Unfortunately I'm probably going to have to do both. I have approximately 250 to 300 of these same SS URD transformers installed in the field already. In order to protect our investment and prolong their life cycle I’m forced into doing CP on them. In the mean time I need to come up with a...
Recently we've had a couple of stainless steel (409) subsurface transformer tanks corrode through and fail. The transformers are only 3.5 yr old. They're located in a concrete vault and have standing water around them pretty much 24/7. I'm not sure whether to install CP and/or change our spec...
Gents,
I'm not a corrosion engineer, I'm an EE, but recently we've had a couple of stainless steel (409) subsurface transformer tanks corrode through and fail. The transformers are only 3.5 yr old. They're located in a concrete vault and have standing water around them pretty much 24/7. I'm...
Thanks for all of your comments. That is exactly what I was looking for. FYI, from a utilities perspective, I found the following information based on a Google seach.
http://www.utahpower.net/File/File22465.pdf...
I've heard the terms "Grade A Voltage Range" and "Grade B Voltage Range" used to differentiate between the fluctuations in voltage between what the utility delivers to the customer and what the range of voltage certain equipment can operate at. Typically a utility will provide plus or minus 5%...
Gents, good point. Possibly a series of events slowly degrade the motors enough that they eventually fail.
The cap bank is on time and temp. It switches on at 8 AM and off at 8 PM or at an 80 degrees F threshold.
I just analyzed our most recent data from our monitoring equipment. I had...
Busbar you are correct. We're not PG&E, but our Electric Service Rules state that voltage balance between the phases will be maintained as close to practible to 2.5% maximum deviation. The HVAC equipment is electromechanical and I have no knowledge of any pulse width modulation circuitry...
The 1.5% volt phase imbalance was measured at the equipment subpanel (near the motors) on the roof top. The subpanel has 7- 40 amp breakers that feed each separate motor. The case ground is only connected to the subpanel and then to the building. No neutral wire to the motors. Does that...
It is a Delta-Wye grounded. The perurbations are subcycle of less than a 1/4 wave form. The building houses a lot of computers and single phase fluorescent lights that can add to the 3rd harmonic (non linear loads).
We're in the central valley in California. Hot dry climate. I don't suspect that it is environment related. They are delta connected and our Rustrak monitoring equipment only shows some short duration peturbrations in the current wave form, but of high magnitude. We have a cap bank close...
Thanks for your response. The case study that I was looking for was just for my own edification and nothing else. It wasn’t related to a specific problem.
I do have a question regarding a commercial building though. The building has a 480/277, 4-wire service with a 1200 amp panel. He has...
I remember browsing a thread that talked about a case study detailing the existence of high neutral current within an industrial building that caused multiple motors to subsequently fail. Does anyone remember the thread or could provide me with that study? I think it was started by a member...
I have a table that our power co uses for wind load calcs for wood poles of different types and classes. I'm wondering if anyone can tell me how these were calculated. Per the CPUC GO 95 (State of CA) we are required to use a safety factor of 4 for class "A", SF of 3 for class...
Our utility offers residential developers an option of (for a fee) having subsurface single-phase transformers installed instead of pad mount ones. I’ve been tasked with evaluating the cost differential. I know there is the most obvious incremental cost difference of the sub vs pad, but I was...
