US2713081A

US2713081A - Cable systems

Info

Publication number: US2713081A
Application number: US241556A
Authority: US
Inventors: Edwin J Merrell
Original assignee: Phelps Dodge Copper Products Corp
Current assignee: Phelps Dodge Copper Products Corp
Priority date: 1951-08-13
Filing date: 1951-08-13
Publication date: 1955-07-12
Anticipated expiration: 1972-07-12

Description

E. J.` MERRELL July 12, 1955 CABLE SYSTEMS 2 Sheets-Sheet l Filed Aug. 13. 1951 JNVENTOR. bw/N Aff/wia July 12, 1955 E. 1. MERRELL 2,713,081

, CABLE SYSTEMS Filed Aug. 13, 1951 2 Sheets-Sheet 2 1N V EN TOR. raw/,v d MEE/Pa L United States Patent Ehce Zifiti Patented duly 12, 1955 CABLE SYSTEMS Edwin J. Merreli, Scarsdale, N. Y., assigner to Phelps Dodge Copper Products Corporation, New York, N. Y., a corporation of Delaware Application August 13, 1951, Serial No. 241,556

1 Claim. (l. 174-14) This invention relates to an improvement in` electric cable systems of the type wherein one or more insulated cables are loosely immersed in oil, or equivalent liquid insulating medium in pipe. v

In such systems the ends of the cables are enclosed in terminations or potheads which also contain oil.

The oil in the pipe is not under electric stress and therefore a moderate amount of contamination is not of great importance. The oil in the terminal is under electric stress and contamination would be liable to lead to terminal failure.

It is not practicable to merely seal the entry of the cable into the pothead in order to effect separation of the two oil systems because expansion of the oil, both that in the pothead itself and that from the cable insulation, would result in excessive pressures in the potheads which, usually having porcelain walls, would be thereby endangered and failures would likely occur.

The objects of the present invention are to equalize pressures in pipe and terminals, to prevent excessive pressures in the terminals, to ensure the retention of oil in the terminals in the event of loss of pressure in the pipes and to prevent contamination of the oil in the terminals by that in the pipe.

It is therefore necessary, not only to seal the entry of the cable into the pothead by means of a stuing box, but also to provide a by-pass to the seal to relieve the pressure. Means to accomplish this are well known, one being to provide a pair of valves in the by-pass, which permit the egress of oil from the pothead when the pressure reaches a predetermined value and the other to permit of entrance of oil to the pothead when the pressure in the latter drops\to a predetermined value.

This means has the disadvantage of permitting contaminated oil from the pipe oil system to enter the potheads. Another means provides a movable diaphragm in the by-pass which expands or contracts in accordance with the pressure requirements of the pothead. These both have the disadvantage of moving parts with im evitable wear and unpredictable life.

The present invention, like the latter system, provides means for pressure equalization and prevention of oil contamination but does so without moving parts.

The means employed consists in the use of an oil filter in the by-pass. Such a device may be of the tilterpaper type or the adsorbent powder type commonly used for oil lltration. Oil will pass through the iilter only when there is a difference of pressure across it.

The foregoing and other features of my invention will now be described in connection with the accompanying drawing forming part of this specification in which I have illustrated my cable system in its preferred form, after which l shall point out in the claim those features which I believe to be new and of my own invention.

In the drawings:

Figure l is a sectional View of a cable terminal to which my invention is attached.

Figure 2 is a section along the line 2--2, Figure 1.

Figure 3 is a modification shown in diagram which I may employ, adapted to a three cable termination.

Figure 4 is a further modification showing a crosssection similar to that shown in Figure l with a different iilter attachment.

In the carrying out of my invention, 16 is a pipe containing a cable 11, ending in a terminal 12. A stuffing box seal is shown at 13. A by-pass is shown at 14 which for simplicity, is shown exterior to the terminal (see Figures l and 3) but which may be incorporated in the base of the terminal (see Figure 4). For purposes of illustration, a paper type filter is shown at 15 within the by-pass 14.

In Figure l, l illustrate a paper type filter 15 which is shown in its simplest form and comprises a paper filter element 16 held between two supporting plates 17 and connected in the by-pass line 14.

In Figures 3 and 4 my lter element 16 is shown supported between two

capsules

18 and 19. These metal capsules or cylinders are perforated at 20 and have closed ends 21 and the filter element 16 is packed in between the capsules.

With special reference to Figure 3, I show a diagrammatic sketch of a three cable termination in which the stuffing box element 13 is shown in each cable termination a distance down from the pothead with the element 13 in ali three lines by-passed through a single filter element 16. My filter element in this View is supported between two capsules i8 and 19. The by-pass line in each of the three cables passes through a single filter.

Referring especially to Figure 4: This is an enlarged detail of a mountina which I may use in which 30 and 31 are structural mounting plates and in which the pipe l@ is securely fastened and held. A passage d@ (two are shown) extends through this mounting plate 30 and is adapted to receive the filter element 16 at the upper end, the lower end is exposed to the space 41 which is open to the inside of the pipe line 10. It will be readily understood that with any differential of pressure the uid in the pipe 1l) will pass through the filter 16 and into terminal 12. The fluid travels through space 41, passageway and filter element 16 which is supported between the perforated plates 1S and 19. Any impurities of the insulating fluid in the pipe line will therefore be kept out of the fluid in the terminal and will thereby eliminate terminal failures.

In operation when high ambient temperature or heat from the conductor within the terminal or exudation of oil from the cable, or any combination of these, causes a rise in pressure within the terminal, so that the pressure is in excess of that in the pipe, oil will be forced through the iilter element 16 and the pressure in the terminal relieved. lf, due to low ambient temperatures, drop of load or any combination of these or other causes, the pressure in the terminal should drop below that in the pipe, oil will be forced through the lter element 16 and will restore the pressure in the terminal and, at the same time filter it, so that the oil that enters the terminal will be free of any impuriy that may have contaminated the pipe oil.

Due to the alternating llow of the oil through the filter, there will be a tendency for the filter to be selfcleansing. However, provision would be made for the replacement of the ltering medium without loss of pressure, such as by means of valves 46 and 47 in the by-pass pipes.

I wish it distinctly understood that my cable system herein described and illustrated is in the form in which I desire to construct it and that changes or variations may be made as may be desirable or convenient without departing from the salient features of my invention and I therefore intend the following claims to cover References Cited in tl'ie flle of this patent UNITED STATES lPATENT-S Eby Nov. 3, 1931 Hochstadter et al. May 11, 1937 Whisler Oct. 19, 1937 Unger Apr. 25, 1950 Nelson May 30, 1950