DETERMINATION OF BUS VOLTAGES, POWER LOSSES AND LOAD FLOW IN THE NORHTERN NIGERIA 330kV TRANSMISSION SUB-GRID

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1 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March Internatonal Journal of Advancements n Research & Technology AJ DETERMINATION OF BU OLTAGE, POWER LOE AND LOAD FLOW IN THE NORHTERN NIGERIA 330k TRANMIION UB-GRID Amnu A. Maruf Emal: maruf.amnu@gmal.com Kangwa U. Garba Emal: rjyarumar@gmal.com Department of Electrcal Engneerng, Wazr Umaru Federal Polytechnc, Brnn Kebb, Kebb tate, Ngera. KEYWORD: Bus, Power, oltage, Current, Transmsson ABTRACT In ths paper an attempt has been made to nvestgate power flow n the northern Ngera 330k transmsson sub grd usng PowerWorld software. The 13 bus sub grd was developed on base values of 100MA and 330k (transmsson lne) usng data obtaned from the Natonal Control Center, Osogbo, Ngera. The data s vald through 31st December, The power flow was run usng Gauss edel power flow algorthm and low voltage volatons were found at buses 1, 7, 8, 9, 10, and 13. To mnmze these voltage volatons, shunt capactor compensators were placed at affected buses, resultng n a network wth a mnmum bus voltage of 0.95 p.u.. The voltage control also resulted n reduced reactve demand on two of the three generators, wth the slack bus experencng a decrease of The results also ndcated that ncorporaton of compensators yelded a reducton n 8.76 and lne power losses, justfyng the study. 1 NIGERIAN ELECTRIC POWER TRANMIION YTEM The Ngeran electrc power transmsson network, operated by the Transmsson Company of Ngera (TCN), operates at a hgh pressure of 330k whle ts lower transmsson pressure s 132k. The grd s an ntegrated network consstng of sxteen generatng statons and twenty four 330k transmsson sub-statons; two of the generatng statons (Trans Amad G.. and Copyrght 2013 crespub. Omoku G..) are run on sland operaton. Only three generatng statons (Jebba, Kanj and hroro Hydro power statons) and eleven transmttng statons were sted n the northern part of the country as at data collecton tme. Three of these transmttng statons (Damaturu T.., Madugur T.., and Yola T..) had no record of operaton as at data collecton tme [3].

2 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March oltage nstablty n the Ngeran 330 k transmsson grd s very hgh due to low generaton, radal and fragle nature of the transmsson lnes and poor system protecton [4], [ 6]. 2 LOAD FLOW ANALYI The plannng, desgn and operaton of power systems requre load flow computatons to analyze the steady state performance of the power system under varous operatng condtons and to study the effects of changes n equpment confguraton. These load flow studes can be performed usng computer programs desgned specfcally for ths purpose [5]. Essentally, there are four bus types n a power transmsson network. These are generator buses, load buses, swng buses, and dsconnected buses. 1. Generator Bus/oltage Controlled Bus (P, bus) Ths s a bus that has a generator connected to t. The generated real power P and voltage are usually specfed whle the reactve power demand and voltage angle are to be computed. The voltage s kept constant by adjustng the feld current of the synchronous generator excter connected to t. The voltage controlled bus can be grouped wth the generator bus, but t has voltage control capabltes and uses a tap adjustable transformer and/or a statc Ar compensator nstead of generator. 2. Load Bus (P, Q bus) A load bus s any bus that does not have a generator connected to t. It s not compulsory for a load bus to have a load; t may smply be an nterconnecton for two or more lnes. In a load bus the real and reactve powers are specfed from whch the voltage and voltage angle are to be computed. 3. lack Bus (or wng Bus or Reference bus) The slack bus s a specal type of generator bus that s needed by the soluton process. The swng generator adjusts ts scheduled power to supply the system and MAr demand and losses. There s normally only one swng bus. Its real and reactve powers are not specfed, but ts voltage magntude (normally set to 1.0 p.u.) and voltage angle (normally set to 0 o ) are specfed. The swng bus serves as a reference bus and s large enough to supply the requred power, keepng Copyrght 2013 crespub.

3 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March the system balanced n terms of power flows [1]. 4. Dsconnected Bus A dsconnected bus s a bus that s temporarly de energzed. It s usually not ncluded n the load flow soluton and must not have n servce lnes connected to t. Its data s retaned so that t could be re energzed later n the studes f necessary [4]. A system comprses of several buses nterconnected through transmsson lnes. Power s njected nto a bus from generators, whle the loads are tapped from t. Of course, there may be buses wth only generators, and there may be others wth only loads. ome buses may have both generators and loads whle some others may have statc capactors (or synchronous condensers) for reactve power compensaton or voltage control. The surplus power at some of the buses s transported through transmsson lnes to the buses defcent n power [2]. Fg. 1 shows a one lne dagram of a smple 4-bus system wth generators and loads at each bus. To arrve at the network model of a power system, a short lne may be represented by a seres mpedance, long lne by a nomnal π model whle very long lne by equvalent π. It s convenent to consder Copyrght 2013 crespub. loads as negatve generators and lump together the generator and load powers at the buses. Fg. 1. One lne dagram of a 4-bus system The net complex power G denotes the 3- phase complex generator power flowng nto the th bus and D denotes the 3-phase complex power demand at the th bus. Then G and D may be represented as n (1) and (2). G D P G P D jq jq G D (1) (2) Where P and Q are real and reactve power values respectvely. The net complex power th bus s gven by (3). P jq ( PG PD ) j( QG QD ) njected nto the (3) For a system of n buses, (3) can be wrtten as n(4).

4 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March P jq I 1,2,3,...n Where matrx, and s the (4) n bus voltage I s the complex conjugate of source current njected nto the th bus. The general equaton for I n bus network based on Krchhoff s current law n admttance form s gven n (5). I Y bus matrx. Where Ybus (5) s the bus admttance Because t s more convenent to handle load flow problems by usng I rather than I, the complex conjugate of (4) was taken to obtan (6). P I jq (6) From (6), the current whch flows through the th bus s gven n (7). I P jq (7) Usng the Gauss edel method of load flow, t can be shown that for an th bus ts voltage power, real power Q are related by (8). P and reactve 1 P jq Y Where n k1 k Y kk (8) Y s the drvng pont admttance matrx of the th bus [2]. The solutons of ths load flow equaton for the n buses were acheved usng Gauss edel numercal teratve method. After computng bus voltages (magntudes and phase angles) for all the buses, njected powers usng (6) and lne flows were computed usng the nodal voltages obtaned from (8). 3 METHODOLOGY, ANALYI AND REULT The data employed n ths analyss was obtaned from the Natonal Control Center (NCC) Osogbo, Osun tate, Ngera. The per unt values of the lne mpedances were computed on the followng base values: = 100MA, = 330k Usng PowerWorld program, the northern Ngera 330k network was developed and the load flow was run. The network showng connected devces s depcted n fg. 2. It depcts a soluton wth Newton Raphson power flow algorthm. Tables 1 and 2 show generator records and bus records after load flow, respectvely. The results n table 2 Copyrght 2013 crespub.

5 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March show voltage volaton n the p.u. values of buses 1, 7, 8, 9, 10, and 13. The normal range of bus voltages s assumed to be p.u. [7]. Table 1a: Generator records after load flow (before compensaton) Bus No. Bus Name tatus Gen. Gen. AGC AR Mn. Max. Mn. Max. 2 (slack Kanj Closed YE YE bus) 5 hroro Closed YE YE Jebba Closed YE YE Table 1b: Generator records after load flow (after compensaton) Bus No. Bus Name tatus Gen. Gen. AGC AR Mn. Max. Mn. Max. 2 (slack Kanj Closed YE YE bus) 5 hroro Closed YE YE Jebba Closed YE YE Table 2a: Bus records after load flow (before compensaton) Bus No. Name Nom k P.U. olt olt (k) Angle (Deg) Load Load Gen Gen 1 Brnn-Kebb T.. 2 Kanj G Kanj.Y Jebba T hroro G hroro.y Katampe T Kaduna T Jos T Kano T Jebba G Jebba.Y Gombe T Table 2b: Bus records after load flow (after compensaton) Bus Name Nom P.U. olt Angle Load Load Gen Gen wtched No. k olt (k) (Deg) hunts 1 Brnn-Kebb T.. 2 Kanj G Kanj.Y Jebba T hroro G hroro.y Katampe T Kaduna T Jos T Kano T Copyrght 2013 crespub.

6 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March Jebba G Jebba.Y Gombe T Table 3: Lne losses wthout and wth voltage control Wthout Compensaton Wth Compensaton From Name To Name Loss Loss Loss Loss Kanj.Y. Brnn-Kebb T Kanj G.. Kanj.Y Kanj.Y. Jebba T Kanj.Y. Jebba T hroro.y Jebba T hroro.y Jebba T Jebba T.. Jebba.Y Jebba.Y. Jebba T hroro G.. hroro.y hroro.y Katampe T hroro.y Katampe T hroro.y Kaduna T hroro.y Kaduna T Kaduna T.. Jos T Kaduna T.. Kano T Jos T.. Gombe T Jebba G.. Jebba.Y avngs Fg. 2. Northern Ngera 330k sub grd showng load flow To compensate for the voltage volatons, capactor banks were placed as shown n fg. 3. Copyrght 2013 crespub.

7 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March Fg. 3. Northern Ngera 330k sub grd showng swtched shunts (compensators) 4 CONCLUION AND RECOMMENDATION Although ths study does not represent the entre Ngera ntegrated 330k grd, t surely provdes mmcry of the entre network. The very low bus voltages and poor power magntude obtaned from ths study wthout voltage compensaton at Gombe T.., Kano T.., Jos T.. Kaduna T.., and Katampe T.. revealed the realty of the perpetual poor power supply at the North Western part of Ngera. In order to augment ths dsturbng stuaton, t s recommended that relevant stakeholders ensure constructon of power generatng Copyrght 2013 crespub. staton(s) at ths regon of the country and ensure constructon of 330k transmsson lnes connectng Madugur, Damaturu, and Yola. ACKNOWLEDGMENT The authors wsh to thank the entre staff of the Natonal Control Centre (N.C.C.) Osogbo for provdng us wth the data used n ths study. We also sncerely apprecate the contrbuton of the entre staff of Transmsson Company of Ngera (TCN) Brnn Kebb. REFERNCE [1] F. I. Izuegbunam,. I. Durube, and G. G. Ojukwu, Power Flow and Contngency Assessment mulaton of the expandng 330k Ngera

8 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March Grd usng Power World mulator, Journal of Emergng Trends n Engneerng and Appled cences (JETEA), cholarlnk Research Insttute Journals, IN: , 2011, vol. 2, pp [2] J.B. Gupta, A Course n Electrcal Power,. K. Katara & ons, Delh, 2008, pp [3] Natonal Control Centre Osogbo, Power Holdng Company of Ngera (P.H.C.N.), Hydrologcal and Reservor Operatons Data, [4] O.. Onohaeb and.t. Apeh, oltage Instablty n Electrcal Network: A Case tudy of the Ngeran 330k Transmsson Grd, Meddwell Onlne Research Journal of Appled cences, IN: X, 2007, vol. 2, pp [5] O.. Onohaeb, Power ystem Analyss: MEng lecture notes, Department of Electrcal Engneerng, Unversty of Benn, Benn Cty, Edo tate, Ngera. [6] Omoroguwa Eseosa and Emmanuel A. Ogujor, Determnaton of Bus oltages, Power Losses and Flows n the Ngera 330k Integrated Power ystem, Internatonal Journal of Advances n Engneerng & Technology, July 2012, IN: , ol. 4, Issue 1, pp [7] Fve Bus Network, olutons. ABOUT THE AUTHOR AMINU A. MARUF Engr. Amnu A. Maruf earned BEng. degree n electrcal and electroncs from Abubakar Tafawa Balewa Unversty Bauch, Ngera as best graduatng student. He earned Master of Engneerng degree n electrc power and machnes from Unversty of Benn, Ngera. He s a recpent of Natonal Electrc Power Authorty (NEPA) award for the best student n power and machnes engneerng. He also receved the AHAKA CEMENT award for the best fnal year student project n year Amnu A. Maruf s a regstered engneer wth The Councl for the Regulaton of Engneerng n Ngera (COREN). Engr. Amnu A. Maruf s a Member of The Ngeran ocety of Engneers and Member Insttute of Electrcal and Electroncs Engneers. He s currently a lecturer wth Wazr Umaru Federal Polytechnc Brnn Kebb, Ngera. Hs research nterests nclude power system modelng and generaton economcs, power transmsson qualty and power management systems. KANGIWA U. GARBA Engr. Kangwa U. Garba holds M. A. ED., Bc Elect. (Tennessee tate Unversty, U..A), PGD Elect. (Cranfeld Insttute of Tech., U.K) and HND Elect. (Polytechnc Brnn Kebb). He s a Chef lecturer wth the Wazr Umaru Federal Polytechnc Brnn Kebb. He held several postons of academc responsbltes ncludng Head of Department (Electrcal Engneerng), Coordnator olar Energy Research Unt, Copyrght 2013 crespub.

9 Internatonal Journal of Advancements n Research & Technology, olume 2, Issue3, March Dean chool of Industral Engneerng, Drector College of Engneerng and currently Actng Rector, Wazr Umaru Federal Polytechnc, Brnn Kebb. Engr. Kangwa U. Garba s a regstered engneer wth The Councl for the Regulaton of Engneerng n Ngera (COREN) and Member Insttute of Electrcal and Electroncs Engneers. Copyrght 2013 crespub.