Recent content by ppaya

Thanks everybody. I can sum up what I heard from all of you by quoting OldFieldGuy: :In my experience, the idea of testing saturation from in the relay house is an expedient to keep from having to stand out in the weather at the breaker, but it can provide useful data" If this is the only...

OldFieldGuy: if you apply voltages from relay room, I don't quite understand what is it that you achieve with this, for following reasons: 1. between current links of the CT in entry Panel in the Relay Room and actual CT in the Yard is usually only wire (tech-cable). Applying voltages remotelly...

I was asked to test CT's in new substation from breakers itself (OK with me) and from relay room(this is part I don't quite understand why)??? I am not sure if there is such a practice since I haven't seen one in my 10 years of field service. Any thoughts guys?

we set 51 element to be higher then 2xMAX load on the feeder + to be sensitive to see all faults to the end of the protected feeder. Instantaneous element 50 will be generally set to the same value (50PU=51PU) , CLPU scheme blocks 50 element for 10 sec after closing of the breaker (manual). This...

Stevean, thanks for correcting me. I meant Substation transformers ( I am not sure how IEEE calls this class of transformers - Power Tx?)

Guys, in North America distribution transformers are 10MVA and 5MVA most of the time. Mome of them is equiped with IEEE 49 protections. Big transformers YES. Also distribution transformers are always Delta-Wye. Very few exceptions

O, yes for the second part of your question, the answer is NO. Your 10MVA Tx will never go that high.

Typicaly, you will put transformer base FLA (on ONAN rating) into your software for inrush current of 12 times FLA for 100 mSEC. Now, it is not strictly accurate to do so. Here's why: transformer inrush current consist of 2 components, first one is magnetizing current (which is for larger...

Jghrist: is pavement (ashfalt) considered insulator?

I assume your generator neutral point will be connected to swbd grounding rod? (if you have single phase load you need neutral from the generator)? Isolated Wye configuration doesn't contribute to ground faults on Utility side , is this what you try to achieve?

shnshn: 200A Panel is installed (connected ) KVA. Demand is something else.

Cuhead: min SC contribution could be significantly lower then max due to system configuration change in the upstream transformer stations. Utility will provide you with "bolted" fault values, no resistance in the fault, and X/R ratio.

I am not sure why do you need 12kW? North America Utility usually calculate with demand 4KVA load for residential connection. 120/240V connection is typical for this. You say you have 120/280V What is your load you want to support on one leg ph-ph? There are LDC requirements in place for...

I found some threads that are useful but can't read it because there is no "left and right scroll" in the bottom og the page. So text is cut off. Have you been able to fix this? example is Feb 2006 thread named:" Advantages and Disadvantages of Delta-Wye and Wye Delta ... )

what winding configuration of generator step-up transformer is most used in North America when generator is connected to LDC feeder? delta on HV side or delta on LV side?