451
51491
Jan.
1.94
116941
5924082
6041023
Jan.
2.59
1352
50865
52217
AVG
2.51
1069300
41616022
42685322
TOTAL
to
Ul
26
Table 4.6
Voltage Reduction Test Results
SCE System
Circuit
Substation
No.
Voltage
Voltage
Avg. (%) Reduct.
Cycle
Load Mix
Volt
kWh
kW
Daily
98% Res.
2.43
3.58
4.08
2.05
4.78
5.32
2.88
4.79
4.09
2.40
2.09
2.02
2.29
5.72
5.33
2.29
2.98
4.23
2.29
2.99
3.98
2.29
5.55
4.24
(KV)
Covina
1
4
2% Comm.
2
4
Daily
80% Res.
20% Comm.
Harvard
3
12
Weekly
80% Agri.
10% Res.
10% Comm.
Vernon
4
7
Daily
92% Res.
8% Comm.
Walnut
5
12
Weekly
90% Res.
10% Comm.
6
12
Weekly
80% Indus.
10% Res.
10% Comm.
7
12
Weekly
75% Res.
25% Comm.
8
12
Weekly
100% Comm.
2i
4.6
SAN DIEGO GAS AND ELECTRIC (SDG&E) COMPANY TEST
In 1978 SDG&E began a voltage reduction test program which involved
eleven distribution circuits, each from different substations.
Circuits were
selected to obtain a diversity of load characteristics including residential,
commercial, industrial, military and agricultural.
The bus voltage of these
circuits was reduced by 2.5% for a 24-hour period and returned to normal for the
next 24-hour period. Eight circuits from the group of eleven circuits produced
significant results.
The other three circuits gave unusual results which made
SDG&E believe that voltage regulation equipment had been added or changed by
major customers supplied from these three circuits. As a result, data collected
from these three circuits was ignored. Table 4.7 presents the results of this test
[3] .
By trial and error examination, SDG&E have obtained two factors K and
D (percent change in energy and demand for 1% change in voltage on residential
and commercial circuits) as best predictors of load response to voltage change on
their system.
Table 4.8 presents the values of these factors (K and D) in the
SDG&E system. Based on these two factors (K and D), SDG&E calculated the
response of various load combinations between 40% and 100% residential load as
shown in Table 4.9 [3].
28
Table 4.7
Voltage Reduction Test Results
SDG&E System
Test
Circuit
Load
Period
% Res % Com % Inds
% Agr "K"
"D"
1.04
0.96
11
0.744
0.54
1
0.983
*
0.774
0.77
Clairmont 275
8.2
3/79-3/80
84
16
Encinitas 287
7.3
3/79-10/80
60
26
Felicita 471
6.5
1/79-12/79
87
12
Genessee 271
5.3
3/79-3/80
Imperial 156
8.4
3/79-2/80
63
34
3
0.825
0.94
Rincon 217
5.1
5/80-10/80
39
17
44
0.470
*
Scripps 435
7.6
12/77-6/79
60
39
1
0.770
0.67
Kettner 135
12.5
2/79-2/80
3
95
2
0.648
*
4
100
"K" is the percent change in kWh consumption for a 1% voltage change.
"D" is the percent change in peak demand for a 1% voltage change.
29
Table 4.8
Load Response to Voltage on SDG&E System
Type of Load
Residential
1.14%
1.14%
Commercial
0.26%
0.08%
("K" is the percent change in energy for a 1% change in voltage. "D" is
the percent change in peak load for a 1% change in voltage.)
Table 4.9
Calculated Response of Various Loads
SDG&E System
Residential
Commercial
o
100
80
60
40
1.140
1.140
20
40
0.964
0.928
0.788
0.716
60 -
0.612
0.504
*
*
Less than 40% residential load should not be used with these "K" and "D"
factors.
30
Chapter Five
VOLTAGE REDUCTION STUDY
5.1
INTRODUCTION
Three distribution circuits have been selected for this voltage reduction
study.
They were chosen to represent all three types of loads:
commercial and residential.
industrial,
The nominal voltage of these circuits is 12.47 kV.
Their voltage was designed in compliance with the ANSI voltage standard
(C84.1-1977).
This means the primary voltage of each circuit spreads from
126-Volt maximum to 117-Volt minimum as a worst-case scenario.
data used in this study was obtained from two different sources:
Circuit
First, the
monthly energy consumptions and power demand levels for the three distribution
circuits have been supplied by the operating utility company, and they are actual
circuit data for the year 1989. Table 5.1 presents the monthly energy consumptions and power demand levels for each circuit.
Second, the percent energy savings and percent power demand reductions
applied on these three circuits are actual data, and they resulted from experimental studies performed by three utilities: AEP, SDG&E and SCE. Table 5.2
presents the results of these utilities (percent energy savings and percent power
demand reductions) that were utilized as the data in this study.
5.2
CIRCUIT CHARACTERISTICS
5.2.1
Circuit No.1
The load composition of the first circuit is 100% industrial. This circuit
load consists of a large food processing facility. The only voltage regulating equipment existing on this circuit is a feeder voltage regulator which is located in the
1998000
1309000
6500
3876
2700
2166000
1078000
6400
4086
2200
2041000
1175000
6400
4250
2500
2
3
2
3
3168000
2745000
2865000
March
Feb.
Januarv
Circuit
Number
2600
3388
6400
1253200
2000
3145
6300
1220000
1859000
3048000
3340000
2140000
May
April
2500
2766
6900
1358000
2280000
3600000
JY!I
2800
3235
6800
Demand (KW)
1250000
1758000
3753000
June
Energy (KWH)
2892
2100
3033
3000
3953
2700
3279
2400
2200
tN
........
14727000
1340000
2831
24454000
2104000
5000
38316000
2541000
4700
1181000
1078000
1027000
1458000
Total/Year
Dec.
7900
1946000
2074000
1970000
2118000
7500
1764000
3880000
3945000
3667000
7400
Nov.
Oct.
Sept.
August
Table 5.1
Energy Consumptions and Power Demands
for the Three Distribution Circuits (1989)
5%
4.5%
3.65%
5%
3
5%
4.3%
4.2%
5%
2
N/A
2.65%
AEP (Test II)
%
%
%
Energy
Demand Volt
Savings
Reduct Reduct
2.45%
5%
1
Circuit
Number
%
Volt
Reduct
5.7%
1.3%
N/A
Energy
Savings
SDG&E
%
2.29%
2.43%
5.7%
N/A
0.4%
N/A
%
%
Demand Volt
Reduct Reduct
Utilities and Their Test Results Used in the Study
of the Three Distribution Circuits
Table 5.2
3.58%
5.5%
N/A
Energy
Savings
i%
SCE
4.08%
4.24%
N/A
%
Demand
Reduct
vl
N
33
substation and equipped with a 5% voltage reduction apparatus.
The circuit
voltage is at its maximum level of 126 Volts in the substation and at its
minimum level of 120.6 Volts at the food processing facility's meter point, often
referred to as the service delivery point.
In addition to the feeder voltage
regulator, five line capacitor banks (switched and fixed) exist on this circuit that
affect its voltage. These capacitor banks have been installed primarily for power
factor correction purposes. This circuit is heavily loaded; it reached a peak load
demand and an annual energy consumption of 7900 kW and 38,316 MWHR,
respectively, in 1989.
Power is delivered to the food processing facility at 12.47 kV. Inside the
plant, the distribution voltage is stepped down to utilization voltages by
customer-owned and controlled distribution transformers which are equipped
with manual load tap changers.
5.2.2 Circuit No.2
The second circuit provides power to a commercial city downtown area.
This circuit load which is 100% commercial consists of many office buildings,
restaurants and commercial shops. Presently, the circuit voltage is regulated at
the substation by a feeder voltage regulator which is equipped with a 5% voltage
reduction apparatus. The circuit maximum voltage is 126 Volts and exists at the
substation while the circuit minimum primary voltage is 124.4 Volts. Four line
capacitor banks exist on this circuit which have been installed primarily for
power factor correction purposes.
The circuit peak load demand and annual
energy consumption during 1989 reached 4250 KW and 24,454 MWHR,
respectively.
34
5.2.3 Circuit No.3
The characteristics of this circuit are significantly different from those of
Circuit No. 1 and Circuit No.2.
Not only is its load composition 100%
residential, but it also splits into three distribution lines that travel in three
different directions, with many long single-phase laterals exist on this circuit.
These single-phase laterals travel cross country and feed rural area loads. The
voltage of this circuit is regulated at the substation and at two locations on the
distribution line. The maximum and minimum primary voltages existing on this
circuit are 126 Volts and 120.5 Volts, respectively. The feeder voltage regulator
which is located in the substation is equipped with a 5% voltage reduction
apparatus. Like the first two circuits, this circuit has four line capacitor banks
which have been installed on the distribution line primarily for power factor
correction purposes.
The circuit peak load demand and annual energy
consumption reached 3000 KW and 14,727 MWHR, respectively, in 1989.
5.3
STUDY CONDITIONS
The three distribution circuits in study are not under the AEP system,
SDG&E system or the SCE system. The data utilized in this study resulted from
tests performed on distribution circuits existing under these utility systems, so an
assumption was necessary to be made.
This assumption was that the three
distribution circuits would respond to voltage reduction just as if they existed
under these utility systems.
The reason that test results of these three utilities were utilized in this
study was that these utilities implemented a twenty-four hour voltage reduction
in their experimental studies.
Also, because these utilities extended their
experiments over a long period of time to cover all load conditions and climates.
35
5.4
DISTRIBUTION CIRCUIT ANALYSIS
A distribution circuit analysis (DCA) program was used to analyze the
voltage of the three circuits. This DCA program generates a voltage profile for
each circuit and determines the number of voltage regulators required and their
locations on the circuit based on preset conditions.
This DCA program was
supplied for use in this study by the utility that operates the three distribution
circuits.
5.4.1 Voltage Drop Calculation
Because angles between the source voltage and the end-of-line voltage are
small, the voltage drop can be calculated by the following equation:
Voltage Drop
where R
L
is the line resistance, I
R
= RL )(
IR
+ XL )(
is the resistive line current, XL is the line
inductive reactance and IX is the inductive current.
Example:
= 0.35 n
XL = 0.61 n
I L = 366 A
RL
Power Factor = 100%
Circuit Voltage
= 7.2 KV
IX
(line to ground)
Calculate the line voltage drop.
36
Solution:
I
I
R
= 366 A x
R
= 366 A
IX
= 366 A x
IX
=0
cos 90°
sin 90°
Voltage drop (in line)
= R L )(
I
R
+ XL )( IX
Voltage drop (in line) = (0.35) (366)
Voltage drop (in line)
ot
10
+ (0.61) (0)
= 128.1 Volts
V0 1tage drap (.In 1·me ) = 128.17200
x 100
=1. 80t
10
5.5
STUDY RESULTS
5.5.1
Introduction
The study of the effect of permanent voltage reduction on energy
consumption and demand level on the three distribution circuits produced
significant but different results. These results varied from circuit to circuit, from
load type to load type and, of course, from utility data to utility data.
The
following paragraphs present these results as well as the cost that would be
required to implement permanent voltage reduction and the benefits that would
result from such voltage reduction.
It should be noted, however, that all cost
estimates were calculated based on today's dollar value.
5.5.2
Study Results Corresponding to AEP Data (Test II)
Circuit No.1:
Reducing the distribution voltage of this circuit permanently by 5% would
result in 2.45% energy saving and 2.65% demand reduction. Table 5.3 presents
the monthly energy consumptions and demand levels under normal and reduced
2794807
Reduced
Voltage
6400
6230
170
Normal
Voltage
Reduced
Voltage
Differ.
10193
2865000
Normal
Voltage
Differ.
Jan.
Month
170
6230
6400
67253
2677747
2745000
Feb.
172
6328
6500
77616
3090384
3168000
March
170
6230
6400
81830
3258170
3340000
April
183
6111
6900
91949
3661051
3753000
June
89842
3577158
3667000
180
6620
6800
196
7204
1400
Demand (KW)
882000
3511800
3600000
Energy (KWllR.)
August
JuLY
Circuit NO.1
Load composition is 100% industrial
5% Permanent voltage reduction
2.45% Energy savings
2.65% Demand reduction
167
6133
6300
14676
2973324
3048000
May
Table 5.3
Energy Savings and Demand Reductions
Corresponding to AEP (Test II) Data
7691
209
199
7900
95060
3784940
3880000
Qct.
7301
7500
96653
3848347
3945000
Sept.
124
4575
4100
43218
1720782
1164000
Nov.
133
4867
5000
62255
2478145
2541000
Dec.
938742
37377258
38316000
Total/Year
tN
"'-]
38
voltages. Under normal voltage, the circuit annual energy consumption is 38,316
MWHR.
Under reduced voltage, this energy consumption would drop to
37,377.26 MWHR. Therefore, the energy saving that would result from voltage
reduction would be 938.74 MWHR annually. At an average generation cost of
$0.015 per KWHR, the energy that would be saved annually would cost $14,081.
However, in order to implement a permanent 5% voltage reduction on this
circuit, three single-phase line voltage regulators would be required to maintain
a minimum primary voltage of 117 Volts.
approximately $6,500 including installation.
Each voltage regulator costs
In addition, routine maintenance
and inspection of the voltage regulators would cost approximately $200 annually.
Because the life span of a voltage regulator is 20 years under normal conditions,
the total voltage reduction cost was calculated over a twenty-year period and
then annualized. Therefore, the cost of routine maintenance and inspection over
20 years would be $4,000.
Adding the cost of the voltage regulators to their
twenty-year operation cost would be the total voltage reduction cost over 20
years, which carne out to be $23,500. Dividing this total voltage reduction cost
of $23,500 by 20 gives $1,175, which would be the annual voltage reduction cost
for this circuit. The difference between the generation cost of energy that would
be saved annually and the annual voltage reduction cost would be the annual
benefit of this circuit. Therefore, the benefit that would result from a permanent
5% voltage reduction on this circuit would be $12,906 annually. Also, as stated
above, permanent voltage reduction would impact the demand levels of this
circuit.
A 2.65% reduction in demand would be realized by a 5% voltage
reduction. The greatest reduction in demand would be realized in the month of
September during which the peak demand of 7900 KW would drop to 7691 KW
to result in a reduction of 209 KW.
39
Circuit No.2:
Reducing the distribution voltage of this circuit permanently by 5% would
result in 4.2% energy saving and 4.3% demand reduction. Table 5.4 presents the
monthly energy consumptions and demand levels of this circuit under normal and
reduced voltages.
This table also presents the monthly energy savings and
demand reductions that would be realized by voltage reduction.
voltage, the annual energy consumption is 24,454 MWHR.
Under normal
However, under
reduced voltage, this energy consumption would drop to 23,426 MWHR, resulting
in an annual energy saving of 1027.07 MWHR. The generation cost of 1027.07
MWHR would be $15,406.
Because the primary voltage of this circuit would not drop below the
minimum voltage level of 117 Volts under voltage reduction conditions,
additional voltage regulating equipment would not be required.
Therefore, the
cost to implement voltage reduction on this circuit would be zero and the
resulting benefit would be the generation cost of energy that would be saved
annually by voltage reduction.
The benefit would be $15,406.
The greatest
reduction in demand would be realized in the month of January, during which
the peak demand of 4250 KW would drop to 4067 KW, resulting in a reduction of
183 KW.
Circuit No.3
Reducing the distribution voltage of this circuit permanently by 5% would
result in 3.65% energy saving and 4.54% demand reduction. Table 5.5 presents
the monthly energy consumptions and demand levels under normal and reduced
voltages.
This table also presents the monthly energy savings and demand
reduction that would result from a permanent 5% voltage reduction.
Under
normal voltages, the annual energy consumption of this circuit is 14,727 MWHR.
18018
89880
83916
90912
85722
3910
176
4067
183
Reduced
Voltage
Differ.
4086
4250
Normal
Voltage
Differ.
1180922
3242
146
167
3388
3709
3876
139
119
135
2168
124
131
2892
82740
1887260
1910000
Sept.
2902
Circuit No.2
Load composition is 100% commercial
5% Permanent voltage reduction
4.2% Energy savings
4.3% Demand reduction
3096
3235
3033
88956
95760
2647
2166
2029044
2118000
August
2184240
2280000
J.YlY
Demand lKW)
13836
1684164
1158000
June
3010
3145
1859000
2050120
2140000
1914084
1998000
2015028
2166000
1955218
May
Reduced
Voltage
April
2041000
March
Normal
Voltage
Feb:.
Jan.
rvtonth
Energy (KWHR)
Table 5.4
Energy Savings and Demand Reductions
Corresponding to AEP (Test II) Data
3138
141
122
3279
81732
1864268
1946000
Nov.
2109
2831
81108
1986892
2014000
October
170
3783
3953
88368
2015632
2104000
Dec.
1027068
23426932
24454000
Total/Year
~
0
112
99
2101
Reduced
Voltage 2388
Differ.
2200
2500
Normal
Voltage
121
2579
2700
47778
37347
42887
Differ.
1251222
1132113
Voltage
Reduced
1309000
March
1038653
1078000
1175000
Voltage
Normal
Eeb.
Jan.:.
Month
117
2483
2600
45742
1207458
1253200
April
112
2388
2500
49567
1308433
126
2674
2800
Demand (KW)
45625
1204375
1358000
J.!!ly
Energy (KWHR)
1250000
June
135
2865
3000
53217
1404783
1458000
A!!gust
Circuit No.3
Load composition is 100% residential
5% Permanent voltage reduction
3.65% Energy savings
4.5% Demand reduction
112
2388
2000
44530
1175470
1220000
May
Table 5.5
Energy Savings and Demand Reduction
Corresponding to AEP (Test II) Data
94
2006
2100
37486
989515
1027000
Sept.
99
2101
2200
39347
1038653
1078000
Oc-l
108
2292
121
2579
2700
48910
43106
2400
1291090
1340000
Dec.
1137894
1181000
Nov.
537536
14189465
14727000
Total/Year
~
~
42
Under reduced voltage, this energy consumption would drop to 14,189.47
MWHR.
This drop in energy consumption would result in an annual energy
saving of 537.54 MWHR. The generation cost of 537.54 MWHR is $8,063.
However, in order to implement voltage reduction and maintain the
minimum primary voltage level required, four line voltage regulators would be
required for this circuit. The cost to implement voltage reduction on this circuit
would be $1,700 annually.
Therefore, the benefit that would result from a
permanent 5% voltage reduction on this circuit would be $6,363 annually.
Table 5.6 presents a summary of the cost-benefit analysis for the three
distribution circuits. This table presents the annual cost that would be required
to implement voltage reduction on each circuit as well as the annual benefit that
would be expected from each circuit. Results presented in this table correspond
to AEP data (Test II).
The results of Circuit No.1 (industrial circuit) were not as great as the
results of either Circuit No. 2 (commercial circuit) or Circuit No. 3 (residential
circuit). This was because data collected by AEP on the industrial circuits were
incomplete and insufficient for analysis. AEP believed that the majority of the
industrial customers regulated their voltage internally by their own voltage
regulation equipment during the experiment period.
5.5.3 Study Results Corresponding to SDG&E Data
Circuit No.1:
The impact of voltage reduction on energy and demand on this circuit
cannot be determined because SDG&E didn't quantify the energy saving and
demand reduction that would result from voltage reduction on circuits of 100%
industrial loads.
126.0V
126.0V
100%
Commercial
100%
Residential
2
3
120.5V
124.4V
120.6V
Voltage
Min.
Max.
126.0V
Load
Composition
100%
Industrial
Circuit
No.
120.0V
120.0V
120.0V
117.0V
118.4V
117.3V
Voltage
Min.
Max.
3.65%
4.20%
2.45%
% Energy
Savings
537.54
1027.07
938.74
Energy Savings
~MWHR)
er Year
Results Corresponding to AEP (Test II) Data
Voltage Reference = 120V
Voltage Reduction = 5%
Circuit Voltage = 12.47 KV
14,727
24,454
38,316
Per Year
(MWHR)
Energy Usage
Existinz Voltaae Case
Summary of Cost-Benefit Analysis
Table 5.6
11,700
Zero
11,175
Cost of Additional
Vol ta~e R~ulators
Inclu ing aintenance
Per Year
Voltage Reduction Case
18,063
115,406
114,081
Save
Per Year
Ener~y
Cost of
16,363
115,406
112,906
Benefit
Per Year
~
tN
44
Circuit No.2:
Reducing the distribution voltage of this circuit permanently by 5% would
result in 1.3% energy saving and 0.4% demand reduction. Table 5.7 presents the
monthly energy savings and demand reductions that would be realized by voltage
reduction on this circuit. The annual energy consumption of this circuit under
normal voltage is 24,454 MWHR.
This energy consumption would drop to
24,136.09 MWHR under reduced voltage. This means an annual energy saving of
317.90 MWHR would be realized by voltage reduction on this circuit.
generation cost of the energy saving would be $4,769 annually.
The
However,
additional voltage regulating equipment would not be required to implement
voltage reduction on this circuit.
This is because under voltage reduction
conditions, the circuit primary voltage would spread from a maximum voltage of
120 Volts to a minimum voltage of 118.4 Volts.
Therefore, the benefit of this
circuit would be the generation cost of energy that would be saved by voltage
reduction. This benefit would be $4,769 annually.
Demand reduction that would result from voltage reduction would not be
significant for this circuit.
The greatest reduction in demand that would be
realized by voltage reduction on this circuit would be 17 KW and would occur in
the month of January.
Circuit No.3:
Reducing the distribution voltage on this circuit by 5% permanently
would result in 5.7% energy saving and 5.7% demand reduction.
Table 5.8
presents the monthly energy savings and demand reductions that would result
from voltage reduction on this circuit. Under normal voltage, the annual energy
consumption of this circuit is 14,727 MWHR. Under reduced voltage, this energy
consumption would drop to 13,887.56 MWHR. This drop in consumption would
,.
3
0
0
P
a!
2
0
C
w
0
2
3
0
3
81
1
F
h
m
P
"
w
h
0
N
N
01
m
m
3
h
8
3
0
3
m
h
Q'
C
2
c
N
0
m
2
N
2n
El
N
2
0
P
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i
z
r
PI
O
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w
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N
5
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rO
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result in an annual energy saving of 839.44 MWHR.
The generation cost of
839.44 MWHR would be $12,592. The cost to implement voltage reduction on
this circuit would be $1,700 annually. Therefore, the benefit that would result
from voltage reduction on this circuit would be $10,892 annually.
The greatest reduction in demand would be 171 KW and would occur in
the month of August.
Table 5.9 presents a summary of the cost-benefit analysis for the three
circuits. This table presents the primary voltage levels for normal and reduced
voltage conditions. It also presents the annual energy consumption as well as the
energy saving that would be realized annually by a permanent 5% voltage reduction on the three circuits. The annual cost that would be required to implement
voltage reduction as well as the annual benefit that would result from voltage
reduction are also presented in this table.
Results presented in this table
correspond to SDG&E data.
The results of Circuit No. 2 (commercial circuit) were much lower than
the results of Circuit No. 3 (residential circuit). Unfortunately, SDG&E did not
provide any explanation for their calculated low energy savings and demand
reductions on the commercial circuits despite the fact that two of their
commercial circuits produced an average of 3.56% in energy saving and 3.6% in
demand reduction for 5% voltage reduction.
5.5.4 Results Corresponding to SCE Data
Circuit No. 1:
The impact of voltage reduction on energy and demand on this circuit
cannot be determined because SCE did not quantify the energy saving and
demand reduction that would result from voltage reduction on circuits of 100%
industrial load.
Circuit No. 2:
Reducing the distribution voltage of this circuit permanently by 2.29%
would result in 5.55% energy saving and 4.24% demand reduction. Table 5.10
presents the monthly energy savings and demand reductions that would result
from 2.29% voltage reduction on this circuit. Under normal voltage, the annual
energy consumption of this circuit is 24,454 MWHR. Under reduced voltage, this
consumption would drop to 23,096.80 MWHR. This drop of 1357.20 MWHR in
energy consumption would be the annual energy saving for this circuit.
The
generation cost of 1357.20 MWHR would be $20,358.
Voltage reduction of 2.29% could be implemented on this circuit without
the need of additional voltage regulating equipment. This is because the primary
voltage of this circuit could be lowered by 2.29% and still be maintained above
the minimum level of 117.0 Volts with the existing circuit conditions. Therefore,
the voltage reduction cost of this circuit is zero and the annual benefit of this
circuit would be the cost of energy that would be saved annually by voltage
reduction. This benefit would be $20,358 annually.
The greatest reduction in demand on this circuit would be realized in the
month of January during which the peak demand of 4250 KW would drop to 4430
KW to result in a reduction of 180 KW.
Circuit No. 3:
Reducing the distribution voltage of this circuit by 2.43% would produce
significant results. A 3.58% energy saving and 4.08% demand reduction would be
realized on this circuit from such voltage reduction.
Table 5.11 presents the
monthly energy savings and demand reduction that would result from 2.43%
voltage reduction on this circuit.
Under normal voltage, the annual energy
consumption of this circuit is 14,727 MWHR. Under reduced voltage, this energy
consumption would drop to 14,199.23 MWHR to result in an annual energy
saving of 527.73 MWHR. The generation cost of this energy saving would be
$7,908.
As in the case of Circuit No. 2, additional voltage regulating equipment
wouldn't be required to implement voltage reduction on this circuit. Therefore,
the voltage reduction cost would be zero and the annual benefit that would result
from this circuit would be $7,908.
The greatest reduction in demand that would result from 2.43% voltage
reduction on this circuit would be realized in the month of August during which
the peak load of 3000 KW would drop to 2878 KW t o result in a reduction of 122
KW.
Table 5.12 presents a summary of the cost-benefit
analysis of the two
distribution circuits. The table presents the annual cost that would be required
to implement voltage reduction on each circuit as well as the annual benefit that
would be expected from each circuit. Results presented in this table correspond
to SCE data.
The results of Circuit No. 2 and Circuit No. 3 correspond to a voltage
reduction of 2.29% and 2.43%, respectively.
The reason a 2.29% and 2.43%
voltage reduction, and not a 5% voltage reduction, were used in this study of
these two circuits was because SCE did not quantify their test results for 5%
volt age reduction.
Chapter Six
CONCLUSION
6.1
CONCLUSION
The results of this study show that both energy consumptions and demand
levels can be reduced by voltage reduction but the amounts are influenced by
conditions such as load type, geographic location, demography, etc.
The results of the industrial load corresponding to the AEP data were
much lower than those of the commercial and residential loads. AEP believed
that the reason for which their industrial circuits produced low results was that
their industrial customers supplied off these circuits changed their voltage using
their own voltage regulating equipment.
The results of the commercial load corresponding to the SDG&E data
were much lower than those of the residential load. Unfortunately, SDG&E did
not provide any explanation for the low energy savings and demand reductions
resulting from their commercial circuits.
The results of the residential load corresponding to the AEP data,
SDG&E data and SCE data were very close to each other. Also, the results of
the commercial load corresponding to the AEP data and SCE data were very
close t o each other.
However, they were much higher than the results
corresponding to the SDG&E data.
Results of the AEP test and SCE test seem to be the most applicable
towards energy conservation and demand reduction. This is because both AEP
and SCE covered all types of loads and ran their test for a long period of time to
cover all weat her conditions. Also, neither system reported major problems that
could have affected the results of their tests.
Judging from the results of this study and from those of all experimental
studies performed by utilities nationwide, voltage reduction has merits and
should be investigated further. It should be noted, however, that operating with
five percent voltage reduction may require additional voltage regulating equipment and/or reconductoring of distribution circuits, all of which require
additional capital expenditures. However, revenues or resulting benefits would
have to offset these expenditures in order to justify the implementation of a
permanent voltage reduction on distribution circuits.
Chapter Seven
DISCUSSION AND RECOMMENDATIONS
7.1
DISCUSSION
Energy is defined as work and energy consumption is the result of
requirements for work such as heating, cooling, lighting and motive power.
Therefore, in order to save energy, it is necessary to reduce the requirements of
those energy end uses.
Lowering the utilization voltage of a light bulb reduces its lumens output,
i.e., a lower level of illumination. In this case, energy can be saved only if the
consumer accepts the level of illumination resulting from lower voltage.
However, if the lower level of illumination is not accepted, then the consumer will
either replace the light bulb with a higher wattage or simply turn on another
light. In either case, more energy is consumed and the result may be energy loss.
In applications involving heating or cooling, a fixed amount of energy is
required for a room to reach a certain level of temperature. In other words, the
utilization voltage of a heating or cooling unit affects the time it takes to reach
the desired temperature, but the total energy consumed over the period to reach
that temperature is the same as it would have been had the voltage stayed
constant. So, energy can only be saved if the consumer lowers the final desired
temperature.
Reducing distribution voltage on circuits supplying power to industrial
consumers may result in energy loss because most industrial consumers control
their voltage by their own voltage regulating equipment which utilities have no
control on. In other words, consumers can undo what utilities can do simply by
changing taps of their step-down or distribution transformers.
Also, reducing
distribution
voltage may increase the likelihood of consumers'
voltage
complaints, especially those whose present voltage is substandard.
In application of induction motors, the change of energy consumption by
motors depends on whether the utilization voltage is closer or further from the
motor's rated volt age. Lowering the utilization voltage from the rated conditions
of induction motors causes the full load current to raise and the rotor slip to
increase.
Also, the efficiency of this type of motor declines slightly and the
torque drops steeply as the voltage applied on the motor terminals is reduced.
When operating under voltage reduction, utilities may not be able to
maintain the voltage at the end-of-line consumer at the calculated minimum
level of 114 V because unexpected variations in load may occur on distribution
circuits. These unexpected variations in load, such as unexpected load growth,
failed switched capacitor banks, failed voltage regulators and system re-routing,
may cause the voltage to dip below the permissible level of 114 V.
While reduction in energy consumption cuts power generation costs, it
may backfire on utilities by reducing their revenue. Should this condition exist,
it may result in a rate increase which may upset consumers.
Finally, it should be noted that the voltage reduction phenomena is a
moving target with consumer energy consumption patterns shifting with time,
geographic location, demography, etc.
7.2
RECOMMENDATIONS
One definite factor does emerge from the controversy over energy conser-
vation by voltage reduction and that is whatever effects do result, they are very
dependent on the particular power system, geographic location, demography, etc.
58
This, coupled with the fact that many other factors are uncertain and difficult to
determine, make it advisable to offer the following recommendations:
7.2.1 Energy Conservation Experimental Studies
Public utilities commissions nationwide should require all utilities to
perform permanent voltage reduction tests on their distribution systems. During
the test, utilities should perform o n s i t e measurements of composite loadingvoltage characteristics in order to build up a much larger data, to better quantify
energy savings and to obtain more realistic answers to their power system
dynamic simulation.
7.2.2 Cost-Benefit Analysis
To help rationalize the planning, design and operating options related to
permanent volt age reduction, utilities and regulatory agencies need to quantify
the resulting benefits and weigh them against the expenses associated with
permanent voltage reduction which are normally passed on to the consumer in a
form of a rate increase.
7.2.3 Energy Use
Power utilities are not the only users of energy. In fact, they only use
25% of the total energy supply for power generation [12]. The remaining 75% of
the total energy supply is used by three groups of energy users. These three
groups are manufacturing plants which use 27.5%, transport ation systems which
use 24.4%) and finally householders and commercial consumers which use 23.1%
of the total energy supply [12]. These three groups should also participate in
energy conservation. Manufacturers should improve the efficiency of their energy-
59
consuming products. This group should also increase the use of solar and wind
energy. The public should use public transportation systems when possible for
fuel conservation. Finally, householders and commercial consumers should use
energy wisely.
60
REFERENCES
Wheeler, P.L., Dickenson, A.H. and Gibbs,T.J., "The Effect of Voltage
Reduction on Distribution System Loadstt, IEEE Conference Paper A-78-542-3,
Presented at the Summer PES Meeting, Los angeles, July 16-21, 1978.
Priess, R.F. and Warnock, V.J., "Impact of Voltage Reduction on Energy and
Demand", IEEE Transactions on Power Apparatus and Systems, Vol. PAS-97,
No. 5, Sept./Oct. 1978, pp. 1665-1671.
Erickson, J.C. and Gilligan, S.R., "The Effects of Voltage Reduction on
Distribution Circuit Loads", IEEE Transactions on Power Apparatus and
Systems, Vol. PAS-101, No. 7, July 1989, pp. 2014-2018.
Warnock, V.J. and Kirkpatrick, T.L., "Impact of Voltage Reduction on Energy
and Demand", IEEE Transactions on Power Systems, vol. PWRS-1, No., May
1986, pp. 92-97.
Chen, M.S., Shoults, R. and Fitzer, J., "The Effects of Reduced Voltages on the
Efficiency of Electric Loads", IEEE Transactions on Power Apparatus and
Systems, Vol. PAS-101, No. 7, July 1982, pp. 2158-2166.
Carr, J., "Voltage Reductiont1, Report for the Canadian Electrical Association,
February 1980.
" L-oltage Ratings for Electrical Power Systems and Equipment (60 HZ)",
American National Standards Institute, New York, Standard No. C84.1-1977.
Paula, G., "Conservation Impact of Voltage Reduction Minimal", Electrical
World, April 1990, pp. 58-60.
Westinghouse Electric Corporation, "Distribution Systems", East Pittsburgh,
PA, Irste, 1965.
Paula, G., "The Peaks of Summer", Electrical World, Sept. 1988, p. 25.
11,
Amarolli, G.A. and Ajello, J.E., "Electric Utility Distribution Feeder Voltage
Regulation for Effective Energy Conservation", San Francisco, California,
January 27, 1978.
12.
American Electric Company, "Energy Management Report". The author's name
is not available. This report was provided by American Electric Company at a
lighting seminar in Memphis, Tennessee (July 1989).