Earthing While Working on Dead OHL

i forget to mention that the line is off

TonyS is right here. I'd like to add, if you are not qualified to perform HV work you are better not touching it.

The terminology we use to describe what TonyS is telling you are Proving Earths and Working Earths. To isolate for electrical access takes a well worked out switching sheet and access permit. There is no room for argument and if arguments are ensuing then don't sign on the access permit and definitely don't touch.

The hardest thing can be identifying all the "Sneak Sources" such as Voltage transformers and the items mentioned by other posters.

Radial feeders are not too diffucult but if the circuit is ring fed, then more than one Proving Earth will be needed to protect from each direction of supply. Your working earth needs to be close to you and must be visible. For ring fed circuits you need to be working between two working earths. Obviously all earths and isolation points must be accounted for in the switching sheet.

I can't speak for other juristictions but where I work one person alone cannot devise and authorise the switching sheet and perform the switching. It takes a minimum of two qualified people to sign off before any switching can commence and the switching officer must have a qualified Safety Observer watching the procedure. The preference is for prewritten fully risk assessed switching sheets which are reviewed against the schematic at each use unless the work is proven routine.

I have done a lot of HV work but am as wary as all hell when performing any of the tasks I'm qualified for and therefore discuss with my colleagues to ensure no errors creep in.

Further to the above two posts: If you have not been trained - worry! I suspect that you work in a less formal environment? If your company does not have a formal switching and isolation and earthing procedure for work on transmission lines, try and get something started, even if it is via your safety office or engineering head office. You don't have to go first world with everything, but you only have one life and this is one instance where very formal systems are essential. It does not have to be complicated, just formal. The system should make that you and the supervisor come to the same answers independently, removing room for arguments.

Anyway, from an energy supply point of view, you ALWAYS work between earths, preferably visible earths:

1. You may think of a "source", but you may not know where all the sources are. You don't know what your clients are doing!
2. As the others stated, lightning can be an unwelcome surprise, and you may not even know about the strike a few kilometers away.
3. If there are other power lines in close vicinity, they may cause induced currents in your lines.
4. Once our utility's 22kV power wires fell over our wires, but my linesmen was OK, because he put up the earth connection very close. He was therefore not injured, even though he could see the earth wire "snaking" due to the short circuit current.
   

Switched earths should be as near as possible to the work position along the line. Working earths,weither to a mat or stake should be within sight of the work area.

Guest and Tony here have the correct ideas. You must follow your job specified safety procedures because many people will be relying on how your safety controls are configured. If your safety controls permit more than one ground connection (I suspect they do) then a safety ground upstream and downstream of your work line will maintain a ground on both sides of your line if the cable becomes disconnected.

But don't get in the habit of analyzing your safety rules and regulations. Sometimes the rules are made for your safety, sometimes they're for somebody else's safety (rescue worker, colleagues). The rules did not come from people just engineering what they want to happen. They came from analyzing mishaps that people did not anticipate. Safety rules are not flawless, but modifying them casually in the field is a recipe for disaster.

In addition to TonyS's response, make sure the protective grounding clamps and cables are rated as safety grounding assemblies. Conventional tap clamps are not safety grounding clamps nor are they rated as such.

I don't know your location but in the U.S. safety grounding and standards are the responsibility of the IEEE/ ESMOL Subcommittee (Electrical Safety & Maintenance of Overhead Lines) and IEEE Standard 1048 covers Protective Grounding. You might take a look at www.ieee-esmol.org. Protective grounding is also covered in ANSI C2 (National Electrical Safety Code). Comparable IEC and standards of other countries also exist.

toward the source. the voltage will not get to you if the grounding is between you and the source. also you should as a safety precaution ground after you to the load. there might be a switch that some one pulls on so grounding on both sides is best.

Jonathan Schultz

Schultz Electric

Dear it is sure towards SOURCE. Putting it towards load will not affect much because the "final outcome of damage" is very slow than the speed of electricity! But it is general safe practice to put earthing or shorting towards source while working on OH lines for maintenance.

Do you heard about Earth switch???........Oh..have you seen HV switchgear?

Have you worked on it? If not keep quiet!

I've voted a GA for that.
Our friend Guest is getting to be a total pain, I've reported several of his posts but the moderators must be asleep.

Any ground and/or short circuit jumpers should be on the supply side. if on the load side you lose your protection when you open the line. P.S. Install them on both sides. There is always some clown who will start up a generator without a transfer switch. Although illegal, some home owner kills 3-4 linemen every year. Don't let it be you! P.P.S. Since you asked the question, I applaud your concern for safety but seriously question the company's knowlege of, and training in safety protocols. Good luck and I hope I don't read about your death in the newspaper. SAFETY IS EVERY-ONE'S RESPONSIBILITY!!!

if you're a journey lineman, you already know what to do.

Ok, I am a self studied layman but I'd like to put it out there to see if I am right. My thoughts: The flow of electrons follows the easiest path. The flow will not go against itself, like putting two positive leads together. If you are not grounding to ground (neutral) which links to the earth from what I know, then the most logical place to ground to would be the load side which theoretically accept the flow of electrons should something go wrong. One electrician I had discussions with equated electricity to the flow of water. If it is this simple, the above makes sense.

I bear no responsibility for the above theory. I don't want anyone to be killed. Be careful boys. I have a lot of respect for you guys. Scary and dangerous stuff.

NO!

Every conductor has resistance. MASSIVE fault current flowing past your access point raises the voltage at your access point which causes current to flow through you because you are only a resistor ( a dead or injured one to be sure, but just a resistor).

Any current above about 30 Milliamps through your body will kill you, end of story.

Portable earths in a 3 phase system firstly short the phases together (to operate the protection) and then via a cable suitably sized for the fault current bonds the system to the ground network. The ground is necessary in the common case that all three phases don't trip simultaneously. Take the case of fuses, typically only 2 actually blow in a 3 phase event which does not also have the extra return path provided by the earth / ground conductor. If the HV system connectioin to ground is not present the remaining live conductor will be held at ground potential preventing rise of voltage at any point after it in the circuit.

In a single phase earth return system the ground is the only protection.

I reiterate, High Voltage is a specialised field.

Now to the water analogy. Say you have water from a piston pump designed to power a water blaster that puts out 50,000PSI at 200 litres (55US Gals, 44 IMP Gals) per minute but capable in a fault of producing 5000 litres per minute, yet the delivery hose is designed for the 200 liter flow. Imagine you have opened the end of the hose by removing the nozzle and then the system starts delivering 5000 litres while you are working at the start of the hose. The pressure drop along the hose will assure that you suffer high pressure at your (line side ) end (try it with a garden hose, as you will know a leak at the tap still occurs even when you are flowing water through the hose at full bore).

Hope that helps, I realise you are interested rather than shooting off, but the consequences of getting it wrong are deadly.

Something all of us who are actually high voltage qualified should have noted earlier is a HV cable is not "Dead" unless it is proven de-energised and earthed. This is the proving earth and it is ALWAYS at the point of supply.

What may help you is some knowledge of those who post trying to help.

Some comment on everything regardless of actual knowledge others try to only comment in actual fields of expertise. I am one of the latter and I have 37 years experience in the Electrical Game. A couple of other posters to this thread clearly have similar experience.

The way to sort out the former is look at the amount of time subscribed to CR4 and the amount of posts placed. Some posters manage over 2000 posts in 6 months on every topic know to man, would you want to entrust your safety to such a person?

"The way to sort out the former is look at the amount of time subscribed to CR4 and the amount of posts placed"

So how does Guest with 3 GA's fit in this scheme?

Interesting leap to kudos, when the question asked is about the surety of the method of evaluation proposed.

What if the OP applied that 'formula' to say the person/knowledge behind MoronicBumble or say TonyS in a few months time?