Derrick Truck Grounding - What's are Your Practices?

[nolaproud]

OK, so let me begin by saying that I'm not a Lineman, I'm an Engineer, and I work for a utility in the deep south. I got involved in some discussions with some of the linemen in the local area networks regarding mobile equipment grounding, specifically derrick trucks. Our current practice is to use a single "T" ground rod, with an auger tip for grounding the derrick, with no connection to neutral. Our primary is almost exclusively Y-grounded.

Evidently, in the past we used to bond to the system neutral as well, but no longer do. I asked some guys about what work practices were at other companies, but no really had much experience outside of our company. I researched some IEEE documents on the subject, and many seem to imply that bonding the neutral is preferred.

I figured I'd try to reach out here to ask you all to see what do. Anyone care to share work methods?

Thanks,

Bryan

[cedar stick]

The system neutral is the option that most outfits use. You can bond the trucks on the job site together for conveinance, but one needs to go to the line neutral.

[nolaproud]

The system neutral is the option that most outfits use. You can bond the trucks on the job site together for conveinance, but one needs to go to the line neutral.

Thanks for the feedback! Hopefully I'll get more input on the topic.

[US & CA Tramp]

The term equal potential grounding is what you would need to refer to in IEEE and the OSHA standards. Basically what you need to do is make everything that could possibly touch or induct current all at the same potential. Example: two trucks working on the pole both have to be grounded. The boom truck/derrick and bucket truck should be grounded to a pole ground if possible or to the neutral. This will cause the circuit to trip out if a contact happens. All vehicles in close proximity should be bonded together and the screw in rod you refer to needs to be installed. If you can touch the truck while on the ground or any other vehicle at the same time everything is at the same potential. The higher the voltage being worked on or around the better grounding and attention to these rules. All Lineman in the trade will have a slight variation to these rules, the key is the same potential or isolate yourself and equipment. If you don't believe in equal potential grounding park a truck under a 230 or 500 line and walk away from the vehicle for a time then walk back and touch it. Equal potential ground or Isolate and insulate. Those are your options.

[nolaproud]

The term equal potential grounding is what you would need to refer to in IEEE and the OSHA standards. Basically what you need to do is make everything that could possibly touch or induct current all at the same potential. Example: two trucks working on the pole both have to be grounded. The boom truck/derrick and bucket truck should be grounded to a pole ground if possible or to the neutral. This will cause the circuit to trip out if a contact happens. All vehicles in close proximity should be bonded together and the screw in rod you refer to needs to be installed. If you can touch the truck while on the ground or any other vehicle at the same time everything is at the same potential. The higher the voltage being worked on or around the better grounding and attention to these rules. All Lineman in the trade will have a slight variation to these rules, the key is the same potential or isolate yourself and equipment. If you don't believe in equal potential grounding park a truck under a 230 or 500 line and walk away from the vehicle for a time then walk back and touch it. Equal potential ground or Isolate and insulate. Those are your options.

Thanks for your feedback Mr. Tramp!

I completely agree with your assessment, especially as it relates to the making the connection between the pole ground and neutral if possible. Our current practice in distribution is to use a "T" handle ground (like a screw in type) as the only grounding connection to the derrick, without installing a solid bond to the neutral or pole ground, even when it is available. We have fairly low ground resistance in my area for the most part, but this could still take quite a bit of time to trip the feeder depending on location, or worse no trip at all....

[US & CA Tramp]

Mr? that was my father.

[nolaproud]

Mr? that was my father.

Yeah, I keep telling the younger folks around the office that "sir" is my father too. They don't seem to get it do they????

Thanks for your help Tramp!

[rob8210]

The utility I am doing work for right now requires the rbd to be bonded to the system neutral. Other utilities I have done work for have varied practices. We always ground our truck some way or another , to the neutral , or a pole ground, maybe a temporary ground rod, some places even allow you to ground to an anchor rod. When 2 or more trucks are close together we bond them together. Bucket trucks are another matter depending on if the lower boom has a fibreglass insert and how high the primary voltage is.

[nolaproud]

The utility I am doing work for right now requires the rbd to be bonded to the system neutral. Other utilities I have done work for have varied practices. We always ground our truck some way or another , to the neutral , or a pole ground, maybe a temporary ground rod, some places even allow you to ground to an anchor rod. When 2 or more trucks are close together we bond them together. Bucket trucks are another matter depending on if the lower boom has a fibreglass insert and how high the primary voltage is.

Thanks for the feedback Rob! Bucket trucks are also a different animal with us as well.

How often would you say, percentage wise, would use only a temporary ground or anchor rod when working the derrick?

We are currently 100% temporary ground even when accessible pole ground or neutral is available.

Thanks!

[copperlineman]

I'm over 50 years in the business and most of my work was with an Investor owned. The system neutral was our preferred ground and used whenever we could. Steel structures, down-grounds, anchor rods, etc. were next, and that T Rod thing your talking about was a distant last and was hardly ever used with a digger derrick, because it was not connected to the system and it would most likely NOT trip a circuit out. A breaker would probably see it as more AC units/load coming on. Even worse, the T rod could set up a ground gradient as it sought out a path to the station. When connected to the system neutral, the system will see a large increase in current very quickly and the protection device will open quickly. That's why are ground/neutral connections are clean and tight, and the grounding jumpers are large enough in size to handle to current they have to carry. A T rod won't come close to doing that.
We ground trucks for a few reasons, the most important is a fast trip out of the circuit. This is not an I&I issue as I've read here. I&I is for working equipment energized (isolate & insulate). We are grounding a piece of equipment that we're using NEAR energized stuff so it does not stay energized in case of contact.
When the boom of a derrick truck is in the air and close to the primary zone (10 feet), NO ONE should approach that truck. The operator stays on the truck until the load is secured. If contact is made, the truck will be energized until the grounding method works and the circuit protection opens (the breaker or fuse). If anyone is contacting the truck when contact is made, that person is in great danger whether the truck is grounded or not. We want the circuit to open as fast as we can, so we ground it to the system neutral to achieve that. We also keep everyone away from the truck and the operator on the truck until the fuse or breaker opens and the danger is past.