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We have an analog input module (Adam 4017) that needs to be connected to our data constrictor; they communicate via RS-485. The analog module has two pins (RS485+, RS485-) dedicated for communication. Instead of buying RS-485 cable/converter to connect these two modules, I was wondering if I can...

Appreciate the response. There are plenty of documents on breaker failure protection schemes. I wanted a specific detail on Stuck Breaker protection. But I appreciate the help.

Could somebody give a primer on Stuck breaker protection, beyond the basic understanding (i.e. these are used in case a breaker is not tripped when asked to do so; a timer starts when the trip signal is sent and when the timer expires stuck breaker initiates and trips other breakers around that...

Hello To expand my knowledge on Electrical Engr subjects, I am assuming a new role as Protection and Control Engineer. I am told I’d be dealing with a lot of relay setting calculations and communication network issues involving, RTUs. What book/material would you recommend for me to not only...

Thanks both to dpc and magoo2. @magoo2, you gave me the answer I was looking for. I am right now downloading their demo version. Thanks.

Hello I’d like to practice the power flow analysis, short circuit modeling etc I had learned few years ago on my personal time. My company doesn’t have any of the tools such as SKM Power Tools or ETAP. As such, I want to personally invest on this and practice myself. Any suggestion as to where...

Dpc, Thermal current and Mechanical current for the new unit and old units match (50 kA and 125 kA respectively). I am assuming that Dynamic short time current and Mechanical current are pretty much same thing. Where would you adjust the meter multiplier that you are suggesting? Scottf, I will...

Hello We are considering replacing the current revenue meters (CT/VT) for our 230 kV line (secondary of the GSU). The accuracy and burden and most other specs match. However, we need current ratio of 1000:5 and the unit that the vendor is offering has multi-tapped ratios: 200/300/400 X...

Thanks all for the answer. It is copper bus by the way.

We have to cut a small section (about 3 feet) of our non-seggregated 10 kV bus bar (all three phases) since the ends are not aligning with the bar holes at the generator end (other end of the bus bar is connected to the transformer low voltage bushing stubs). Instead of cutting the bar at the...

I had actually gone through all the standards you mentioned but didn't find the limits compared to the transformer winding. However, your answer on SC helped immensely. Thanks for the help.

First of all thanks to PRC. I’d have preferred a reference in IEEE or even NEMA document to IEC (specially since we don’t follow it and we don’t have access to those documents), but still I am thankful. Wouldn’t this also depend upon what is the fault availability in the area? I mean, if the max...

Thanks Scotty. Anybody has any idea if there is a standard that dictates the ampere (current) rating of the bushing as compared to the transformer winding? Like I mentioned, ours says it should be 120% compared to the winding.

Our Transformer standard specifies that Bushing ampere rating shall be at least 20% higher than the respective transformer winding ampere rating at maximum transformer nameplate rating. Does anybody have a basis for this standard? I checked c57.19 series on bushings but couldn’t find anything on...

Appreciate the prompt response and confirming our concern. I have two follow up questions: 1. The change in SC fault shouldn't be too high, do you agree? The X/R between the existing and new are pretty different and we already expect the fault to be higher in the new. THe difference in zero %...

I know that the zero percent impedance of a transformer is important primarily for fault calculation and could effect reactive output. However, if a transformer spec doesn't specify this value, how do we obtain this? We have an old transformer (750 MVA, 24 KV to 230 KV GSU-Westinghouse) with...

dpc Thanks for the response. I understand your point and now I have come to the understanding that different method yields different answer. This makes sense theoretically, but in real life we have to chose one method. Now, practically speaking, if a vendor tells me that the breaker is lab...

Can somebody please explain why the asymmetrical current calculated using Total current method is significantly different to that calculated using Symmetrical current method? I know the X/R multiplier is different for these methods, but why should a fault current (asymmetrical) calculated using...

Thanks for the discussion. ASPEN aside, if I have a Symmetrical current and X/R over 17, then I need to multiply this by that X/R multiplier obtained from figure 8 of IEEE c37.010 right? How do you get Asymmetrical value then?

Thanks but I want to understand what I am seeing.