Paper insulated cables

Until a few years ago paper insulated cables had a dominant position but not so with the advent of XLPE cables (a devclop-ineni of the 1960s). in view of their higher thermal rating and availability in all voltage ranges up to 400 kV and above. This situation is almost similar to SF, technology over vacuum (Chapter 19), While vacuum is prefened it has limitations in HT above 33 kV as have paper insulated cables, which are available up to. 33 kV and have limitations beyond this. Hence the use of XLPE cables for HV and EHV installations... 

Figure A16.1 Different constructions of paper-insulated cables...

Table A16.8 6.35/11 kV (Grounded system) paper insulated belted cables (IS 692)...

Paper insulated lead sheathed cables for voltages up to 33 kV Tests on cables and their accessories 692/1994 BS 6480/1997 -... 

BS6480 Power cables, impregnated paper - insulated, lead or lead alloy sheathed. 

Telephone Cable Plug Compounds - Co-reacts with epoxy and amines to form dam in lead-sheathed cable and polyethylene covered cable. Prevents moisture intrusion and permits pressurization of cable. Does not interfere (electrically) with transmission with paper insulated conductors. 

The extension of this technique to the distribution board or feeder pillar where four or five core cables are concerned is relatively simple. Traditionally this termination was made using the iron box filled with bitumen. The cable box was replaced by a preformed plastics glove which is pulled down over the prepared cores so that the lower end overlaps the cable sheath and is then shrunk into position. The individual paper-insulated cores are protected by shrinkable tubing and the terminating lug is sweated or compressed on to the end of the conductor. In a conventional termination the cable box itself forms the direct connection between the cable sheath and the neutral earth bar. 

In the past the copper conductor pairs in telecommunication cables were insulated with paper pulp, and the outer sheath, which serves as an electric shield and provides corrosion-resistant physical protection, was made of a lead alloy containing 1.0 mass% antimony. The connections (splices) between the individual conductors were enclosed either in lead sleeves or in closures consisting of two galvanized half shells of gray cast iron, held together with stainless steel bolts and nuts. Although there is still a considerable amount of lead-sheath cable, lead sleeves, and galvanized cast iron closures, the modem telecommunication cable plant relies heavily on plastics as the material of constmction. 

In the main, only competent people should be used for making joints and connections in wiring systems. Skilled cable jointers, for example, should be employed to make joints in paper-insulated lead-sheathed steel... 

In the past, there were fewer accidents because buried cables were better protected. Most of the supply authorities used paper-insulated, lead-sheathed, single-wire or steel-tape armoured and served cables and very often protected them with cable tiles. For economic reasons cable tiles are seldom used now and many of the mains laid in recent years are unarmoured CNE cables with plastic insulation and sheathing, such as PVC and cross-linked polyethylene (XLPE). The outer concentric conductor, which is the earthed neutral, is copper or aluminium tape and consequently more vulnerable to damage than a steel-wire-armoured cable. Every year more new mains cables of this type are laid so the resultant hazard to excavators is growing and more accidents can be expected to occur unless the construction industry becomes more effective at taking precautions against striking buried cables. 

Older installations usually have an armoured paper insulated and lead sheathed service cable providing an SNE supply. The consumer s earthing terminal should be connected to the lead sheath of this service cable. Look out for earthing to the incoming water service pipe, which is no longer permitted. Check that the size of the earthing conductor complies with BS 7671, section 543, or, if the consumer has his or her own buried earth electrode, is in accordance with both sections 542 and 543. 

Paper insulated lead-covered steel wire armour cables are only used in systems above 11 kV. Very high-voltage cables are only buried underground in special circumstances when overhead cables would be unsuitable, for example, because they might spoil a view of natural beauty. 

Paper insulated lead covered steel wire armour cables... 

Table 16.7 Comparison of full-load capabilities for paper, PVC and XLPE insulated copper cable...

London, Institute of Materials, 2001, Paper 28, pp5,012 DEVELOPMENT OF AN HDPE COMPOUND FOR INSULATION OF COMMUNICATION CABLES BY THE GAS INJECTION PROCESS... 

This paper discusses the latest advances in manufacturing Community Antenna Television (CATV) cables via the gas injection process. Developments in polymer technology are discussed which have led to the production, by gas injection, of highly expanded, ultra low dielectric loss PE cable insulation for CATV and data transmission 3 refs. 

Other significant uses of PCBs included heat exchangers and hydraulic fluids. Prior to controls PCBs were also used in adhesives, coatings, plasticizers and inks for microencapsulating dyes for carbonless duplicating paper as extenders in pesticide formulations and catalyst carriers in olefin polymerizations to impart hydrophobicity to materials and surfaces in bactericide formulations (combined with insecticides), and in immersion oil for microscopes. Mixed with chloronaphthalenes, PCBs were also used in wire and cable insulation in the mine and shipbuilding industries (ref. 80, p. 455). 

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