How to create a totally selective network?

[Christopher_D]

I need to create a totally selective network for my client. I am exploring to see how I can use Ecodial to achieve this. Sometimes I get some errors and I can only get limited selectivity. Are there any specific ways to work on this?

[Genghiz · Accepted solution]

Thanks for your query on achieving the 'Total Selectivity' in your network design. The following comments would help you in understanding the same.

Principles of Selectivity

Selectivity is achieved by overcurrent and earth fault protective devices.

If a fault condition, occurring at any point in the installation, is cleared by the protective device located immediately upstream of the fault, while all other protective devices remain unaffected.

Applications

• Selectivity is required for installation supplying critical loads where one fault on one circuit shall not cause the interruption of the supply of other circuits.
• In IEC 60364 series it is mandatory for installation supplying safety services and in some special applications like
  • Medical
  • Marine
  • High-rise building
  • Data centers
  • Infrastructure (Tunnel, Airport…)
  • Critical process

How to achieve the Selectivity

• From installation point of view, Selectivity is achieved when the maximum short-circuit current at a point of installation is below selectivity limit of the circuit breakers supplying this point of installation.
• Selectivity shall be checked for all circuits supplied by one source and for all type of fault:
  • Overload
  • Short-circuit
  • Earth fault
• When system can be supplied by different sources (Grid or generator set for instance) selectivity shall be checked in both cases.
• Selectivity between two circuit breakers may be…
  • Total     : Up to the breaking capacity of the downstream circuit breaker.
  • Partial   : Up to a specified value according to circuit breakers characteristics.
• Different solution is provided to achieve selectivity based on…
  • Current
  • Time
  • Energy
  • Logic

Selectivity verifications at Ecodial :

• The electrical network design in Ecodial, will check the "selectivity" between the two protective devices by default.
• This supported by the backend data, defined from the "complementary technical guide."

Verification of the Selectivity at Ecodial

• Once after completing the network calculation, this can be verified by "selecting the protection device" and launch the "Curve" section.

[Genghiz]

Further detailed information you can see a similar discussion under the "Power Foundations Forum" as well.

[Christopher_D]

Thank you for your answer. Helped me understand this subject in detail.

Cheers,

Chris