XLPE insulated heavy duty cables were introduced worldwide in mid-sixties and it is getting famous everyday due to its properties like higher insulation resistance, higher current rating, higher short circuit rating, etc. XLPE is the abbreviation of cross-linked polyethylene.
XLPE or Cross-linked polyethylene is a thermoset insulation material. Crosslinking polymers is a process which changes the molecular structure of the polymer chains so that they are more tightly bound together and this crosslinking is done either by chemical means or physical means. Polyethylene (PE) material itself has excellent dielectric strength, high insulation resistance, and a low dissipation factor at all frequencies making it an ideal insulator; however it is limited in its temperature range. Cross-linking the PE to become XLPE increases the temperature range of the insulation whilst maintaining the electrical properties.
XLPE cable Properties and advantages over PVC cable
- Working temperature of conductor and Higher current rating:
PVC insulated cables has a maximum working temperature of 70°C whereas XLPE has a maximum working temperature of 90°C. So cables that are insulated with XLPE can run a higher current in the conductors.
- Maximum short circuit temperature (For < 5 Second):
PVC insulated Cable can withstand 160 Centigrade while XLPE is 250 Centigrade under short circuit condition.
- Lower Installation Cost- Lighter In Weight, Smaller Bending Radius:
Density of XLPE is lower than PVC so XLPE cable is with smaller diameter with lower bending radius. So it requires less space for installation.
- Higher Insulation Resistance:
XLPE cable is having higher insulation resistance capacity compared to PVC insulated cable.
- Improved Water tree Resistance
Improved water-tree resistance is another benefit of XLPE insulation for LV cables and MV cables over other cables. Water treeing is a defect which is the result of imperfections in the insulation where fracture lines occur and grow in the direction of the electric field, increasing with electrical stress. It has 100 times more moisture resistance capacity compared to PVC.
- Durability and Service life:
Molecules in XLPE are chemically bonded together and are more durable contributing to more life as compared to PVC cables. XLPE can be used for both high-and-low tension applications. Its structure provides great resistance to abrasion, stress, and other wear and tear. PVC insulation cannot withstand as much pressure, meaning it is only suitable for low tension applications.
- Environment Protection aspect:
XLPE cables insulation is not containing chlorine material which releases toxic gases once burn. So XLPE insulated Cable is environment friendly compared with PVC insulated Cable.
- Commercial Aspects:
XLPE cables are little expensive than the PVC cables. But considering the properties of cable, performance, lower laying and installation cost and it requires one size lower as compared to PVC cable; it has high cost performance.
Cable recommendation as per the DG set capacity:
Assumptions for above table
The ampere rating of cable is considered as per duct laying method with ambient temperature 40 deg Celsius.
For grouping of cables (multiple runs) the de-rating factors are considered as per duct laying method of cable. The distance between two parallel cables is considered 30 mm for duration.
Typical cable sizes provided in the table are indicative. Please refer to cable manufactures for details.
Cable Installation and termination:
- Power Cable Cabling from Alternator to Panel should be done with proper size of cable and lugs. Ensure tight crimping / terminations to avoid overheating and burning of the cable and terminals.
- Ensure correct size of gland & gland plates are used to avoid tension on alternator terminal , terminal box and control panel terminations.
- Ensure phase colour coding is adopted while terminating cables at both the ends of alternator and control panel.
- Ensure proper bending radius is given to the cable to avoid excessive tension on cable termination.
- For extended control cabling use 10/12 core 2.5 sq. mm. of armoured copper cable.
- Any type of control & monitoring cables should be sheathed and should be within 5 meters length of accurate performance.
- Ensure that the weight of cables does not rest on alternator terminations. Proper support to be provided from the ground separately through cable tray.