This is a ungrounded neutral capacitor bank tied to a 34.5kV main power transformer Y grounded. All the A phase fuses blew, not sure why currently. I'm looking at the event and the neutral voltage before the event was 1.2 kV < -178, likely due to voltage imbalance. After the event, before it...
What are the best practices for settings the fan control temperatures on a 50-100 MVA, 65C rise, ONAN/ONAF/ONAF, mineral oil transformer? What temperatures should the fans be set to operate at?
Usually I have seen 65C/75C or 75C/85C. We are in process of startup and the manufacture is...
This is at a wind farm site where the cables are underground going to multiple padmounts connected in parallel, standard setup. The main power transformer is Wye connected on the 34.5kV side. The collector string is connected delta-Wye. We had a padmount nearest to the substation (connected...
What is your take on the rating provided. The system is connected to a 13.8kV ungrounded system, the PT's are PTG5-1-110-842F, see attached spec sheet. The PT's are connected phase to ground, the max system voltage rating is 15.5kV.
Is the PT with the primary voltage rated at 8400 volts...
Is a site required to report to NERC if the protection system would not have operated if there was a fault? The equipment is tied to the bulk electrical system that would not have operated if there was a fault, fortunately no fault happened and it was found and corrected (relay programming...
I have a contactor for a synchronous motor that has no nameplate. The current motor field is rated at 75 amps and the contactor has a 100 amp shunt attached. I am being asked if it would support a 150 amp synchronous motor field. Could anyone provide feedback as to the size and rating of the...
This isn't a question but something I learned over the past month due to a loss of exciter failure.
The generator was being commissioned and the exciter feeder breaker was undersized and tripped, causing a loss of excitation. It did not trip on loss of excitation, but caused some serious...
A 5MVA (rewound to 10MVA), 13.8kV steam turbine generator was operating normally. Some of the control screens started operating oddly and the operators decided to trip it off, so the power was lowered to 0.5MW and the stop valve tripped. It turned out the control screen issues were due to low...
I am reviewing a coordination study and all the TCC's and pickup points are shifted by varying amounts. The explanation given is
All of the graphs have the curves aligned to the “total fault current”.
Have any of you heard of this? Is it a common practice? I haven't and have been doing...
I was asked to investigate imbalanced currents in a new installation. Location is in rural NW USA, estimated about 7-10 miles from the substation. Loads are mostly motors and lighting, it's a brick plant.
There are two buildings, with two services, the transformer (500kVA; 20.5kV/480...
I was at a wind park substation (345 kV / 34.5 kV) in the central US (Oklahoma) working on other projects and was asked to look at the main 345 kV breaker control panel. It is grounded to the ground mat (4/0 bare copper), both at the control panel and the breaker frame. When touching the...
5kV GE Power Vac 1200 amp breakers are being used for motor starters to start a 1061 amp motor. They have been in service since 1980. We have had two failure in the past couple of months involving the line side stabs failing during motor starts. The stabs are vaporized, the breaker ejected...
At what transformer size would you normally put in a CT to monitor the current on the tertiary winding of a Y-gnd/buried delta/Y-gnd transformer? I am dealing with wind farm applications, 100-150 MVA, 240kV/34.5kV sized transformers and would like to find some information on how to set them (I...
There are three cap banks (7800kVAR, 130 amps, 34.5kV) at a outdoor substation. The 34.5kV is hard neutral grounded at the transformer. They have an neutral unbalance relay that trips them off with an unbalance if the individual caps blow fuses.
Each cap bank is grounded through a PT (175/1)...
I am involved in commissioning wind park in Calif.
They have two substations about 200 meters apart attached to a 5 mile line going to the 230kV utility grid connection. Sub 2 has been in operation for 2+ years, sub 2 is new. There are two line protection relays in sub 2, CT's in both...
I am working on a relay upgrade of an existing switchgear. (CA,USA) The utility comes in at (fused at 80E) 60kV, and feeds the switchgear at 5kV though a 5MVA Y-Y transformer with a NGR on the secondary. The switchgear has 3 breakers feeding the plant load and a 5MVA generator which also has a...
There are two idential 550kVA transformers in an industrial plant. Durning a infared scan one core was recorded at 300F. They are 4160 delta/460 delta 220C insulation, 150C rise, dry type transformers. One is at 95% tap, the other at 100% tap. Tests on the transformer (power factor...
