POWER CABLE TERMINATION AND SEALING

 

Power Cables Termination and Sealing End Requirements

The servicer should terminate and connect up the power cables in accordance with diagrams or details approved by the employer Engineer. Considering the followings requirements, power cable along with others controlling and communication cable sealing end should be terminate in an adequate manner.
High Voltage Cable Termination


For control wiring, the cable tails shall be so bound that each wire may be traced back to its associated cable without any difficulty; cores in twisted pairs or groups shall be kept together; nay spare cores shall be numbered and terminated on spare terminals.
The servicer is to be responsible for the correct phase rotation and connections in accordance with information approved by the Employer. Particular care is to be taken in the case of these cables, where sub-sequent correction may be difficult. Phase tests should be carried out by the servicer to the satisfaction of conformation. Necessary equipment may arrange to carry out these tests.
Where insulated glands are provided it should ensure that the insulation is maintained after jointing the cable and shall demonstrate this to the satisfaction.

Termination and Jointing Conductors for Cable End Sealing

The use of either welded soldered or compression type lugs and ferrules is may be permitted depending the requirements. If compression lugs and ferrules are used the tools for making compression joints must be those recommended by the manufacturer of the lugs and ferrules.
It’s very important to consider the factor of bimetallic for any jointing of copper to aluminum conductors.
On stud type terminals approved compression lugs or claw type washers shall be used. All conductors excluding those terminated into clamp type terminals shall be connected in the foregoing manner.

Core Identification Ferrules

During power cable termination, don’t forget to provide core identification ferrules for terminating pilot cores in the marshaling boxes.
The ferrules or sleeves shall be of insulating materials which shall be white and shall have glossy finished. Ensure the ferrules or sleeves should be unaffected by oil or damp. Characters should be suitably marked in black. Additional red ferrules or sleeves especially marked “TRIP” in white shall be fitted on all wires associated with trip circuits.

Cable Identification

Each end of a cable run must be provided with phase markers for identification. The markers to be fitted in a suitable position under the cable termination. Where cables enter and leave ducts and at cable joints suitable identification markers shall be fitted.
The material of the markers and of the labels and fastenings shall be such as to avoid corrosion due to incompatibility of materials, and to ensure permanent legibility.
Cable identification marker may be labeled or painted.

Cable Pulling

Oil-filled cables should be bond pulled or drawn in by powered rollers during installation. Bend shall be so arranged that the whole of the mechanical tension is concentrated in the steel carrier wire.
XLPE and pilot cables may be hand pulled or nose pulled provided that for nose pulling the power winches used shall be fitted with a safe tension automatic trip limiting device.
A sufficient number of rollers over which the cable can ride without tendency to rotate or twist on its longitudinal axis shall be used. Particular attention shall be given to the provision and placing of rollers at bends to ensure that the minimum bending radius of the cable is not reached. Details of proposed pulling methods are described in other post Cable Pulling Procedure and Following Conditions in Field.

Cable Terminations

Power cables should be terminated into outdoor sealing ends, cable boxes or heat shrink type pole terminations as appropriate.
The on-site termination of conductors and cables into equipment can often be an issue. The equipment layout, the design of the building skid base frame, the numbers of and the  method of termination can all influence the speed and ease of installation.
Choosing a correct and perfect termination method significantly decrease installation cost and reduce complicacy the ability to install cables and conductors in the future.

Traditional and Improved Transit Cable Termination System

There are several cable termination methods are practicing  to terminate the industrial cable conductor on substation or switchgear equipment.
Some are prefer to terminate the cable from top of the substation or control equipment; when these equipment are mounted inside the building, cable transit barrier is often used to allow cables to pass through an exterior wall.
Cables may terminated into the floor of a substation where steel removable panel is used to facilitate the pre-drilling of holes for the cable connectors prior to the field installation, or
Terminating cables may illustrate in a section of the floor is removed and the cable is terminated directly into the floor mounted equipment.
In the transit entry system, the transit frame is welded or bolded to the equipment mounted floor where cable will be terminated. Cable then pulled into the transit frame and sealed using cable transit block. this system provides  cable retention, fire resistant, environmental safety, gas seal to equipment etc.


Modules of Cable Termination
Cable Termination Module


The typical modules of a modern medium voltage termination should consider the following facts-
  1. Moisture sealing
  2. Compact and versatile stress control
  3. Non-tracking insulation tubing
  4. Void filler
  5. Earthing
Porcelains For Cable Sealing
Porcelain using in cable sealing is ll cable sealing end porcelains should be of the one piece type and be sound, free from defects and thoroughly vitrified so that the glaze is not depended upon for insulation. Cable sealing ends assembled from multiple porcelain elements would not be be good practice. The glaze shall be smooth and hard, completely cover all exposed parts of the porcelain and be of a uniform shade of brown. Notable that outdoor sealing ends and fittings should be unaffected by atmospheric conditions proximity to the coast, funs, ozone, acids, alkalis, dust or rapid changes of air temperature (like for humid area  between 4ºC and 40º C) under working conditions. Porcelain must not engage directly with hard metal and where necessary, gaskets should be interposed between the porcelain and the free fittings. All porcelain clamping surfaces in contact with gaskets shall be accurately ground and free from glaze. A minimum creep age distance of 30 mm/kV of rated service voltage is required.
Arching Horns
Arching horns are also important part to cable sealing end. So, all outdoor type sealing ends should be provided with adjustable displace double gap arcing horns.

Cable Sealing Glands

All cable sealing end bases should be insulated from the surrounding metalwork by means of porcelain or molded resin insulators interposed between the sealing end based and the supporting structure. Phase colors also should be indicated in an approved manner.
Cable sealing glands are also known as cable gland or cable connector or fitting that secured the cable end and isolate it from the metallic base of the equipment.
Types of Cable Glands

Generally following materials are used to produce cable sealing glands:
  • Plastic
  • Brass
  • Alluminium
  • Stainless Steel
Cable gland uses in all types of electrical power cable, control cable, instrumentation, data and communication cables for sealing and termination devices.



Final Talk:The power cable termination and sealing  must be coordinated with the location of the electrical and control equipment and the skid frame steel members supporting the cable.

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