A Study of the Pasadena Power and Light System Citation Batchelder, Dean Eildermann and Butler, Albert and Olmsted, Ennis Gunning and Wright, Lowell John (1932) A Study of the Pasadena Power and Light System. Master's thesis, California Institute of Technology. doi:10.7907/vggb-gt59. https://resolver.caltech.edu/CaltechTHESIS:09172024-204614121 Abstract No abstract. Item Type: Thesis (Master's thesis) Subject Keywords: (Electrical Engineering) Degree Grantor: California Institute of Technology Division: Engineering and Applied Science Major Option: Electrical Engineering Thesis Availability: Public (worldwide access) Research Advisor(s): Unknown, Unknown Thesis Committee: Unknown, Unknown Defense Date: 1 January 1932 Record Number: CaltechTHESIS:09172024-204614121 Persistent URL: https://resolver.caltech.edu/CaltechTHESIS:09172024-204614121 DOI: 10.7907/vggb-gt59 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 16738 Collection: CaltechTHESIS Deposited By: Benjamin Perez Deposited On: 18 Sep 2024 18:09 Last Modified: 18 Sep 2024 18:20 Thesis Files PDF - Final Version See Usage Policy. 16MB PDF (Chart 4: 16,5 KV distribution system) - Final Version See Usage Policy. 3MB PDF (Chart 5: Map showing territories served by feeders) - Final Version See Usage Policy. 2MB Repository Staff Only: item control page

A STUDY OF THE PASADENA POWER AND LIGHT SYSTEM Thesis by Dean Eildermann Batchelder Albert Butler Ennis Gunning Olmsted Lowell John Wright In partial fulfillment of the requirements for the degree of Master of Science California Institute of Technology Pasadena,California 1932 ACKNOWLEDGEMENT We wish to express our appreciation to Mr. B. F. DeLanty, manager of the Pasadena Municipal Power and Light Department in extending to us the use of the records of the department. We also wish to express our appreciation to the other members of the department, Messrs. E. L. Bettanier, M. W. Edwards, and K. R. Birge, who assisted us in obtaining necessary information. Mr. W. E. Alworth of the Planning Commission of the City of Pasadena, Mr. A. E. Hall of the Westinghouse Electric and Manufacturing Company, and Mr. N. B. Hinson of the Southern California Edison Company helped at various stages of the work and we gratefully acknowledge their assistance. TABLE OF CONTENTS Page INTRODUCTION 1 HISTORY OF THE DEPARTMENT 1 GROWTH OF PASADENA 3 PRESENT DISTRIBUTION SYSTEM 6 LOAD SURVEY 8 FUTURE DISTRIBUTION POLICY 11 A LOW VOLTAGE NETWORK IN PASADENA 15 CONCUJSIONS 22 APPENDIX: MEDIUM VOLTAGE NETWORKS 23 REFERENCES 26 BIBLIOGRAPHY 27 INTRODUCTION Due to its rapid growth in the last ten years, the Pasadena Municipal Light and Power Department has had difficulty in maintaining good operating performance at all timee, and overloading of the system has caused undesirably wide voltage variations and uneven loading of transformers and feeders. The study of this con- dition and remedies for it constitute the substance of this report. The present conditions were studied by means of load charts of various kinds. These load charts were then correlated to an analysis of the future growth of Pasadena, thus obtaining a definite idea of the conditions of the present and the likely conditions of the future. A study of various types of distribution systems showed only two feasible solutions and these have been discussed at length and their application described. HISTORY OF THE DEPARTMENT Before starting on the present system let us hastily review the growth of the Department(l)*. - In . 1906, a bond issue of $125,000 provided a 250 H.P. unit and a street lighting system, which replaced the system then in use. In 1908, another bond issue of $50,000 was used to extend the street lighting system * References are listed on Page i2. fo 2. and to provide for distribution to the public, and in 1909, a bond issue of $150,000 was used to install a 1000 H.P. unit and to enlarge the distribution facilities. These units were soon too small and in 1914, a 1250 kw. Westinghouse, and in 1916, a 3000 kw. Allis Chalmers unit were added in order to care for the rapidly growing load. In 1920, a bond issue of $500,000 provided for the purchase of the Southern California Edison Company's system within the city limits, a very wise step, securing better coordination of the system and eliminating undesirable operating conditions. When Pasadena annexed La.manda Park, this policy of eliminating competition was continued and $65,000 of bonds bought out the Southern California Edison Company's interest in this region. With these purchases, re- adjustment and expansion of the system was necessary and $350,000 of bonds provided new substations, distribution facilities, and auxiliary equipment. In 1924, this was augmented by a 10,000 kw. Allis Chalmers unit provided by an issue of bonds totaling $250,000. This unit was unable to satisfy the needs of the Department for long and a 15,000 kw. Allis Chalmers unit was added in 1928, this machine being purchased from current earnings. By 1931, the load had grown so that more capacity was needed and a 25,000 kw. Allis Chalmers unit is now being installed which as can be seen from the production curves given in the next article, will carry the system for a considerable length of time. ;,_,al. ·} As we shall see, thef growth of Pasadena 1e decreasing, and the future demands on the power system, while increasing constantly, will not have the skyrocketing characteristics of the last ten years, so that with ample generating capacity provided and a distribution system expanded to care for the present load and allowing for future growth, the Department will be able to give steady electrical service at a minimum expense. GROWTH OF PASADENA When we began our study of present conditions, an investigation ~nto the probable future growth of Pasadena was undertaken. On the first chart there is shown a curve of population of Pasadena drawn through the five points given by United States Census Figures for each decade. The curve has been fitted according to the theory of population of Dr. Raymond Pear1(2) and its extension into the future has been according to the same theory. For a detailed discussion of the biological and mathematical basis for this treatment, the reader is referred to Dr. Pearl's works. The major point of interest in this curve is the decrease of the 4. rate of growth. To follow out this point, the four curves of Chart 2 were plotted. The first curve, school children, emphasizes strongly the decreasing slope observed in the first chart. In the next two curves, light meters and water meters, we see the reason for this population trend. Both of these curves are tending to become asymptotic and when these curves were shown to Mr. W. E. Alworth of the Planning Commission, he stated that the reason for this saturation is the fact that around 90 percent of the lots in the city limits were occupied by one or more residences, leaving only 10 percent of the building sites available for future expansion. From this it follows that future growth can come in only one way, namely, the development of apartment houses or duplex bungalows. At the present time there is a local prejudice against this type of construction so that the growth for the near future will come only from a slow using up of the little vacant property and a slow infiltering of apartments. During the meantime there will be fewer new meters installed, most of the electrical growth being shown in increased use per capita. The fourth curve of this group is the generated power of the Pasadena :Municipal Light and Power Department, this including purchased power less bulk sales to 5. other systems. Since this curve is of vital importance in our study, we have projected it into the future. Thie projection has been done in two ways, first, it was drawn as a straight line since the past points follow a straight line, and secondly, the 1940 value was estimated as a ratio based on the Southern California Edison Company's estimated gain and a smooth curve was drawn between 1930 and 1940. The estimation on the Southern California Edison system was obtained from Mr. N. B. Hinson's paper(3) on population growth. In estimating kw.-hr. demand Mr. Hinson has reverted to Dr. Pearl's theory of the logistic curve. Kr. Hineon's estimation is the only scientific estimate of the two projections, there being no basis for a straight line projection. It is given only to show the extremely high value that is obtained within a few years. In Mr. Hinson's article kw.-hr. is plotted against population, obtaining a straight line. Taking values from the curves of population and kw.-hrs. we have plotted in Chart 3 these values, and obtained a straight line relation which has been projected to the abscissae of population of 91,500 giving an ordinate of 95,000,000 kw.-hrs. The value of91,500 for population is taken from Chart 1 for the year 1940. The value of 95,000,000 kw.-hrs. agrees with the value of 85,000,000 which was 6. used for curve 4 on Chart 2, the latter value having been obtained by proportion from another chart. These curves taken as a group lead to several 1: conclusions, first, the dirowth of Pasadena as a city will be at a much slower rate in the future; second, the growth of generated kw.-hrs. will tend to be a function more and ~ore of kw.-hrs. per capita; and third, the future load will not require the continual increasing of distribution facilities that have been necessary in the past. From the power generation curve we see that if the present system is modified so that the present conditions are alleviated and provision for future expansion of a normal rate is made, the system should be able to prevent future unbalancing with only minor adjustments. PRESENT DISTRIBUTION SYSTEM The power supply for Pasadena is supplied from the steam power plant located in the south west portion of the city. The present machines generate at 11,000 and 2400 volts which is transformed to 16,500 volts before going to the main bus, while the alternator now being installed will generate at 16,500 volte and will go to the main bus direct. Located in the northern and the eastern parts of the city are substations which receive power from a loop line which comes from the 16.5 kv. bus. This arrangement is shown in Chart 4 which shows aleo the switching diagrams for these stations and the tie-in lines with the Southern California Edison system. At both sub- stations and the power plant are transformers which supply 2400 volt busses from the 16.5 kv. bueses, and from this 2400 volt bus there are feeders which supply the load in a designated portion of the station's district. There are 22 of these radial feeders and the 5 district served is shown in Chart~- There are six from the Lamanda Park substation in the eastern part of the city, six from the Raymond substation in the northern part of the city, and ten from the Power Plant. When new load was added in a district it was connected to the feeder through step-down transformers, with the result that as districts have grown the load on the feeders has increased, not uniformly, but as the growth of the districts. Voltage regulation on the 2400 volt feeders has not always been sufficient to prevent "lamp flicker''. Adjustment of this con- dition has been attempted by changing transformers to nearby feeders, giving temporary relief but causing confusion of the feeders. 8. LOAD SURVEY Since more permanent reform 1e needed, an extEmeive survey of the load conditions on these feeders and district was made. To do this we investigated four sets of load data, (1) kva.load per feeder, (2) connected kva.transformer capacity per feeder, (3) kva.. load per block, and (4) the kva.density per square mile by blocks. In determining the load per feeder, data was obtained from the Power Department on all of the feeders. It has been found from previous experience that the peak load of the system comes at .the end of December. This made it possible to find the peak from an examination of the data taken in December and the beginning of January. The data included the current, voltage, and power factor on each feeder. In all but a few exceptions the time of reading the instruments was at 6:00 P.M., approximately the point of peak demand at this time of the year. The information ob- tained is given in Table 6 in a condensed fonn. The kva. transformer capacity of each feeder was obtained so that conditions of unequal distribution of load on transformers could be determined, thereby giving an indication of where the load was increasing beyond the feeders capacity and to help in the rearrangement Chart 6. Distribution Feeders District Date '30 Current Max. Kva. A 12-22 135 557 B 11-14 71 293 C 12-23 115 510 D 11-19 150 697 E 12-22 125 542 F 11-10 195 933 Orange Grove 12-23 189 835 Los Roblee 12-23 185 801 Washington 12-23 185 833 Lincoln 12-23 157 680 Villa 12-24 196 891 Elizabeth 12-23 190 823 2 12-22 264 1210 3 12-18 300* 1380 4 12-22 240 1055 5 12-24 177 750 6 12-24 151 648 7 12-10 190 823 8 12- 5 208 973 9 12-24 150 660 10 12-18 183 847 * Meter read off scale Chart 6. Dietribution Feeders District Con. Kva. Con. Kva. Max. Kva. Sq . .Mile _ Con . .Kva. Max. Kva. Sq. Mile A 1203 830 .462 385 B 1464.5 2810 .200 561 C 405.5 707 1.260 887 D 2048.5 3970 .340 1001 E 494.5 3015 1.100 3300 F 2519.5 3230 .371 1180 Orange Grove 1471 1635 .576 927 Los Robles 627 866 1.280 1120 Washington 715.5 1125 1.165 1310 Lincoln 1245.5 458 .546 235 Villa 757.5 2005 l.175 2360 Elizabeth 894.5 1058 .921 970 2 2856.5 26700 .423 12900 3 1004.5 10260 1.326 14100 4 893 7780 1.185 9200 5 699 2210 1.075 2370 6 1454.5 1820 .446 810 7 2823.5 10300 .392 3000 8 2875.5 15150 .339 5120 9 1473 2190 .448 983 10 1442.5 5800 .586 3400 - of feeders if necessary. The data was obtained by carefully compiling the transformer capacity of each district fed by the individual feeders. Thie data was taken from maps upon which all distribution transformers are marked by the engineering department. The transformer capacity found on each feeder is listed in Chart 6 and there is also given on this same chart the ratios of kw. per kva. of connected transformer. This may be called the percentage load or overload on the transformers. The kva. load and the kva. density per block were obtained,as they gave a basis upon which comparison between different systems of distribution could be made. The load density is also important in the con~ sideration of the arrangement of feeders in any kind of power distribution. The only figures available for this study were the monthly meter readings of the customers. As the compilation of the data involved the record of every meter in the district to be studied, it was decided to use only figures for the most heavily loaded section of the city. Thie included the area bound on the north by Orange Grove Avenue, on the east by Allan Avenue, on the south by Del Mar Street, and on the west by Vernon Avenue. This district is indicated on Chart 5. The highest value of kw.-hr. used in one month was chosen from the readings for the year 1931 for each meter and the total for each block was obtained. 10. In changing from kw.-hrs. per month to kva. of load a factor of 200 was ueed in residential districts and 250 in industrial and business areas. These factors h have been obtained by the Light Department from experience and are used by the Department in determining transformer capacity to be used to supply loads. The data was then compiled by blocks and charted on a map of the district. The area of each block was then found and with its corresponding kva. the load density was obtained. Another map was then made up with all of the blocks tabulated as to density of load. These maps are shown in Charts 7 and 8. An examination of the data shows that some feeders are over-loaded to a considerable extent. The rated current of these primary feeders is 200 amperes. Feeders 2,3,and 4 are carrying heavy overloads. Those in the outlying sections will have to be rearranged or new ones installed. As the areas served are in some cases quite large there is not much possibility of rearrang~ment. The low density of load is such that any but the radial type of distribution system is out of question at present. Zoning laws are such that industria,l areas will invade but very few of the sections in the future,so expansion will have to take place by installing new feeders in the old system. 11. FUTURE DISTRIBUTION POLICY The d1etr1ct wherein the load density was calculated offers a different situation. Feeders 2,3,and 5 are overloaded and should be relieved. These are all in the heavily loaded district with a load density of over 6000 kva.per square mile. This part,at t he present time,is all served from the Power Hous e over 2,300 volt feeders. The load is now at such a point that it is not feasible to continue to supply future growth from there, so the section will have to be supplied from another source and the feeders rearranged for a more even load distribution. In the develo nment of a local distribution system the load density at certain points tends to increase to such a degree that the increasing use of power can more economically be supplied by a higher voltage. One method of doing this is by placing a substation at the center of the increased load density. The substation involves an investment in real estate(or a rental charge),transformers,switchboards,etc. and an operating expense for attendance and repairs. On the other hand the feeders running into a district to be served by the substation occupy valuable duct or pole space and require a large investment in conductors. The Power and Light Department has at the present time property near the corner of Los Robles and Colorado 12. Street which is in approximately the center of the overloaded district. The project of placing a substation on thie property has been given consideration. The present feedere would be disconnected and left in place to be used as emergency lines. This would eliminate the present congestion but the defects of a radial system would still be present. If the load is underestimated then obsolescence expense is incurred, while if the load 1s over-estimated, or the growth slower than expected, excess capital is invested withM out returning proper revenue. There is a delay in restoring service to miscellaneous lighting and power consumers in time of outage. As the loa.d increases the voltage regulation becomes poorer. Feeders must be rearranged at intervals as the load changes. Service to the consumer must be discontinued when a feeder is killed for repairs or the men :giust work on the feeder while alive. There may be the necessity of duplicating feeders to supply a bulk load. In the present case the substation would have to be a three story building due to lack of ground space. This may cause difficulty with the neighbouring business men. There is also the objection of placing a substation where it will be subject to the complaints of residence owners in the immedia.te vicintty. The people of Pasadena would be averse to having any unsightly apparatus in the 13. open and this would necessitate increased expense in a substation. There would be numerous complaints if a circuit breaker should explode. The initial investment will be high and will not be utized completely until the load has grown up to the substation capacity. The fixed investment in a company should be kept as low as possible. Within the last five years the use of networks has increased rapidly in distribution practice and soon after work on this project was etarted,the suggestion was made that the possibility of using a network in Pasadena be considered. The load in Pasadena comprises a very high percentage of residential and commereial lighting,a load which requires closer regulation than the average commercial load. The alternating current network gives this needed regulation and ie the most satisfactory permanent solution. With a network,unite are added as needed so that investment cost and charges are kept as low as possible. However,a network can be added to as frequently as desired withoui being overloaded. By its nature the network does not require any substation and this is an 1mportatnt point when it eliminates downtown substations. Up to the last year most of the Pasadena distribution system hae been overhead but with a large group of laborers 1n the organization as their part of the unemployment program the Department hae placed a number of ducts underground, 14. so that the installation of a network would be more of changeover than a new construction program. While the underground lines were being constructed, underground vaults have been installed and these have been constructed of ample size to hold the necessary low voltage transformers for a network. However before discussing their application to this problem it has been thought desirable to include a discussion of networks and their operating principles. DESCRIPTION OF THE ALTERNATING CURRENT NETWORK The low voltage alternating current network 1e formed by combining all low voltage lines into a grid, the grid being supplied with power at the intersections from high voltage sources. When networks were originally started protection was obtained with fuses but they were inadequate so that the network protector was developed. q The protector consists of a circuit breaker actuated and controlled by relays operating on reverse power flow. These protectors are used on large systems very successfully but on smaller systems fusee are still used in the low voltage mains with circuit breakers in the feeders. A feeder fault may trip out any feeder with ite transformer banks which are supplying part of the alternating current network and that part of the network must then be supplied from the adjacent feeders and their trans- 15. former banks. Upon a short circuit in the network all transformers remain in the circuit and assist in supplying current to burn off the fault~ A network fault close to a transformer may burn out the fuse in the network protector although the duration and severity of the network faults are seldom of such magnitude. Obviously it is necessary to limit the size of conductors used in the network so that sufficient current ie always available to burn off a fault. Aleo slow burning off of the fault may overheat and destroy a long length of cable. The cable sizes usually used in the alternating current network have been 250,000 and 500,000 c.m. Teets(4) however have shown that cables larger than 250,000 c.m. have sometimes failed to burn off quickly enough so that the latest designed networks have used 250,000 c.m. cables almost exclusively. If when new load is added to a network the nearest transformers become overloaded, a new feeder is brought into the district and a new unit added and the system gives the new load as good service as the rest of the system. With these general facts of a network system let us consider Pasadena in particular. A LOW VOLTAGE NETWORK IN PASADENA . Refering to Charts 6, 7, and 8, we see that feeders 2, 3, 4, and Villa have caused overloading up to Oakland Street; knowing that the trend in growth of the system is eastward on Colorado Street it is evident that feeder 8 also will soon have to be relieved. Therefore figures from Chart 7 have been taken for three different districts and compared. (1) Walnut, Lake, Green, De.Lacy. (2) Villa, Lake, Green, DeLacy. (3) Villa, Hill, Green, Delacy. Kva. per sq. mile. District. Area sq. mile. Kva. (1) .384 3,657 9,520 (2) .827 4,167 5,040 (3) 1.218 5,075 4,160 Since these figures include only the load within these streets, it is estimated that district No. 2, which is the largest district having a satisfactory load density for networking, would have a total load of 5,000 kva. As the system has a total load of 25,000 kva. at the peak, the removal of this portion of the load with a redistribution of present feeders would provide adequate distribution for the future. Furthermore the area covers that portion of town in which future commercial growth will most likely take place, so that future loading would be easily cared for from the network. Thie area still has overhead distribution in parts and this will soon have to go underground so 17. that this item of expense will be incurred with any system of distribution. The primary feeders into this district could be either 2400 volt or 16 kv. since both voltages are in use. 2400 volts would be more convenient in that it allows the use of much more of the present equipment, however, the distance from the power house and the two substations is very long and the capacity of the feeders would be small if the losses are to be kept at a reasonable figure. A variation of this would be to change to a Y connection thus giving 4000 volts and reducing the losses to some extent, but it is doubtful if the saving would be worth the extra cost of changeover. The 16 kv. feeders would be more desirable because of avoiding the large voltage drop. If 2400 volt feeders were used, the feeders would be used as radials, that is, they would go direct to the transformers from the power house, but if 16 kv. is used, these feeders can be run either radial or ring. The ring feeder goes from the source of supply to one unit through to another unit, and to as many as it can supply, then returns to a source of supply. Thie provides a two way feed, and when a fused secondary is used in the network, the ring feeder is an aid in stable operation. 18. A 16 kv., 4/0 feeder would be able to supply 7 transformer vaults, thus requiring 3 feeders for the network. These feeders can be run from one substation to another substation if costs and reliability indicate this to be the best method rather than bringing the feeder back to the original point, however, the 16 kv. busees at both stations must have a good tie-in to prevent the loss of a feeder during time of trouble. The present street vaults are of sufficient size to hold 3- 100 kva. transformers, and since many networks have found this to be a satisfactory unit, it would be logical to continue with this arrangement. Since the loss of a transformer vault does not impair the efficiency of a network, 3 phase transformers are often used because of the saving in space and first cost. Their use is generally governed by the size of the manhole since the 3 phase transformers are larger than the single phase transformers and frequently they can not oe handled conveniently. The cables used on the network could be 250,000 c.m., an accepted standard, with fuses in the low voltage mains just before they go into the network. Cables of a larger size can not be used for fear of failure to burn off quickly on a secondary fault, while 19. smaller cables although satisfactory for the present might not be able to care for f uture loads. When considering the item of relative costs we were hindered by lack of time and of experience in making cost compar1sions, but we accepted as comparable the results from other systems. The costs(5) as determined for an alternating current network for Portland, Oregon are given in the following table. Construction Coste Per Installed . Kva. Carrying Charges Investment Energy .14% Per Losses Total Kva. Per Kw-Yr . 2.4 kv. radial $101.00 14.15 5.00 19.15 2.4 kv. radial primary 117.00 17.00 5.00 22.00 11 kv. radial primary 77.00 10.80 2.20 13.00 68.00 9.50 2.20 11.70 11 kv. duplicate primary network secondary 79.00 11.10 2.20 13.30 11 kv. primary radial secondary 67.50 9.45 2.20 11.65 11 kv. primary 78.50 11.00 2.20 13.20 network secondary network secondary 11 kv. duplicate primary radial secondary network secondary As shown the costs of all the high voltage systems ran approximately equal. The duplicate primary system gives improved voltage regulation and increa sed reliability but it is best suited to serve heavy concentrated loads 20. and would not be ne eded for load such as is present in Pasadena. Network protectors are used in this system and increase the relative cost for the networks. In the Electrical World for March 5, 1932 an article gives comparative costs for networks compared to radial systems. This article is un- signed, and the amount of load and the location is not given so that the article is of use only as a general comparison. Secondary Network Radial System Network Supplied from the Supplied from from Generating Station. Substation. Substation. Investment% 100.00 110.30 115.60 Energy Loss at Annual Peak 100.00 393.10 395.00 Total Annual Loss 100.00 281.00 281.90 Total Annual Cost of Losses 100.00 315.70 317.40 Total Annual Cost 100.00 125.20 130.40 These figures show the big saving in energy loss obtained by the elimination of the substation. The Spokane, Washington system gives cost data(6) as follows. 4,000 volt Ring 4,000 volt Radial 13,200 volt Ring 13,200 volt Radial Feeders 7 8 2 3 Vaults 56 56 56 56 Trans. 16,800 16,800 16,800 16,800 Feeder 14,000 16,000 14,000 21,000 Load 14,000 14,000 14,000 14,000 %Cost 100.00 92.84 103.39 99.45 21. The load of 14,606 is the estimated load in 1940 for this system,the preeent load being about 3,300 with 7,000 kw. of direct current soon to be converted. This system used the fused secondary and 1n many respects is quite similar to the local situation. The ring system was adopted in Spokane,Washington because it improved operating conditions even though the coet was somewhat higher. The 4000 volt system was used because the substation was within 2000 feet of the load center whereas in Pasadena, the sources of supply are 6500 feet from the load center. This excessive distance would improve the cost ratio of the higher voltage system. Considering the future need of underground duct construction with the need of relief from present overloads, it seems that a network will not cost any more than the necessary extensions to the present system and it would provide for future growth in a more satisfactory manner. With a network installed the feeders would have as a group only 75 percent of their former load, so that a complete readjustment would be needed, but with that portion of the load which is farthest away from the substations removed, these feeders can be adjusted to give better voltage regulation, more even distribution of transformers, and more uniform balancing of load. At this point we might mention the 22. latest devolopment in network appliances,namely,an overhead network switch for use 1n overhead distribution syeteme. Thie switch can be used for loads of low density, such as 1500 kva. per square mile, which would include a great deal of Pasadena's residential district. This development has not been full described yet and prices are not quoted at date of writing; it may become useful 1n the near future. CONCLUSIONS We believe that a downtown substation would relieve the present congestion, but it will be crowded, expensive,and may prove objectionable to the neighboring business men. The relief will be only temporary, since the radial system tends to become unbalanced unless constant rearranging is done. We believe that a low voltage,120~208 volt secondary network fed by 16.5 kv. ring feeders will relieve the congestion,provide for future growth, provide good voltage regulation,at no greater expense. 23. Appendix: MEDIUM VOLTAGE NETWORKS. In the previous discussion no mention has been made of the network formed by tying primary mains together and feeding this grid by high voltage feeders. This medium voltage network ie generallyn operated at 4000 volts. Standard 2300 volt transw formers may then be connected between the lines and a. grounded neutral while transmission is at a higher voltage. The medium voltage network may be composed largely of the original feeders reconnected to form the circuits of the network. Power transmission to the transformers is at 11 kv. or higher. A relatively small number of transformer banks are required but these will be of large capacity compared with those which would be distributed over a low voltage network covering the same load district. Reliability requires that the network should continue to operate successfully with one transformer bank and its high voltage feeder out of service. As a means of accomplishing this the network is sectionalized by automatic oil circuit breakers in each branch. The Edison Electric Illuminating Company of Boston has recently installed four 1500 kva. medium voltage network unite . The primary network supplied by these unite was obtained by reconnecting the former feedere,none of which were smaller than 1/0 24. cable and no new cables were installed. The transformers are three phaee,rated 1500 kva. self-cooled or 2000 kva. with blowers circulating air through the vault from the street above. The voltage rating is 13.8 kv. to 4,330 volte with a provision for tap changing under load in eight steps over a ten percent range. A contact making voltmeter controls the motor driven tap changer, maintaing constant network voltage at the transformer terminals. The medium voltage network is claimed to be adapted to load densities of 600 to 20,000 kva.per square mile.With that increase in load the short circuit duty kva. on the circuit breakers is said to increase only three times for the above maximum load density with 1500 kva. network units a quarter of a mile apart. In the case of underground cable, reactors may be installed between the network transformers to limit the short circuit kva. When load densities require the installation of a low voltage network it may be supplied directly from the medium voltage network without voltage regulators. Additional regulation would probably be obtained by transformerswhich reduce the 11 kv. or 16.5 kv. to 120/208 volts for the four wire network. The medium voltage network units with circuit breakers and control would eventually be 25. removed and used elsewhere in the system as the low voltage network progressed. The primary network while xmi:t(7) ''not eliminating transformer substations,eimplifies them by reducing their individual capaeity,by building them as factory unite and installing them in vaults similar to distribution transformer vaults except for eize. Primary feeder lengths are reduced and there are also other economies claimed for primary networks. However, the chief feature is considered to be the improvement of reliability of service by the interconnection of primaries into a sectionalizes network. Primary natworks appear to be a rather uneatis• factory general solution to the question of economy, although economies may be sometimes shown in individual cases. Aleo they tend to perpetuate the use of intermediate voltages for primary circuite;that is 4 kv. and 2,300 volts. During recent years such voltages have been found inadequate,in many situations,to serve properly the loads encountered. And with the present trend toward widespread use of major appliances and the steady increase of energy consumption per customer in residential districts it is inevitable that the present more usual primary voltages must give way generally to the higher voltages. In Pasadena this steady increase has caused the 26. present need for revision of the distribution system eo that 1t ie felt that this eyetem would be more of a makeshift nature than of a permanent and that even if it emlved the needs for the present,in the near future increased demands would require more revision of the system. For this reason 1t has not been included in the main body of the report. REFERENCES 1. History of Pasadena 1 s Municipal Light and Power Plant C.Wellington Koiner 2. Biology of Population Growth Raymond Pearl Studies 1n Human Biology Raymond Pearl 3. A.I.E.E. Journal August 1929 4. Electrical Engineering August 1931 p.662 5. Electrical Engineering August 1931 p.645 6. Electrical West December 1,1931 p.287 7. Electrical World April 23,1932 p.745 TABULAT.D:D DATA For Chart 1 Year Popul at i on of Pasadena 1890 1900 1910 1920 1930 438 2 911? 30291 45 354 75 875 United States Census Data For Chart 2 Elementary School Children in Pasadena Via ter Meters in Pasadena Date r ater iJie ters Nov. 1,1912 7279 8685 10107 10597 10842 107 89 10905 11110 11888 1 2815 14895 16851 18269 18960 19416 19796 20052 20346 20460 Je,n.30, 191 4 II II 1915 II II 1916 II II 1917 II II 1918 II II 1919 II II 1920 II II 1921 II 1922 "II II 1923 II II 1924 II II 1 9 25 II II 1926 II II 1927 II II 1928 II 11 1929 II II 1930 II II 1931 School Year Ending June Number of School Ch il dren 1908 1909 1910 1911 1912 1913 1914 1915 1916 191 7 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 4106 41 8 3 4352 4510 49 53 5127 53 ~2 5393 5627 5616 5639 5595 6568 7432 7825 8830 10597 109 63 1 1234 12016 120 68 12329 12541 13017 Switchboard K. W. - Hou rs J e r y ear sold Residence Li ght Meters Date De c. 31 , 1 924 Dec. 31, 1925 June 30, 1 926 Dec. 31, 1926 June 30, 1927 Dec. 31, 1927 June :7,0, 1928 June 30, 1929 Dec. 31, 19~9 Jun e 30, 1 930 Dec. 31, 1 930 June 30, 1 931 Dec. 31, 1 931 Year K. W.-Hours 1920 10, 0 00 , 000 App rox. 1 921 16,00 0 , ~oo " 1922 22,0 00,0 00 " 1923 29,448,100 1924 35,740,422 192 5 37,758,117 1926 42,177, 66 2 1927 46,118, 200 1 928 52,434,940 1929 57, 616~480 1 930 62,7 99,089 1931 65,990,807 Note: Switchbo a rd K . Vif .hours per ye a r sol d is p owe r g ene rated plus p ower purchas ed min us power s old outsi d e of Pasadena. Li gh t 1Leters 21302 227 66 237 0 6 235 4:4 23787 24054 24 509 25017 25208 25 368 25 519 25667 25761 Sources of Da t a for Cha rt 2 Reside n ce Li ght Me ters, swi tch-bo,:ud pmv-er sold were obte,ined from the Pasadenc,., Department of Li ght and Power. Water Meters - this data was ob ~ained fr om the Eighteenth Annual Report of the Pasadena Water Depa rtment. Elementary School Children - this da t a wa s obtained fro m the a ccounting department of the Pasadena Boa rd of ~ducati on. For Chart 3 Ye a r 1920 1921 1922 1923 1924 1925 1926 19 27 1928 1929 1930 1931 Population of Pasadena in thous a nds 50 53 56 68 60 63 67 69 72 73 76 78 Milli on of Switchbo a r d K. W. ~ hours per ye a r so l d 10 16 22 27 31.5 37 42 46 53 59 63 67 No te: This da te f or po pul a ti on a nd p owe r s oJ d from t he curves of chart 2 . were ob tained BIBLIOGRAPHY Twenty Fourth Annual Report of the Pasadena Municipal Light and Power Department Electrical Eng1neer1ng April 1931 Electrical Engineering June 1931 Electrical Engineering December 1931 Electrical World March 5 1927 Electrical World October 19 1929 Electrical World February 15 1930 Electrical World June 14 1930 Electrical World July 19 1930 Electrical World October 25 1930 Electrical World May 16 1931 Electrical World March 5 1932 Electrical World April 16 1932 Electrical World April 23 1932 Electrical Journal July 1925 Transactions A.I.E.E. 1929 Westinghouse Trade Literature General Electric Trade Literature Regional Survey of New York and Environs 1931  : Arroya Weli P*#IR | / VenturaWel/ P*® 68 7 ; en, | -WL"37 WL *42-~ P#59 Windsor We // fFiguerca Wel/ P63 Bus To Pas See ci Q l65KV Water Dept. Lines Raymond Susp To L.P Sus. AVE. La Manoa Park WASHINGTON Sus HILL ALLEN P*55 Monte Wista Weld P453 Wilson Well WILSON “6 P#5E Craig Well MAR VISTA _ WEE AT | PALOVEROE ST ft b s 2 VILLA OAK Hlee to——= WL#, Woodbury Wel/ P#¥ nan hirer w v > <j ANITA SANTA PARKWOOD ALLEN HUDSON WILSON , Lane 2 LOO nciican: ave CAL-TECH SUB Mittion Vott LAB. } Epison Line ee Raymono Line Water Dert Line La Manoa Parr Line a Cac-Tecn Line Beeesd tt} ea < ——-—t— + ry coy oO eh GRAIG HUNTINGTON SANTA ANITA 7o L.P Line N re La eee To Pasadena Sub thE A Ave Q 8 6 g iN 4 Q 8 Q 2 : » g IN S 5 z 2 & ze - 8 w = 3 cee ee 8 peg 2 } < . «© / : FooTHiLL eLvo | nT waLNuT st: COLORADO ST o > a © MORNING sior . PARK ri BLANCHE x a < CJ Zz < P san PASQUAL— ST ~N ~“ obey or Fa Cat-Tech Sus Mituion Vort Las +. +4 Pe 20 a a eg os ia ore Sass | Sr0756 oe || | | ! MONTANA ST ib, SS = Ry or 2 “ By Sz Sig ° \ ee 3 > wef oe ' HOwarn BOF iy | ea ae * + RAYMOND SUB { Hy] "ai LL E — wastineTon s | s NT nd ' ry |) ea b = rae | ° F | : Ale} » 3 \ “4 8 | ve oS SS 2| o 2 ‘ < o ° oe Tt Oe a a wre 00*/ , Pg as ee : 3 e < f y Ei ay = a 2 > ST a) WL “28 MOUNTAIN Bisaced p= suger z a 3| RY a x| 83 a < ~ 5 is \ “ eee te ‘ Oe | ° Y Fe) A | aa WS Ee. > | : | ) : see See > | gee Ste os sg COLORADO < : st | i th \ : (GREEN ; es : 1b © alle o al z t aly o. Zi t's ar) a x Nae SP see 3 4 Si <oLoRAce © rr 128) (0 3 Ee DEL MAR” 4} q] & : tJ § ° . 5 os i) t CALIFORNIA t + NO | WATER DEPT PUMPS (Ro, 7 | 1 *| Casitas 150 KVA,440 ¥. ic | 2 Shelden ao | 3 *| Copelin 333 KVA, A40v i / t a | iS Ohio s # | x Devils Gate r é, € i des 3 |} : F| 9 * Atlonta 333 KVA,440 ia. ae PASADEN Es /3 ah: 40 * Woodbury 500 KVA, 2200 i “sy, s| SUB TOs rifles see sx? 3 4 Windsor 150 KVA 440V $ ao ae Seo, tal paces | yf 12 * Garfield 750 KVA 2200V z é i PLN, 1) 5 ié 1/4 %* Wilson SOOKVA 440 z s : . ay 15 *| Monte Vista 500 Kva2200 us cu Ne fagtumen at a 16 San Rofoe/ / i | SS eee 71% *e, AZ Brigden | Je H os Soca 18 *% Sunset Booster 445.0" ee a 1g oss 4 eset ud FE : r99 *, unse ee br “ <Oen 21 *| Ventura 200KVA 440V A PU Sets cREVILEA qe a 22 *% Craig SO0OKVA AAOV es Xe d Ue 23 *| Villa See #12 ee 40 24 Post Well a Sx 26 Jour dan a” 27, Fogle Rock a 28 Annandale 29 Eofon HIGH LINES : LEGEND Jo Aller Booster ——_ Raymond, LaManda Park —e— Pole top Switch Main Line 3/ *| Figueroa 200 KVA 440v and Loop Lines —o— Pole top Switch for Pump. 32 LEVANT EN Sang SAP LY rere rater Ga/-7ech. Line —2- O11 Circuit Breaker 25 *| Arroye Well 200 KVA440 ——- ——Wo/ver Dep? Pump Lines —< Disconnect Switch ---So.Cal. Lassen /6.° KV Lines + i Transformer —-— — LosAngles 33 KV Lines Woes AAO Transformer {<u Lightning Arrestors * Indidates Pumps on 165 Kv System Ce A Gen. #7 15,000 K 00 taal a Gen *8 25,000 KW Gen *6 10,000 KW 2s MUNICIPAL LIGHT AND POWER DEPT. CITY OF PASADENA 165 KV Distrisution System Chart 4 Mech Enos, ||CORRECTED| TS aNBEROVED onawn | AR Gye | (eA races | WA Girge (0-24-31 CHECKED CHANGES Fe ik in GEES on A-|80 2713 ey Lt bf cca) ome N ae Charl 5 MAP. SHOWING TERRITORIES DAE bY FELL SONS wee © S oS, fit Boundary of Area off ZZZZZZE Scale in Feet ry was /ade Study ich Load (eS w/?, or) ee 1000 °