Earth Potential Rise (EPR) Computation for a Fault on Transmission Mains Pole

Transcription

1 ACN: ABN: NATIONAL ELECTRICAL ENGINEERING CONULTANCY Earth otential Rie (ER) Computation for a Fault on Tranmiion Main ole repared by: M. Naereddine

2 ACN: ABN: Abtract The prologue of new High Voltage (HV) tranmiion main into the community neceitate earthing deign to enure afety compliance of the ytem. Conductive tructure uch a teel or concrete pole i widely ued within HV tranmiion main; the earth potential rie generated by a fault on thee tructure could direct to an unafe condition. Thi paper endeavor to provide information on the input impedance of the OHEW ytem for finite and infinite tranmiion main, the definition of finite and infinite ytem wa dicued, maximum ER due to pole fault were dicued, and implified equation for ER aement were introduced and dicued for the finite and infinite condition. T I. INTRODUCTION he benefit of electricity are numerou but mihandling it can caue damage to propertie and may inflict injurie and fatalitie. High voltage tranmiion deploy conductive pole uch a teel and concrete tructure. The aumption that any grounded object can be afely touched i not alway correct. A eriou hazard may reult during a ground fault. Fault on tranmiion main tructure create an earth potential rie (ER) which could lead to unafe touch condition on thee tructure or unafe tranfer voltage to nearby conductive infratructure. High voltage ubtation are fed by tranmiion main. The route of tranmiion main could be in cloe proximity to reidence and community infratructure, many people believe touching tranmiion main are afe, thi tatement i not alway correct, thi tatement only tand if the earthing ytem at the bae of the pole i capable on aborbing the fault energy generated by the high voltage fault. The ER generated on the tructure could lead to unafe voltage tranfer to near by conductive infratructure uch a metal fence, water pipe line and telecommunication circuit. Tranmiion main pole are expoed to two type of fault condition: Fault at the high voltage ubtation due to the plit factor concept Fault at the tranmiion pole Alo tranmiion main are divided in two categorie depending on it length: Infinite tranmiion main Finite tranmiion main Thi paper dicue the tranmiion main ER under pole fault for the two length condition, it examine the ER on the faulted pole and it maximum poible magnitude. Alo thi paper introduce an etimated methodology for quick aement on the maximum ER under pole fault. A. Deign Factor II. THEORETICAL TUDY The earth potential rie on the tranmiion pole under fault will depend on the following factor; thee factor are conidered the mot important element when it come to pole ER aement: Fault Location Fault Current Magnitude on the tructure Infinite or finite tranmiion main ubtation earth grid reitance ole earth grid reitance a een from the OHEW connection point Conductor arrangement on the tranmiion pole Type of the OHEW Number of the OHEW (in thi paper, ingle OHEW were ued) oil Reitivity tructure ole urrounding infratructure In thi paper, tranmiion main pole fault i aumed to have the ame magnitude a ubtation fault. B. Line Impedance Figure repreent an overhead tranmiion line that connect two ubtation,

3 ACN: ABN: Figure: OH tranmiion main layout with OHEW C. Infinite ytem For an infinite tranmiion line, equation can be ued to determine the OHEW input impedance = () 2 e p i the OHEW elf impedance for the average pan in ohm i the pole earth grid reitance in ohm p e i the line impedance a een from the fault Figure 2 repreent the line impedance e under a fault at the ubtation, Figure 2: Line impedance for a fault at the ubtation Figure 3 repreent a pole fault located in the middle of the tranmiion main, if half the tranmiion main line i conidered to be infinite, equation can be ued to determine e and e2 Figure 3: Fault at the tranmiion pole

4 ACN: ABN: Under the infinite condition, the maximum pole earth potential rie can be found uing equation 2: ole ER ( ς) I f T = (2) ς i the coupling factor I f i the fault current T i the total impedance a een from the fault location The wore cae cenario i repreented by a fault on the phae located at greater ditance d d i the ditance between the hae conductor under fault and the OHEW Figure 4 how the phae conductor arrangement in relation to the OHEW, in thi figure, fault on phae C repreent the wore cae cenario when aeing the ER for a fault on thi pole. Figure 4: Conductor hae arrangement on tranmiion pole D. Finite ytem If the tranmiion line i conidered to be finite, the input impedance of the OHEW can be computed uing equation 3: OHEW In connection ( ) e = OHEW In connection i the ling impedance for N number of pole g // (3) i the OHEW elf impedance between the lat pole and the ubtation Figure 5 how a fault on a pole for a finite tranmiion line, e can be found uing equation 5, imilar

5 ACN: ABN: computation for e2 Figure 5: ole fault for finite tranmiion line The finite impedance on one ide can be found uing the following approach OHEW In = NEEC etablihed equation 4 to compute the finite ytem OHEW input reitance 2 A OHEW In NEEC = B C A, B and C are function of N N i the number of ection in an infinite ytem... (4) imilar to the infinite line, the eparation ditance between the OHEW and faulted phae ha an impact on the pole ER, the worth cae cenario i repreented with the fault on the phae located far to the OHEW, imilar to the infinite line, the finite line with pole arrangement a hown in figure 4, fault on phae C repreent the wore cae cenario. III. ER UNDER OLE FAULT The wore cae ER under a pole fault can be divided into two ection. Fault under finite ytem 2. Fault under infinite ytem Figure 6 how the ER for a pole fault under tranmiion main where half it length i conidered to be finite, which mean the fault on the middle pole ha a finite line both it end. The lowet ER i preented in the middle a both ubtation earth grid for a part of the OHEW input impedance due to the finite line, the wore cae cenario i repreented by a pole fault near the ubtation.

6 ACN: ABN: Figure 6: ole ER for a finite middle line Figure 7 how the ER for a pole fault under tranmiion main where half it length i conidered to be infinite, which mean the fault on the middle pole ha an infinite line both it end. The wore cae cenario i repreented by a pole fault in the middle of the line Figure (7) ole Fault ER for an infinite ytem

7 ACN: ABN: IV. CONCLUION Thi paper provide a proce on how to ae the maximum ER under pole fault; it how that for infinite tranmiion main it i poible to etimate the maximum ER value with minimum input data. Alo thi paper how how it i poible to etimate the ER along the feeder route under different pole fault location, it how that the wore cae cenario i preented with a pole fault near the ubtation for a finite ytem and by a pole fault in the middle of the line for an infinite ytem. Thi approach enhance the proce of earting deign when it come to tranmiion main, it give the deigner guidance if further pole earth grid deign i required for touch and tep voltage compliance. It hall be noted that the pole earth grid hall comply with the lightning protection requirement. REFERENCE [] Andrenyi J. Analyi of Tranmiion Tower otential During Ground Fault 967 IEEE Tranaction on ower Apparatu and ytem, Vol. a-86, No. 0 [2] Naereddine M, Hellany A, Rizk J, 2009, How to deign an effective earthing ytem to enure the afety of the people, 2009 International Conference on Advance in Computational Tool for Engineering Application, pp 46-42, [OR ID: 20202] [3] Naereddine M, Hellany A, Nagrial M, Analyi of the impact of the OHEW under full load and fault current 200, International Jurnal of Energy and Environment (IJEE), Volume, Iue 4, pp [OR ID: 26605] [4] Naereddine M, Hellany A, Nagrial M. Rizk J. oil Reitivity tructure and it implication on the Earth Grid of HV ubtation 20 World Academy of cience, engineering and Technology, Vol 60, pp , [OR ID: ] [5] Naereddine M, Hellany A, 2009, AC Interference tudy on ipeline: the Impact of the OHEW under Full Load and Fault Current, roceeding in the 2009 International Conference on Computer and Electrical Engineering, pp , [OR ID: 2920] [6] Naereddine M, Hellany A. OHEW Earthing Deign Methodology of Traction ubtation 200 World Academy of cience, engineering and Technology, Vol 66, no. 0, pp , IN , [OR ID:27809] [7] Naereddine M, Hellany A, Nagrial M. Rizk J. afety Compliance of ubtation Earthing Deign 20 World Academy of cience, engineering and Technology, Vol 60, pp , [OR ID: ]