Fault Analysis And Fault Location For Four-parallel Transmission Lines On Same Tower

Because four-parallel transmission lines on same tower have the advantage of narrow land corridor, increasing transmission capacity and saving investment, it becomes an inevitable trend for building power grid in China. Fault analysis is not only an important part of power system analysis but also an important foundation for planning, design, protection and fault location of power system. And the important basis of finding and removing faults is fault location theory. Fault location has the advantage of reducing workload for discovering faults, shortening time for getting rid of faults. So, fault location plays an important role in power system safe and reliable operation. However, due to mutual electromagnetic effect complexity between four-parallel transmission lines on same tower, fault analysis and fault location are faced with technical difficulty. Therefore, this dissertation researches on decoupling method, fault analysis method, fault lines selection theory and fault location scheme for four-parallel transmission lines on same tower. The main research works and results are shown as following:1. According to the structure of pole and tower and the lines arrangement causing different mutual inductance, the comparatively actual impedance model of four-parallel transmission lines on same tower is constructed. After the impedance model is decoupled by the symmetrical components method, this dissertation analyses the symmetrical components method disadvantage for fault location and illustrates the necessity of eliminating zero-sequence coupling mutual inductance.2. Based on the proposed impedance model, a decoupling method for four-parallel transmission lines on same tower is proposed by analyzing the characteristic of coupling mutual induction. Thus, two corresponding transformation matrices are deduced for frequency domain and time domain analysis respectively, which are the foundation of fault analysis, fault lines selection and fault location.3. According to the characteristic of sequence components and the relationship between phase components and sequence components, a type of simple and general model for all kinds of short-circuit and open-conductors faults of four-parallel transmission lines on same tower is constructed. Thus, based on the fault boundary conditions and decoupling transformation analysis, this dissertation proposes a novel fault calculation and analysis method for four-parallel transmission lines on same tower. The proposed calculation method has the advantage of no compound sequence networks, practicability and university. Based on the ATP/EMTP, the comparatively actual model of four-parallel transmission lines on same tower is constructed for the simulation verification.. 4. Based on the decoupling analysis for four-parallel transmission lines on same tower, this dissertation analyses the relationship between the equal directional components and the equal system of two terminals; the relationship between the circulation components and the equal system of two terminals. And then, based on the characteristic of phase angles between circulation components, a new method for fault lines selection of four-parallel transmission lines on same tower is proposed. Because the circulation components are unrelated with system impendence, the proposed method improves accuracy for fault lines selection. Based on the ATP/EMTP, the comparatively actual model of four-parallel transmission lines on same tower is constructed for the simulation verification.5. For fault location of whole four-parallel transmission lines on same tower, a novel parameter adaptive fault location scheme based on two terminals data of four-parallel transmission lines on same tower is proposed. In order to eliminate the effects of transmission line parameter uncertainties for fault location, the redundant information of the normal voltage and current are used to construct the transmission lines parameters adaptive frequency domain equation. Then, the circulation components are extracted to establish the frequency domain fault location observation equation of four-parallel transmission lines on same tower. Thus a novel parameter adaptive fault location scheme based on two terminals data of four-parallel transmission lines on same tower is proposed. Using ATP/EMTP, the comparatively actual four-parallel transmission lines model is constructed for simulation. Simulation results demonstrate that the proposed fault location scheme is not only capable of eliminating the effects of transmission line parameter uncertainty but also endureing higher transition resistance.6. For three terminals four-parallel transmission lines on same tower, this dissertation proposes a novel frequency domain fault location scheme firstly. Based on constructing the fault branch selection method, a novel frequency domain fault location scheme of three terminals four-parallel transmission lines on same tower is proposed by establishing the fault branch frequence observation equation. Using ATP/EMTP, the model of three terminals four-parallel transmission lines on same tower is constructed for the simulation verification. Simulation results demonstrate that the proposed scheme is very accurate and easily applied to engineering practically.