Another piece of information I remembered last night. My friend indicated that when he arrived at the bank, the two outside transformer secondary to tank ground were hot enough to burn high-voltage rubber gloves so there was a significant amount of current flowing through them. It was probably...
You are absolutely right waross. The issue I have is that I have seen two different drawings... one drawing shows the secondary neutral bonded to each of the three transformer lugs and one drawing shows the secondary neutral bonded to only the center transformer lug. I've got a friend that...
I am receiving some conflicting information on a Wye-Wye transformer connection. Concerning a three transformer bank connected wye on the secondary side, should the neutral wire that connects all three transformers be grounded to the transformer tank lug of just the center transformer or should...
Since we have been serving the load (since 1996), the plant calls us when they have a shut down and we physically remove the underground cable from our bus to give them an air gap to work behind in doing their maintenance.
jghrist... you are right, anyone can be sued for anything, anytime... its risk management. The way I see it is if we provided something specific for that chip mill and did not provide the same thing across our entire distribution system, we stand a better change of being sued because we did...
cranky108... it splitting hairs... we would be willing to own the fuses (and responsibility) that would blow if the customer got into something or we would own the breaker (and responsibility) that would trip if the customer got into something? I'm not able to distinguish between the two...
After consideration, the fuse idea is really no different that letting the chip mill trip our breaker... we are still accepting part of the responsibility (and thus part of the liability) for proper operation and design as it relates to the reduction of arc flash at the customer's equipment...
Update... now the customer is asking if we can support S&C SMU-20 type fuses at our station. If we did that, I would remove the breaker all together and install the fuses only. But now the question would be if we are any more or less subject to liability with fuses as we would be allowing the...
I represent a utility that serves a chip mill. The chip mill’s MCC room is served by a 1500 kVA, 4160/480V transformer. The MCC room has no main disconnect, just individual disconnects serving various equipment. The chip mill is asking us if they can install a protection relay in their MCC...
We recently received a re-manufactured 3 phase transformer with a HOXO connection on the secondary side. (The transformer is a 24940Y/14400 480Y/277 1500kVA transformer) I know that a lot of transformers have a removable link to separate the HO and XO connection. This particular transformer...
Update... We got the third oil analysis back last week. Acetylene is staying pretty steady at 89 ppm. We've decided to change out the transformer. We are looking at getting it changed sometime next week. Thanks for everyone's input.
I'm not positive this transformer has taps, but if it does, I am certain that no one has changed taps (energized or otherwise) without myself or my employees knowing about it. I agree that if that were done that it would possibly create acetylene in the oil.
As I've indicated at the beginning of this thread, this is a small 2000 kVA transformer. We usually do not pull dga on transformers this small. We had a small leak after someone made contact with one of the cooling fins last year. We pulled the dga after a request in response to a quote for...
We have tested again... acetylene is down to 85 ppm. I know its still very high but it is coming down. We have scheduled another test I believe next week to see if we can establish a downward trend. The plant that the transformer serves is planning some work that may force us to move the...
Just received a dissolved gas in oil analysis on a 2000 kVA 25kV/480V three phase transformer. Acetylene is 102 ppm and total combustible gas is 212 ppm. Having another sample pulled tomorrow. How dangerous a transformer do I have? Should it be de-energized immediately? From what I have...
I know some of the old city systems were 2.4kv and the like, but what about true rural distribution to farms and such. Traveling such distances, I would not think 2.4kV would travel very far. Any more thoughts on the subject? I am more interested in voltages used to supply spread out farms as...
I am writing an article about some of the history of the electric coops’ beginnings in the 1930s. Does anyone know for sure what primary voltage was used on the old REA distribution systems in the 1930s? I am guessing 7.2/12.47kV but I cannot verify that.
Waross, we float the primary neutral on our wye-delta banks. Therefore, the primary neutral of the bank is not connected to the system neutral. How does this change your response to my question?
In this scenario, it seems to me that voltage would have to come through the consumers’ equipment on a Wye-Wye bank. Would the same be true for a Wye-Delta bank? Or could you see back feed on a Wye-Delta bank simply because of the secondary connections?
Hi Guys, first post on this forum.
I work for an electric distribution utility with a primary voltage of 14.4/24.9kV.
Recently, we had an outage on a 3Ø line involving only one phase… the other two phases remained “hot”. There are several banks on this line both Wye-Delta and Wye-Wye. The...
