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Transformer Riddle No.43- Transformer Secondary Side cabling
In Oil or Dry Type Transformers, Why do they lay 7×1Core Single Core 800 or 630 Sq.mm Cables Instead of 3×Core cables like the Primary Side of the Tx. If during the Cable laying of 2 Tx's on the Secondary Side to MV panel on the Cable Tray, if the Cables Cross on the Cable Tray, is it acceptable or if not what is the Solution?
Author : BABA - From: Qatar
Sat, May 8th, 2010 - 18:24
In low voltage systems below 600 A are generally provided by multicore cables. Because of some installation problems the larger sizes need single-core cables to provide the necessary capacity.
The installation of single-core armoured cables requires care because generally there is a considerable current circulating in the armouring. The rating of the circuit depends on how the cables are laid, i.e. in trefoil, flat touching or flat separated. The use of two cables per phase is not unusual and these should be laid in accordance with the manufacturer’s instructions to avoid overheating within a cable or at the terminations.
Single-core cables may cause overheating of adjacent metalwork and can also produce high induced voltages under fault conditions. They are also a source of interference unless suitable precautions are taken to segregate them from sensitive equipment.
Author : Hamid - From: Iran
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