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Reducing the induced voltage for the HV Cable system

Ziad Abdelaziz

Hi everyone,

recreantly, i had a discussion with my colleague regarding reducing the induced voltage on the HV Cable system, as for short and medium length, we are using single point bonding and mid point bonding, while for long distances, we will have to use the cross bonding system, but what is the concept of that system and its really useful or not and is there much advanced way to reduce the induced voltage on the HV Cable system?

  • 0

    but what is the concept of that system

    I think the concept is fairly straight-forward - in a 3-phase system with single core armoured cables, the voltages induced across the ends of each section of armour will be in phase with the line current of that cable - and as with any balanced 3-phase system if you add all three phases together you get zero. So if you chop cable run into three equal lengths and then cross-connect (i.e. rotate) the armours at the two intermediate points, so within the overall length, one continuous armour spends 1/3rd of its length influenced by L1, 1/3rd influenced by L2 and 1/3rd influenced by L3 (although not necessarily in that order), then in a perfect system the voltages along each section will neatly cancel each other out. I guess you can sub-divide into a greater number of shorter lengths if you wish (e.g. to keep the voltage along each length acceptable) so long as it's still a multiple of 3 overall. Others here will know more about the practical limitations of the approach, but I understand it's common practice by DNOs for long underground systems.

    * in this context "cross bonding" means the armour bonds are crossed (rotated) - not to be confused with the old school term of the same name which referred to ordinary main bonding within an installation that went across different services (electricity, gas, water, etc.).

       - Andy.

  • 0 in reply to AJJewsbury

    Hi AJJewsbuy, thanks for your reply its more clear now for me 

    here, we are using term crossbonding system as (Rotate) for each phase (Cable) and for the long length we are considering Major section and Minor section, i.e one major section = 3 Sections, noting that, the system balance must be consider during choosing the cable length.

    Many thanks 

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