Paramount Communications Ltd, part of the Paramount group of companies, is one of India’s leading cables manufacturing company, having the experience of over 5 decades. Over the years the group has widened its product portfolio to cater wide span of industries including power, railways, telecom, construction, defence and space research projects. In the recent months they were facing the persistent complaints with regards to the consignment of AB cables (aerial bunched cables) they have supplied. This has prompted them to visit the sites and look out for the real problem. Team WCI interacted with the technical team of the company and explored in detail about the shortcomings and the solution provided.
Areas of Contention
Explaining the issue Mr. D.S. Muchhal, President Operations, & Mr. R.K. Marwah, Vice President Technical, Paramount Communications Ltd, Dharuhera stated “we are the biggest suppliers of AB cables across India manufacturing 1.1 kV, 11 kV and 33 kV, along with exports. But, with the complaints of faulty cables being constant particularly from unorganized sectors. So, our team went to the sites to observe the problem areas. Having gone through the total exercise we analyzed the process and came to the conclusion that there were 3 areas, which were leading to such complaints of faulty cables. These were handling, laying and jointing/termination of cables.”
11 kV AB cables handling is comparatively new concept as compared to handling of 11 kV underground cable, which are in use for long time are having adequate protection against mechanical damages in the form of plastic inner sheath, galvanized steel amour and plastic outer sheath. Moreover it is laid underground directly in to trenches or duct, so no chance of mechanical damages by rollover. Roads are crossed through underground ducts. Contrary to this, 11 kV AB cables are three single core unarmored cables twisted around messenger conductor (messenger which carry the load of cable on the poles). These cables are laid (hanged) on poles. Presently all the contractors which were handling U/G power cables are being engaged to install 11 kV AB cables. Most of the contractors or manpower has no experience of how to handle, lay & install AB cables. Besides subcontractor is given contract on the basis of minimum contract value & without considering subject knowledge of AB cable which results in to bad handling of cables as shown in pictures at latter stage faults are developed.
To understand basic difference in construction of cable design for 11 kV power cable & 11 kV AB cable
Analysis of the Total Exercise
The biggest loophole was that, the whole process of cable handling, laying and jointing was carried with careless working and lack of technical expertise. In the process we identified major area of weakness such as:
1. Incorrect method of taking out cable from the drum, which causes the entanglement of the cables and damages sheath/insulation of cores.
2. The cable is laid manually over ground, below the points of hanging on poles, cable get rubbed on the surfaces like hard stone, concrete, iron surface & other hard sufaces, causes mechanical damage to the sheath/metallic screen/ insulation of cable.
3. Cable lying on the ground for long time where it gets tempered through different activities on ground like moving traffic over the cable.
4. Inappropriate laying technique due to lack of understanding and technical expertise.
5. Improper jointing, termination and earthing techniques are applied like
I. Damaged outer sheth is separated by the wooden piece to isolate phases.
II. When the joints are made in the three phases it is not properly tightened to the messenger and left open with metallic screen not connected for continuity.
III. Sometimes no earthing is provided to the metallic screen of the phase. Latches of jointing kits are left opened without proper earthing.
Steps Taken to Resolve the Issue
On the basis of above observations, Paramount Cables decided for following improvements in the areas of handling, laying and jointing/termination/earthing etc. First and foremost we prepared certain guidelines for un-loading, storage & handling of the cable drums at site which were:
- The unloading of the cable drums should be done either by crane or by hoist or on raised platform at a level of truck body. It shouldn’t be thrown/dropped from the truck on to the ground.
- The drums shall be stored on metal floor or floor made of bricks. Flanges shall be in vertical position with space in between the drums as unsystematic keeping of the cable drums will result in damage to the cable.
- Drum shall be rolled in the direction of arrow marked on the drum and unwinding of the cable from the drum should be done by loading the drum on the jacks and rotate the drum or by putting it on turn table, flat on the flange.
- Before laying AB Cables ensure cable drum number and its length, check screen continuity of each phase and make sure that required size & numbers of pulleys are available for pulling cable from the drum for laying.
- And most importantly, ensure cable is not laid on the ground. In case it is laid on ground then ensure that any kind of traffic shall not passes over cable, which is on ground.
- Dragging of cable on road/hard irregular surface/rocky area shall not be done.
- The unreeling of AB cables shall be continuous so as to prevent the formation of loops between the supports.
Secondly, to avoid the damaging of cable during laying at any critical sites, Paramount Cables developed the mechanism in house for laying of cable without touching the ground to avoid the cable failures. We decided to train people on overhead laying of AB cables, was a new concept. We first prepared a demo and then executed it in our own factory. It took us 3 months to prepare and train our people. Recently, we executed one project in Faridabad successfully, by applying the same concept.
Concept and Trial Project
It was an 11 kV project in Faridabad, where cable has to be laid to 5 km from prime source to the society. Out of this 5 km we laid 2 km in 2 days i.e. one day for preparation and another day for laying. If this 5 km stretch had been done manually it would have taken many days or so. But with our concept we did 40% of the job in just 2 days and that too without touching the surface. Moreover without interruption of traffic on the road. The idea that was in the mind when the concept was being developed is that the cable should not touch the ground surface. First the poles were erected, after that pulleys were tied on the poles. We developed the pulley system and from the drums the cables were directly aerialed to the pulleys and from other side the stretch was being given through a developed mechanism. The pulleys are made of ABS plastics, which doesn’t damage the cables.
About AB cables and its Potential in India
AB cable is comparatively a new concept for overhead power distribution in India. When compared to the conventional bare conductor it provides safety and reliability, reduces transmission losses and offers economy by reducing installation, maintenance, operative cost & preventing thefts. This system is ideal for rural distribution and especially attractive for installation in difficult terrains such as hilly areas, forest areas, coastal areas etc. These cables are also considered to be the best choice for power distribution in congested urban areas with narrow lanes and by-lanes. With the advantage of flexibility for rerouting, it is being demanded by changes in urban development plan. Many discoms have already replaced/replacing their bare wires with AB cables.