Fault location methods

Fault location methodsAbstractThis paper presents a comparative have between two displacement location methods in distribution engagement with Distributed Generation (DG). Both methods are ground on computing the impedance using fundamental electric potential and veritable signals. The first method uses one-end instruction and the game uses both ends. A 30 kV three-phase birth was studied in the presence of a 3 MW firm vivify turn turbine.Index Terms-Fault location, Distribution network, Distributed Generation, Fixed Speed Wind TurbineIntroductionFault location fuss in transmission networks has been studied deeply because of its importance in the mightiness system and because its difficult to physically check long transmission contrasts 1. Nowadays, the problem of prison-breaking location was extended to distribution network in order to identify the fault location as quickly as possible to improve the cater quality and the system reliability.The application of unspo tted techniques, presented in Section 2, is not easy due to the complexity of the distribution systems which are characterized by the non-homogeneity of line, the load uncertainty, the phase unbalance 2Fault location problem in the distribution network becomes more complicated with the presence of the Distributed Generation (DG). In fact, the DG resources, connected to the distribution system, which are in general, wind turbines and bitty hydro-electrical plants 3, contribute to the fault level of the network and their effect depends on their size, type and placement 4. The infeed legitimates from the DGs cause errors in the theme of the distance of the fault point since they arse affect the amplitude, the direction and, indirectly, the duration of fault trues 3.In this paper, we present two fault location methods which have been successfully applied to a hearty fault that occurred on a 225 kV transmission line in 5. They will be, first, tested on a simple distribution line wi thout DGs. Then, we consider a fixed speed wind turbine connected to the other side of the line.FAULT LOCATION TECHNIQUESFault location methods can be classified into polar categories rules based on travelling waves in faulted line in 6, authors present a travelling wave based fault location method, which was successfully applied on a transmission line, and extended to distribution line with DGs. The main advantages of this apostrophize are its insensitivity to the contribution of the DGs during fault and the requirement of fault signal unless from the substation end of the faulted line.Methods based on harmonics analysis those methods are not frequently used since grid operators have the aim to reduce harmonics in the power system.Method based on computing the short circuit power, using the voltage and the actuals, to determine the fault location 5.Method using instantaneous voltage and stream available at both ends of the line 5.Methods based on determining the apparent impeda nce using the fundamental components of voltage and current this method is the roughly widely used because of its simplicity and efficiency, and it does not require a big investment in equipment 1, 2. Those methods can be divided into two groups Methods using one-end information and Methods using both ends of the affected line.Fig. 1 shows a simple three-phase distribution line with a load connected via a transformer (30 kV/ 575 V). The basic approach used for determining the fault distance d is to calculate the impedance seen from substation (NL) during the fault. This paper presents two fault location techniques.Method using one-end informationWhere Vk is the voltage of the faulted phase and Vf is the fault voltage. Vk and Vf depends on the fault type as given in table I.Method using both ends informationThe voltage and the current of the two ends line are related with this expressionWhereVLi, VRi, ILi, IRi are resp. the voltage and the current of the left and the right side of t he phase i.VLj, VRj, ILj, IRj are resp. the voltage and the current of the left and the right side of the phase j.Zik,Zjk elements of the impedance matrix of the lineL line lengthd fault distanceSimulation and resultsIn order to show the effectiveness of the presented algorithms, the system presented in Fig. 1 is tested with the source, the line and the load parameters given in table II.Where dest and dreal are respectively the estimated and the real fault distance, and L is the line length.Fig. 2 shows the estimated error for the simulated system of Fig. 1 for different fault resistance value to compare the two techniques depict above.Fig. 3 shows the fault location results for different load power. It can be seen that as the load power increases, the estimation error also increases.For the first technique, the estimation error is less than 1.5% and can still be acceptable, but for the second technique, the estimation error can reach 30% for a 5 MW load.In fact, the accuracy of th e algorithm, for variable load, depends on the short-circuit power of the source. Fig. 4 shows that the estimation error decreases if the ratio between the load power and the source short-circuit power decreases.In order to study the influence of the integration of the DGs into the distribution networks on the fault location accuracy, a three-phase line integrating a 3MW fixed speed wind turbine at the right side of the line is considered in Fig. 5. A 1MW local load has been connected to the WT.Fig. 6, 7 and 8 present the WT characteristics the nominal wind speed is 9 m/s the wind speed is imposed equal to 8 m/s that makes the WT generating 0.66 pu of its active power. The reactive power is generated by an 800 kVAR capacitors. The WT speed is fixed to 1 pu.A one-phase fault, during 600 ms, that occurs on the line with different fault resistance value and different load power, is used to try the presented methods.Fig. 9 presents the estimated error for the simulated line with wind t urbine. It can be seen that the error is higher than in the first case because of the participation of the WT to the fault current which is not delivered only by the source. Then, the source voltage increases and the impedance seen from the source will be higher than the impedance of the very(prenominal) fault on the line without WT.Comparing with the results presented for a line without DGs, we can see that the contribution of the WT in the fault current increases widely the estimation error of both methods, especially the second one that uses the recorded information from the source bus and the WT connection point.The effect of the uncertainty of the load is investigated by varying its value from 0 to 5 MW, for a fault located at 20 km from the source. Fig. 10 presents the accuracy of the described methods darn varying the load.Unlike the result presented for the line without GDs, the estimated error decreases while increasing the load impedance. This result shows that convention al methods cant be well used for network with DGs.It is known that an increase in generation capacity, increases the fault current, because the participation of the DGs to the fault level will increase too. For that, we consider two wind turbine of 3MW each one, connected to a distribution network at the same connection point. The wind reference of the first WT is fixed to 8m/s, and for the second, it starts with a wind speed of 8m/s then it increases to 9m/s to simulate the two wind sources with different rate of penetration. Fig. 12 shows the characteristics of both WTs.ConclusionThis paper presents two impedance based fault location methods tested on a distribution line with and without distributed generation. The two techniques present an interesting precision for fault location in distribution system that does not integrate GDs. But, with the existence of the WT connected to the grid, those methods are not applicable especially for a high fault resistance value or variable loa d impedance. Thus, integration of the DGs into the distribution network requires further study on the existing fault location techniques to adapt them with the DGs state when a fault occurs.ReferencesJ. Mora, J. Melendez, M. Vinyoles, J. Snchez, M. Castro, An Overview to Fault Location Methods in Distribution System base on Single End Measures of Voltage and Current, Journal Name, vol. 1, no. 3, pp. 1-10, Mar. 2000.Y.-J. Ahn, M.-S. Choi, S.-H. Kang and S.-J. Lee, An accurate fault location algorithm for double-circuit transmission systems, in Proc. IEEE Power Eng. Soc. Summer Meeting, vol. 3, 2000, pp. 1344-1349.TH. Boutsika, S. Papathanassiou, N. Drossos, deliberation of the Fault Level Contribution of Distributed Generation According To IEC Standard 60909, NTUA-Electric Power Division, Athens.V.R. Kanduri, Distributed Generation Impact on Fault Response of A Distrubution Network, Thesis of the capacity of Mississippi State University, 2004.A. Abadlia,La Localisation des Dfauts dans les Lignes Electriques, Thesis of the National School of Engineers of Tunis (ENIT), 2007.C.Y. Evrenosoglu, A. Abur, Fault Location in Distribution Systems with Distributed Generation, 15th PSCC, Liege, 22-26 majestic 2005, Session 10, Paper 5, p. 5.