The IET is carrying out some important updates between 17-30 April and all of our websites will be view only. For more information, read this Announcement

Rules and Guidelines

Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

State Not Answered
Locked Locked
Replies 11 replies
Subscribers 31 subscribers
Views 5021 views
Users 0 members are here

Options

You may also be interested in

This discussion is locked.

You cannot post a reply to this discussion. If you have a question start a new discussion

80A BS1361 Time Current Curve

Farmboy over 5 years ago

Hi all

Does anyone have a copy of the graph / curve please, either on its own or perhaps along with a 60A curve?

Thanks

F

Parents

0 Farmboy over 5 years ago

davezawadi:

I assume that you have now done the calculation farmboy and realised you don't have to change the Earth conductor. You can use the old figures for a BS1361 fuse and you will see you are very safe unless the PSSC is very low, in which case you may need to fit an overall RCD to get a reasonable trip time in case of a short circuit (which is very unlikely on the tails if they are fitted properly). The main cutout fuse is for overall maximum demand protection, protecting the service cable rather more than in case of a short circuit, but it does that as well providing the PSSC is high enough. Some rural supplies have PSSCs in terms of less than 200A, so fusing times can be very long even with a direct short, then the main earth cable could get somewhat warm, but nowhere close to failure.

... in which case you may need to fit an overall RCD to get a reasonable trip time in case of a short circuit (which is very unlikely on the tails if they are fitted properly)...

Sorry if I'm being dense but just checking my understanding of what you're referring to here. An RCD won't trip on short circuit, will it, so did you mean earth fault current?

F
Cancel
Vote Up 0 Vote Down

Cancel

Reply

0 Farmboy over 5 years ago

davezawadi:

I assume that you have now done the calculation farmboy and realised you don't have to change the Earth conductor. You can use the old figures for a BS1361 fuse and you will see you are very safe unless the PSSC is very low, in which case you may need to fit an overall RCD to get a reasonable trip time in case of a short circuit (which is very unlikely on the tails if they are fitted properly). The main cutout fuse is for overall maximum demand protection, protecting the service cable rather more than in case of a short circuit, but it does that as well providing the PSSC is high enough. Some rural supplies have PSSCs in terms of less than 200A, so fusing times can be very long even with a direct short, then the main earth cable could get somewhat warm, but nowhere close to failure.

... in which case you may need to fit an overall RCD to get a reasonable trip time in case of a short circuit (which is very unlikely on the tails if they are fitted properly)...

Sorry if I'm being dense but just checking my understanding of what you're referring to here. An RCD won't trip on short circuit, will it, so did you mean earth fault current?

F
Cancel
Vote Up 0 Vote Down

Cancel

Children

No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.