Search

Premium Membership ♕

Limited Time Offer: Save 15% on PRO Plan with discount code: LRN15 and study specialized LV/MV/HV technical articles and studies.

Industrial XLPE Underground Cables
Industrial XLPE Underground Cables (photo by Havells)

XLPE cable system configurations

Trefoil and flat formation

Trefoil or flat formation of three-phase XLPE cable
Trefoil or flat formation of three-phase XLPE cable?

The three cables in a 3-phase circuit can be placed in different formations. Typical formations include trefoil (triangular) and flat formations. The choice depends on several factors like screen bonding method, conductor area and available space for installation.


Bonding of the metallic screens

The electric power losses in a cable circuit are dependent on the currents flowing in the metallic sheaths of the cables. Therefore, by reducing or eliminating the metallic sheath currents through different methods of bonding, it is possible to incresase the load current carrying capacity (ampacity) of the cable circuit.

The usual bonding methods are described below:

Both-ends bonding

A system is both ends bonded if the arrangements are such that the cable sheaths provide path for circulating currents at normal conditions. This will cause losses in the screen, which reduce the cable current carrying capacity. These losses are smaller for cables in trefoil formation than in flat formation with separation.

Single-point bonding

A system is single point bonded if the arrangements are such that the cable sheaths provide no path for the flow of circulating currents or external fault currents. In such case, a voltage will be induced between screens of adjacent phases of the cable circuit and between screen and earth, but no current will flow. This induced voltage is proportional to the cable length and current.

Single-point bonding can only be used for limited route lengths, but in general the accepted screen voltage potential limits the length.

Cross-bonding

A system is cross-bonded if the arrangements are such that the circuit provides electrically continuous sheath runs from earthed termination to earthed termination but with the sheaths so sectionalized and cross-connected in order to eliminate the sheath circulating currents. In such case, a
voltage will be induced between screen and earth, but no significant current will flow. The maximum induced voltage will appear at the link boxes for cross-bonding.

This method permits a cable current-carrying capacity as high as with single-point bonding but longer route lengths than the latter. It requires screen separation and additional link boxes.

Title:XLPE Underground Cable Systems – ABB
Format:PDF
Size:1.3 MB
Pages:28
Download:Right here | Video Courses | Membership | Download Updates
XLPE Underground Cable Systems - ABB
XLPE Underground Cable Systems – ABB

Premium Membership

Get access to premium HV/MV/LV technical articles, advanced electrical engineering guides, papers, and much more! It will help you to shape up your technical skills in your everyday life as an electrical engineer.
50% Discount 💥 - Save 50% on all 90+ video courses with Enterprise Membership plan.

More Information

3 Comments


  1. Inductance or Capacitice Effects
    Aug 19, 2023

    What is the capacitive or inductance effects on XLPE cable acording to layout (trefoil,flat) ?


  2. Pritam
    Jul 03, 2020

    Hey guys check out the below video on termination
    https://youtu.be/2fkxS39egdg


  3. Anwar
    May 04, 2020

    For single point bonding,ECC cable must be used for fault current .

    for cross bonding ,sections to be divided in 3 x 120 degree phase and transposition required with additional link boxes.

Leave a Comment

Tell us what you're thinking. We care about your opinion! Please keep in mind that comments are moderated and rel="nofollow" is in use. So, please do not use a spammy keyword or a domain as your name, or it will be deleted. Let's have a professional and meaningful conversation instead. Thanks for dropping by!

58  −    =  fifty four

Learn How to Design Power Systems

Learn to design LV/MV/HV power systems through professional video courses. Lifetime access. Enjoy learning!

Subscribe to Weekly Newsletter

Subscribe to our Weekly Digest newsletter and receive free updates on new technical articles, video courses and guides (PDF).
EEP Academy Courses - A hand crafted cutting-edge electrical engineering knowledge