Live Line Measuring the Parameters of 220 kv Transmission Lines with Mutual Inductance in Hainan Power Grid

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1 Egieerig, 213, 5, doi:1.4236/eg b27 Published Olie Jauary 213 ( Live Lie Measurig the Parameters of 22 kv Trasmissio Lies with Mutual Iductace i Haia Power Grid Zhogzhu Xu 1, Zhijia Hu 2, Chuaqi Li 2 1 Haia Power Techology Research Istitute, Haia Power Grid Corporatio, Haikou, Chia 2 School of Electrical Egieerig, Wuha Uiversity, Wuha, Chia zhijia_hu@163.com Received 213 Abstract A live lie measuremet method for the zero sequece parameters of trasmissio lies with mutual iductace is itroduced. The mathematical models of the measuremet method are give. Global Positioig System (GPS) is used as the sychroous sigal for the measuremet carried out at differet substatios simultaeously. The measuremet ad digital simulatio results are give. Fially, the live lie measuremet results of two 22 kv trasmissio lies with mutual iductace i Haia grid are give. Results from both simulatio ad o-site measuremet show that the live lie measuremet method is feasible, ad its measuremet accuracy ca satisfactorily meet the requiremets of egieerig measuremet. Keywords: Trasmissio lies; parameter; Mutual iductace; Live lie measuremet; GPS 1. Itroductio Accurate lie parameters are the foudatio of relay protectio settig calculatio, fault locatio, fault aalysis, etwork loss ad power flow calculatio. With the icreasmet of trasmissio lies o the same towers, zero sequece parameters will affect the fault states ad zero sequece currets of lies [1]-[4]. The traditioal methods have the formulas calculatio method [5] ad the outage measuremet methods [6]-[7]. The zero sequece impedaces of lies are affected by may factors, such as lie aligmet ad groud resistace. The calculated are uable to meet the requiremet of relay protectio settig calculatio. For example, if we use the calculated i the settig calculatio, it will make the protectio refusig actio or mis-operatio. So it is a great threat to the safe ad stable operatio of power. Accordig to the regulatios, the zero sequece impedaces of the overhead lies ad cables should be obtaied by actual measuremet [8]. The traditioal measuremet methods ca oly be used uder the cases that all lies must be withdraw from ormal operatio. Because the trasmissio lies are distributed compoets, the lie legth is over 1 kilometers ad the electromagetic couplig betwee lies which cause the measuremet of lie parameters difficulty. To measure the zero sequece self iductace of a ew lie, because the ew lie has electromagetic couplig with other live lies, the parameters of the ew lie caot be measured idepedetly with the traditioal methods. We should withdraw all the lies from ormal operatio before measurig the zero sequece parameters. Obviously, it is ot acceptable for power. So the traditioal measuremet methods caot satisfy the requiremet of moder power. A ew live lie measuremet method based o Global Positioig System (GPS) techology is itroduced ad has bee successfully applied i the live lie measuremet of two 22 kv trasmissio lies with mutual iductace i Haia power grid. The measuremet results of the live lie measuremet method prove that it ca meet the requiremet of parameter measuremet of trasmissio lies. 2. The Theory of the Live Lie Measuremet Method The algebra equatio sets of trasmissio lies with mutual iductace ca be described as follows, Copyright 213 SciRes.

2 Z. XU ET AL. 147 or Z Z Z Z I U i Z21Z22 Z2i Z2 I 2 U 2 = Zi1Zi2 Zii Zi I i U i z 1z2 zi z I U ZI = U (2) Where zii = rii + jxii ( i = 1, 2,, ) are the zero sequece self impedaces. zij = rij + jx, ij ( i, j= 1, 2,, i, j) are the zero sequece mutual impedaces betwee lie i ad lie j. I is the zero sequece curret vector. U is the zero sequece voltage vector. Suppose U are the zero sequece termial U ad pi qi voltage vectors at the two termials of lie i, ad I qi are the zero sequece termial curret vectors at the two termials of lie i, The U i = U pi U is the zero qi sequece voltage drop vectors of lie i, I = ( I + I ) 2 is the average zero sequece curret i pi qi vectors of lie i. It is well kow that the zero sequece voltages of lies are the differece of the zero sequece voltage of both termials. The equatio of ay lie i at the k-th measuremet ca be described as follows, U = ZI + Z I + + ZI + + ZI (3) ki i1 k1 i2 k 2 ii ki i k (1) measured o lie i ( ) From the p (p (+1)/2)idepedece data groups i = 1, 2,,, p idepedece equatios will be obtaied. For the coveiece of calculatio, the p measuremet equatios is rewritte i a matrix, such as U i = AZ i. The ukow parameters are T [ 1, 2,, ] ( 1) ( 1) ( 1 ) I1, I2,, I ( 2) ( 2) ( 2) I1, I2,, I A = ( p) ( p) ( p) I1, I2,, I Z = Z Z Z. i i i i Where A is a p ( + 1) 2 order matrix. The superscripts 1, 2,, p of vectors I are the idepedet measurig cases ad the subscripts 1, 2,, of vectors I are the serial umber of lies. Set (4) T ( 1) ( 2) ( p) i, i,, U = U U U, The U = AZ is a overdetermied algebraic equatio, the least-square estimatio algorithm is used to solve the ukow parameters Z, ils T ( ) 1 T = i ( i 1, 2,, ) Z A A AU LS = (5) Equatio (5) uses the impedace method to measure the zero sequece impedaces of lies. It ca calculate both the zero sequece parameters of the ew lies ad the zero sequece parameters of the origial lies. The zero sequece self impedace Z ii ad the zero sequece mutual impedace Z ij ca be calculated by the computer. 3. Hardware Structure of the Live Lie Measuremet System The hardware structure of a live lie measurig based o GPS techology is show i Figure 1. The measuremet cosists of several sectios, such as the GPS receiver, iput sigal trasformatio chaels, embedded DSP (Digital Sigal Processor) card, double-port RAM (DRAM), Embedded PC card, cotrol sigal output ad other ma-machie iterfaces. The cetral computer stores ad processes the sampled data, calculates lie parameters ad outputs measuremet results. PPS GPS atea GPS receiver filter A / D CPU iterface lie computer GPS atea GPS receiver CPU iterface Figure 1. The hardware structure of the live lie measuremet 4. Digital Simulatio Results Accordig to the above method, the zero sequece parameters of two trasmissio lies with mutual iductace are simulated uder the measuremet cases for sigle-phase wire break, sigle-phase groudig, ubalaced load ad exteral power source. The parameters of two coupled 22 kv lies are show i table 1. Lie I is 1 km ad Lie II is 5 km. The voltage level of the lies source is 22 kv ad the PPS A / D filter Copyright 213 SciRes.

3 ji 148 Z. XU ET AL. load is 1 MW. Put the measured voltage ad curret data ito the computer, the measuremet results are show i table 2. The simulatio results validate the live lie measuremet method is correct. Table 1. The Parameters of Two Lies with Mutual Iductaces lies resistace (Ω/km) iductace (mh/km) capacitace (µf/km) Lie I Lie II Measuremet cases Ubalaced load Sigle-phase groudig Sigle-phase wire break Two-phase groudig Zero sequece mutual resistace (Ω/km) mutual iductace (mh/km).1 1. Table 2. The Digital Simulatio Results self self impedace of lie impedace of lie I II Measurig j j j j Relative error% Measurig j j j j Relative error (%) mutual impedace Measurig j j j j A Example of Live Lie Measuremet Relative error (%) The schematic diagram of the two 22 kv trasmissio lies with mutual iductace i Haia power grid is show i Figure 2. Luoji substatio Yagluo lie I Yagluo lie II 47.8 km Yagpu power plat Figure 2. The diagram of two lies with mutual iductace i Haia grid The legth of two coupled 22 kv Yagluo I ad Yagluo II lies is 47.8 km. Accordig to practical situatio, the exteral voltage source is applied at 22 kv Luoji substatio. Live lie measuremet equipmets are put at Luoji substatio ad Yagpu power plat. The exter voltage source is applied to the outage lie whe 22 kv Yagluo I ad II lies rollig blackouts. The zero sequece currets are take from of lies. The zero sequece voltages are take from the ope delta widig of of lies or buses. The measuremet wire diagram with a exter voltage source is show i Figure 3. I Live lie measuremet U Cotrol sigal Test traformer Regulator Switch Distributio trasformer Figure 3. The measuremet wire diagram with a exter voltage source The cotrol sigal is geerated by the measuremet equipmets, ad it cotrols the air switch to supply zero sequece voltage. The measuremet wire of two coupled lies is show i Figure 4. Live lie Measuremet 3U tio sta b su o u L 3I 3I Lie I withdraw from ormal operatio ad with a exteral voltage source Lie II uder ormal operatio 3I Yagpu power plat Figure 4. The wire diagram of live lie measuremet 3U Live lie Measuremet (B) The measuremet cases of the lies are give i table 3. Table 3. Live Lie Measuremet Cases Case Lie I Lie II 1 Withdraw from ormal operatio, with a exteral voltage source 2 Uder ormal operatio Uder ormal operatio Withdraw from ormal operatio, with a exteral voltage source Copyright 213 SciRes.

4 Z. XU ET AL. 149 The zero sequece voltages ad currets recorded by the measuremet are show i Figure 5 to Figure 8. Voltage ( V ) Figure 5. The voltage wave recorded i Yagluo I lie Curret ( A ) Figure 6. The curret wave recorded i Yagluo I lie Voltage ( V ) Figure 7. The voltage wave recorded i Yagluo II lie Curret ( A ) Figure 8. The curret wave recorded i Yagluo II lie The measuremet results of the zero sequece parameters of the two lies are give i table 4. Table 4. The Measuremet Results of Zero Sequece Parameters Cases Average measuremet Traditioal method measuremet Average measuremet error self impedace of lie I j j j j j57.48 self impedace of lie II j j j j j57.48 mutual impedace j j j j j % 1.37% 5.51% 6. The Aalysis of Measuremet Results The traditioal measuremet method calculatig Z ca be described by (6), Z U = I (6) Where I is the zero sequece curret vector. U is the zero sequece voltage vector. The method ca oly be used uder outage coditio. Mutual iductace must be take ito accout if there are electromagetic couplig betwee lies. The results of traditioal method are show i table 5 ad table 6. cases Table 5. The measuremet results of Yaluo I lie Curret iput voltage (V) curret impedace j j j j j j j j j j j j4.63 average j cases Table 6. The measuremet results of Yaluo II lie Curret iput voltage (V) curret impedace j j j j j j j j j j j j4.617 Copyright 213 SciRes.

5 15 Z. XU ET AL. average j4.132 The model of two lies with mutual iductace is show i Figure 9. U 1 Lie 1 Lie 2 I 1 Z 11 I 2 Z 22 Z 12 Figure 9. The model of two lies with mutual iductace The voltammetry characteristic ca be writte as follows, U = I Z + I Z (7) So whe we measure the zero sequece self impedace of the lie I, the zero sequece curret of lie II which iflueces the zero sequece voltage of lie I should be take ito accout. The traditioal method igores the ifluece of lie II, so there are theoretical mistakes i (9). U = I Z (8) The, Z U = I 1 1 (9) From (7), we ca get, U1 U1 Z12I2 Z1 = (1) I 1 I 1 I fact, it idicates that whe the curret of lie I reaches 1 A ad the curret of lie II reaches 47 A, Z12I 2 ca t be igored. So the error of zero sequece self impedace measured by traditioal method is great. I this measuremet, the error has reached above 3%. Measure the zero sequece voltages ad zero sequece currets of all trasmissio lies, the calculate (1) ad obtai zero sequece self impedace ad zero sequece mutual impedace. The live lie measuremet method ot oly has high precisio, but also is accurate ad reliable. The measuremet results of zero sequece parameters are show i table III, it shows that the average measuremet error of zero sequece mutual impedace is about 5.5% ad zero sequece self impedace is about 2%. It shows that there are still certai differece betwee theoretical ad measuremet. It is well kow that the computatio formulate for zero sequece parameters are derived from Carso formula. The traditioal method eeds the resistace of earth, the equivalet depth of wires, the legth of lies ad the arragemet of wires. But it is difficult to get the resistace of earth ad the equivalet depth of wires. So the theoretical are oly used as referece, they caot be used as accurate parameters. I the case of disturbig, i order to obtai the accurate parameters of zero sequece self impedace, the zero sequece self impedace ad the zero sequece mutual impedace should be measured at the same time. 7. Coclusio The field live lie measurig results have prove that the live lie measuremet method is correct ad the measuremet ca meet the requiremet of measuremet. I additio, i order to elimiate the iterferece of lies, usig the live lie measuremet method to calculate the zero sequece self impedace parameters ad the zero sequece mutual impedace parameters simultaeously ca improve the accuracy of the measuremet results. 8. Ackowledgemets This work was fiacially supported by the Ph.D. Programs Foudatio of Miistry of Educatio of Chia ( ). REFERENCES [1] Z. Fu, Power System Electrical Equipmet Selectio ad Utility Computig, Chia Electric Power Press, Beijig, 25. [2] J. Li ad K. Zhu, High Voltage Electrical Equipmet Test Methods, Chia Electric Power Press, Beijig, 25. [3] Z. Hu, M. Liu, C. Zhag, et al, Priciples ad realizatio of live lie measuremet to parameters of trasmissio lies with mutual iductace, Automatio of Electrical Power Systems, Vol. 23, No. 24, 1999, pp [4] Z. Hu, Y. Che, W. Xu, et al, Priciples ad realizatio of live lie measuremet of parameters of trasmissio lies with mutual iductace based o differetial equatios, Proceedigs of the CSEE, Vol. 25, No. 2, 25, pp [5] Z. Hu, Y. Che, New method of live lie measurig the iductace parameters of trasmissio lies based o GPS techology, IEEE Trasactios o Power Delivery, Vol. 23, No. 3, 28, pp [6] N. Hu, Z. Hu, G. Zheg, Live lie parameter measuremet of trasmissio lies with mutual iductace based Copyright 213 SciRes.

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