Muhanad Sharaf/USABB/ABB               To Normann_Fischer@selinc.com,            Phone: +1 614 818 6393 , Mobile:         ...
345KV TRANS SYS                                                                                                           ...
Positional Protection Technique (Transient-Based Protection for Detection of                    Broken Conductors )       ...
Special case-of-broken-conductor-on-transmission-line
Special case-of-broken-conductor-on-transmission-line
Special case-of-broken-conductor-on-transmission-line
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Special case-of-broken-conductor-on-transmission-line

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Detailed analysis demonstrating detection of such event is virtually impossible using conventional loss-of-phase schemes.

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Special case-of-broken-conductor-on-transmission-line

  1. 1. Muhanad Sharaf/USABB/ABB To Normann_Fischer@selinc.com, Phone: +1 614 818 6393 , Mobile: cc Albert J Keri/USABB/ABB@ABB, bob_morris@selinc.com +1 614 397 4150 bcc 07/31/2012 07:40 PM Subject Fw: Broken Conductor Detection on Transmission LineHi Normann,I have not heard from you in a long time and hope youve been in good health and all is well with you.I really wanted to have a closure to the subject matter that started back in Chicago during the conference.So, I set out to do my own independent looking into it and have the last word based on establishedmathematical tools including symmetrical components.Attached below is my work that shows Phase-A is re-created by the delta-backfeed with no distortion inphase or in magnitude. This agrees with my colleague Albert Keris earlier statements.What you had demonstrated to me at the conference is true whether Phase-A is lost or intact. In brief,polarity is the key thing and when you were summing the two healthy phases which are in series in theDelta after loss of the third phase, the sum was equal to the lost phase but inverted. However, that is truewhether Phase-A is lost or not. And that same sum is actually reversed again when measured withrespect to the polarity of the lost phase. Again, the attached work depicts that.Actually, what you had thought is true for Delta(HV) - WYE-G(LV) configuration though the inverted phaseis on the HV side and about half of the PU Ph-N voltage. So, there is a distinction between WYE(HV) -Delta(LV) and Delta(HV) - WYE(LV) configurations as far as voltages are concerned under no load andwith a radial feed (only one feed source). Under load, the relative magnitudes of load currents forWYE(HV) - Delta (LV) are 1, 1, 1 (Outside of Delta) and 0.5, 0.5, 1 (or 1,1,2) for Delta(HV) - WYE-G(LV)for a phase loss.The conclusion in the attachment is the same for 3X1, 3-legged core, 4-legged core, or 5-legged shelltransformers. So, the loss of phase for a WYE-G(HV) - Delta(LV) configuration is not affected by thetransformer core form as it is the case in the rare configuration of WYE-G - WYE-G where loss of phaseon a 3X1 transformer results in complete loss of phase on both sides but not on a 3-legged coretransformer where the flux sharing re-generates the lost phase just as the delta electrically does in theWYE-G - Delta configuration.Open Phase Analysis in BW.PDF Open Phase Analysis.PDFBest Regards,Muhanad N. SharafSenior Electrical Engineer, P.E.ABB Inc.Integrated Services Instrumentation,Control, & Electrical579 Executive Campus DriveWesterville, Ohio 43082-8870Phone: +1 614 818 6393Mobile: +1 614 397 4150email: muhanad.sharaf@us.abb.com
  2. 2. 345KV TRANS SYS kV 5 34 TX-1 450 / 750 MVA 138KV TRANS SYS 345 - 138 kV 8% kV 8 13 1-266.8 Partridge/acss ACSS, 0.25 mi. kV Phase-A conductor broke off 5 34 while Emergency XFMR is energized with no load. Can this Loss-of-Phase be detected on the delta side of the EMERGENCY XFMR Emergency XFMR? 20 / 26.67 MVA 345 - 13.8 kV 7% GSUT 450 / 750 MVA 138 - 13.8 kV 7.69% kV kV .8 .8 13 13GEN BUS OPEN EMER. FEED CB NORMALLY OPEN AUX LOAD CB Broken Conductor Scenario Electrical Oneline GEN AUX LOAD Muhanad N. Sharaf, P.E. 15 MVA Senior Electrical Engineer Printed by EasyPower
  3. 3. Positional Protection Technique (Transient-Based Protection for Detection of Broken Conductors ) Muhanad Sharaf to: Albert J Keri 06/21/2012 05:10 PM Phone: +1 614 818 6393 , Mobile: +1 614 397 4150From: Muhanad Sharaf/USABB/ABBTo: Albert J Keri/USABB/ABB@ABB,Albert,This is the IEEE paper I ran into a couple of months ago. I downloaded it yesterday and it is interesting toread. Detection of Broken Conductors .pdfThe concept is simple but it doesnt seem to be promising in the specific case of detecting a brokenconductor with no prior load. Aside from its ability to make a distinction for the type of fault in addition topinpointing its location, the scheme philosophy is basically built on the phenomen where a sudden changeof power flow or interrupt of current due to a fault (e.g. high short-circuit current or very high-impedancefault which is similar to a broken conductor scenario) causes high-frequency voltage signal. In the caseof a broken conductor, the reflected and refracted transient waves are propagated into the healthyconductors (or phases) via the mutual coupling between the broken and the healthy ones.As the paper mentions, the magnitude of this fault-generated high frequency voltage signal is influencedby two factors (i) fault inception angle, and (ii) the pre-fault loading in the broken conductor (See Page1166). The paper does not treat the case where there is little or no load prior to loss of one phasepotential; nor does it provide a minimum sensitivity for this technique to detect a broken conductor.Whether the interruption of excitation current will generate a good enough magnitude of high-frequencyvoltage signal for the transient capture unit to be able to declare a broken conductor incident is not known.But, it certainly must first be answered before we can say this technique is a solution.Muhanad N. SharafSenior Electrical Engineer, P.E.ABB Inc.Integrated Services Instrumentation,Control, & Electrical579 Executive Campus DriveWesterville, Ohio 43082-8870email: muhanad.sharaf@us.abb.com

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