Recent Blog Entries

  •   When generator sets operate in parallel, the engine speed governor of each generator set determines the proportional sharing of the total active power requirements (kW) of the system.  For two systems to be paralleled, each must have the following matching characteristics for correct...
  •     Load management systems may prioritize loads based on the load type or importance. Load importance may vary widely depending on the application and facility, but often fall generally within one of the following categories: Non-Critical Loads These are loads that, if removed, will...
  •     When the system is totally isolated from the ground circuit, except through indicating, measuring or protective devices, which are normally grounded and possess a high impedance to ground, the ground fault factor     This may become higher, depending upon the circuit...
  •     Download     What is X/R ("X over R") ratio, and why is it important? First, X/R ratio is simply the ratio of the system reactance to the system resistance, looking back to the power source from any point in a power circuit, assuming that a short circuit is applied t...
View All


Demands 12/24 kV medium voltage room

  • Demands 12/24 kV medium voltage room

    The room where the switchgear will be setup should comply with building standard demands made on electrical rooms as soon as the installation is start. Due to the switchgear’s unique characteristics the room does not need to be equipped with special devices for pressure relief or for the evacuation of flue gases. The room shall be ventilated in accordance with building standards. The floor should be of the following type:

    Concrete floor with a flatness according to building standards (class B as set out in BYGGAMA).

    Switchgear floor/raised floor (intermediate floor type ISO Floor or the like) that withstands the weight of the switchgear) approved for electrical rooms


    Plan the type of fire seals to be used on cable lead-throughs in the floor, walls or ceiling at an early stage. Bear in mind that a sealing system also protects against water, gas, smoke, pressure and small animals. Many sealing systems can also be ordered with EMC protection (Electromagnetic compatibility) and protection against electromagnetic pulses and interference (EMP/EMI).


    Most sealing systems require rectangular metal frames or round metal sleeves for embedding or building-in, which makes it necessary to plan and prepare the cable lead-throughs before the switchgear is installed.


    Concrete floor

    Holes for power cables should be made as small as possible so as not to weaken the floor more than necessary. The holes should be sealed if necessary once the cables have been installed to protect against fire and small animals.

    Bear in mind it is not permitted to route single phase cables in individual holes with reinforcement steel between the holes. This allows eddy currents to be formed in the reinforcement steel, which can have a negative effect on the strength of the floor.


    If single phase cables are routed through holes with reinforcement steel between them, a slot should be made between the holes so that a gap is obtained to separate the reinforcement steel.


    Switchgear placement

    The switchgear can be positioned with its rear against a wall or free-standing on the floor. With a free-standing arrangement switchgear can be separated and positioned back-to-back. 


    1. The service area in front of the switchgear should comply with applicable standards and provisions.
    2. There must be a ceiling clearance of at least 0.4 metres to permit installation and future maintenance.
    3. There should be a clearance of at least 0.5 metres at one end of the switchgear. If possible this amount of clearance should be left at both ends of the switchgear.

    When assembling applicable installation drawings should be followed.


    Reference: ABB

Share this article on...