Power Cables Operation, Maintenance, Location and Fault Detection

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Power cables: Operation, Maintenance, Location and Fault Detection

Technology Training that Workswww.idc-online.com/slideshare

Topics

• Need for high voltage cables• Advantages of using cables over overhead

transmission lines• Disadvantages of cables • Various types of high voltage cables• Need for cable jointing • Need for termination • Various types of jointing kits and termination

kits


What is a CABLE?

• Cable: Denotes a bundle of wires– e.g: A wire rope is a type of cable

• Electrical cable is a bundle of electrical conductors used for carrying electricity– Bare conductors– Insulated conductors

• In electro-technology, cable means an insulated electrical conductor used for transmitting electrical energy


Function of electrical lines• Transmitting power from generating source to

load centers• Distributing power from main substations to

individual consumers• Lines can be overhead conductors or underground

cables• Long transmission lines and rural distribution by

overhead lines• Shorter/urban feeders by cables


Typical overhead line

Technology Training that Workswww.idc-online.com/slideshareSlide 6

Section of typical HV cable

Alum inum conductorSem icon XLPE(C onductor sh ie ld)XLPE insula tion

Sem icon XLPE(Insula tion screen)

C opper tape

PVC S t2O uter sheath


Why high voltage?

• Higher the voltage, lower the current for a given value of power

• More energy transmitted for a given conductor section

• Lower conductor losses


Relation between voltage and load rating

Motor rating in kw Operating voltages in Volts

Up to 200kw 415V

Between 200 to 500kw 3300V

Between 500kw to 2500kw

6600V

Above 2500kw 11000V


Cables-Advantages

• Less space compared to overhead lines• No visual intrusion (also called visual

pollution)• Not susceptible to atmospheric activity

(wind/lightning)• Higher surge impedance reduces severity of

switching overvoltages• Ideal way to transmit power across a water

body (Ex: supply to an island)


Cable-drawbacks

• Fault location is difficult and time taking

• Expensive

• More monitoring (for certain types of cables)

• Jointing/termination require persons with high skill levels

• Joints/terminations become weak points

• Testing is difficult and time-consuming


Common types of cables

• PVC insulated cables

• VIR insulated cables

• Low pressure oil filled cables

• High pressure oil filled cables

• Paper insulated cables

• Polyethylene (PE) insulated cables

• Cross linked polyethylene (XLPE) cables


Need for jointing (Splicing)

• Cables are heavy and difficult to transport

• Fixed drum lengths (ex: 500m) are typical packaging norm

• Longer feeder lengths need joints

• Joints are needed for partial replacement(in case of a cable fault)

• Joints are also needed for specific purposes


Types of joints

• Straight through – Long routes and repaired sections

• Branch Y joints– For branching of a feeder

• T joints– For branching of a feeder

• Transition joints– Special joints between two different types of

cables (Oil filled/XLPE)


Straight-through joint


Making of a T-Joint


A typical Y-branch joint


Need for termination

• A cable needs to be connected to an equipment or another cable

• A connection between two cables is called a joint• A connection to an equipment is called a termination• Termination can be indoor type or outdoor type• End sealing kits are used to cover the cut end of a cable

against moisture entry


Typical outdoor termination


Installation steps

• Preparation of installation site• Arranging cable supports• Unwinding of cable from the cable drum• Laying along the supports and clamping to

prevent dislocation• Threading through pipes where a cable duct is

used• Jointing/Termination• Testing


DO YOU WANT TO KNOW MORE?

If you are interested in further training or information, please visit:

http://idc-online.com/slideshare

Date post:	24-May-2015
Category:	Engineering
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Power Cables Operation, Maintenance, Location and Fault Detection

Engineering