busbar trunking system and Cables Difference

Planning concept for power supply:

When a planning concept for power supply is developed, it is not only imperative to observe standards and regulations, it is also important to discuss and clarify economic and technical interrelations (cables and/or busbar trunking systems depending on situations).

The rating and selection of electric equipment, such as distribution boards and transformers, must be performed in such a way that an optimum result for the power system as a whole is kept in mind rather than focusing on individual components.

The most important is that all components must be sufficiently rated to withstand normal operating conditions as well as fault conditions.

Further important aspects to be considered for the creation of an energy concept are //

• Type, use and shape of the building (e.g. high-rise/low-rise building, multi-storey building)
• Load centers and possible power transmission routes and locations for transformers and main distribution boards
• Building-related connection values according to specific area loads that correspond to the building’s type of use
• Statutory provisions and conditions imposed by building authorities
• Requirements of the power distribution network operator
• The following requirements are the main points of interest //
  • Easy and transparent planning
  • Long service life
  • High availability
  • Low fire load
  • Flexible adaptation to changes in the building

  Most applications suggest the use of suitable busbar trunking systems to meet these requirements.

  For this reason, engineering companies increasingly prefer busbar trunking to cable installation for power transmission and distribution. The most common busbar trunking systems ratings are from 25 A to 6,300 A.

Planning Notes

Considering the complexity of modern building projects, transparency and flexibility of power distribution are indispensable requirements. In industry, the focus is on continuous supply of energy as an essential prerequisite for multi-shift production.

The five main advantages of busbar trunking systems are //

1. Straightforward network configuration
2. Low space requirements
3. Easy retrofitting in case of changes of locations and consumer loads
4. High short-circuit strength and low fire load
5. Increased planning security

Power transmission

Power from the transformer to the low voltage switchgear is transmitted by suitable components in the busbar trunking system. These components are installed between transformer and main distribution board, then branching to sub-distribution systems.

Trunking units without tap-off points are used for power transmission. These are available in standard lengths. Besides the standard lengths, the customer can also choose a specific length from various length ranges to suit individual constructive requirements.

Power distribution

Power distribution is the main area of application for busbar trunking systems. This means that electricity cannot just be tapped from a permanently fixed point as with a cable installation. Tapping points can be varied and changed as desired within the entire power distribution system.

In order to tap electricity, you just have plug a tap-off unit on the busbar at the tap-off point. This way a variable distribution system is created for linear and / or area-wide, distributed power supply.

Tap-off points are provided on either or just one side on the straight trunking units. For each busbar trunking system, a wide range of tap-off units is available for the connection of equipment and electricity supply.

Comparison of Busbar and Cables: Temp response derating

Table 1 – Cable / Busbar comparison

Characteristic	Cables	Busbar
Planning, calculation	High determination and calculation expense, the consumer locations must be fixed	Flexible consumer locations, only the total load is required for the planning
Expansions, changes	High expense, interruptions to operation, calculation, risk of damage to the insulation	Low expense as the tap-off units are hot pluggable
Space requirements	More space required because of bending radiuses and the spacing required between parallel cables	Compact directional changes and fittings
Temperature responses and derating	Limits depend on the laying method and cable accumulation. The derating factor must be determined / calculated	Design verified switchgear assembly, limits from manufacturer’s catalogue
Free from halogen	PVC cables are not free from halogen. Halogen-free cables are very expensive	Principally free from halogen
Fire load	Fire load with PVC cable is up to 10 times greater, with PE cable up to 30 times greater than with busbars	Very low, see manufacturer’s catalogue
Design verified switchgear assembly	The operational safety depends on the version	Tested system, non-interchangeable assembly