# Fastest trip



## ponyboy (Nov 18, 2012)

Please elaborate. You don't think it's okay to trip a circuit breaker by shorting it out do you?


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## ponyboy (Nov 18, 2012)

I just noticed this is in line work so I probably have no idea what you're talking about...carry on


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## Black Dog (Oct 16, 2011)

ponyboy said:


> Please elaborate. *You don't think it's okay to trip a circuit breaker by shorting it out do you?*


At 12,470 volts--- what could go wrong?:blink::laughing:


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## Black Dog (Oct 16, 2011)

ponyboy said:


> I just noticed this is in line work so I probably have no idea what you're talking about...carry on


Shorting 13,000 volts will cause issues..:laughing:


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## lagunavolts (Jan 9, 2011)

Pony boy, I'm not intentionally tripping out the circuit, but if there was a phase to phase fault, would that trip the cb quicker than a phase to neutral fault


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## 3D Electric (Mar 24, 2013)

lagunavolts said:


> Pony boy, I'm not intentionally tripping out the circuit, but if there was a phase to phase fault, would that trip the cb quicker than a phase to neutral fault


I would think a phase to neutral fault would trip faster than a phase to phase fault. I would believe that there would be less resistance through the neutral than the phase conductor. An easier fault path.


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## lagunavolts (Jan 9, 2011)

The basis of this question comes from Osha new grounding procedures. Equipto-potential grounding. We run a 12470 y system and our company is requiring us to ground excessively on an outage. Our brilliant methods committee seems to think that we need in addition to working between grounds on a wye system, we need an additional ground at the pole we are working on bonded to a driven ground rod. This is fine for accessible work, but the problem we face is in an easement. Does anyone else know about this?


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## macmikeman (Jan 23, 2007)

lagunavolts said:


> On a 12470 y system, what is the fastest way to trip the cb on the primary side? Phase to phase or phase to neutral?



Before all these other experts chimed in, I was thinking you take Flyboy's plane into the tension lines at full speed. That should probably work, unless his dangfangled flyin contraption is made out of polymer's and carbon fibers.


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## lagunavolts (Jan 9, 2011)

Mackman , r u a lineman? How about some serious thought!


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## wendon (Sep 27, 2010)

I'm not a lineman but I'd think the phase to phase would trip sooner. Think about the secondary side of the XFMR. Where's the highest amperage, on a phase to phase (240 vac) or phase to neutral (120vac)? Too bad you don't have AFCI's like we do: just touch the neutral (Grounded Conductor) with the ground (Grounding Conductor) and the breaker trips. No messy arcing!!:laughing:


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## Zog (Apr 15, 2009)

lagunavolts said:


> The basis of this question comes from Osha new grounding procedures. Equipto-potential grounding. We run a 12470 y system and our company is requiring us to ground excessively on an outage. Our brilliant methods committee seems to think that we need in addition to working between grounds on a wye system, we need an additional ground at the pole we are working on bonded to a driven ground rod. This is fine for accessible work, but the problem we face is in an easement. Does anyone else know about this?


Phase to phase typically, that is why your protective grounds should be 3 phases to a single point which is then connected to ground. Of course the grounds need to be tested and rated for the available fault current in the system you are working on. 1910.269 details the requirements of your protective ground set.


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## Big John (May 23, 2010)

I hate to say it, but my understand is they aren't wrong. The idea behind the EPZ is that it accounts for voltage drop created by conductor resistance during a fault.

In your case, if there was an overhead contact that occurred between your two sets of grounds, there would still be a significant voltage-drop-to-ground based on the impedance of the conductor back to each grounding-cluster.

Think of it this way: The upstream and downstream grounds are there to clear the fault, they are not considered worker shock protection. The local grounds are there to provide bonding that protects the worker from step or touch potential in the event that the fault occurs. 

If you can place your clearance clusters close enough to your work area where you can also bond all the equipment in the work zone, you can get away without having the set of local clusters. Otherwise I'm not sure how you'd do it, because it's not a problem I've run into.


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## bobelectric (Feb 24, 2007)

If your metering is set right, phase-phase would take longer because of travel time through the xfmr windings.


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## Caseyrey (Jun 27, 2011)

Depends on what relays it has. It could be an instantenous or a time delay. On a typical 12kv circuit in most of our subs the phase to phase trip setting is 720 amps and 180 amps phase to ground IIRCC. Also keep in mind the same style relay is used for both phase to phase and phase to ground faults typically. When you get into transmission lines and transformer protection that's when you'll have multiple relays and some will act quicker then others. As far as the new grounding goes I know all of ours is based off fault duty and sources but I work inside the fence, everyone outside has their own grounding manual to follow.


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## JW Splicer (Mar 15, 2014)

Electricity doesn't take the path of least resistance, this is a lie that has been told over and over. It takes all parallel paths. In the event of a fault or accidental energization, the entire area becomes energized at the line potential, including workers, protecting against touch and step potential. Bird on a wire.


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## Big John (May 23, 2010)

Caseyrey said:


> ...Also keep in mind the same style relay is used for both phase to phase and phase to ground faults typically....


 You guys just have 50/51 for each phase and neutral?


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## Bipeflier (Jan 16, 2013)

What you are talking about is known as "system grounds" which are typically phase to phase and then phase to ground.

Equipotential grounding is all about a low resistant path that is parallel to the worker in order to limit the current across the body.

Any grounding configuration that will cause the upstream protection to trip is fine just as long as the "personal protective ground" is in place.

Here is a link the to CHANCE grounding encyclopedia. It covers a lot of situations you will see in the field.
http://www.hubbellpowersystems.com/literature/encyclopedia-grounding/

Be careful and make sure you do whatever is necessary to go home to the family.


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## Caseyrey (Jun 27, 2011)

Big John it depends on the line but for distribution lines that's the typical setup. With the newer stuff being a solid state relay and the old electro mechanical being 4 separate relays of the same type. Some will have both a 50/51 being used wear others won't. Then if you wanna dig deeper it depends on the ground return for the substation and length of the line that'll determine what relays the line will need. That's my understanding of how it works, my main work area is the high voltage breakers, not the relays.


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## Meadow (Jan 14, 2011)

Theres not enough info to answer this. Load, line inductance, fuse saving, the list goes on and on. Phase and ground can be set at anything depending on what needs to be accomplished.


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## dtmartin408 (Nov 11, 2012)

so in regards to your question there are a ton of variables that play into how fast the circuit breaker would trip at the station. For instance how far away the fault is out on the line. What type of relaying is actually on the circuit to protect it from fault current and what that relaying is set at.


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