Indian Cables & Electricals Pvt. Ltd is a authorized distributors of POLYCAB LT XLPE CABLES in Pune, Maharashtra.
XLPE INSULATED HEAVY DUTY CABLES 650/1100V.
All sizes of POLYCAB XLPE cables are designed to standard operating conditions in India and abroad. The standards adopted are considering the geographical/ climatical conditions and general applications of power for utilities, distribution and generation purposes. The cables are manufactured conforming to Indian & International cables specifications for XLPE Insulated cables. Customer specific requirements can also be met.
The XLPE insulated heavy duty cables were introduced worldwide in mid sixties. These cables have overcome the limitations of PVC Insulated Cables such as thermal degradation, poor moisture resistant and thermoplastic in nature. The advantages of XLPE Insulated cables in comparison to PVC insulated cables are as under:
Technical Advantages :
- Higher current rating, higher Short Circuit Rating Approx 1.2 times that of PVC.
- Thermosetting in nature.
- Higher insulation resistance – 1000 times more than PVC cables.
- Higher resistance to moisture.
- Better Resistance to surge currents.
- Low Dielectric Losses.
- Better resistance to chemicals.
- Longer service life.
- Comparatively higher cable operation temperature 90°C and short circuit temperature 250°C.
- Lower laying cost because of comparatively smaller diameter of cable and lighter weight*.
- Lower installation charges as the diameter of cable is comparatively lesser with smaller bending radius, requiring less space requirement for laying of cables.
- **One size lower cable can be used as compared to PVC insulated cable.
- * Density of XLPE is lower than PVC
- **For longer cable length voltage drop shall be considered
Advantages of Polycab XLPE Cables
- Higher Electrical Strength Retention
- Higher Short Circuit Rating
- Better Electrical, Mechanical &
- Thermal Properties
- Easy Jointing & Termination
The cables are suitable for use on AC single phase or three phase (earthed or unearthed) systems for rated voltage up to and including 1100 volts. These cables can be used on DC systems for rated voltage up to and including 1500 volts to earth. CONDUCTOR The most acceptable metals for conductors are copper and aluminium due to their higher conductivity and ductility. As copper has got higher affinity for sulphur, it corrodes in the atmosphere where sulphur fumes are present. In these conditions tinned copper should be used. Aluminium oxide film which is always present on Aluminium conductor surface acts as barrier and it protects the Aluminium conductor from corrosion in fumes laden atmosphere. CONDUCTOR CONSTRUCTION The most economical construction for conductor is solid conductor i.e. conductor is made of one single wire. As the area of conductor increase, solid conductor becomes more stiff and hence difficult to handle. In this case stranded construction is adopted. Here the conductor is made of number of strands. The strands are arranged in spiral layers in 1+6+12+18+…….. formations. This construction provides more flexibility. Where crimping of lugs are required, the conductor has to be of stranded construction only. To economise in insulating material, weight and overall diameter, shaped conductors are employed in bigger sized cables. Here the stranded conductor is shaped in to a segment of a circle so that when all the cores are laid, they form a complete circle. These segments are identified as 2 Core – 180 degree, 3 Core – 120 degree, 4 Core – 90 degree and 3.5 Core – 100/60 degree. I.S. 1554 permits solid conductor construction upto 10 sq.mm in Aluminium and upto 6 sq.mm in copper. It permits the use of shaped conductors for sizes from 16 sq.mm onwards. INSULATION The PVC covering over conductor is called insulation and is provided by extrusion process only. The insulated conductor is called core.
I.S. 1554 permits two types of PVC insulation as follows : 1) Insulation with TYPE A PVC compound as per I.S. 5831 which is suitable for 70 deg.C continuous operation. 2) Insulation with TYPE C PVC compound as per I.S. 5831 which is suitable for 85 deg.C continuous operation. The following colour code is used for identification : Single Core : Red, Black, Yellow or Blue. Two Cores : Red and Black Three Cores : Red, Yellow and Blue. Three & Half : Red, Yellow, Blue and Reduced neutral Black. Four Core : Red, Yellow, Blue and Black. Five Core : Red, Yellow, Blue, Black, & Grey Six Cores : Two adjacent cores. Blue and Yellow (Counting and direction core) And remaining Grey in each layer. OR By printing numbers on each core. LAYING UP The cores are laid up with suitable lay. The final layer always has a right hand lay i.e. if you look along the cable, the cores move to your right hand. INNERSHEATH Innersheath is provided over the laid up cores. It is provided to give circular shape to the cable and it provides bedding for the armouring. I.S. 1554 permits following two methods of applying the innersheath of any thermoplastic material i.e. PVC, Polyethylene, etc. a) EXTRUDED INNERSHEATH: Here the innersheath is provided by extrusion of Thermoplastic over the laid up cores. This type of the innersheath is generally provided in cables having round cores i.e in control cables and in power cables upto 10 sq.mm size. This type of the innersheath also acts as a water barrier between cores and outersheath. In case of a puncture in the outersheath the water can not reach to the cores and hence we recommend that cables for outdoor underground uses should have extruded innersheath.
b) TAPPED INNERSHEATH: Here the innersheath is provided by wrapping a thermoplastic tape over the laid up cores. It is generally employed in cables having sector shaped cored i.e. multicore cables of 16 sq.mm and above. This method saves a process and hence manufacturers always provide this type of innersheath unless the purchase specifications ask for extruded innersheath. ARMOURING In case of armoured cables, generally galvanized steel wire / strip armouring is provided over the innersheath in multicore cables and Aluminium Round Wire or Aluminium Strip over the insulation in single core cables. It provides mechanical protection to inside cores and it carries earth return current in case of a short circuit of a core with armour. As per I.S. 1554 (Part I) 1988, round wire armouring is provided in cable, where calculated diameter under armour is upto 13 mm. Above this the armouring is either with round wire or strip of size 4 mm x 0.80 mm. As strip construction is economical, the manufacturers always provide steel strip armouring unless wire armouring is specially specified. In long run of cables and in case of mines, round wire armouring is must, as strip construction provides higher resistance to earth fault current and sometimes this current may not be sufficient to operate the circuit breaker in case of earth fault. In mines, the resistance of the armour in no case should exceed the resistance of the main core by more than 33% for safety reasons. To achieve this, sometimes tinned hard drawn copper wires are required to be used along with galvanized steel wires. Sometimes two layers of Round Steel Wire or Steel Strip are applied in opposite direction with barrier tape in between are provided to give extra protection. In case of single core armoured cables for use in AC circuits, the material for armouring has to be non magnetic, as in this case the return current is not passing through the same cable and hence it will not cancel the magnetic lines produced by the current. These magnetic lines which are oscillating in case of AC current will give rise to eddy current in magnetic armouring and hence armouring will become hot, and this may lead to the failure of the cable. Generally hard drawn aluminium wires / strip are used for armouring in this case. OUTERSHEATH The PVC covering over the armouring in case of armoured cables and over the innersheath in case of unarmoured cables is called outersheath. I.S. 1554 specifies nominal and minimum thicknesses of outer sheath for unarmoured cables and only minimum thickess of outer sheath for armoured cables. It permits the following types of outer sheath PVC compounds. 1) Outer sheath with type ST1 PVC compound as per IS-5831, which is suitable for 70°C continuous operation. 2) Outer sheath with Type ST2 PVC compound as per IS-5831, which is suitable for 85°C continuous operation. PVC has got fire retardant properties due to its halogen content. The fire in the cable gets extinguished immediately on removal of the fire source. In the modern Power, Chemical, Fertilizer and Cement Plants many PVC cables are bunched in the cable shaft or on cable trays. In case of fire in these cables, the fire becomes self sustaining. Moreover due to the burning of PVC a dense corrosive smoke is emitted which makes fire fighting very difficult, due to poor visibility and toxic nature of the smoke. HCL content of the smoke, not only damages other costly equipment lying nearby, but also penetrates the RCC and corrodes the steel reinforcement. Due to this there is an extensive damage to the property. To overcome these deficiencies FRLS i.e. Fire Retardant Low Smoke PVC was developed. If required, we can provide Fire Retardant Low Smoke (FRLS) PVC Inner sheath and / or outer sheath. This PVC compound, apart from meeting the requirements of Type ST2 as per IS-5831, has got better fire retardant properties and it emits lower smoke and acid fumes when it catches fire. (For more information please refer our catalogue on FRLS cables)
Information Source – Polycab