Keep in mind that IEEE Std 18 call for a tolerance of -0% to +15%. This is a much wider range than most other equipment. Trying to select precise values may lead to problems if future replacements have different actual capacitance. Also, the capacitance of a specific can can change over time...
The region I work is winter peaking, so it is fair for me to assume some moisture exists in typical utility duct banks serving residential load. My residential loads only peak for a few days year. For loads serving loads that are constant 24x7 or loads that peak during the dry season, I would...
How is a "non-directional" 67N different from a 51N? Depending on your specific relay manufacturer, problems with the voltage measuring circuit may still cause unexpected response of a directional element programmed as non-directional during a loss of potential situation.
Lowering the voltage from the inverter will also reduce losses in the transformers.
The statement about 10% current from the batteries seems surprising unless the battery capacity is quite small compared to the AC portion of the system. The current flowing to unloaded transformers will be...
Although 67N is more secure than 51N, the tradeoff is that it is less dependable. The 67N relies on extra measurement sources, and has the possibility of being incorrectly set to look in the wrong direction. I would only use the 67N where there is a specific reason that the directionality is...
Is 2000/3600 KVA AA/FA rating a typical value for a dry type 15kV/480V transformer? I mostly deal with oil filled transformer that typically have stages of 1.00/1.33/1.66 PU ONAN/ONAF/ONAF, so just wanted to make sure the FA rating of 1.8 PU was not a typo.
It might depend on which studies you are referring to. Even if the impedance changes beyond 10%, it might not make a practical difference to the grid.
For voltage control purposes, two windings would change some things.
The-why-of-the-wyes is a good explanation of transformer configurations.
I am unfamiliar with that style of transformer notation. Is that a delta/delta/wye transformer? The picture on the nameplate looks like 400 kV style bushings, but the text looks like it reads 400 volts.
Were both the 25 Hz and 60 Hz portions synchronous motors, which would require the 25 Hz and 60 Hz systems to be in sync at a common multiple? Or was it something more like https://en.wikipedia.org/wiki/Rotary_converter?
Our line crews use a hot stick device for measuring amps on energized bare wire. I am not sure of the brand or model. The model you posted is intended to be used with a hot stick. Are you already familiar with hot stick technique, and just wondering what additional precautions are needed for...
The speed data was only available for the period after the generator breaker finally opened, so all I cannot tell if the unit stayed at synchronous speed or if it was operating with slip.[sad]
Ah, that make sense that the immediate closing of the wicket gates would have made this much less severe than having the turbine continue operating will full water flow.
Casey- I'll ask whether there is enough speed data to determine if it stayed synchronous. I think it is a Francis turbine...
From what I can piece together so far, the generator circuit breaker stayed closed for 15 minutes after the exciter tripped. As far as I can tell from limited very limited data, the unit drew 1.4 MVA. I am trying to figure out how it could have stayed online that long if damage to brazing...
For a 2 MVA synchronous hydro generator, what are the impacts of running without excitation for 15 minutes with the wicket gates closed? How much reactive power would you expect to see flowing into the generator. How much real power losses might occur? Would you expect an in service failure...
Do have the cut sheet for the cable you are considering? The southwire catalog shows an 8.7% increase going from 4000 kcmil to 5000 kcmil conductors...
As a super simplified problem of how to maximize real power transfer across the cable, the transfer can be maximized by controlling voltage at each end of the cable to force half of the reactive current to flow from each end. Shunt inductors can be a tool control voltage, as well as to avoid...
As an anecdote about transformer LTCs, we have connections to two different utilities. We typically operate with a slightly lower transmission voltage that our 115 kV neighbor A, so we often import vars from neighbor A and export the vars to neighbor B at 230 kV. Depending on the position of...
The OATT tariff for my utility for Reactive Supply and Voltage Control service is a rate of $0.14/MWh . The actual power factor of the transaction is not included in our billing data.
The somewhat more complicated rate for BPA starts on page 44 of...
The surge arrestor on a transformer is intended to limit the voltage magnitude between components inside the transformer. As long as the voltages inside the transformer stay within the rating, the relative voltage been the top of the pole versus the bottom of the pole is irrelevant.
So rather...
