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I'm linesman and Electrical Fitter in powerline distribution in Australia AMA ?

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I wonder if the allocated supply to the average house is getting more and more.

Once upon a time a house would have a handful of 60W incandescent light bulbs, a single TV and so on.   While inefficient by today's standards, they would not draw a lot of electricity.  Compared to today with 100" TV's and more lights then you can poke a stick at and every gadget under the sun.  Air con's everywhere and so on.

Air-conditioning has been a source of big load increases.

I mentioned some of the great test gear used in the power industry on the podcast, here is an example..

Hi Optoisolated,

When travelling around the states i can't help but look at the electrical infrastructure wherever i go  :)

Almost all of the networks i have seen follow the same basic design of three phases of HV and three phases of LV with a neutral.
What tends to differ the most is the layout and construction methods.  Although most networks also have a range of designs in their book that can work for any given situation. 

For example in NSW most of the newer constructions have the HV as the top set of conductors with a single or double crossarm holding the two outer conductors and the center phase on a pin at the very top of the pole, this is called a delta construction (eg a triangle)
It can be in bare aluminium or covered conductor such as CCT.

However there are many "flat constructions" still where the centre conductor is also on the crossarm, swapping sides each alternate pole.

As for the LV circuits, they are usually similar with four conductors per xarm, some regions having the neutral on the roadside (vehicle safety?), some on the footpath side (pedestrian/property safety?) and some in the middle closest to the pole (easy access for lineworkers?)

The poles can be timber, concrete, steel or composite.

Often each state will pick and choose the pole to suit the conditions it is in or availablity and cost.  Most of the switchgear, terminations and conductors are from the same big manufacturers and so are quite recognizable between states, however they often may choose one style of gear over another, eg, ceramic string insulators vs poly insulators Although most networks will have a mix of both..

Sometimes a network will have piece of unique hardware such as a center conductor riser/extension bolted to the top of the pole to increase its height etc and keep a pole in service longer,  usually these are things that have been added over the years to allow a pole or something to continue to be useful or fit into a new design/augment.

As for electrical safety, its the most important thing of course and there are very rigorous procedures to be followed, but easy to to do and simple to follow.   Try looking up "Electrical Safety Rules" for Endeavour Energy or Essential Energy, all the field staff will need to pass an annual test/quiz (100% required!) to be able to continue to work on the network. Any updates or incidents are always communicated to all workers.

*  ISOLATE - the apparatus
*  SECURE - the isolation eg locks and danger tags
*  PROVE DE_ENERGISED -check the isolation through testing means, (and test the tester against a live supply!) NOTE: All the people out there using proximity detectors, they are not approved and are a bad idea!
*  EARTH and SHORT CIRCUIT - all conductors.  This is what a lineman will look for on a job site, big bright and hanging off the mains, these will tell you that the line must be off. Shorting ensures conductors are de-energised, and stay that way not allowing volts to rise     
    and ensure protection will trip ASAP if accidentally energised.
*  ISSUE an ACCESS AUTHORITY - A paper/digital form ensuring that all members of the work party sign on to and the isolations are listed and you can see what is isolated. Additionally the AA cannot be surrended and re-energised until all members of the work party have
    signed off.

As for working around power at home or in the workshop etc , "test before you touch" is pretty much the best method, and ALWAYS test your meter immediately after (dont change multimeter settings etc.) on a known live supply. Tag your breakers out to be the safest.

And yes SF6 is the "deep voice" gas , Its a super dense gas that can suppress arcs very well. Must be captured and contained as its a potent greenhouse gas. Not recommended to breathe is as there can be toxic products in gas exposed to arcs etc. and yep it will sit in your lungs and stay there? 

Thanks for the feedback on the episode ! really enjoyed recording it with Dave.


--- Quote from: optoisolated on July 31, 2023, 09:36:30 am ---Hi Toby,

Is there much variation with how the networks operate and the equipment used between states, or are they generally quite similar in that regard?

Also, as someone that doesn't deal with anything above about 30 volts, how do you get in the mindset build up the trust in process/safety systems in order to have the confidence that the HV systems you're working on are actually safe? Is it just through training and procedure or is there more to it?

Also, Sulfur Hexafluoride, that's the "anti-helium" gas, isn't it? The one that makes your voice really deep when you inhale it. But if I recall correctly you have to take special precautions to exhale it all otherwise it takes up the space of oxygen in your lungs because it's heavier than air :P I remember reading about how it was a very good insulator but didn't know what its use cases were. Now I do :D

Thanks :) Great Amp Hour episode.  :-+

--- End quote ---

I think one of the most fascinating pieces of equipment used in electric power distribution that you never find anywhere else is the zig zag transformer, aka grounding transformer. Somewhat analogous to when you feed three *identical* 120 degree separated sinewaves into three resistors terminated to a common point, the measured voltage at that point will be zero, if you feed the same three sine waves into a zig zag transformer the nett effect will be zero. But if those sine waves start to differ from each other as regards voltage, phase separation degrees, distortion, they will fight each other in order to maintain exact balance. Much like a rigid crankshaft maintains precise relative movement in a 3 cylinder piston engine.


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