How to Solve Transmission Line Capacitance and Reactance Problems (Electrical Power PE Exam)

[@electricalpereview]

0:22 Problem Statement 1:03 a) Capacitance to neutral in Farads per Mile [F/mi] 11:02 b) Capacitive reactance to neutral in ohm miles [Ω·mi] 13:46 c) Capacitive reactance to neutral in ohms [Ω] 15:32 d) Charging current to the nearest ampere [A]

[@michaelghaly9635]

You made it sound very simple, thanks Zach

[@rjulian1]

So glad I took this course and passed. This just gave me PTTS - post traumatic test syndrome

[@electricalpereview]

Happy to have you as a student and happy that you passed. The hard work is over!

[@rishabhahake7646]

A 50 Hz over head line has the line to ground capacitance of 1.2µF.It is decided to use a ground-fault neutralizer. Determine the reactance to neutralize the capacitance of (i)100% of the length of line and ( ii) 95% of the line.

[@bgallagher16]

Great video, just wish the equations you used were the same as in the reference book we get to use on the test.

[@electricalpereview]

Hi bgallagher16, this is an older video from the paper and pencil format before the exam changed to CBT. We updated all of the course on-demand videos and live classes to use the Reference Handbook formulas. If you're looking for help with transmission lines like this video, some of the newer videos that use the Reference Handbook formulas are availble on KZbin here: Transmission Lines - Solid cd Stranded Conductors: kzbin.info/www/bejne/aITafYh7pt56b7s Transmission Line Bundle Conductors GMR and Radius: kzbin.info/www/bejne/n56WoIako75me7M Single phase Transmission Line Capacitance (C) & Capacitive Reactance (Xc): kzbin.info/www/bejne/bGHUqqJ7eceanrc Single Phase Transmission Line Inductance (L) and Inductive Reactance (XL): kzbin.info/www/bejne/ZpamiKyvbsSXb68 Here is the entire playlist: Transmission Lines for the NCEES® Electrical Power PE Exam kzbin.info/aero/PL8UEnCgTyXQt4HCGjMaoQ8vNRHivDotpv Hope this help!

[@YM-po5mo]

In the handbook (pe-ecp-handbook) page 75, it seems that you use the formula for GMR to calculate r3 (minute 3:45). Does not the problem already give us the GMR (unless that is another sort of GMR)? One more question, do you have a video or lesson(s) in which you explain GMR and GMD for ground zero??

[@electricalpereview]

Hi YM, the problem gives the GMR of each individual conductor in the bundle. Since there is a bundle being used in this transmission line (more than one conductor per-phase), we have to calculate the overall GMR of the bundle instead. I'm not sure what you are referring to in regard to "ground zero", however, here are a couple of more recent Transmission Line videos from our KZbin channel that you may find helpful: Single-phase Transmission Line Capacitance (C) & Capacitive Reactance (Xc) kzbin.info/www/bejne/bGHUqqJ7eceanrc Transmission Line Bundle Conductors GMR and Radius kzbin.info/www/bejne/n56WoIako75me7M Single Phase Transmission Line Inductance (L) and Inductive Reactance (XL) kzbin.info/www/bejne/ZpamiKyvbsSXb68

[@RBCaskey]

Hey Zach! How and why did you derive capacitance to neutral in [F/ft] and then convert to [F/mi], rather than using the [F/m] equation given in the PE Exam Reference Book (5.1.8) and convert to [F/mi]? Is that absolutely necessary? I seem to be getting different answers using matching units for each formula variation. Additionally, the Reference Book uses ln() rather than log10(). Why is it necessary to modify the formula so that log10() is used instead? This difference seems to be related to my question above as well. And finally, why is the constant in the single-phase capacitance to neutral formula half of the constant in the three-phase variation? Would greatly appreciate a response! I'm going crazy trying to reverse engineer this and I don't believe the derivation was ever shown while taking your course (unless I missed it)!

[@electricalpereview]

Hi @R. Caskey, great questions. This video was made priro to the release of the Reference Handbook and uses transmission line formulas that are more commonly found in transmission books. Any of the formulas may be used as long as you pay attention to the units. Here is a newer video on your KZbin channel that uses the same formulas as the reference handbook for transmission line capcatiance (C) and capactive reactance (Xc): kzbin.info/www/bejne/bGHUqqJ7eceanrc Both formulas in the reference handbook for transmission line capcatiance (C) and transmission line inductance (L) solves for line to neutral values (what the reference handbook refers to as "average values"). When dealing with a single-phase transmission line (like the video linked above), you can have to values. The line to neutral capacitance (C) and line to neutral inductance (L), which only accounts for the "average" value of just one of the conductors (like the hot conductor), or, you can have the "total" capacitance (C) and "total" inductance (L) of a single-phase transmission line which accounts for both the value of the hot AND neutral conductor. Since capacitance (C) in the unit farads [F] in series sums in reciprocals: 1/C = 1/C1 + 1/C2 + ... + 1/Cn Two equal capacitors in series equal half: C_total = C/2 We explore all of this in much greater depth during our live class on transmission lines.

[@electricalengineernoobie9503]

That is funny, I thought the same thing! I actually thought it was a cool challenge to try and do it in F/m while he did it in F/mi. It makes you think about the units instead of just following his example. Once I got my answer in F/m I just converted it to F/mi.

[@electricalpereview]

@@electricalengineernoobie9503 good job!

[@wanher33]

Appreciate the good work Zach! Keep it coming.

[@AlbertaDMode]

Yuip. NCEES PE exam book problem 536. By the way... is TI-36X Pro is still OK for CBT exam?

[@electricalpereview]

According to the NCEES Calculator Policy, yes, the TI-36X Pro is still an approved calculator for the PE exam. It is also my personal favorite and the one that we teach during live class. ncees.org/exams/calculator/

[@honeymehta7434]

You take log of base 10 but i think log of base e should be there. Please tell @7.58

[@electricalpereview]

There are two sets of formulas depending on if you are solving for capacitance (C) in imperial units (F/ft) or metric units (F/m). This video solves for capacitance (C) in imperial units (F/ft) and uses the formula that includes log base of 10 instead of the natural log (log base e).

[@honeymehta7434]

@@electricalpereview thanks. I got it

[@kozaTG]

the 3 phase line inductance video is unavailable or is that just me?

[@electricalpereview]

Which video? Link it here and I can check it

[@kozaTG]

check for the video titled "How to Solve Transmission Line Inductance and Reactance Problems (Electrical Power PE Exam)". i can't link it because it says unavailable@@electricalpereview

[@kozaTG]

inductance for 3 phase@@electricalpereview

[@electricalpereview]

@@kozaTG I was only able to locate single-phase transmission line inductance and inductive reactance: kzbin.info/www/bejne/ZpamiKyvbsSXb68 Can you tell me where you are seeing the link for three-phase that will not open?

[@kozaTG]

yeah that's what i mean where's the 3 phase one?@@electricalpereview

[@somosayid2702]

Why don't you guys just use the metric system , what's up with all the feet 🤦‍♀️

[@electricalpereview]

The USA uses mostly U.S. customary units (sometimes referred to as imperial units). This video for the PE exam which is a USA based licensing exam. I guess you could say we like our feet 🦶😀