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.

Home / Technical Articles / MV network diagrams for feeding secondary switchboards and MV/LV transformers

MV network diagrams

Let’s take a look at the main MV network diagrams and structures used to feed secondary switchboards and MV/LV transformers. The complexity of the diagrams differs, depending on the level of power supply security required. Note that there are many other variations of presented medium voltage network diagrams, we shall focus on the five most common.

MV network diagrams for feeding secondary switchboards and MV/LV transformers
MV network diagrams for feeding secondary switchboards and MV/LV transformers (photo credit: Leonhard Weiss)

The following MV network supply arrangements are the ones most commonly adopted.

  1. Single fed radial network
  2. Dual fed radial network with no coupler
  3. Dual fed radial network with coupler
  4. Loop systems:
    1. Open loop
    2. Closed loop
  5. MV parallel feeder

1. Single fed radial network

MV single fed radial network
Figure 1 – MV single fed radial network

Network characteristics:

  • The main switchboard is fed by 2 sources with coupler.
  • Switchboards 1 and 2 are fed by a single source, and there is no emergency back-up supply.

This structure should be used when service continuity is not a vital requirement and it is often adopted for cement works networks.

Go back to contents ↑


2. Dual fed radial network with no coupler

MV dual fed radial network with no coupler
Figure 2 – MV dual fed radial network with no coupler

Network characteristics:

  • The main switchboard is fed by two sources with coupler.
  • Switchboards 1 and 2 are fed by two sources with no coupler, the one backing up the other.
  • Service continuity is good. The fact that there is no source coupler for switchboards 1 and 2 means that the network is less flexible to use.

Go back to contents ↑


3. Dual fed radial network with coupler

MV dual fed radial network with coupler
Figure 3 – MV dual fed radial network with coupler

Network characteristics:

  • The main switchboard is fed by two sources with coupler.
  • Switchboards 1 and 2 are fed by 2 sources with coupler. During normal operation, the bus coupler circuit-breakers are open.
  • Each bus section can be backed up and fed by one or other of the sources.
This structure should be used when good service continuity is required and it is often adopted in the iron and steel and petrochemical industries.

Go back to contents ↑


4. Loop system

This system should be used for widespread networks with large future extensions. There are two types depending on whether the loop is open or closed during normal operation.


Open loop (see Figure 1-20a)

MV open loop system
Figure 4 – MV open loop system

Network characteristics:

  • The main switchboard is fed by two sources with coupler.
  • The loop heads in A and B are fitted with circuit-breakers.
  • Switchboards 1, 2 and 3 are fitted with switches.
  • During normal operation, the loop is open (in the figure it is normally open at switchboard 2).
  • The switchboards can be fed by one or other of the sources.
  • Reconfiguration of the loop enables the supply to be restored upon occurrence of a fault or loss of a source.
    (The loop heads at A1 and B1 are fitted with circuit-breakers, and phase and earth fault protection devices. The substations are fitted with switches. Fault detectors are installed on each switch. They indicate the passage of a fault current.)
This reconfiguration causes a power cut of several seconds if an automatic loop reconfiguration control has been installed. The cut lasts for at least several minutes or dozens of minutes if the loop reconfiguration is carried out manually by operators.

Go back to contents ↑


Closed loop

MV closed loop system
Figure 5 – MV closed loop system

Network characteristics:

  • The main switchboard is fed by two sources with coupler.
  • All the loop switching devices are circuit-breakers.
  • During normal operation, the loop is closed.
  • The protection system ensures against power cuts caused by a fault.
    (Each link end is fitted with a circuit-breaker. During normal operation, the loop is closed. The protection systems will allow power cuts to be avoided when a fault occurs.).
This system is more efficient than the open loop system because it avoids power cuts. However, it is more costly since it requires circuit-breakers in each switchboard and a complex protection system.

Go back to contents ↑


MV parallel feeder

MV parallel feeder network
Figure 6 – MV parallel feeder network

Network characteristics:

  • Switchboards 1, 2 and 3 can be backed up and fed by one or other of the sources independently.
  • The main switchboard is fed by two sources with coupler.
This structure should be used for widespread networks with limited future extensions and that require good supply continuity.

Go back to contents ↑

Reference // Protection of Electrical Networks by Christophe Prévé

Premium Membership

Get access to premium HV/MV/LV technical articles, electrical engineering guides, research studies and much more! It helps you to shape up your technical skills in your everyday life as an electrical engineer.
More Information
author-pic

Edvard Csanyi

Electrical engineer, programmer and founder of EEP. Highly specialized for design of LV/MV switchgears and LV high power busbar trunking (<6300A) in power substations, commercial buildings and industry facilities. Professional in AutoCAD programming.

5 Comments


  1. Bezabih Tegegn
    Oct 21, 2019

    thanks bro for all


  2. NguyenCao Ky
    Oct 21, 2019

    Thanks so much


  3. José Aular
    Oct 20, 2019

    Excellent!. Thank you


  4. Leone Takeshi Uema
    Apr 02, 2018

    Gostei da apresentação, gostaria de receber mais matérias sobre assuntos Tecnco.


  5. ADOLFO PONCE DE LEON
    Aug 04, 2017

    edvard I was paid to develo procedures e . specially years ago when it was protected . interesting that I am not copmpemsaed for comtributig to your site. on the subject matter.
    very clever. God speed.

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!

four  ×  nine  =  

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