Why wouldn't you sectionalize and thump each section without anything connected?
By doing this you will also do a high-pot test on each section of line.
I'm assuming that all three phases are currently de-energized.
Happiness is a way of travel, not a destination.
I get this question all of the time. Here in North Carolina, USA. We will install our power conduit between two and three feet deep, then backfill at least twelve inches, and put the communications on top. Depending on the load of your home and the size of the knockout in the meter base, a 2"...
Here are the pictures we have so far.
This picture shows the top of the breaker. You can see some of the flash damage to the line side and load side connections.
http://files.engineering.com/getfile.aspx?folder=d8d86d2b-62f5-4a89-a0b7-446de3b29ce2&file=04-12-11_0752.JPG
This picture shows...
I wanted to get your opinion of this situation.
We have an electric substation that was built in the late 1950's early 1960's. It is a steel structure with an exposed copper IPS bus on top. The voltage is 12,470 wye/7200.
Two years ago we had a lightning strike at the station. It damaged one...
As a utility engineer, I have seen a similar problem in one of our neighborhoods. It ended up being a loose neutral connection on some of our 120 volt street lights. I am not sure if it was the same harmonic that you are seeing.
We typically size our services by the projected load of the...
In my area there are three main suppliers, Okonite, Pirelli, and southwire. I don't know any of the marketing information you asked for, but I do know that pricing is based on the volume of wire purchased. The pricing is very volatile and changes almost daily. When I need pricing, I send a RFP...
We are a small utility with limited resources. The largest standard transformer size that we hav on our system is a 1500 kVA. We limit the size because we do not have the equipment needed to lift any larger transformers in an emergency situation.
We are monitoring and collecting load data from...
Thank you everyone for your replies. We have had some major snow here in the South East United States so I have been away from the desk for a few days. Before I left though, we actually found that the new connections in the transformer were not tightened properly. We made the customer shut down...
Both transformers were fed from a common source. Actually, transformer two is fed from transformer one.
Tap selectors were the same. These transformers had operated with no symptoms for four years.
When i arrived at the scene of the smoldering transformer, it was still energized, with the...
This week we had an interesting situation here that still has some of us scratching our head. We have an industrial customer that is supplied by two parallelled pad mounted transformers. The primary voltage is 12,470/7200 GND-Y. the secondary is 480/277 GND-Y. Both transformers were installed...
What type of fuse are you using? Are you using the fastest fuse but it still will not coordinate with the utility?
I agree that you should work with the utility coordination engineer to solve your problem. Have they supplied you with their coordination curves?
Happiness is a way of travel, not...
THis is why you should proof-read your posts before submitting them.
"They are manually operated, so they cost less than a relay controlled circuit switcher or breaker. Our 15kV, 600 amp switches cost us around $2,000.00."
This refers to the gang operated switches, not the fused cutouts.
It...
Where is the metering point? Typically the utility will provide fault protection up to that point.
Does the transformer have internal fusing, or protection?
Absolutely check with your local inspector to see if he will even take on the responsibility of looking at it.
As a utility, we have...
Much depends on your basic fuse coordination philosophy. Do you want the circuit breaker in the station to trip and save the fuse? Or do you want the fuse to melt so the breaker does not operate?
Here we use a combination of the two. Our trip levels on our breakers are set to the fault current...
I think the utility should be involved if this is a re-occuring problem. They should be able to tell you if the breaker operations are due to normal switching, or if there have been fault situations on their lines.
Bulsara brings up a good point about the fused cutouts. Typically they are...
What is your line distance from the utility breaker? What size is the utility conductor? What size is the utility transformer that steps down to the 480 volts? What is the primary voltage to the transformer?
I am just trying to get an idea to see if there are any limiting factors on the...
You would be better served in the event of an incident to have followed the NEC. I work for a utility and even though we do not have to follow the recomendations of the NEC, we do. This gives us the ability to say that even though the minimum standards were all we had to achieve, we went above...
I wanted to thank all of you for your input and ideas. Hopefully when they decide to install more of these systems (and I know they will), they will remember the problems they had with this one. Maybe they will even ask me for my input ahead of the installation. (Probably not)
Happiness is a...
Well after two weeks, the engineer that they were consulting with came up with the idea to connect the generator neutral to the transformer neutral.
He is a brilliant man! I wonder which one of the electricians I have been telling this to for the past two weeks mentioned it to him.
They have...
