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Load Flow Study for Nablus Network Improvement

Investigating and improving the operation of the Nablus network through load flow analysis, reactive power compensation, and economic analysis. Addressing problems such as high drop voltage, low power factor, and low load factor. Utilizing Etap Power Station program for load flow analysis.

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Load Flow Study for Nablus Network Improvement

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  1. Name : Ahmad Sobhi Abu Sadah Hemzeh Ahmad Qados

  2. Criteria For The Load Flow Study Ch.1: Load Flow Concept • Collection of all data about the Nablus network including the one-line diagram, information about the power stations, transformers, transmission lines and loads. • Investigating the problems from which the Nablus network suffers in max., min load & fault condition • Applying method of reactive power compensation to improve the operation (using tap changer transformer, capacitor bank) • Performing the economical analysis of the saving achieved by the implementation of reactive power compensation

  3. CH:2 Existing SystemThe present load in the West Bank is supplied from several points within the IEC network. There are supply points at • 22 KV supplying Qalailya and Tulkarm • 33 KV feeders from Beisan (in Israel)supplying Jenin ,Tubas and Nablus as well as feeders from M. Afraym and feeders from portable substations.

  4. Load Forcast

  5. 3.1: Element Of The NetworkA. Sources. Generators are one of the essential components of the power systems. Synchronous generators are widely used in power systems. . Nablus are fed from 3 connection point by Israel Electrical Company (IEC), at 33KV.1.Asker (odeleh & Almeslekh) →→→30MVA namely2.Quseen →→→18MVA namely3.Innab →→→5MVA namely CH.3: Electrical Network Study

  6. There are two type of Transformer (power & distribution Transformer ) which is ∆-y connected So, the source always balanced without looking to the load since the P.T is ∆-y ground connected The distribution Transformer capacity & its voltage are summarized in table (1) B. Transformers & load

  7. There are also 3 power Transformer with (10MVA capacity,33/6.6KV& %Tap=±12 ;for 17 taps with1.5% for each step changer) • Note the impedance of each transformer are determined by the typical value at ETAP program • The loads will be seen later in the table of L.F of transformer

  8. C.Transmission Line • There are two type of conductor 1.O.H lines →→→ACSR 2.cables →→→ cu XLPE which have these rating as in table (2) . In Quseen they use double T.L (3*95mm2ACSR) for the transmission of power since the current is above 400A in max load

  9. 3.2 : Electrical Problem In The Network • High drop voltage • Low power factor • Low load factor at most of distribution transformer which reduce the efficiency of transformer & so increase the losses (the electrical losses in distribution network must not exceed 8-10 % from total active power) • Exceeding the permissible capacity of each connection point MVA

  10. Remedy • High drop voltage & low power factor problem • It is important to keep the power factor above 0.92 on the distribution transformer so as to minimize the electrical losses in the network & do not paying penalties • For max load the voltage of buses must rise to (1.05Vnom<= Vbus <=1.1Vnom) as we can to decrease the current & so to decrease the losses • The first step for this improvement is done by using the taps , if not enough it can solve by adding capacitor banks

  11. Low load factor problem • Re-arrange the distribution transformer (if it can be) to increase the load factor • LF=[.65-.75] give the max. efficiency distribution transformer • The engineers choose the transformer in distribution network with load factor [.45-.55] expressed to the growth of the load by years • Capacity problem • For the fourth problem there is a study to get another connection point or to move the connection to another point as in Qussen

  12. Taps • Almost all transformers provide taps on windings to adjust the ratio of transformation by changing taps down when we need to raise the voltages up and vice versa • There are two types of transformer taps: • Tap changing without loads (fixed tap) changer on either side or both sides of transformers • Tap changing under load (LTC)

  13. capacitor banks • Shunt capacitor banks is very important method of controlling voltage at the buses at both transmission and distribution levels along lines or at substation and load . • Essentially capacitor is a means of supplying mega-vars (MVAR) at the point of installation. • Capacitor banks may be permanently connected, or regulators • Switching may be manually or automatically controlled either by time clock or in response to voltage or reactive - power requirement • capacitor reduces the line current necessary to supply the load and reduce the voltage drop in the line as the power factor is improved

  14. 4.1: Etap Power Station Program CH.4:Load Flow Analysis • It is a load flow program which can simulink the power system receiving the input data (source ,transformer ,T.L & loads) as One Line Diagram schematic And results output report that includes bus voltage , branch losses , load factors power factors …etc. • It is also able to do the Fault analysis .. Harmonic analysis .. Transient stability analysis.

  15. 4.2: Simulation For Max. Load Case This step done by the following criteria • drawing the one line diagram (source ,transformer T.L, buses & loads) • entering R&X in Ω or (Ω /any unit of length) & its length. note (Y) value is not important since the T.L is short (L<80Km) • entering the typical value (X/R & %Z) for each transformer • entering the rated voltage for each bus • entering the actual MVA & P.F for each load • entering the source as a swing bus, for load flow studies a swing power grid will take up the slack of the power flows in the system, i.e., the voltage magnitude and angle of the power grid terminals will remain at the specified operating values ( V & δ are given ,P & Q are unknown) • run the load flow analysis to get the output result

  16. A: Max. load case results without improvement • The total demand for Qussen Swing bus P= 20.27MW Q=14.846MVAr S=24.929MVA pf= 80.33 lagging ∆P=1.06 ∆Q=2.555 I=436A ∆P%=1.06/20.27=5.456% • The total demand for Innab Swing bus P= 5.702MW Q=3.741MVAr S=6.82MVA pf= 83.61 lagging ∆P=.075 ∆Q=.307 I=119A ∆P%=.075/5.695=1.31% B: Qussen-with tap changer improvement Swing bus P= 19.841MW Q=14.318MVAr S=24.467MVA pf= 81.09 lagging ∆P=.920 ∆Q=2.026 I=428A ∆P%=.92/19.841=4.63% Method of iteration: Newton Raphson method Number of Iterations: 3

  17. L.F for Quseen

  18. L.F for Innab

  19. P.F for Quseen

  20. P.F for Quseen

  21. P.F for Innab

  22. V% for Quseen

  23. V% for Quseen

  24. V% for Innab

  25. Problems In The Network • we notice # of problems: • low load factor (L.F<.45) for the most of transformer • high load factor (L.F>1) for some transformer {T82,T103 in Quseen} • The P.F for all buses are low (P.F<.92) except {bus.33,34 in Quseen & bus 25,27,29,54 in Innab} • %V does not lies between(1.05Vnom-1.1Vnom) for any bus • considerable losses in Quseen (∆P%=5.456)

  26. V% for Quseen with Taps

  27. V% for Quseen with Taps

  28. V% for Quseen with Taps

  29. For this case we notice the following result • there is a small increase in the P.F • 36% of buses lies between(1.05Vnom-1.1Vnom) & the other is >95% Vnom • P.F of the swing bus increase from 80.33 to 81.09 • The current decrease from 436A to 428 A • the losses decrease in Quseen .826% from the original case • There is a saving in the capacity of .5MVA

  30. C:Max.load with capacitor improvement * Capacitor bank are used to solve P.F problem & its penalties, we put these capacitor bank at the load side (0.4Kv side) * Qc=pold(tancos-1p.fold-tancos-1p.fnew) Where standard capacitor are:- 0.4Kv→→→25,40,60,100KVAr 6.6or11Kv→3,6MVAr

  31. 1.Quseen Qc=19.841*(tancos-1.8109-tancos-1.92) =5.866MVAr Qcact=5.476MVAr for P.F=.9202 2.Innab Qc=5.702(tancos-1.8361-tancos-1.92) =1.312MVAr Qcact=1.3MVAr for P.F=.9221 for each load towe use suitable rated capacitor bank *rise its p.f above .92,so to increase the overall p.f of swing bus

  32. PF for Quseen with cap

  33. PF for Quseen with cap

  34. PF for Inab with cap

  35. 4.2: Simulation For Min. Load Case A : Min. load case results without improvement The total demand for Qussen Swing bus P= 7.721MW Q=5.21MVAr S=9.348MVA pf= 82.59 lagging ∆P=.152 ∆Q=.354 I=164A ∆P%=1.96% The total demand for Innab Swing bus P= 2.262MW Q=1.421MVAr S=2.672MVA pf= 84.69 lagging ∆P=.012 ∆Q=.047 I=47A ∆P%=.53%

  36. V% for Quseen without tap

  37. V% for Quseen without tap

  38. B: Qussen-with tap changer improvement Swing bus P= 7.709MW Q=5.2MVAr S=9.32MVA pf= 82.72 lagging ∆P=.141 ∆Q=.32 I=163A ∆P%=1.82% At this case half turn of tap changer are used* to increase the voltage of the bus (vbus>=vnom) [only Quseen region have under this value Vbus=.95-.98.5Vnom] .tap changer have affect to increase the voltage but less affect on p.f.

  39. V% for Quseen with tap

  40. V% for Quseen with tap

  41. C: Min load using capacitor 1.Quseen Qc=7.709*(tancos-1.8272-tanco-1.92) =1.952MVAr Qcact=1.995 MVAr for P.F=.9224 2.Innab Qc=2.262(tancos-1.8469-tancos-1.92) =.456MVAr Qcact=.547 MVAr for P.F=.9209

  42. PF for Quseen without cap

  43. PF for Quseen without cap

  44. PF for Inab without cap

  45. PF for Inab with cap

  46. PF for Quseen with cap

  47. PF for Quseen with cap

  48. At min load less capacitor bank are used to * rise the p.f at the load & so the overall p.f. the losses in the network are become very low since the currents is reduced . Some of these capacitor bank are used at * max &min which is called fixed capacitor bank. And other capacitor which only used at max or at min are called regulated one. regulated capacitor bank are more expensive than fixed since it need to controller for use.

  49. Ch.5:future project Changing of the switch gear & connection point simultaneously • change the switch gear from 33/6.6KV to 33/11KV except Jumblat region • Jumblat region will kept as it is to exploits the distribution transformer which have two level voltage at primary side (11, 6.6KV/.4KV) at Jumblat with transformer have only 6.6/.4KV side at other places ( East & West Mojeer aldeenregion ) • This operation will save the price of a new transformer with 11/.4KV • The change of position of the connection point is from Qussen to sarrah with 3Km double T.L

  50. The change is starting from replacing the distribution transformer of 6.6/.4KV in East & West Mojeer aldeen region to 11,6.6/.4KV(from Jumblat & East part region from Nablus) • This step also taken some case of the L.F distribution rearrangement which are sumerize at the next table

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