Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Shane Regan — Wed, 10 Apr 2019 14:13:51 GMT

Hi Jonathon,

Yes, update 8 has been released for this - please see further information here.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Jonathan Marsh — Wed, 10 Apr 2019 14:09:23 GMT

Hi Shane

Has a fixed been issued for this yet?

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Jonathan Marsh — Tue, 12 Mar 2019 09:28:15 GMT

I found that by selecting the other box it allowed for 0.4 and 5 seconds.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Yadagani Balakrishna — Fri, 01 Mar 2019 04:14:22 GMT

Hi Shane,

Many thanks for the information and suggestion. We are looking forward to see the update. Much appreciated.

Regards,

Y Balakrishna

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Shane Regan — Thu, 28 Feb 2019 16:15:01 GMT

Hi Balakrishna,

Our developers have examined the code behind the calculation and we confirm that there is an issue with this value for disconnection time in the latest version. Apologies for any inconvenience in this regard and many thanks for bringing this to our attention.

A fix is being worked on and once approved it will be released as soon as possible. I will keep you informed of any developments.

In the meantime the only workaround I can suggest would be to revert to the 17th edition calculation result.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Shane Regan — Thu, 28 Feb 2019 10:37:36 GMT

Hi Balakrishna / Yadagani,

Many thanks for the clarification above. I am consulting the support manager and development about this issue and will get back to you as soon as I have further information.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Yadagani Balakrishna — Thu, 28 Feb 2019 06:40:26 GMT

Hi Shane,

This is Balakrishna, Project engineer working in Aecom Bangalore office. Thank you for the further information provided in trailing email notification from Bentley Communities.

But the actual issue is not just the display error. In fact the calculation is considering the disconnection time of 1 Sec for other circuits (typically 5 Sec as per BS 7671) in TN systems. Ideally, when we run a project in both versions the submain cable should not have a problem with regards to the disconnection times as the table 41.1, as defined in clause 411.3.2.2 of BS 7671:2018 is only for final circuits mentioned therein.

Please see the below snaps for calculations performed in both 17^th edition (using previous Hevacomp version V8i SS1 SP5) and 18^th edition (new version V8i SS1 SP7). For this case the same project has been calculated in both versions and the submain cable results are presented below for verification.

Also, I am wondering why the foot note “Earth fault failure (Ref 411.3)” is referring to a disconnection time of 0.4 Sec instead of 5 Sec for a submain distribution cable? We appreciate your time and effort in resolving the issue.

17^th edition calculation:

18^th edition calculation:

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Thanks & Regards,

Balakrishna Y B, MIET
Project Engineer - E&P, Transportation - Rail
Yadagani.Balakrishna@aecom.com

AECOM
Ferns Icon, 3rd Floor,
Survey Number 28, Doddanekundi Main Road, Doddanekundi, Mahadevpura,
Bangalore – 560037, India
aecom.com

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2018 Time Inc. Used under license.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Shane Regan — Wed, 27 Feb 2019 14:45:55 GMT

Hi Yadagani,

This may just be a display issue as I believe the software does take the figures you mention into account - please see the following excerpt from the manual:

I am consulting our development team to see if this is the case.

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Yadagani Balakrishna — Wed, 27 Feb 2019 12:32:32 GMT

Hi Shane,

My query is regarding the disconnection time fixed 1 Sec (as in snap below) for "Other circuits" in TN system. This value is same in a new project with default 18th edition also. Should the value be 5 Sec as per BS 7671:2018?

RE: Changes for the 18th Edition - Disconnection times for distribution circuits in a TN system

Shane Regan — Wed, 27 Feb 2019 12:18:38 GMT

Hi Yadagani,

The reference here to the previous 17th edition regs is included for consistency with older 17th edition projects so that they are compatible in the latest version . This option will be disabled if you create a new project as the 18th edition will be chosen by default.