[j_0|L FILLED
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1. United States Patent 19 u 4 419 056 Ege 45 Dec 6 1983 54 BACK UP FOR HIGH VOLTAGE CABLE 2 817 396 12 1957 Booth nnnnvenrenenerneneenen 417 428 PRESSURIZING SYSTEM 3 388 207 6 1968 Lansch 137 567 3 782 863 1 1974 Rupp 417 393 75 Inventor Sigmund Ege Oslo Norway 4 080 107 3 1978 Ferrentino 417 273 4 341 508 7 1982 Rambin Jr nnen 417 426 73 Assignee International Standard Electric 4 Kine Corporation New York N Y Primary Examiner Carlton R Croyle Assistant Examiner Paul F Neils 21 Appl No 285 700 Attorney Agent or Firm John T O Halloran Alfred 22 Filed Jul 22 1981 C Hill 30 Foreign Application Priority Data 57 ABSTRACT Aug 4 1980 NO Norway annuus 802327 A back up system is provided for a pumping plant or a pressure reservoir system used to maintain insulating oil 51 Int C3 nnen F04B 23 04 FO4B 43 06 under pressure in high voltage submarine power cables 52 US Cl orein 417 426 417 53 which includes a gas driven membrane pump to insure 417 393 92 5 R a small outflow of oil at a rupture point in the power 58 Field of Search 417 63 374 425 426 cable to prevent water from penetrating the cable The 417 434 435 53 393 395 92 5 R 91 1 51 proper operation of the membrane pump is insured by 60 571 p References Cited U S PATENT DOCUMENTS 1 627 257 5 1927 Stevens cecsesererereeeseeseeees 417 63 56 OIL INLE2. the membrane pump 5 is kept full of oil on both sides of the membrane On the suction side a the oil is maintained at a pressure equivalent to the head of oil in the storage tank this tank being kept under vacuum while the oil on the gas side of the pump will be maintained under the same pressure as that provided by the electrical pump 2 for the cable at 4 In order to test that the membrane pump 5 is opera ble without introducing gas into the pump all valves but valve 9 are opened Valve 11 opened slightly only Oil will now flow from the tank 1 via the electrical pump 2 and valve 10 to operate the membrane pump 5 because the outlet d is opened by the open valve 8 As a result the pump 5 will pump oil from its a side to its c side the pumped oil being drained through valve 11 The drained oil from valve 11 as well as oil exhausted through valve 8 should be tested for deteriorations to 4 419 056 5 obtain indication of the condition of the back up system The drained oil should if necessary be degasified and pumped back to the tank 1 The test mode is also illus trated in FIG 4 If the electric power should fail so that the electrical pump 2 is unable to maintain the required pressure in the cable at 4 valve 10 will be switched from open to closed and thereafter valves 8 and 9 from closed to open In this mode which is illustrated in FIG 5 the gas which is supplied from the gas bottle battery 6 will first force
3. if the back up system should ever be called upon to maintain pressure on the cable but at this time the power will have been shut off the cable and the introduction of dry nitrogen is therefore not so serious The gas will not cause an electric breakdown of the cable and may be removed by subsequent treatment of the cable oil prior to reenergizing the cable An alternative solution to the problem outlined above is to introduce an additional diaphragm type pump so that the drive side of the main pump is always operated by degasified oil supplied from the additional pump The additional pump may be operated during its test and operation mode by pressurized gas or air While the possibility exists with the additional pump that its dia phragm may rupture and gas or air may be introduced into the oil system on its pump side the risk of transfer ring deteriorated oil into the pump side of the main pump is negligible because the oil on the pump side of the additional pump and on the drive side of the main pump is frequently degasified BRIEF DESCRIPTION OF THE DRAWINGS To give a better understanding of the invention two examples of its application will be given below with reference to the accompanying drawings in which FIG 1 shows the invention used in conjunction with a pumping plant FIG 2 shows a legend of valves FIGS 3 5 schematically illustrate three modes of operation of the arrangement of FIG 1 FIG 6 shows how a back up
4. oil supply and a second valve arrangement coupled between said degasified oil supply and said drive input of said one diaphragm type pump and to said oil output of said one diaphragm type pump 20 A back up system according to claim 19 wherein said first arrangement includes a third valve arrangement coupled between said reservoir and said drive input of said one dia phragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation
5. the stand by oil within the pump 5 out through valve 8 while operating the pump 5 and finally operate the pump 5 on gas as intended By operation of the pump 5 oil will be supplied from the tank 1 to the cable at 4 When reinstating the stand by mode after repair of a fault which caused the back up pump to operate the system should first be switched to the test mode The oil tank 1 must not be completely filled with oil since the space above the oil is to be maintained under vacuum provided by a continuously running vacuum pump not shown In FIG 6 is illustrated a different embodiment of the invention used in connection with a standard pressure reservoir systems where pressure reservoirs 20 provide oil for the cable at 4 The elements 5 9 11 and 12 which are the main parts of the back up system are the same as in FIG 1 A valve 21 is introduced between the back up system and the pressure reservoir system The tank 22 is different from the tank 1 shown in FIG 1 in that it is maintained completely full of degasi fied dil To compensate for variation in volume of the oil in the tank 22 as the temperature varies a pressure reservoir 23 is connected to the tank 22 by means of a valve 24 Finally there is provided a valve 25 for inter connecting the two inputs a and b to the membrane pump during the stand by mode and a valve 26 to be used in the test mode to ascertain that the membrane pump 5 operates and when filling the tank 22
6. valves 21 and 25 so that the supply of degasified oil operates the pump Oil from the tank 22 is exhausted through valve 11 as in the case of FIG 1 and the oil on the a c side of the pump 5 can be tested for deteriora tions Also the oil drained at pump outlet d should be checked for deteriorations If the cable should start leaking oil asa result of exter nal mechanical damage or for other reasons the pres sure reservoirs 20 will feed additional oil to the cable at 4 whereby the pressure will gradually decrease When the pressure approaches a critical low limit as sensed by a pressure switch not shown valve 25 will be closed first and valves 8 and 9 will open This will initiate operation of the membrane pump and valve 21 is finally opened to allow the oil to be pumped from the tank 22 and into the cable at 4 This is illustrated in FIG 10 Since vacuum will be created above the oil in the tank 22 as soon as the pump 5 starts pumping the gas driven pump 5 must be located far enough below the tank 22 to give sufficient head of oil at least 3 4 feet to make certain that the pump 5 will prime itself According to one embodiment of the invention the suction line is hinged just below the tank so that the lower portion of this line with the pump 5 may be rotated 90 in the middle of the skid to reduce the space requirement during shipping In FIG 11 is schematically illustrated the back up system of FIG 6 mounted on a s
7. Oil for initial filling of the tank 22 and for testing of the pump is provided from a source of degasified oil 27 The back up system may be assembled in the factory where the tank pump and pipes are evacuated and filled with degasified oil There are generally four modes of this system an evacuation filling mode a stand by mode a test mode and a back up operation mode The state of the various valves is given in the table below and the various modes are illustrated in FIGS 7 10 Mode Valve No 24 Evacuation Filling Stand by Test Operation m N oon Aja Ona ale aon a Oona a aa an aa aon In the evacuation and filling mode FIG 7 all valves but Nos 25 and 26 are closed in order to first evacuate the tank 22 pump 5 and associated piping and there upon fill or pump oil into the system The tank 22 must be provided with a vacuum pump not shown for use prior to and during filling Once the back up system is ready for transportation to the cable pressure reservoir site valve 26 should be closed and valve 24 opened whereby the stand by mode of FIG 8 is obtained In order to test the membrane pump for proper opera tion on site without introducing gas into the pump 5 a 15 20 25 30 35 40 45 50 55 65 6 portable source of degasified oil 27 will have to be brought in and connected to valve 26 The test may be performed by opening valves 26 and 8 after first having closed
8. T OIL FILLED POWER CABLE CHAMBER J introducing degasified oil at the drive side of the pump during the stand by and test modes of operation of the back up system 20 Claims 19 Drawing Figures U S Patent Dec 6 1983 Sheet 1 of 5 4 419 056 Fig 2 OIL FILLED POWER CABLE j Fig 1 U S Patent Dec 6 1983 Sheet 2 of 5 E 25 En ne lt lt LS Dn 23 E 9 8 me m c 11 Daan Jas 20 Dm are Og Fig 7 Fig8 Fig 9 4 419 056 VY U S Patent Dec 6 1983 Sheet 3 of 5 4 419 056 U S Patent Dec 6 1983 Sheet 4 of 5 4 419 056 Fig 13 Fig 14 Fig 15 U S Patent Dec 6 1983 Sheet 5 of 5 4 419 056 Fig 17 Fig18 Fig 19 4 419 056 1 BACK UP FOR HIGH VOLTAGE CABLE PRESSURIZING SYSTEM BACKGROUND OF THE INVENTION Paper and oil insulated high voltage power cables rely on maintaining the insulating oil under pressure for the proper functioning In the case of the so called Pipe Type Cable three insulated conductors pulled into a common steel pipe the pressure is normally maintained by a pump drawing oil from an oil tank The so called Self Contained Cable is normally kept under pressure by means of static oil reservoirs although in certain cases a Pumping Plant may also be used for this type of cable particularly in the case of long submarine crossings One reason why pumping plants are being used also for Self Contained Submarine Cables is that with th
9. d by mode of oper ation 2 A back up system according to claim 1 wherein said oil source includes an oil pump coupled to said reservoir and said first arrangement includes a valve arrangement coupled between said oil pump and said drive input of said one dia phragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation 3 A back up system according to claim 1 further including a second diaphragm type pump having two spaced diaphragms interconnected by a rod a gas drive input coupled to a source of driving gas and to a first chamber of said second diaphragm pump dis posed between said two diaphragms a gas drive _ 5 20 25 30 35 40 45 50 55 8 output coupled to said first chamber of said second diaphragm type pump a suction input coupled to an additional supply of said electrical insulating oil and a second chamber of said second diaphragm type pump adjacent one of said two diaphragms and an oil output coupled to a third chamber of said second diaphragm pump adjacent the other of said two diaphragms and to said drive input of said one diaphragr type pump said second diaphragm type pump supplying said oil to said drive input of said one diaphragm type pump during said stand by said test and said operating mode of operation 4 A back up system according to claim 3 wherein said additional oil supply is a degasified electrical
10. e oil side and the gas side of the membranes including the valve system which makes the rod connecting the two membranes reciprocate While the pump is still under vacuum it is filled with degasified oil One added advantage of the invention is that all the critical parts in particular the valve system will be kept in good condition by the oil so that one may be certain that the pump really will work after having been standing idle maybe for years When the back up system has performed its function the pump can again be evacuated and filled with degasi fied oil This could conveniently be done at the time that the oil storage tank is being evacuated to be refilled with degasified oil According to one embodiment of the invention which is particularly convenient when the invention is used in connection with a standard pumping plant it is possible to make a periodic check on the functioning of the gas driven pump without introducing gas into the gas chamber of the pump This is accomplished by driving the pump by means of oil under pressure sup plied by the electric oil pump which normally applies pressure to the cable system Such a test will first of all prove that the pump really will operate should it be asked to take over the pumping action and the oil which during stand by has been sitting in the oil cham ber of the pump during this time could be checked for gas content and power factor With oil on both sides of t
11. eed for a rotating seal on the shaft between the motor and the pump Such a shaftseal is particularly undesirable in the case of a pump which is to stand as a back up maybe for several years before it is called upon to pump oil Hermetic motor pump combinations for air driven motors without a rotating seal do not exist The pumps which come closest to being hermetic are those using the diaphragm or membrane principle One such pump marketed by THE WARREN RUPP CO Mansfield Ohio under the trade name Sand Piper Pump Model No SAI A or SB1 A utilizing two membranes con nected by a rod and with a driving gas in contact with the rod side of the two membranes seems particu larly well suited for the purpose A diaphragm or mem brane pump of this type is shown in Operating Instruc tions Service Manual and Repair Parts List issued as Form No SPL 2 77R by The Warren Rupp Co and fully disclosed in U S Pat No 3 782 863 whose disclo sure is incorporated herein by reference The only dis advantage is that it utilizes a membrane which is not made of metal and therefore in time will allow gas and 25 30 35 40 45 50 55 60 65 2 moisture to permeate through the membrane to the cable oil on the other side SUMMARY OF THE INVENTION The main object of the present invention is to over come the disadvantage of the previously known back up systems The present invention overcomes the disadvanta
12. ges of known back up systems by comprising at least one diaphragm pump for pumping cable oil from an oil reservoir to the cable core in case of rupture of the cable sheath causing oil leaks and means for providing that the drive or gas side and the inlet outlet or suction side of the diaphragm of the pump are subjected to oil at least during the stand by mode of the pump By filling the gas side of the membranes with degasi fied cable oil this part of the pump may be maintained under a positive pressure by means of the same type of pressure reservoir which is used on the cable or in the case of a system with pumping plant from the electric pump which maintains pressure on the cable until the pump is called upon to provide additional oil to the cable for instance due to a leak developing or in the case of a system with pumping plant to take over from the electric pump in case of power failure At this time the oil on the drive side of the membrane will of course be replaced by the driving gas but this condition will only persist until such a time as the leak in the cable has been stopped or the cable end capped in case of a com plete severance and the cable again can be kept under pressure by the reservoirs This time period will be fairly short and moisture and gas will not have time to permeate the membrane to any detrimental degree In preparing the pump for stand by vacuum can be pulled on the whole pump both on th
13. he membrane it will also be possible to make sensitive tests for possible cracks in the membrane by valving off the two sides of the membrane and monitoring the dif ferential pressure 4 419 056 3 The above test could also be made on the back up system for cables supplied with pressure oil reservoirs but in this case a separate degasifier and an oil pump will have to be used to perform the test According to one embodiment of the invention the back up system is mounted on a skid containing all the required units such as storage tank pressure reservoir pump and gas bottles Such a back up may be evacuated and filled with treated oil at the factory shipped to site and hooked up to the existing pressurizing system either of the reservoir or the pumping plant type The inven tion may be used to advantage even in the case where a pump with a metallic membrane is being used particu larly if one should require that the pump should be started up occasionally in order to make sure that it really will pump effectively if called upon to do so If such a test were to be made with gas rather than oil on the gas side of the membrane it may have serious consequences to the cable if a crack should develop in the membrane since the gas immediately will enter the cable With the present invention the danger is elimi nated since we have degasified oil on both sides of the membrane It is true that gas could still come through a broken membrane
14. he scope of the present invention which is delimited solely by the appended claims I claim 1 In a system for pressurizing oil filled power cables including an electrical insulating oil source coupled to said power cables to fill said power cable with said oil and to maintain oil pressure in said power cable a back up system to supply said oil to said power cable in case of a rupture of said power c cable causing oil leaks com prising a reservoir of said oil at least one diaphragm type pump having two spaced diaphragms interconnected by a rod a gas drive input and a gas drive output coupled to a first chamber disposed between said two diaphragms a suction input coupled to said oil reservoir and to a second chamber adjacent one of said two dia phragms and an oil output coupled to said power cable and to a third chamber adjacent the other of said two diaphragms said back up system having a normal stand by mode of operation when said power cable is not ruptured a test mode of opera tion to enable testing of said diaphragm pump and an operate mode of operation when said rupture occurs and a first arrangement coupled to said drive input to provide said oil in said first chamber during at least said stand by mode of operation said second cham ber being coupled to said oil reservoir during all operating modes such that said second chamber and said first chamber have said oil therein simulta neously during at least said stan
15. id second arrangement includes a degasified oil supply and a first valve arrangement coupled between said degasified oil supply and said drive input of said one diaphragm type pump and said oil output of said one diaphragm type pump 11 A back up system according to claim 10 wherein said first arrangement includes a second valve arrangement coupled between said reservoir and said drive input of said one dia phragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation 12 A back up system according to claim 1 further 65 including a source of driving gas and a first valve arrangement coupled to at least said first chamber of said one diaphragm type pump and said 4 419 056 9 source of driving gas to enable said driving gas to operate said one diaphragm type pump when said rupture occurs and to simultaneously drive said oil from said first chamber of said one diaphragm type pump 13 A back up system according to claim 12 wherein said oil source includes an oil pump coupled to said reservoir and said first arrangement includes a second valve arrangement coupled between said oil pump and said drive input of said one dia phragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation 14 A back up system according to claim 12 wherein said first arrangement includes a second valve arrangeme
16. insulating oil supply 5 A back up system according to claim 1 wherein said first arrangement includes a first valve arrangement coupled between said reservoir and said drive input of said one dia phragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation 6 A back up system according to claim 5 further including an oil pressure tank and a second valve arrangement coupled between said tank and said reservoir to compensate for pressure variations in said reservoir 7 A back up system according to claim 1 further including a second arrangement coupled to said drive input of said one diaphragm type pump to drive said one diaphragm type pump by pressurized oil during said test mode of operation 8 A back up system according to claim 7 wherein said oil source includes an oil pump coupled to said reservoir and said second arrangement includes a valve arrangement coupled between said oil pump and said drive input of said one dia phragm type pump and to said oil output of said one diaphragm type pump 9 A back up system according to claim 8 wherein said first arrangement includes a portion of said valve arrangement coupled be tween said oil pump and said drive input of said one diaphragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of operation 10 A back up system according to claim 7 wherein sa
17. is system it is reasonably inexpensive to store a large quan tity of oil in case the cable should become ruptured so that one might prevent water from entering the cable by creating a certain small outflow of oil at the rupture point The pumping plant is however dependent on supply of electricity The oil reservoir system does not require electricity but the cost of providing extra oil capacity for a possible cable rupture becomes prohibi tive For pumping plants pumps relying on means other than electric motors are known to have been used as a back up in case of power failure The back up pump may have been driven by an air motor fed either with air or nitrogen stored under high pressure in gas cylin ders If a suitable system could be developed which could act as a back up for a pumping plant such a system ought to be suitable also as a back up for pressure reser voirs in case a leak should develop in the cable system Unfortunately the oil in a Self Contained Cable must be virtually completely free from moisture and gas in order to function properly as an insulation together with the paper For this reason it is for instance not permissible to store such oil under a blanket of nitro gen such as is normally the case for a pipe type cable pumping plant For this reason it is known to use so called canned motors to drive the pump in pumping plants for this type of cable Use of these hermetic mo tors excludes the n
18. kid 30 for pre fabrica tion and transportation to site The membrane pump 5 is shown in two positions the full line position being the installed position in order to obtain the necessary head of oil while the broken line position illustrates the trans portation position In FIG 12 is schematically illustrated a back up sys tem for a pumping plant This is an alternative to the system illustrated in FIG 1 in that the drive or gas side b d of the main diaphragm pump 5 is subjected to pressurized cable oi at all times during the stand by test and emergency operation modes This is obtained by letting the pressurized gas or air supplied from the tank or bottle 6 operate a second diaphragm pump 14 identical to the main diaphragm pump 5 i e the gas enters at inlet b and is exhausted through outlet d on the drive or gas side of this pump 14 thereby obtaining circulation of degasified cable oil from the a c side of the pump 14 through the b d side of the main pump 5 Pressure is maintained in this loop by a pressure tank 15 and the oil may occasionally be circulated via a degasi fier not shown to degasify the oil and refill the tank 15 In comparison with the FIG 1 layout the valves 8 10 and 13 have been omitted The stand by test and emer gency operation modes of FIG 12 layout is schemati cally illustrated in FIGS 13 15 In FIG 16 is schematically illustrated an alternative back up system to be used in connection with a press
19. may be provided for a cable installation using pressure reservoirs to maintain pressure on the cable FIGS 7 10 schematically illustrate four modes of operation of the arrangement of FIG 6 FIG 11 shows how the back up system may be mounted on a skid for pre fabrication and transporta tion to site FIG 12 schematically illustrates a back up system for a pumping plant employing two diaphragm pumps FIGS 13 15 show the three modes of operation of the arrangement of FIG 12 FIG 16 schematically illustrates the two diaphragm pump solution in connection with pressure reservoir plant and 0 20 25 30 40 45 50 65 4 FIGS 17 19 show three modes of operation of the arrangement of FIG 16 DETAILED DESCRIPTION OF THE INVENTION In FIG 1 only three elements of a standard pumping plant have been included namely an oil storage tank 1 an electrical pump 2 and a check valve 3 which pre vents oil from returning to the tank when the pump is not running The oil ducts of the oil filled cables are connected to the pumping plant at 4 In FIG 2 is given the legend of the valves shown in FIG 1 and also in FIG 6 A illustrates a manually operated valve B illustrates an electrically operated valve and C illustrates a so called check valve allowing fluid flow in the direction of the arrow only Turning now back to FIG 1 the standard pumping plant has been provided with a back up system consist ing mainl
20. nt coupled between said reservoir and said drive input of said one diaphragm type pump to provide said oil in said first chamber of said one dia phragm type pump during said stand by mode of operation 15 A back up system according to claim 14 further including an oil pressure tank and a third valve arrangement coupled between said tank and said reservoir to compensate for pressure vari ations in said reservoir 16 A back up system according to claim 12 further including a second arrangement coupled to said drive input of said one diaphragm type pump to drive said one 25 30 35 40 45 50 55 60 65 10 diaphragm type pump by pressurized oil during said test mode of operation 17 A back up system according to claim 16 wherein said oil source includes an oil pump coupled to said reservoir and said second arrangement includes a second valve arrangement coupled between said oil pump and said drive input of said one dia phragm type pump and to said oil output of said one diaphragm type pump 18 A back up system according to claim 17 wherein said first arrangement includes a portion of said second valve arrangement cou pled between said oil pump and said drive input of said one diaphragm type pump to provide said oil in said first chamber of said one diaphragm type pump during said stand by mode of opera tion 19 A back up system according to claim 16 wherein said second arrangement includes a degasified
21. ure reservoir plant described in connection with FIG 6 As in the system described above in connection with FIG 12 there is introduced an additional diaphragm pump 14 and a pressure reservoir 15 so that degasified oil may be circulated through the two diaphragm pumps 5 and 14 i e from the a c side of the pump 14 through the b d side of the pum 15 so that the main pump 5 at all times during the stand by test and emergency operation _ modes is filled with degasified oil The circulating oil 4 419 056 7 should occasionally be passed through a degasifier not shown The source of degasified oil 27 needs only to be connected to the system via the manual valves 25 and 26 when required for filling purposes It will be seen that the valve 8 has been omitted It should be mentioned that the principle of the two series connected diaphragm pumps may also be used for circulating oil through the degasifiers In FIGS 17 19 are schematically illustrated the stand by test and emergency modes of the layout shown in FIG 15 A back up system of the type outlined in FIG 16 may of course be installed on a skid 30 as outlined in connec tion with FIG 11 Although the invention has Been described in connec tion with particular embodiments those skilled in the art will perceive modifications not mentioned above that can be made without departing from the spirit of the invention Therefore the above description is not intended to define t
22. y of a membrane pump 5 like that described above under the heading Background of the Inven tion marketed by The Warren Rupp Company under the trade name Sand Piper Pump Model No SA1 A or SB1 A utilizing two membranes 5a and 5b connected by arod 5c and having a driving gas in contact with the rod side of the two membranes 5a and 5d in a first chamber 5d a suction input a terminating in a second oil inlet chamber 5c and an oil outlet terminating in a third or oil outlet chamber 5f The driving gas is provided by a battery of gas bottles 6 via a pressure reducing valve 7 The inlet and outlet of the rod side or gas side of the pump are indicated by b and d respectively while a represents the oil suction side and c the oil outlet The back up system also includes three electrically operated valves 8 9 and 10 these valves are operated by DC current from a stand by battery one manually operated valve 11 apart from those connected directly to the gas bottles 6 and two check valves 12 13 The pumping back up system has three modes of operation a stand by mode a test mode and a back up operation mode In order to give a clear understanding of the various modes of operation the state of the valves is given in the table below where O open valve C closed valve Mode Valve No 8 9 10 11 Stand by Cc C Q C Test 0 Cc o o Operation o o Cc C In the stand by mode which is also schematically illustrated in FIG 3
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