Cable Movement Research Articles

U.S. Patent Specifications

In an aircraft, a fuselage having a tail portion, said tail portion including a stabilizer, a control surface pivotally mounted upon said stabilizer, a tab pivotally mounted upon said control surface, actuating mechanism for deflecting said tab for the actuation of said control surface, deformation sensing means including a cable anchored to said fuselage at each of its ends at vertically spaced points above and below the centre of gravity of the aircraft, said cable having an intermediate portion operatively connected to said tab actuating mechanism whereby deformation of said fuselage initiates relative movement of said cable and corrective movement of said tab and said control surface.

A Review and Analysis of Equipment for Running Electrical Cables Under Pressure

Abstract Developments in permanent-type well completion techniques have accentuated the need for improved equipment to handle cables under pressure. Existing conventional packoff devices were tested and their dynamic performance established at 200 to 600 psi with electrical conductor cables. A new packoff technique is reported that permits operating stranded cables at moderate running speeds up to pressure as high as 3,000 psi. In the higher pressure ranges a new commercial device is reported for running cables against well pressure as high as 6,000 psi. These new developments open wide the doors to improved well completion practices, resulting in improved well productivity and more precise well control. Introduction Field experience with some phases of permanent-type well completions uncover a need for more adequate and simplified means of running conductor cables into wells under pressure. This paper concerns armored electrical cables usually used in service company work, although the findings are equally applicable to other stranded cables. The construction of a reverse armor electric conductor cable is such that 20 per cent of the cross section area is pore space. The difficulty in sealing this amount of space has dictated, in the past, the use of small diameter cables for even medium pressure work. Early experiments with packing glands used with conductor cables revealed that a complete high-pressure shutoff could only be obtained by filling the pore space within the cable with heavy grease or packing gland pressures, which prohibited or retarded cable movement. Recently a new concept has developed of handling cables under pressure. Tests have shown that with a stranded cable located in a closely fitting metal sleeve, the flow through and around the cable is not great and can be controlled. This is known as the controlled blow-by principle and its use has opened up a new approach to the stuffing box problem.

Evaluation of Cable Movement due to Cyclic Loading [includes discussion

Evaluation of Cable Movement due to Cyclic Loading [includes discussion

Evaluation of cable movement due to cyclic loading

POWER CABLES undergoing daily load cycles are alternately heated and cooled, building up internal stresses which manifest themselves by the longitudinal movement of the cable into and out of adjacent manholes. This movement subjects the cable sheath to cold working ultimately causing it to fail. It is therefore desirable to determine what factors affect the cable movement, how the amount of movement may be calculated, how this movement may be decreased, and to what extent decreased movement is desirable.

Protective covering for lead-sheath power gables

THE MAJORITY of failures of impregnated-paper or varnished-cambric lead-covered power cable are due to the entrance of moisture through a break of some kind in the lead sheath. The sheath failures may be due to corrosion, electrolysis, mechanical damage, fatigue attributable to either vibration or cable movement, or high internal pressure. Corrosive action or electrolysis in some degree are fairly common to all lead-covered cables installed in ducts while damage due to mechanical failure is generally confined to those cables which are subjected to large daily variations in load. This latter type of failure has become of increasing importance with the higher loads which have been imposed on power cables during recent years.

New 138-Kv Cable Lines in Los Angeles

The first 138-kv underground transmission cables to be installed west of Chicago and the largest now in use at this voltage (except for short station runs) were placed in service during 1943 by the Los Angeles Department of Water and Power. While generally similar to 138-kv lines previously installed in the East this installation involves a number of novel design features which make it of more than usual interest. The paper describes these features and some of the studies of carrying capacity, cable movements, sheath voltages, oil supply and alarm, and sheath corrosion, which led to their development, and includes a summary of significant data and characteristics of the installation.

Cyclic Movement of Cable-Its Causes and Effects on Cable-Sheath Life

Results of a field survey and laboratory tests are presented in this paper showing the relationships between loading, conductor-temperature changes, movement in manholes and ducts, and sheath life for paper and lead cable. The record on underground 15-kv cable is included to emphasize the noninherent failures attibutable to physical proportions of underground structures. Improvements in modern cable have permitted operation at increasing temperatures with few inherent failures. The tests and operating experience indicate that unsatisfactory sheath life caused by fatigue of lead can result from cyclic tempratures allowed in standard cable specifications. A method is outlined for computing sheath strains for given cable off-sets and movements at the duct mouth. Fairly reasonable estimates of sheath life can be prepared. The tests indicate also that snaking of cable within the ducts may impose severe cyclic strains on the lead and become the determining factor for optimum sheath life.

An Investigation of the Relationship Between Temperature and Movement of Cables in Ducts

MANY complex thermal and mechanical influences govern the relationship between electrical loading and the movement of cable in an underground conduit line. It is probable therefore that a knowledge of the relationship will come only through the analysis of many careful observations of the movement of cable in conduits of different types and in different locations and also under the influence of electrical loadings of various magnitudes and durations. It is apparent that engineers now appreciate the importance of a knowledge of the factors that influence cable movement as well as of the control of these factors as a requisite for higher loading of cables that operate under the load factors normally encountered.

Load ratings of cable — II

Since the author's 1939 paper, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> further data have been obtained regarding the loading of underground power systems having impregnated-paper-insulated lead-covered underground cable. The results of the studies may be summarized as follows: 1. The factors affecting the setting of maximum safe conductor temperatures are so numerous that no fixed value (or values) can be assumed as applicable to all installations of a given design and size of cable in this country. 2. For some cables, the present temperature limits for normal day-in and day-out operation may be safely exceeded, especially for wartime conditions. 3. For emergency operation safe temperatures may be even higher than listed in the previous paper, especially for wartime operation. 4. Operation in wartimes at special temperatures will mean in some cases substantial shortening of the life of underground circuits and an accompanying increase in service interruptions. 5. Wartime increases in usual maximum daily loading and in load factors may cause large increases in duct and copper temperatures, even if past current ratings are maintained. These temperatures will sometimes exceed those in the present standards. 6. The safe temperature for emergency operation, particularly for extra-high-voltage cables, may be limited by the joints. Also, for all kinds of cable sufficient room must be provided to avoid mechanical damage of cable or joints in manholes with cable movements incidental to emergency loads. 7. Cracking of lead sheaths due to reciprocating cable movement into manholes may limit the temperature range for usual daily loading, but has little effect on the safe emergency loading. 8. For three-conductor solid-type cable, the insulation of the shielded type can safely withstand higher temperatures than the belted type, but the reverse is true as to the allowable daily temperature range with regard to its effect on the sheath in manholes. 9. Cable movement increases with length of conduit sections up to about 250 feet but shows little change with further increases in length up to 1,025 feet. 10. Changes in installation methods and the use of new types of repairs may help to mitigate troubles due to sheath cracking. 11. Copper shielding tape in three-conductor cable with relatively thin insulation has little effect in reducing the thermal drop from the conductor to the sheath. 12. In some cases considerable thermal advantage may be gained economically by making relatively deep installations of conduit. 13. In most cases, the maximum conduit temperature of 50 degrees centigrade given in the previous paper may be safely exceeded.

Load Ratings or Cable-II

Since the author's 1939 paper, <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> further data have been obtained regarding the loading of underground power systems having impregnated-paper-insulated lead-covered underground cable. The results of the studies may be summarized as follows: 1. The factors affecting the setting of maximum safe conductor temperatures are so numerous that no fixed value (or values) can be assumed as applicable to all installations of a given design and size of cable in this country. 2. For some cables, the present temperature limits for normal day-in and day-out operation may be safely exceeded, especially for wartime conditions. 3. For emergency operation safe temperatures may be even higher than listed in the previous paper, especially for wartime operation. 4. Operation in wartimes at special temperatures will mean in some cases substantial shortening of the life of underground circuits and an accompanying increase in service interruptions. 5. Wartime increases in usual maximum daily loading and in load factors may cause large increases in duct and copper temperatures, even if past current ratings are maintained. These temperatures will sometimes exceed those in the present standards. 6. The safe temperature for emergency operation, particularly for extra-high-voltage cables, may be limited by the joints. Also, for all kinds of cable sufficient room must be provided to avoid mechanical damage of cable or joints in manholes with cable movements incidental to emergency loads. 7.

Load ratings of cable

Operating and test data concerning the maximum safe loading of impregnated-paper-insulated lead-covered cable are presented. The results of the study may be summarized as follows: 1. The occasional operation of cable at higher temperatures than are permitted by present temperature rules effects considerable economy. 2. During emergencies, temperatures of 5 to 35 degrees centigrade (depending on kind of cable) above those permitted by the rules are safe for the insulation. 3. For extra-high-voltage solid-type cable, void formation in insulation and expansion of lead sheaths may limit allowable temperatures and temperature ranges. 4. Cracking of lead sheaths due to reciprocating cable movement into manholes may limit the temperature range for usual daily loading. Limitation is more severe for longer conduit lengths up to 500 feet, but changes little with increase from 500-to 1,000-foot lengths. 5. Cracking of sheaths in manholes due to cable movement may be reduced by improving manhole conditions. 6. For many cables a balanced design requires a lead-alloy sheath that gives increased resistance to effects of cable movement and of internal pressures. 7. Continuous field temperature surveys are essential to efficient use of large conduit and cable systems. 8. Only a small fraction of the cable ever operates at the higher temperatures. 9. Data on center empty-duct temperatures and on average heat losses over 24-hour periods give satisfactory results in heat calculations. 10. Other practices which increase load ratings are the use of different ratings for various periods of the year, the replacement of poor soil in special cases, and the use of extra-large conductors in warmer conduits.

Load Ratings of Cable

Operating and test data concerning the maximum safe loading of impregnated-paper-insulated lead-covered cable are presented. The results of the study may be summarized as follows: 1. The occasional operation of cable at higher temperatures than are permitted by present temperature rules effects considerable economy. 2. During emergencies, temperatures of 5 to 35 degrees centigrade (depending on kind of cable) above those permitted by the rules are safe for the insulation. 3. For extra-high-voltage solid-type cable, void formation in insulation and expansion of lead sheaths may limit allowable temperatures and temperature ranges. 4. Cracking of lead sheaths due to reciprocating cable movement into manholes may limit the temperature range for usual daily loading. Limitation is more severe for longer conduit lengths up to 500 feet, but changes little with increase from 500-to 1,000-foot lengths. 5. Cracking of sheaths in manholes due to cable movement may be reduced by improving manhole conditions. 6. For many cables a balanced design requires a lead-alloy sheath that gives increased resistance to effects of cable movement and of internal pressures. 7. Continuous field temperature surveys are essential to efficient use of large conduit and cable systems. 8. Only a small fraction of the cable ever operates at the higher temperatures. 9. Data on center empty-duct temperatures and on average heat losses over 24-hour periods give satisfactory results in heat calculations. 10. Other practices which increase load ratings are the use of different ratings for various periods of the year, the replacement of poor soil in special cases, and the use of extra-large conductors in warmer conduits.