Northwest Electrical Power Dispatching and Communication Center

Fengcheng, China

Northwest Electrical Power Dispatching and Communication Center

Fengcheng, China

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Suonan J.-L.,Xi'an Jiaotong University | Zhang J.-K.,Xi'an Jiaotong University | Jiao Z.-B.,Xi'an Jiaotong University | Su X.-H.,Northwest Electrical Power Dispatching and Communication Center | And 2 more authors.
Gaodianya Jishu/High Voltage Engineering | Year: 2010

Taking the ±500 kV Bao-Dei and Gui-Guang II HVDC projects as model, and basing on a large number of RTDS experiments, we firstly analyzed the AC fault transient characteristic of the AC-DC hybrid transmission grid from the relay application viewpoint. The results show that the harmonic components of fault information are mainly expressed as low frequency and non-integer component, and its content basically does not decay with the passage of time. In addition, due to the nonlinear characteristics of converters, the magnitude and phase of the system positive sequence impedance are no longer equal to those of the negative sequence impedance. Those features have an unfavorable influence on many types of protection such as differential component, distance component, phase selection component, and directional component. The results can be adopted to establish a theoretical foundation for the development and application of relay protection applied to AC-DC hybrid grid.


Suonan J.,Xi'an Jiaotong University | Zhang J.,Xi'an Jiaotong University | Zhang J.,Northwest Electrical Power Dispatching and Communication Center | Su X.,Northwest Electrical Power Dispatching and Communication Center | And 2 more authors.
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2010

In a hybrid AC-DC transmission grid, DC bias and commutation failure have adverse effects on the behavior of transformer differential protection. With the model of an actual hybrid AC-DC transmission grid in northwest of China, the performance of differential protection under these two situations are discussed. Simulation results show that the second order harmonic produced by DC bias may cause miss-operation of differential protection in the event of minor internal faults. The results also reveal that under the circumstances of commutation failure, where the current of the AC system can be seen as a harmonic source, the differential protection may refuse operation when internal faults happen because of the high second order harmonic. The protection scheme based on fault component integrated impedance is used to solve these problems. Theoretical analysis and simulation results show that the scheme is with high sensitivity and reliability even when minor internal faults happen under the situation of DC bias or commutation failure. © 2010 State Grid Electric Power Research Institute Press.


Suonan J.,Xi'an Jiaotong University | Zhang J.,Xi'an Jiaotong University | Zhang J.,Northwest Electrical Power Dispatching and Communication Center | Jiao Z.,Xi'an Jiaotong University | Su X.,Northwest Electrical Power Dispatching and Communication Center
2010 International Conference on Power System Technology: Technological Innovations Making Power Grid Smarter, POWERCON2010 | Year: 2010

In AC-DC hybrid transmission grid, Both DC magnetic bias and commutation failure are common circumstances and which have adverse impact on the behavior of transformer protection in adjacent AC side. Taking the ±500kV Bao-Dei and Gui-Guang II HVDC projects as model, and based on a large number of RTDS experiments, the performance of transformer differential protection under those two situations is discussed in detail. Quantitative analysis indicates that the second harmonic produced by DC magnetic bias may cause transformer protection fail to operate in minor internal faults. On the other hand, the AC system can be regarded as a harmonic source under the circumstance of commutation failure, and the high content of the second harmonic may lead to mal- restraint of transformer differential protection especially in slight internal faults. To solve those problems, a novel protection method based on excitation impedance is put forward in this paper. Simulation results show that the proposed scheme is high in sensitivity and reliability even under condition of minor internal fault along with DC magnetic bias or commutation failure. ©2010 IEEE.


Zhang J.,Northwest Electrical Power Dispatching and Communication Center | Su X.,Northwest Electrical Power Dispatching and Communication Center | Hu Y.,Northwest Electrical Power Dispatching and Communication Center | Li H.,Northwest Electrical Power Dispatching and Communication Center
Dianli Xitong Zidonghua/Automation of Electric Power Systems | Year: 2011

In conventional line protection the return signal of contact in tripping position relay TWJ is usually employed as a criterion of post-acceleration protection startup after analyzing a mal-operation case of pilot post-acceleration protection, it is clear that the design of early TWJ circuit is unreasonable. It shows that the returning of TWJ contact is usually earlier than the tripping of circuit breaker, which frequently leads to the false input of acceleration protection. Meanwhile, there is defect in protection device software and the distance acceleration component may frequently fulfill the operation condition during open-phase operation mode. Factors mentioned above may cause acceleration protection mal-operation. Improvements on field wiring and protection software resulted from the mutual coordination between the secondary circuit and protection device are put forward. © 2011 State Grid Electric Power Research Institute Press.

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