Aerial bunched cables (ABC) are a very novel concept for Over Head Power distribution, when compared to the conventional bare conductor over head distribution system. Insulated aerial bunched cables provide higher safety and reliability, lower power losses and ultimate system economy by reducing installation, maintenance and operative cost. We stand among the predominant bunched cables manufacturers, in India. This system is ideal for rural distribution and especially attractive for installation in difficult terrains such as hilly areas, forest areas, coastal areas etc. Aerial Bunched Cables are also considered to be the best choice for power distribution congested urban areas with narrow lanes and by – lanes. In developing urban complex, Aerial Bunched Cables are the better choice because of flexibility for rerouting as demanded by changes in urban development plan.
Construction of ABC
XLPEIHDPE insulated power conductors of Aluminum (Neutral conductor and street lighting conductor if and when necessary) are laid together (twisted) around a high tensile standard and galvanized steel (Aluminum Alloy may be used) insulated or bare messenger wire to form the Aerial Bunched Cable. This assembly is directly strung on to distribution pole/towers by means of standard hardware 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 Polyethylene) insulation is black in color and is stabilized against deterioration caused by exposure to direct sunlight and ultraviolet radiation. XLPE is cross-linkable low-density polyethylene, which is made thermo set by special formulation from base polymer of thermoplastic low-density polyethylene. XLPE combines the best electrical properties of LDPE and superior thermo mechanical properties.
- Aluminum conductors conform to IS: 8130 (Class-II).
- Standard high tensile galvanized steel messenger wire conforms to IS: 398 (Part-2). Alternatively Aluminum Alloy messenger wire conforms to IS:398 (Part-4)
- XLPE and HDPE insulation of power conductors specify IS: 7098 (Part – I & II) and IS: 6474 respectively.
Since, the tension from the current carrying conductor is totally removed by- introduction of messenger wire the operating temperature of the conductor is 90  C as against 75  C of the bare conductor of the same size.
No difficulty is envisaged during stringing of Aerial Bunched Cables 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 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 within 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 joining is not at all recommended in the case of HT lines our recommendation is for outdoor type HV terminations only. Under unavoidable circumstances, line tapping at the support points may be allowed through suitably designed clamp connectors/ PG clamps. The 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-liner surge arrestor. Attempting to make a tap off from power conductors in region where cetenary is under tension in not recommended.
Aerial Bunched Cables can be conveniently used:
- As replacement of bare lines in Rural Areas, in woods and in other localities & narrows streets where the space limited.
- As replacement of bare lines where reliability of supply is prime importance.
- As replacement of bare lines where high degree of stability of supply voltage is of importance.
- In hilly terrains where cost of erection of overhead lines or under ground cable becomes very high.
- As reinforcement of existing system without increasing voltage.
- For temporary supplies.
In comparison to bare overhead power distribution lines, ABC has very high reliability in maintaining services because power and neutral conductors are insulated with the best dielectric medium resulting in the following advantages:
- Less fault rate on account of good protection against line and ground fault by high winds or falling trees or birds especially in hilly areas & forests as encountered in rural distribution networks.
- High insulation resistance to earth in all seasons and polluted atmospheres. Negligible leakage currents and low losses.
- Multiple circuits of Power and Telephone cables could be strung in the same set of poles or any other supports like walls etc.
- Better adaptability to run concurrently with existing overhead bare conductor system without any interference.
- High capacitance and low inductance leading to low impedance of lines.
- Lower voltage drop, higher current capacities. VIs-A-VIS Better Voltage Regulation.
- Longer spans and longer distance lines are possible with better system stability.
- ABC cables are much safer then bare Conductors.
- It can be over hung in dense vegetation and forests.
- Additional connections can be easily and quickly made with hot-line connectors.
- Maintenance is very easy.
- Total lines costs are reduced.