Fish Plating LV Busbar

Yes, the manufacturer of the stainless steel bolts will know the preferred torque settings. They will also know the grade of stainless steel used to make the bolt and most importantly the pitch of the threads of these bolts. Most likely, their torque value will require some lubricant on the threads. Since this union may conduct current I'd use some metallic based anti-seize compound.

What would be better than asking the manufacturer of the hardware will be to check the installation documentation or ask your on site engineer what is the specified torque. Asking a group of strangers on an anonymous web page is likely to produce many different answers. Some of the answers will probably be close to the correct torque. Then again some answers may just be obtuse and useless.

I'd consider torquing this to 51.73 Sthène cubits.

Thanks for your prompt response. I am located on mine site on Indonesia and the info you recommend is not available. And you are right I have got many different answers from web searches that is why I am seeking expert advise...that's you guys.

I fully endorse your views. GA

Good link, thanks. GA..

Hmm...need more advise then. Given the present conjecture and modern research there is large amount of dispute of the which is more accurate, the Egyptian cubit or Sumerian cubit. As you would know the variance is 0.85% - 2.01% so when transposing back to the sthène I think I would be taking risks using figures you have quoted.

I did warn you that some answers would be obtuse and useless.

You missed the point I hoped you'd grasp from my earlier comment. You've not provided enough information to either give you or for you to find a correct answer. The bolts are an unknown grade of steel and have an unknown pitch to identify a correct answer for the proper torque setting. Don't forget the nut. If you have site assembly documentation that states your hardware and torque recommendations, follow it. That is unless the parts in your hand are not the correct grade of steel for the torque specified. In this case you'll have to identify if you have the wrong parts in hand or the wrong torque specification. It's sadly common for assemblers to not realize there are different grades of hardware, the correct parts may be already used in the wrong location.

Why would you use fishplates? Why not inter-leave them and eliminate one potential trouble spot? i know there will be lots of objections, but generally, they can be overcome.....

I agree. Adding an additional union by using a fishplate adds one more point for failure. Particularly the short gap that the fishplate's smaller cross sectional area will be the sole conductor can quickly become a hot spot. However, I've seen splicing bars of the same cross sectional area called a fishplate. In this case heating won't be a problem but the part increase alone will just make it more likely for a bad assembly.

You seem to be quite serious about doing a good job. So, even though i am no expert in this field, i pass on what i have learned from my friends.

1. 100x10 requires 4 bolt/nuts of M12 (assuming you are in the metric world)... see Datasheet

2. The bolts should be 'high-tensile' ie, grade 8.8 or better. Also the nuts (grade 8) ... check redfred's links.

3. Since steel and copper expand differently, use Belleville washers/springs (refer Schnorr catalogues for more knowledge) so that contact pressure is maintained.

4. Use Raytheon type Infrared temperature scanner periodically to see that the temperature at the joint is within limits.

This will possibly make you the EXPERT on busbars. Everyone will come to you for advice !!!

Good luck

Hi

There are a number of reasons why you would choose to use fish plates rather than interleaving the busbars

1) You can remove that particular section, should you need to, without disturbing the rest of the board

2) Interleaved busbars obviously require the adjacent busbars to be offset by the width of the bars, this means the sections are not interchangeable

3) It's easier to connect the boards on site with fishplate joints making them the most common method of connection.

Yes, interleaved joints would produce a better joint, but with IEC 61439, all equipment should have been design verified, so the fish plate design would be proven.

The following is our list of torques for standard Metric bolts

Craig

Thanks for all help guys. We went for 60Nm for 12mm bolts. The problem we were having was overheating of 2 phases - up to 200 degrees. The problem was found to be bad installation (Tx is only 18 months old). Poor connections had been made at the spades on the LV bushings. Repair done yesterday thermal imaging now 68 degrees all buses. Good result as we thought we may have had internal failure. Cheers.

Of course, using fishplates is normal. Since the OP is at a mine site, it is almost imperative that he uses them to join. One lack of info is that i don't know how many 10x100 flats are being used per phase.

Anyway, i am curious. Why stainless steel hardware? What about Disc springs (Belleville washers), are they of any use ? Just for knowledge, no practical use for me

Using one bus per phase. Unfortunately the original installation was sub-standard. Yes Belleville washers preferably would be used but they were not available. As stated before bus was running periodically at 200 degrees. The whole operation would have been compromised had this bus let go. In the end we used the original plated bolts. drilled 2 additional holes (6 instead of 4) increased the overlap length from 100mm to 200mm. A thin smear of Vaseline was put on surfaces before clamping. All bolts were sequentially tightened.Anyway, at this point in time everything is good and I still have my job.

Way to go ! All your actions are good !

As i said before, you are already quite knowledgeable. Keep that infrared scanner shipshape. Get some disc washers when you have the time and install them.

Your employers are fortunate that they have you. You should be in line for promotion. Good luck

Guys. Thought you might be interested in photo of one of the Tx bush connectors. There were two like this and failure was certain. Just didn't know when. Huge amount of arcing on connection. No wonder it was running hot.