I am trying to calcualte how much fault current this transformer can give. The image might be hard to read but it is 3-1phase 167kVA transformers. from the photo it looks like they are using one input winding and are tapping the windings of each center to get the 240V. never saw this before...
I have a situation where resistors must engage to correct a problem. The Vendor has bought some off the shelf NON UL Listed resisotrs and threw them in a hoffman box UL Listed.
My understanding was everything must be UL Listed.
This is a project in USA. I am asking the AHJ, but in the...
Situation: 12kV switchgear fed from utility. This service entrance switchgear has a 12kV generator connect onto as well as one utility onto the bus and all new SEL-351 relays have been provided for the new incoming generator and utility breakers. All of the existing potential transformers are...
System: (2) 12kV, 2500MW Generators that parallel to a common bus and connect to the main switchgear and power some large loads. The system is a closed transition with the Utility. During normal operation only one utility is present.
I have attached a diagram of the electrical system.
The...
I am at a facility where the utility transformers are solidly grounded and parallel with a cogen unit. The cogen is 5kV solidly grounded, 10MW. It is grounded through a resistor.
if there is an internal fault the resistor will help protect, but won't the utility transformers feed that fault?
I have a 1750kVA, 480D:12000V fuel cell step up transformer that supplies some 12kV switchgear with a main circuit breaker in a supervised location. The 480D primary is protected by a circuit breaker. The switchgear is 10' away from the transformer. I want to tap the line side of that circuit...
I am helping a facility out and noticed that they had a secondary spot network with the fault contribution around 75,000A symm. They have a homemade tap box (no ul listing, field fabricated with bus bars with very small standoffs). Does this box need a ul listing and be properly braced for the...
Why would you run an external ground in a concrete encased medium voltage duct bank? I have found some specs that call for it and don't know why? Is it to ensure a direct connection between manholes, mitigate EMF?
Any standards - trying to educate myself and did a few hours worth of resarch...
I have a switchgear lineup on a concrete pad that is on piers, and runs 100' to the building with 4 sets of 500 kcmil. The switchgear is moving. How could I determine how much it can move before something dramatic happens?
100' seems like it could take some movement
I am working on a project where there are three 12kV generators grounded through a low impedance resistor. The system is 3w+g. The normal power service is fed from a (3) 69kVd:12kVy transformers and protected by a network protector. A fuel cell was just installed at 300V and connects to the...
Dear Experts,
I need some insight on this. I have an ultrasonic machine (attached cutsheet) that is showing false images. This is becoming very problematic. I hired an EMF company they returned and some power quality issue, he was 100% sure and had gray hair, so I believed him. I hired a PQ...
I was hoping I could get some help on this subject.
I am designing a new 480V high impedance, 2500kVA generator paralleling generator system that connects 2 generators to a 12kV bus via seperate 2500kVA Delta/wye-low impedance grounded transformers. The 12kV system feeds 10-1000kVA D-Y...
I found on one of my jobs multiple neutral to ground bonds. They have since been fixed except we need to verify this. The challenge comes from not being able to turn off the substation to test the impedance between N-G. The substation feeds one lighting panel 4w+g and a few MCC's that are all...
I have two UPS systems that feed a common static switch. The first UPS has a delta wye transformer which would have a 30 degree phase shift, while the second UPS has no transformer. Will there be an issue with the static swithc which I remember typically require the sources to be syncronized.
The breaker downstream of the ATS trips. It trips when I go from Generator to Utility. It is a fast break before make, 400A, 480V ASCO ATS that transfers in 51-31msec with a current surge on the C phase of 4100A's. The downstream loads are only transformers from the 400A breaker feeding the...
I installed a main circuit breaker 1600A on the secondary of an existing 1000kVA 12.47kV delta:480Y277V with ground fault protection. I received a call stating the circuit breaker failed the ground fault test because it did not pass the no trip test. It was set at 320A and was tripping at...
I have a 1000kW, 1250kVA, 480Y277V generator. It came with a load bank breaker sized at 1200A. The generator breaker is 1600A. I always matched these two when designing but had a manufacturer tell me that they never utilize a reactive component in the load bank only the resistive element...
I have a situation with (4) 2000A, 480V closed transition switches with (2) ASCO and (2) Russelectrics. They are fed from a 6MW, 480V grounded wye generator plant. The utility has (4) 1500kVA delta grounded wye connected in a spot network.
The situation arose when the secondary spot network...
Working in a sugar factory in Texas. Utility is 13.2kv 3w+g. My switchgear utilizes sel 351 relays. It has a utility input, load breaker, tie breaker that connects another MV breaker to a transformer that has a 1000kw 480v transformer. The generator step up transformer is a 1000kva 13.2kv...
Q1) I have come accross a medium voltage circuit breaker that originally was installed as a feeder breaker to a building. It is being upgraded right now to provide a feed from a generator. The relays are being swapped out and etc. Can this breaker which has labels stating "line" "load" be...
