COMPARISON OF CABLES

Transcription

1 COMPARISON OF CABLES Vigya Electrical Engineering, Harcourt Butler Technological Institute, Kanpur , UP, India Abstract - Insulation is a very integral part in manufacturing of cables. It is very important to decide the type of insulation for each different conditions where cable is to be installed. Different parameters are to be used for the selection of the type of cables which are given in this paper. This paper gives the comparison between the four types of electrical cables in their physical properties as well as the tests conducted on them which is very useful to decide between the cables. I. INTRODUCTION A power cable is an assembly of two or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Cables consist of three major components: conductors, insulation, protective jacket. The makeup of individual cables varies according to application. Power cables use stranded copper or aluminium conductors, although small power cables may use solid conductors. Copper has a higher conductivity than aluminium. It is more ductile and has relatively high tensile strength. However, copper is more expensive and heavier than aluminium. Copper is three times as dense as aluminium, and so aluminium conductor size is much larger and thus its use does not permit the economical use for a cable. The construction and material are determined by three main factors,viz, working voltage, determining the thickness of the insulation; currentcarrying capacity, determining the cross-sectional size of the conductor(s); environmental conditions such as temperature, water, chemical or sunlight exposure, and mechanical impact. II. A. Cross-linked polyethylene TYPES OF CABLES They are commonly abbreviated as PEX or XLPE, and is a form of polyethylene with cross links. The creation of direct links or bonds between the carbon backbones of individual polyethylene chains forms the cross linked polyethylene structure. The result of this linkage is to restrict movement of the polyethylene chains relative to each other, so that when heat or other forms of energy are applied the basic network structure cannot deform and the excellent properties that polyethylene has at room temperature are retained at higher temperatures. The cross linking of the molecules also has the effect of enhancing room temperature properties. 322 The useful properties of XLPE are temperature resistance, pressure resistance (stress rupture resistance), environmental stress crack resistance (esc), resistance to u.v light, chemical resistance, oxidation resistance, room temperature and low temperature properties. The Indian Standard for the cable is IS:7098(Part-I)-1998 and the insulation is set by standard IS:8130. XLPE Cables can be summed up by following points: 1) XLPE cables work for the working voltage of 240 V to 500 KV. 2) Conductor Material can be either Copper or Aluminium. 3) XLPE cables can be either Single Core cables or Multi core cables depending upon the number of cores. 4) They can be Unarmoured or Strip Armoured or Wire Armoured or Tape Armoured type depending upon the presence or absence of Armour. 5) HT / LT Aerial Bunched Cables 6) The Jacketing Material can be of PVC / Flame Retardant / Flame Retardant Low Smoke / Zero Halogen (LSOH). 7) General Applications: Fire Survival, Under Water Cables, Underground burial, installation on trays and ducts B. Polyvinyl chloride They are commonly abbreviated as PVC, insulated cables are widely used in various fields. PVC's relatively low cost, biological and chemical resistance and workability have resulted in it being used for a wide variety of applications. For electric cables the PVC is mixed up with plasticizers. Low voltage copper conductor PVC cables are extensively used for domestic home appliances wiring, house wiring and internal wiring for lighting circuits in factories, power supply for office automation, in control, instrumentation, submarine, mining, ship wiring applications etc. due to its high tensile strength, superior conductivity, better flexibility and ease of jointing. PVC CABLES 1) Power Cables upto 1.1 KV 2) Control Cables upto 61 Cores 3) Railways Signalling & Auto Cables 4) Screened instrumentation Cables 5) House wiring and Flexible cables 6) Flat Cables for submercible pumps 7) Airport lighting and mining cables. 8) FRLS / FR / HR / Fire Survival Cable

2 C. Elastomer Insulated cable These cables are suitable for use where the combination of ambient temperature and temperature-rise due to load results in conductor temperature not exceeding 90 C under normal operation and 250 C under short-circuit conditions. This insulation shall be so applied that it fits closely on the conductor (with or without either separator or screen) but shall not adhere to it. The insulation, unless applied by extrusion, shall be applied in two or more layers and it is applicable to cables with a rated voltage up to volts. The Indian Standard used for the Elastomer Insulated Electric cable is IS Elastomer Cables 1) Elastomeric Cables and Flexible cords 2) Elastomeric insulated heavy duty HOFR Cables. 3) Welding Cables (General Purpose and HOFR) 4) Ship wiring cables, Pressure Tight Cables and cables for submerged connection. 5) Railways locomotives and coach wiring cables. 6) Mining Cables Flexible Trailing, coal cutter, pliable armoured and land line cables 7) Cables for wind Mills 8) Silicone Rubber high temperature cable. D. Rubber Insulated cable These are used in electric utilities such as the generation and transmission of electricity. Long service life under normal environment in Nuclear and conventionally powered generating stations plus safety considerations are the significant factors of these electric appliances. When exposed to fire, Silicon offers circuit integrity, low smoke evolution, and freedom from halogen acids. III. A. Conductors CABLE CONSTRUCTION Either aluminium or copper conductors are used. Conductors up to 800mm² will be circular, compacted & stranded. 1000mm² conductor will be circular stranded type on which a layer of semi-conducting tape will be applied. B. Conductor Screen This will be an extruded layer of semi-conducting cross-linkable compound applied under simultaneous triple extrusion process over the conductor along with the insulation and the insulation screen. The triple extrusion is a single high precision operation that eliminates the possibility of any contamination between the layers which could create irregularities in the electrical field. By careful material selection and special attention to process parameters, the insulation screen layers must have the required degree of stripping force as stipulated by the applicable national or international standard. 323 C. Insulation This will be an extruded layer of XLPE or Elastomer or Rubber or PVC applied over conductor screen under triple extrusion process along with conductor screen and insulation screen. D. Insulation Screen This will be a layer of semi-conducting cross-linkable compound which will be applied by triple extrusion process over the insulation. E. Metallic Screen It consists of a layer of copper tape applied helically with overlap over insulation screen. Other combinations of metallic screens as per customer s requirement can also be provided on request. F. Laying-Up In case of three core cables, the three cores are laid up with non-hygroscopic fillers like polypropylene(pp) fillers at interstices and a binder tape is applied with an overlap. These binder tapes can be of PVC or foamed Polyethylene. Inner Sheath (Bedding) for Armoured Cables. Extruded layer of PVC or PE is applied over the laid up cores for armoured cables. G. Armouring In case of armoured cables, the armour is applied helically over inner sheath. For single core cables, it is of aluminium wires and for multi-core cables, the armour can be of one among the following options: 1) Galvanized steel wire. 2) Galvanized steel strip. 3) Any metallic non-magnetic wire/strip. H. Oversheath An extruded layer is applied over the armour in case of armoured cables and over laid up cores in case of unarmoured cables. Outer sheath material can be either PVC, XLPE or PE. Other colours may be provided to suit a range of installation considerations such as the effect of UV radiations and differing soil compositions. Antitermite formulations can also be supplied in addition to graphite-coated oversheaths where on-site testing of the sheath is required. IV. COMPARISON OF CABLES A. Comparison in Characteristics of Cables 1) PVC is thin insulation mainly used in LT side cables and XLPE is thick insulation used in HT cables. 2) Comparing XLPE with PVC insulated cables, XLPE has higher current carrying capacity as it can withstand higher temperature compared to PVC cable. Moreover, they have high overload capacity, has lower di -electric and constant power factor.

3 XLPE cables are lighter in weight, has smaller bend radius, and hence lesser installation cost. It also has higher short circuit rating. XLPE can withstand higher & lower temperatures insulation is usually thinner but the resistance is higher, XLPE also has a higher moisture & chemical resistance. 3) Furthermore the Cable Installation Job for XLPE is easier than PVC insulated cables because of less Wt, less Diameter and Less Bending radius. The Volume Resistivity (ohm-cm) for XLPE(order of ) is way higher than the PVC cables which are of the order of XLPE cables has insulation resistance of 1000 times compared to PVC cables. 4) Coming to some of the properties of elastomers, Elastomer cables are preferred for flexible application and in congested locations where the bending radii are very small. Elastomer cables are available from low voltage upto 33 kv grade. Elastomer cables are also available with rigid copper conductors and having properties like Fire Survival, Zero Halogen and Low toxicity FS properties. Rubber Cables are predominantly used in special applications like, mining, ship wiring, transportation sector and Defense applications & earth moving machines. These materials have the potential to be recyclable since they can be molded, extruded and reused like plastics, but they have typical elastic properties of rubbers which are not recyclable owing to their thermosetting characteristics. These also require little or no compounding, with no need to add reinforcing agents, stabilizers or cure systems. Hence, batch-to-batch variations in weighting and metering components are absent, leading to improved consistency in both raw materials and fabricated articles. These can be easily coloured by most types of dyes. Besides that, it consumes less energy and closer and more economical control of product quality is possible. 5) Comparing the Elastomer and the rubber cables, The distinction between "elastomer" and "rubber" is often blurred among engineers; according to Indian Standard rubbers are a subset of elastomers, being the materials with irreversible cross-linking, and hence those much more suited for demanding quantitative engineering specifications: "Elastomers = macromolecular material which returns rapidly to approximately its initial dimensions and shape after substantial deformation by a weak stress and release of the stress. "Rubber = elastomer which can be, or already is, modified to a state in which it is essentially insoluble (but can swell) in boiling solvent, such as benzene, methyl ethyl ketone and ethanol toluene azeotrope, and which in its modified state cannot be easily remoulded to a permanent shape by the application of heat and moderate pressure. NOTE: a rubber in its modified state, free of diluents, retracts within 1 minute to less than 1.5 times its original length after being stretched at normal room temperature (18 C to 29 C) to twice its length and held for 1min before release" 6) Comparing Rubber cables with PVC insulated cables, the first point which turns out to be advantageous for Rubber cable is that the Rubber insulation remains in the best condition after a long span of time,say,25-30 years and remain soft and pliable even when the temperature is low. PVC insulation,on the other hand, becomes stiff making it difficult to fold and the soft PVC loosens its softening agent over years, making it brittle and prone to rip. Even at the time of disposing, burning PVC emits toxic dioxin, which is responsible for causing cancer and does, when dumped scantly dissolve. B. Comparison of cables in their testing methods 1) General tests are similar for all the cables. Let the comparison is made in between the cables in the High Voltage test, which is Type, Routine and Acceptance test. On the XLPE cables, High Voltage Test at Room Temperature is performed by testing the cables to withstand a voltage of 3 kv ac (rms) at a frequency of 40 to 60 Hz or an ac voltage of 7.2 kv, between conductors and between conductors and ECC (if any) for a period of 5 minutes for each test connection. On the PVC cables, High Voltage Test at Room Temperature is performed by testing the cable to withstand an a.c. voltage of 3 kv( rms ) or a dc voltage of 7.2 kv. The duration of test shall be 5 minutes for each connection. The High Voltage Test ( Water Immersion Test ) is done in two parts; a.c. Test ;the core or cores ( not exceeding five cores in the case of multicore cables ) shall be carefully removed from a sample approximately 3 m long taken from the finished cable. They shall be so immersed in water bath that their ends protrude at least 200 mm above the water level. The temperature of the water bath shall be 6O C for cores with general purpose PVC insulation and 70 C for cores with heat resisting PVC insulation. After 24 hours, a voltage of 3 kv ( rms ) shall be applied between the conductors and water. This voltage shall be raised to 6 kv ( rms ) within 10 seconds and held constant at this value for 5 minutes. If the sample fails in this test, one more sample shall be subjected to this test. There shall be no failure in the repeat test. And d.c. Test ; the cores which have passed the preliminary test in a.c test shall be subsequently tested with a d.c. voltage of 1.2 kv in the same water bath at the same temperature. The core shall withstand this voltage for 240 hours without breakdown. 324

4 On Elastomer insulated cables, the High Voltage Test is performed as Type/Acceptance Test and Routine Test. The Type test for 1.1 kv grade cables is carried out by removing the power/pilot core(s) from a sample approximately 3 meters long, taken from the finished cable. They shall be so immersed in a water bath at room temperature that their ends protrude at least 200 mm above the water level. After 24 hours, an ac voltage of 3 kv (rms) shall be applied between conductor and water. This voltage shall be raised to 6 kv (rms) within 10 seconds and held constant at this value for 5 minutes. If the sample fails in this test, one more sample shall be subjected to this test which shall pass. For 3.3 kv and above grade cables the type /acceptance tests shall be four hours test. The cables shall withstand without breakdown, an ac voltage equal to 3 U, when applied to the sample between conductor and screen / armour (and between conductors in case of unscreened cables). The voltage shall be gradually increased to the specified value and maintained for four hours. This test is applicable to power cores only. The Routine test is performed by testing the cable to withstand, without breakdown a power frequency ac voltage as specified below in the table. The voltage shall be applied and increased gradually to the full value and maintained for five minutes. The test shall be carried out at room temperature. Table 1: Voltage Grade of Cable for Routine Test 2) Tensile Strength Test and Elongation at break of insulation and sheath. By testing for the Tensile strength and Elongation at break, it is observed that the XLPE cables have a tensile strength of 12.5 N/mm 2 and elongation is of 200 to 300%. PVC cables have tensile strength ranging from 20 to 30 N/mm 2 for the sheath and 15 to 20 N/mm 2 for the core and elongation is of 300 to 400% and Rubber and Elastomer cables have tensile strength depending upon the material as shown below:: Natural Rubber 5 to 7 N/mm 2 Ethlyene Propylene 4.2 N/mm 2 Polychloroprene, Chlorosulphonate and Nitrile Butadiene 8 to 11 N/mm Silicon Rubber 5 N/mm 2 Butyl Rubber 4.2 N/mm 2 3) Hot Set Test is served as a means for determining whether or not the depending properties are fully realized after cross-linking. The temperature for testing for XLPE cables is 200± 3 C under load for 15 minutes and mechanical stress of 20 N/cm 2, elongation under load is 175% maximum and permanent elongation is not more than 15%. For PVC cables, the permanent elongation can be in negative value with maximum limit of 12%. For Elastomeric cable testing, temperature is set at 250±3 C and the maximum limit for elongation and permanent set is 175% and 15%. 4) Cold Bend Test is carried out to ascertain the suitability or withstandability of the insulating materials at low temperatures or frost conditions. The temperature set is around -40 C. The thickness of the insulation is kept such that the insulation doesn t get cracked up. Depending upon the type of cable used, the thickness of insulation is varied. Generally single PVC has insulation thickness of.711mm and wire thickness of 1.88 mm, stranded red copper has and respectively, silicon rubber cable has and respectively. 5) Ageing in air oven test makes an assessment of change in tensile strength and elongation of material. The treatment given to XLPE cable for the accelerated ageing of air consists of keeping the cable in temperature of 135± 3 C. The tensile strength variation is ±25% maximum and Elongation variation is ± 25%. The treatment given to PVC cables constitutes of keeping the cable under temperature of 80 ±2 C,100±2 C,135±2 C for Type A, Type B and Type C insulation respectively for 7 days. Tensile strength variation is ± 20%,25% and 25% respectively and elongation variation is ±20%, 25%, 35%. The Elastomer insulated cables are kept under temperature of 70 C for IE 1, 135 C for IE 2,IE 3,IE 4 and 200 C for IE 5 insulation cable for duration of 10,7,7,7,10 days respectively and Tensile strength variation is observed as ±40%, ± 30%, ±30%, ±50%, ±20% respectively. The variation of elongation at break is ±40%, ± 30%, ±30%, ±50%, ±20%. 6) Shrinkage test is to determine theshrinkages due to residual strain which is relieved on heating. This test is important to be carried out so that these shrinkages do not cause any problem in terminations where heating of cables is observed. The XLPE insulated cables should allow only 4% maximum shrinkage when cable is subjected to 130±3 C for 1 hour duration. And the PVC cables is kept under 150 ±2 C temperature for 15 minutes and the maximum shrinkage has to be 4%. 7) Loss of mass test for insulation and sheath is done to find out the progressive changes in the cable when they are exposed to elevated temperature and the changes depend on the severity of exposures.

5 The cables are exposed to a temperature of 80±2 C for 7 days and maximum loss of mass observed is 2 mg/cm 2. 8) Water Absorption test is carried out to indicate the degree of water absorption and thus the quality of compound used. The XLPE cables are kept under temperature of 85±2 C for 14 days and the maximum water absorbed value is 1 mg/cm 2. PVC cables are given the same treatment but the maximum water absorbed is 10 mg/cm 2. The Elastomeric cables are subjected to average stress of 800 V/mm 2 and the maximum water absorbed is 10% for first seven days and 3% for the next seven days. 9) Cold Blend and Cold Impact test, sometimes the cables have to be laid in the area of low temperature climatic condition or frost. Due to constant exposure of cables to low temperature or frost conditions, the insulation or sheath of the cables becomes hard and brittle. Any impact on the surface of the sheath or cable under these conditions may fracture the insulation, thus making it weak or causing it to fail. The suitability of the insulation material against low temperature brittleness is determined with the help of an impact test conducted on the cable maintained at a specified low temperature. In this test, the cooled cable is placed on an anvil inside a cold chamber and an indenter dropped on its upper surface to give it a specified impact. The effect of impact is then checked to evaluate the quality of the cable insulation. The Cold Bend test is for cables diameter <12.5mm and is subjected to temperature of -15±2 C and the cables under Cold Impact Test have diameter >12.5 mm is subjected to temperature of -5 ±2 C. Mainly PVC cables are used under these cold conditions. 10) Oil resistance test of cables has now become a critical performance parameter as cables that were able to sustain functional and operational integrity a decade ago would not be adequate to survive in the environment of a present day manufacturing site. Certain types of PVC have a lower degree of oil resistance while Elastomeric insulated cables have better oil resistance. The cable is tested at oil temperature of 100 ± 2 C for 24 hours. The tensile strength variation is ±40% maximum and elongation variation is ±40% maximum. 11) Partial Discharge testing of cable is done to check for voids and cavities inside the dielectric of cables. Voids of minimum 1mm may cause Partial Discharge level of about 1pC but the voids lesser than 1 mm can t be detected. 12)Hot Deformation test for cables is designed to determine the resistance of PVC insulation and sheaths to pressure at elevated temperatures. The apparatus consists of a support on which the test specimen is kept and a stainless steel blade of a specified thickness with an arrangement to apply the specified load on the cable under test through the blade. 326 A set of weights is provided to give the specified load on the test specimen. The cable is kept under temperature of 80 C for four hours, and the depth of indentation is maximum 50 percent. 13) Heat shock test is performed to find out cracking of thermoplastic insulation and sheath of cables on overheating. The test specifies the heat treatment given to the thermoplastic insulation and sheath at accelerated temperature of 150 C and duration of one hour to ascertain the withstand ability at that condition. It is only a visual examination. The specimen is wound over a smooth round shaped mandrel for three turns in a close helix and then the mandrel is kept in an oven at a specified temp. and for the duration specified. At the end of this period the samples are cooled in air for one hour. The test specimen is then examined for any cracks visible to naked eye. 14) Ozone Resistance Test is carried out for Elastomeric cable because of concentrations of ozone, that are reached in our natural environment, are able to cause deep cracks in elastomeric materials, that normally lead to a failure of a component. The cables are subjected to.025 to.030 percent for 30 hours and the cable passes this test if the cable is free of cracks. 15) Bleeding and Blooming Test is used to check the stability of colour of the sheath so that there is no chance of staining of the cores. For the test, cable is subjected to 50 C for 72 hours and then filter paper or indicator compound is observed for any stain. 16) Insulation Resistance Test consists in measuring the Insulation resistance of a device under test, while phase and neutral are short circuited together. The measured resistance has to be higher than the indicated limit from the international standards. A mega ohmmeter (also called insulation resistance tester, tera ohmmeter) is then used to measure the ohmic value of an insulator under a direct voltage of great stability. For best result, the insulation resistance of cable is kept around 200 mega ohms per km at starting. For PVC cables, the insulation resistance constant is around 36.7 MΩ km at 27 C and.036 MΩ km at maximum rated temperature. For Elastomer Cables, these values are 700 MΩ km and 3.67 MΩ km. The insulation resistance of XLPE is around 1000 times higher than of PVC cables. 17) Spark Test in cables is done for evaluation of insulation and sheathing materials for specific uses. This test is also used for In-line fault testing on single conductors and jackets during the extrusion or rewinding process. V. PARAMETERS FOR SELECTION OF TYPES OF CABLES The parameters of the cables are selected for determination of the cable type and size. The parameters are as follows:

6 1) Voltage at which the cable is subjected to: Voltage Grade of cables specifies the safe voltages which the insulation of the cable can withstand. Cables are usually classified according to the voltage for which they are manufactured accordingly they are classified as; Low voltage cables, up to and including 1000 volts ; Medium voltage cables, starting 2000 volts up to and including 33kv; High voltage cables, above 33kv up to and including 150kv; Extra high voltage cables, 220kv, 400kv and 500kv. 2) Current carrying capacity; the current carrying capacity of a cable is called Ampacity. Ampacity is defined as the maximum amount of electrical current a conductor or device can carry before sustaining immediate or progressive deterioration and is the rms electric current which a device or conductor can continuously carry while remaining within its temperature rating. In cables, installation regulations normally specify that the most severe condition along the run will govern each cable conductor's rating. Cables run in wet or oily locations may carry a lower temperature rating than in a dry installation. Ampacity rating is normally for continuous current, and short periods of overcurrent occur without harm in most cabling systems. 3) Short Circuit values; the short-circuit current rating is the maximum short-circuit current that a component can withstand. Failure to provide adequate protection may result in component destruction under short circuit conditions. Short circuits and their effects must be considered in selecting cables. These cables should have a short circuit rating which is the highest temperature the cable can withstand during an electrical short circuit lasting up to about half a second. 4) Ambient temperature; Ambient temperature simply means "the temperature of the surroundings. Ambient temperatures play a major role in personal comfort, as well as the function of many types of machines and equipment, and various methods can be used to control ambient temperature. Usually, control methods are designed to keep the temperature stable, as temperature fluctuations can cause discomfort. The transfer of heat, whether by conduction, convection or radiation, depends on temperature difference - heat flows from hot to cold at a rate which depends on the temperature difference between them. Thus, a cable installed near the roof of a boiler house where the surrounding (ambient) temperature is very high will not dissipate heat so readily as one clipped to the wall of a cold wine cellar. 5) Voltage drop; a primary concern when installing lengths of cables is voltage drop. The amount of voltage lost between the originating power supply and the device being powered can be significant. All cables have resistance, and when current flows in them this results in a volt drop. 327 Each current rating table has an associated volt drop column or table. For small cables, the self inductance is such that the inductive reactance, is small compared with the resistance. Only with cables of cross-sectional area 25 mm² and greater need reactance be considered. If the actual current carried by the cable (the design current) is less than the rated value, the cable will not become as warm as the calculations used to produce the volt drop tables have assumed. 6) Method of Installation; there are some basic requirements and characteristics of installation, viz, safety requirements, assessment of general characteristics, low voltage generating sets, standards, under voltage. Scope, object and fundamental requirements for safety applies to all installations and sets out their purposes as well as their status. Assessment of general characteristics is concerned with making sure that the installation will be fit for its intended purposes under all circumstances. The assessment must be made before the detailed installation design is started. There are some regulations where low voltage or extra-low voltage generating sets are used to power an installation; as the sole means of supply, or as a backup in case of failure of the supply, or for use in parallel with the supply. Every item of equipment which forms part of an electrical installation must be designed and manufactured so that it will be safe to use. There is a possibility that low voltage may cause equipment damage. Should such damage occur, it must not cause danger. 7) Mutual heating effect due to cable grouping; when multiple cables are in close proximity, each contributes heat to the others and diminishes the amount of external cooling affecting the individual cable conductors. Therefore, derating is necessary for multiple cables in close proximity. 8) Economics is also an important factor for selecting the type of cable. It is to be kept in mind that the cost of the cable should not be such large that it causes loss and another cable may fetch the same results in low cost and loss. 9) Environmental conditions and applications in which cable operates; each cable operates at its best when it is installed in its optimum environmental conditions. For example, Elastomeric Cable is applied in trailing, coal cutter, wind mill, panel wiring, battery cable and such other areas. XLPE cables work good in areas where moisture content is good. Thus, proper cable should be selected so that the system becomes more efficient. VI. CONCLUSION As per the requirement, the cables need to be chosen for suitable application and optimum parameters are kept for its type and size.

7 They should be capable of operating continuously under the environmental conditions without losing its efficiency. For installing cable for any application, the factors such as Volume resistivity, Voltage drop, Short circuit current rating, disposal etc need to compared and the best cable is chosen so as to optimize the application. REFERENCES [1 ] R.Jocteur et al, Influence of surface and internal defects of polyethylene electrical routine test on VHV cables,ieee Trans. PAS, Vol PAS-96 No.2, March/April [2 ] Hakan Lennartsson,Senior Technical Service Manager, Borouge Hong Kong Pte. Ltd., Modern XLPE Materials for Extruded Energy Cable Systems. [3 ] Rakowska. A, Service experience with PE and XLPE insulated power cables Third International Conference on Nov [4 ] Bernstein, Bruce S., Cable Testing: Can We Do Better? IEEE Electrical Insulation Magazine, Vol. 10, No. 4, July/August [5 ] D.Basak, Testing Of Power Cables And Its Conformity presented in Workshop on Instrumentational & Safety Aspects in Electrical & Environmental Testing of Electrical Appliances, January , NRTC, Parwanoo [6 ] Steiner, J.P, Martzloff, F.D., Partial discharges in low-voltage cables Electrical Insulation, 1990., Conference Record of the 1990 IEEE International Symposium on 3-6 Jun [7 ] Kelly LJ., Cable ampacity practice for low voltage and medium voltage power cables, Textile Industry Technical Conference, 1988., IEEE 1988 Annual on 4-5 May [8 ] For information about cables: [9 ] For information about tests and testing apparatus: arinstruments.com, Wind Systems Magazine, 328