Aerial Bunched Cable (ABC) is a good concept for over head power distribution. When compared to the conventional bare conductor over head distribution system ABC provides reliability and higher safety. Lowers power losses and ultimate system economy by reducing installation, maintenance and operative cost. This system is ideal for rural distribution and specially attractive for installation in diZicult places such as hilly areas, forest ares, coastal areas etc.
XLPE/HDPE insulated power conductors of aluminium (neutral conductor and street lighting conductors if and when necessary) are laid together (twisted) around a high tensile stranded and aluminum alloy with insulated or bare messenger wire to form the aerial bunched cable. This assembly is directly strung on to distribution pole/towers by mean of standard hardwares available in the market but care shall be taken to render the messenger wire completely insulated from earthing at any point of distribution in case of HT ABC. The XLPE (cross-linked polyethelene) insulation is black in colour and its stabilizer against deterioration caused by exposure to direct sunlight and ultraviolet radiation. XLPE is cross-linkable low density polyethylene which Is made thermoset by special formation from base polymer of thermoplastic low density polyethylene. XLPE combines the best electrical properties of LDPE and superior thermo mechanical properties.
No difficulty is envisaged during stringing of ABC in the conventional method but care shall be taken that insulated conductors do not get damaged during installation.
Dragging the ABC on the ground is to be avoided. Tension to be applied during stringing shall be 25% of the breaking load of the messenger wires. This will Allow line to have sag withing specified limit of 1.5% of the span at the lowest ambient temperature.
While mid-span jointing permissible for LT ABC system by conventional technique, our recommendation will be to draw the line in such a way as to bring the joints at the supports. Mid-span jointing is not at all recommended in the case of HT lines our recommendation is for outdoor type HY terminations only. Under unavoidable circumstances, line tapping at the support points may be allowed through suitably designed clamp connectors/PG clamp, semi-conducting screen continuity shall be maintained at all joints as far as possible to avoid fluctuations during system disturbances. The 3 phase screens may be shorted and earthed through suitable non-linear surge arrestor.
ABC Cables are highly reliable and insulation has been developed to with stand heat, cold and intense sunlight. Disturbance and faults occur five to ten times more often in open wire lines than in ABC lines. There is no risk in touching the live cable and the insulation reduces the number of short circuits and over-voltages in overhead cables during thunder-storms. Few hardware accessories are needed as each one can be used with many different sizes of cable. This makes installation and storage easier. Streets can easily be get 1 it at little extra cost by using the ABC cables that have an extra conductor for lighting. The cable can be supplied with one or two insulated conductors for street lighting.
The hardware and accessories for AB cables are made by various reputed manufacturer and is easily available in India. They are similar to the standard hardware available for Bare conductor overhead distribution lines.
This specification covers design, engineering, manufacture, assembly, stage testing, inspection and testing before supply and delivery at site of XLPE. Insulated Aluminum cables twisted over central bare/insulate aluminum messenger wire.
The materials shall conform in all respects to the relevant Indian Standard Specifications with latest amendments thereto, IS-14255/95 Indian Title International & Standard Internationally recognized standard.
| Sl. No. | Description |
|---|---|
| 1 | Aluminum Conductor (Power) |
| 2 | XLPE Insulation |
| 3 | Aluminum Conductor (Lighting) |
| 4 | Bare Al-Alloy Conductor (Messenger) |