Document 10xQyqGGqDvqrxovZBVzBdaXK

Monsanto ONlFROM (NAME & LOCATI M. F. BABER - ST. LOUIS DATE October 13* 1970 cc SUBJECT REFERENCE TO FLUIDS FOR POWER CABLES Underground Power Transmission Conf. Memo by M.F. Baber, 10/2/70 p. G. Benignus J. G. Bryant R. Davis J. R. Fallon/D. E. Roush R. H. Munch W. R. Richard J. J. Roder - CHICAGO Contact: A. Zanona, Transmission Engineer, Commonwealth Edison Co. October 2, 1970 Present consumption of mineral oil and polybutene in underground pipe-type power transmission cables is approximately 2 million gallons, or $1 million at an average price of 50^/gal. Use should increase to $1.5-2 million by 1975* growing steadily thereafter. Most of this will be consumed in 138 KV to 3^5 KV cables, where low viscosity mineral oil and polybutene are satisfactory. To replace these fluids, a new fluid would have to have acceptable physical and electri cal properties and be significantly less expensive than 50^/gal. It is improbable that there are any properties which a new fluid might have which would justify a significantly higher price in the large volume applications. However, by 1980 approximately 200,000 gallons of high performance fluid may be needed for 750 KV underground cables. This fluid would have to be compatible with polymeric papers and might sell for as much as $5/gal if no other satisfactory fluid were found. However, it is probable that a lower cost, satisfactory fluid will be found. Before a new fluid would be used in high voltage power cables, it would have to go through an expensive test ing program and would have to be approved by the major cable companies. In this regard, the two attached timely reports were written by J. Roder. He called on this same utility a few days before my contact, but as of the time of my contact, I did not know of his call. DSW 201830 STLCOPCB4059897 2- - J. L. Williams is referred to in that Call Report. He is Chairman of the Insulated Conductor Insulation Group of IEEE. Cable Oil Consumption The table on the next page shows that the present cost of cable oil is approximately $5,000/mile of installed cable, as compared to a total installed cost of under ground pipe-type transmission cable of $200,000 $1,000,000/mile. It also shows that in 1970 cable oil consumption should be approximately $1,000,000. By 1980, this could be no more than $2,000,000 or could possibly be as high as $10,000,000 depending upon future local and Congressional legislation. Sun Oil is the present supplier of cable mineral oil at an estimated price of 45-50^/gal. It is not obvious why a lower cost, lower viscosity oil could not be supplied. Polybutene at approximately 55-65^/gal is supplied by Cosden Oil and Standard Oil. It is confidential that during the next five years Commonwealth Edison will consume approximately 700,000 gallons of cable oil. They have just placed an order for 150,000 gallons. This will go into 376,000 cir cuit feet or 70 miles of underground cable. Almost all of this will be 138 KV. Most will go into 8 inch pipe, but some 6 inch and 5 inch pipe will be used. During the next five years other utilities will be installing underground systems ranging from 138 KV to 345 KV. Approval of a New Cable Oil For years only mineral oil was used in underground cables. This was produced primarily by Sun Oil and was a higher viscosity oil than that used in trans formers. As the power rating of cables increased, there became a problem with removing heat from the cable; thus recently the utilities started cooling the cables by pumping the oil through the cables and through a heat exchanger. The existing cable oil was too viscous for this, and so in a series of tests at Cornell Univer sity on a 3^5 KV cable, polybutene (polyisobutylene) was tried and was proved to be acceptable. Thus, poly butene is usually used today in forced-cooled pipe-type cables. Since there is no similar driving force to cause the industry to want a new fluid for the bulk of uses, it will probably be very difficult to convince the industry to test a new fluid unless it is consider ably less expensive than polybutene. DSW 201831 STLCOPCB4059898 3- - 138 KV 345 KV 500 KV Cost of Underground Transmission Cables Cost of Overhead (OH) Cable $1000/mile {>35-50 :;6o-8o $85-100 Ratio of * Underground (UG) Cost to OH Cost 4-6 8-13 IO-15 Est. UG Cable Cost $1000/mile $210 $700 $1200 Est. Mineral Oil Cost $1000/mile {55 {15-10 $5-10 * Half of 1967 estimates are felt to be reasonable Underground 1968 1969 1970 1974 Cable Miles Forecasted Cable Oil Consumption Oil Consumption, Gal, per mile Oil Cons. M gal_____ 157 10,000 160 10,000 193 10,000 356 10,000 1,600 1,600 1,900 3,600 Total Potential from Overhead Transmission ** 1968 1974 11,000 10,000 10,000 10,000 110,000 100,000 Oil_ Cons. $M $0.8 $0.8 {>1.0 $1.7 $55 $50 ** Assuming all transmission cable goes underground which will not happen DSW 201832 STLCOPCB4059899 -4- Before an oil will be approved by the utilities it will have to be approved by the major cable companies, be cause the cables are sold under a guarantee. This is true even though the utility normally purchases the oil. Mr. Zanona suggested we contact the following major cable companies as a first step: Anaconda, Phelps Dodge, General Cable, and Okonite Corporation. Since I already have contacts at Anaconda, I plan to visit them on this and other matters at Marion, Indiana and at their New York research labs. Also, apparently Anaconda has ex perimented with new fluids more than other cable companies. The cable oil must pass a series of dielectric tests. Then it must be compatible with the high viscosity oil normally used to impregnate the cables before they are shipped to the utilities to be placed within the pipes. The oil must have proper aging characteristics in combi nation with the paper insulations used, it must not attack the metals used in the system, and it should have the ability to absorb gases such as loose hydrogen. After passing the above tests, then the fluid would have to be tested in the manufacturers' cable designs in test cells at operating stresses of 200 to 400 volts per mil at a range of temperatures. Each sample would re quire from 4 to 6 months to test. Since some tests probably would fail, perhaps from poor construction of test cells, the total testing program would probably take considerably longer. Although it is recommended that the cable companies be contacted first, Arthur D. Little is recognized as a testing authority in the cable industry, somewhat like Dobel is in the transformer industry. They are familiar with cable manufacture and testing. Previous testing programs on Fluids and Papers The Cornell University test concerning the first 3^5 KV cable has already been mentioned. Consolidated Edison of New York City worked with Cornell University on that test and installed the first 345 KV underground cable using polybutene. The Armour Institute, Illinois Institute of Technology (ITRY), performed a 6 year testing program on dielectric fluids and insulations, sponsored by ERC. A lengthy and poorly written report was issued after 6 years with no definite answers being found from the ITRY tests. Mr. Zanona will send a copy of the report to me for review; however, the report will not be issued to the general public until early next year. 0S\N 20A 833 STLCOPCB4059900 -5- As a result of these tests, polypropylene and polysulfone films appeard to be the best solid insulation materials for 750 KV. However, there were problems with using films in the manufacture of cables. About this time 3M Company announced they had the capability of producing syn thetic paper insulations from any of the polymers con sidered. 3M Company was contracted by ERC to produce a batch of polypropylene synthetic paper. This presently is being produced and will be shipped to the four major cable companies for their evaluation. Research and Development Considerations The maximum operating copper temperature of present cables is 85C. Present paper insulation will not last the expected 40 years above this temperature. Present designs are allowed to go to 105C for up to 100 hours each year. Even if a better fluid were provided, at the present time the paper insulation is the limiting factor. If polymer paper insulation were used which could operate at 130C, an oil would be needed which could operate at 130C, and at 150C for up to 100 hours per year. The temperature of the sheath or outer steel pipe still could not go above 60C. Above this temperature the soil dries out and a run-away thermal condition can result. The outer temperature can be kept down by increasing the size of the pipe and the flow of oil through the pipe and the cooling system. However, the pipe cannot be made too large or the cost of installation would be too high. If additional transmission capacity is needed, forcedcooling of a cable in service generally is less ex pensive than installing a higher voltage cable. There is disagreement concerning the value of forced-cooling when a new cable must be installed anyhow. A 7^5 KV cable must be forced-cooled. Below this voltage the utility has a choice, and many have not accepted the con cept of forced-cooling. There are two reasons why synthetic papers are preferred over synthetic films in extra high voltage designs. First, present films do not have sufficient porosity to allow the removal of voids during vacuum impregnation. Second, there is a problem with wrapping and bending of cables which have been fabricated with synthetic films. The films frequently bind and crinkle upon bending of the cable. Papers have much more "give" than films. DsW 201834 STLCOPCB4059901 6- - One major problem with the selection of fluids and syn thetic insulation at higher voltages is obtaining mater ials with low dielectric constants and low dissipation factors (below 0.01) at these voltages. Also at higher voltages more heat is generated in specific areas and many materials increase significantly in dielectric constant and dissipation factor with temperature. A low dielectric constant is needed for two reasons: First, to keep down the capacitance and the need for phase angle correction, and second, to keep down the dissipation factor which is frequently related to dielectric constant. Frequently, there is no problem with the dielectric constant and dissipation factor of individual fluids and synthetic materials. However, when they are combined, for an unknown reason these properties frequently go much higher than acceptable. Therefore, these proper ties have to be checked in a fluid-solid system, and not individually. As would be expected, the purity of the materials is especially important at the higher voltages. ms Atts. 2 MICHAEL F. BABER DSW 201835 STLCOPCB4059902