IET logo
 
IET
Decrease font size
Increase font size
Topic Title: Calling electric fence experts
Topic Summary:
Created On: 10 April 2013 12:00 PM
Status: Post and Reply
Linear : Threading : Single : Branch
1 2 Next Last unread
Search Topic Search Topic
Topic Tools Topic Tools
View similar topics View similar topics
View topic in raw text format. Print this topic.
 10 April 2013 12:00 PM
User is offline View Users Profile Print this message


Avatar for dickllewellyn.
dickllewellyn

Posts: 1150
Joined: 19 March 2010

Morning all

I've just visited a client who's husband had decided he'd like to fit a curtain rail through some cables!

Once I'd mended said cables, consumed my coffee (white with one), and mattered away any profit I'd have made, she took me down to the paddock to look at the electric fencing.

The supply to the fence (is it called a ballast? Transformer? Pulse generator?) is in the barn hidden behind husbands Motorsport hobbies and hence tends to be left permanently plugged in and switched on.

Wife therefore has taken to just taking the crocodile clip off the fence, and putting back on when she wants to isolate or re energise. What she would like is for me to replace the crocodile clip with something sturdier that can't spring off by accident, and to provide her with some isolation localmtomthe fence or on the outside of the barn as she tends to zap herself from time to time.

Can the load side of the fence be switched? What sort of switch would One use for a 9.5kV pulse? Would it be better to install a dedicated socket for the internal gubbins controlled by a switch outside?

All thoughts and input will be appreciated as ever, and there may be a mini chocolate bar from my Easter (or non deity related spring bank holiday) box of celebrations for the best solution (provided that doesn't fall foul of the bribery act!)

Have a nice day all, the sun is trying to peek out from the fog down this end of the country!

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 10 April 2013 12:12 PM
User is offline View Users Profile Print this message



daveparry1

Posts: 6200
Joined: 04 July 2007

All the ones I've come across (admittedly not that many) have had the isolation switch on the primary side,

Dave.
 10 April 2013 12:14 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11442
Joined: 13 August 2003

> Can the load side of the fence be switched?
I don't see why not - it'd be like changing a long fence for a short one... presumably the controller doesn't mind?

I've seen "gates" in electric fences switched by what looks like a hook with a big insulated handle on it - I guess that approach has the advantage that the stock can't escape over other parts of the fence while one small section is isolated.

Switching the controller seems like the simplest option, but presumably it depends on whether it's acceptable to power down the whole fence, rather than just a small section.

- Andy.
 10 April 2013 12:14 PM
User is offline View Users Profile Print this message



AJJewsbury

Posts: 11442
Joined: 13 August 2003

what looks like a hook with a big insulated handle on it

Like these: http://www.ukcountrystore.co.u...og/Gates-Handles.html

- Andy.
 10 April 2013 12:38 PM
User is offline View Users Profile Print this message



dlane

Posts: 690
Joined: 28 September 2007

Countrystore also sell 2 switches that can be used on the output side of the pulse generator

Electric fence items

Scroll down to item 5306053 and item P33.

Kind regards

Donald Lane
 10 April 2013 03:59 PM
User is offline View Users Profile Print this message



ArthurHall

Posts: 735
Joined: 25 July 2008

In my experience the springy hook connectors start to burn at the connection and can burn right through electric rope.
Switching the primary side is best but the hv switches for the load side work ok, be careful when they are wet!
The best tip for working with electric fences is make sure you have a decent earth.
 10 April 2013 08:24 PM
User is offline View Users Profile Print this message


Avatar for KFH.
KFH

Posts: 205
Joined: 06 November 2010

Arthur, I hope you mean a decent earth on the fence :-) Personally I prefer not to have an earth at all when near electric fences, but I have still had shocks even with good dry wellingtons on :-(

The power from mains energisers is usually much higher than the battery ones and will cause sparking and burning if any connection is not perfect. The fence switches suggested work well. Some energisers suggest minimum fence lengths due to the high output being dangerous on shorter runs, it may be worth getting a look at the manual before deciding on input or output switching.
 10 April 2013 09:29 PM
User is offline View Users Profile Print this message



mikejumper

Posts: 1714
Joined: 14 December 2006

Originally posted by: KFH
...Some energisers suggest minimum fence lengths due to the high output being dangerous on shorter runs...

I don't understand that.
How can a shorter run make it more dangerous?
Isn't the idea that you raise the fence to the same specific voltage for a short duration whatever it's length may be?
 10 April 2013 09:48 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3510
Joined: 22 November 2007

I've made connections to the tape using a couple of brass strips before bolted top and bottom, then a lug on to the hv cable. Much better than a croc or spring clip.

As to switching it, when we had our horses I used to earth the fence rather than disconnect the output, was safer as people on the yard used to find it funny to switch the fence controller back on whilst you were fiddling with the hv connection.

Stu
 11 April 2013 07:51 AM
User is offline View Users Profile Print this message


Avatar for dickllewellyn.
dickllewellyn

Posts: 1150
Joined: 19 March 2010

Morning people.

Thanks so far for the helpful and interesting replies. I will give it some thought and work out a solution. I think a simple external rotary switch that can be locked off feeding the socket that supples the energiser. I will try to work out a way of making it a dedicated connection so it can't be unplugged and plugged into another socket or poor lady wife might switch the isolator off, go down to the fence and find it still live!

I'll keep thinking!

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 11 April 2013 07:10 PM
User is offline View Users Profile Print this message


Avatar for slittle.
slittle

Posts: 3510
Joined: 22 November 2007

Cut the plug off the energiser and wire it into a FCU fed from the isolator.


Stu
 11 April 2013 07:47 PM
User is offline View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8843
Joined: 03 October 2005

A number of years ago I had an electric fence for about five years , my daughters and her friends with their nags, anyway for the gate access I used an insulated spring loaded hook and it never burnt out.

I am not keen on the idea of an isolator because if the lady forgets to switch it on you end up spending most of the day chasing the little blighters around the countryside or down the dual carriageway. give them the opportunity and when their gone their gone.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------
 11 April 2013 08:39 PM
User is offline View Users Profile Print this message


Avatar for dickllewellyn.
dickllewellyn

Posts: 1150
Joined: 19 March 2010

Originally posted by: slittle

Cut the plug off the energiser and wire it into a FCU fed from the isolator.





Stu


Out of the question unfortunately, it's a moulded transformer type plug. Good old Scats making cheap off the shelf solutions!

Rock n roll raises an interesting point too. I'll mention it to her.

-------------------------
Regards
Richard (Dick)

"Insert words of wisdom and/or witty pun here"
 11 April 2013 11:49 PM
User is offline View Users Profile Print this message



alancapon

Posts: 5766
Joined: 27 December 2005

In the UK Electricity Supply Industry, Gallagher fences and energisers are popular. They also make the much lower power stock fence products as well as a range of insulated crocodile clips and the isolation switches intended for the HV side of the energiser. Have a look at Gallagher Fence Products.

I have no connection with them other than a user of the high power "commercial" energisers intended to be used for security against intruders. These give about 8kV and can throw you a significant distance!

Regards,

Alan.
 12 April 2013 10:06 AM
User is offline View Users Profile Print this message


Avatar for KFH.
KFH

Posts: 205
Joined: 06 November 2010

Originally posted by: mikejumper

Originally posted by: KFH

...Some energisers suggest minimum fence lengths due to the high output being dangerous on shorter runs...


I don't understand that.

How can a shorter run make it more dangerous?

Isn't the idea that you raise the fence to the same specific voltage for a short duration whatever it's length may be?



Mike,

The larger units will power many tens of kilometers of fencing with outputs of >18Joules. (I had to look it up) compared with the normal battery powered energisers running about 2 Joules. The tape looses current to the air and any nearby vegetation. The impact of capacitance and tape resistance are beyond my befuddled brain I just follow the instructions :-)
I have had many belts of the low energy ones even when the tape is in contact with the vegetation. I do not go anywhere near the mains powered ones when they are on as I am a coward and have seen the arcing at bad contacts which bears no comparison to the feeble sparks of the battery powered units.
Kevin
 12 April 2013 12:14 PM
User is offline View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8843
Joined: 03 October 2005

I am not quite sure of your logic on this one, joules is power so a small 100m portable unit might only need 2 joules to operate but a 1000m static unit might need 18 joules to operate, the longer the distance the more power you need to maintain the operating voltage.

Electric fences need to operate between a range of 500 and 900 volts to earth for them to be effective against livestock, below this figure they will push the fence down and do a runner, you cannot compare the shock you get which could be a low as 70v to the 500v + that is required to keep an animal at bay, they are well insulated against the shock and you are not.

For an electric fence to operate correctly there has to be an effective earth otherwise the voltage level to deter livestock will be too low, on the portable units they are usually pushed into the earth with a spike attached and the cable/ribbon is strung around the area of containment, for larger static units like for instance a kilometre there may be two, three or four wires, one of these wires is the earth and to maintain the voltage level this wire is usually staked at 100m intervals around the containment area. You can get a meter that you clip onto the live cable and push into earth to determine the voltage level, usually just three or four lights are the indicators.

LOL I understand if you are not a country boy who is used to the odd blast from a fence but a townie that panics a bit over a little shock, but the pulse is no worse than the occasional burst of static we get now an again from various sources.

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 12 April 2013 at 01:45 PM by rocknroll
 12 April 2013 03:35 PM
User is offline View Users Profile Print this message



unshockable

Posts: 848
Joined: 18 May 2007

Originally posted by: rocknroll

I am not quite sure of your logic on this one, joules is power so a small 100m portable unit might only need 2 joules to operate but a 1000m static unit might need 18 joules to operate, the longer the distance the more power you need to maintain the operating voltage.



That has me educated! I thought joules were a unit of work or energy. Thanks for clearing that up!

Is it only me that could do with an ironic font?

Simon
 12 April 2013 05:09 PM
User is offline View Users Profile Print this message


Avatar for rocknroll.
rocknroll

Posts: 8843
Joined: 03 October 2005

Originally posted by: unshockable

Originally posted by: rocknroll

I am not quite sure of your logic on this one, joules is power so a small 100m portable unit might only need 2 joules to operate but a 1000m static unit might need 18 joules to operate, the longer the distance the more power you need to maintain the operating voltage.



That has me educated! I thought joules were a unit of work or energy. Thanks for clearing that up!

Is it only me that could do with an ironic font?

Simon


Well you are not wrong except that your reference leads us to the definition of mechanical energy, 1 joule is the amount of work/energy we expend at a force of 1 newton over a distance of 1 metre. In electrical systems Energy / Time = Power therefore 1 Joule / Second = 1 Watt (power).

Electric fences come in all sizes from 1kV for small animals and portable units to 30kV for permanent solutions, zoos, large farms and wildlife parks might have much larger sizes depending on the animal, they all work on the same principle where when a animal is a few cm or mm from the wire a spark jumps out through the fur and travels to earth through its muscles, you can prove this yourself, pick a heavy night and move your finger closer to the cable and even at around four inches a spark will jump to your finger if you are not a wimp, as I pointed out it is very much like a static charge although a bit longer in duration.

90% of the problems with electric fences is earthing because the unit relies so much on this especially single wire units, the first 3 metres of the ground dries very quickly and is not stable, the bigger more permanent units use multiple rods of 4 metres or so to maintain continuity, as I pointed out once the voltage drops below 500 - 900v then the animals are off like a shot and this does happen a lot.

The subject of using electricity whether for discharge purposes or electric fences to deter or contain humans is a controversial and highly restricted subject that I am not willing to comment on because it involves something which is sacred and that is 'human life', to touch on Alan's reference to electric fences at sub-stations they are primarily designed to stop animals like foxes, badgers, cats and dogs causing havoc amongst all the exposed cables and terminals, they must be contained within a safe area and the level of shock must not be not enough to kill a human being, as I said this is an area where I dont wish to go.

regards

regards

-------------------------
"Take nothing but a picture,
leave nothing but footprints!"
-------------------------
"Oh! The drama of it all."
-------------------------
"You can throw all the philosophy you like at the problem, but at the end of the day it's just basic electrical theory!"
-------------------------

Edited: 12 April 2013 at 05:27 PM by rocknroll
 12 April 2013 05:30 PM
User is offline View Users Profile Print this message



mikejumper

Posts: 1714
Joined: 14 December 2006

Originally posted by: rocknroll
...For an electric fence to operate correctly there has to be an effective earth otherwise the voltage level to deter livestock will be too low...

Isn't the voltage level fixed by the generator, not the earth?

The effectiveness of the earth detemines how much current flows through the animal when they complete the circuit by making contact with the ground and the fence simultaneously.
 12 April 2013 07:27 PM
User is offline View Users Profile Print this message


Avatar for weirdbeard.
weirdbeard

Posts: 1522
Joined: 26 September 2011

Originally posted by: KFH


I have had many belts of the low energy ones even when the tape is in contact with the vegetation. I do not go anywhere near the mains powered ones when they are on as I am a coward and have seen the arcing at bad contacts which bears no comparison to the feeble sparks of the battery powered units.


This is a myth, i can assure you, that battery powered fence energisers are less effective than mains powered ones!

Properly installed within their limittations of length, with a good earth and sound connections to the fence you will get just as good a belt from a battery operated unit as that of a mains powered one, the only difference is/should be that mains powered units do not require battery replacement/recharging.
IET » Wiring and the regulations » Calling electric fence experts

1 2 Next Last unread
Topic Tools Topic Tools
Statistics

See Also:



FuseTalk Standard Edition v3.2 - © 1999-2014 FuseTalk Inc. All rights reserved.