High ish Ze

[uksparks]

Hi

ive been at my mates today between Boston and skeggy in the middle of knowhere surrounded by cabbages.

hes on the very end of an overhead supply, it's PME.

the Ze is 0.56 ohms, would you say this is a big on the high side? I know it's on a long run and they can be high but just wondered what your thoughts were.

ivd just been putting a sub main up to some out buildings and a caravan pitch and earth rods, quite pleased as put one heap of 4 x 5/8 rods and got 5.7 ohms!

 

[davesparks]

Where what?

Where are those values in bs7671?

 

[LeeH]

No idea, thought the typical values were in there.

I'll ask at the bar see if they have a copy on my next round.

 

[davesparks]

No idea, thought the typical values were in there.

I'll ask at the bar see if they have a copy on my next round.

Then why make a statement about something being in the regulations when it is not?

 

[Lagentium]

I got a -------ing off Dave once, it scarred me for life.

 

[uksparks]

Dave I know full well what the relationship of fuse size is to loop impedance, what I was saying is that j thought the figures of .35 and .80 etc for supply types were relatively fixed as that was the point in having them printed in regs etc.

i was about 12" from the cutout where I took that reading with 25mm tails into it.

 

[davesparks]

Dave I know full well what the relationship of fuse size is to loop impedance, what I was saying is that j thought the figures of .35 and .80 etc for supply types were relatively fixed as that was the point in having them printed in regs etc.

i was about 12" from the cutout where I took that reading with 25mm tails into it.

Why on earth would they be fixed? You can't have a guideline loop impedance the same for a 100A supply as a 1000A supply


Where are they printed in the regs?

 

[sparky1508]

Check out the on site guide page 11, paragraph d.

Sent from my SM-G361F using Tapatalk

 

[davesparks]

Check out the on site guide page 11, paragraph d.

Sent from my SM-G361F using Tapatalk

The onsite guide is not the regulations, this is an important fact which is often overlooked.

 

[Andy78]

The onsite guide is not the regulations, this is an important fact which is often overlooked.

And in this case it is not even offering guidance on the regs, but offering guidance on max Ze figures that may typically be found to be used by network operators for installations 100A or less.

 

[davesparks]

These two table from UKPNs network design guide give you an idea of what the DNOs have to say on the matter.