Abstract:Chained static synchronous compensator and its phase current control is a common method for the unbalanced problem of power grid and load. This paper proposes a method to employ proportion-resonance integration to trace phase current. Also, a design method for controller parameters selection using closed loop system's root locus, which can not only meet the stability requirement of current inner loop's closed loop system, but also have excellent dynamic performance is provided based on the mathematic model of STATCOM. Finally, PSCAD/EMTDC Simulation results verify the correctness of proportion-resonance integration controller's parameter selection method based on root locus method.

Abstract:On the basis of the mathematical model for doubly-fed induction generator (DFIG) in positive and negative dual synchronously rotating frames under unbalanced grid-voltage, a control method for rotor-side convertor is proposed, which chooses constant electromagnetic torque as the control target and uses proportional-integral-resonant (PIR) controller as the rotor current controller. Without PI controller in synchronously rotating frame and inner loop of rotor current, the control structure is simple and easy for practical use. Besides, the controllable range of unbalance has been analyzed. Simulation results verify the validity of theoretical analysis and the efficiency of rotor current PIR controller.

Abstract:For analyzing the partial discharge ultrasonic wave characteristic of typical defects in SF₆ gas insulation switchgear (GIS), a 110 kV GIS is taken as an object to design typical partial discharge models, namely point electrode model, floating electrode model, air interstice model in insulator and metal particle and iron core electromagnetic shock model for GIS. Experiments using ultrasonic method to detect PD signals for different defects thus have been implemented. The experimental results show that the ultrasonic signals of different defects have different characteristics in waveform, amplitude and phase resolved partial discharge chart, which is helpful in PD pattern recognition for GIS.

Abstract:Winding deformation is the main reason of transformer short circuit which results in damage. In Jiangsu province, the 220 kV auto-transformers are commonly used in the 220 kV power grid. The low impedance value and poor anti-short circuit ability of earlier transformers may result in winding deformation fault and unexpected accident. This paper analyzes a fault of 220 kV autotransformer winding deformation and thus proposes a criterion for judging transformer winding deformation. The disintegration analysis of transformer winding proves that the comprehensive analysis method that combing the low-voltage short-circuit impedance test and the capacity and dielectric loss test is effective. A new way to diagnose transformer winding deformation is proposed to ensure safe and stable operation of transformers.

Abstract:The fail-to-break of circuit breaker is extremely serious to the power system. Considering frequently occurred fail-to-break, a comprehensive analysis on the external control system, internal electrical circuits and transmission mechanism of the ZN65A-12 hand trolley vacuum circuit breaker is introduced. The testing result shows that the initial opening moments of the vacuum circuit breaker mechanism is much less than normal, and it leads to the fail-to-break of circuit breaker. By adjusting the angle of the spindle moment arm, the switching off reliability of the vacuum circuit breaker is effectively improved, and then the serious potential safety hazard is eliminated.

Abstract:A comprehensive testing analysis, including oil chromatographic analysis, DC resistance test, winding capacitance measurement, low voltage short-circuit impedance test and transformer winding deformation test, on a 220 kV transformer's nearby short-circuit fault is implemented. Through this analysis, a serious distortion winding fault is found on the low voltage side of the C-phase winding. The finding is proved by hanging hood check. The testing analysis supplies an effective reference to transformer short-circuit testing and troubleshooting.

Abstract:Different implementations are possible for the automatic switchover system of the power network with a chain structure. This paper proposes a method for comprehensively evaluating different solutions of power network automatic switchover system. Firstly, hierarchical structure of the evaluation index is build. Then, the weight coefficient are determined. Finally, the overall evaluation results are obtained. Analysis on the Nantong regional power grid shows that the comprehensive evaluation method is effective. This evaluation method provides a power network automatic switchover system selection decision support for enterprise.

Abstract:The visual partial discharging UHF spatial positioning system uses four UHF antenna array at different heights to detect the UHF signals to locate discharging signals based on the signal delay estimation and space geometric analysis. Also it visualizes the discharging point using camera. Firstly, UHF radiation and electromagnetic of partial discharge and its positioning principle are introduced. Then, the components of visual-able UHF spatial positioning system for partial discharging is introduced. Finally, the delay estimation method based on the threshold method and zero-crossing interpolation point method are studied. Testing results verifies the effectiveness and practicality of the system.

Abstract:This paper emphatically introduces the scheme, detection function and some functional tests of physical simulation laboratory. Testing methods for parallel compensation type, series compensation type and parallel- series hybrid compensation type using physical simulation laboratory are proposed. With the methods, temperature rise and double pulse tests for valve are implemented. A description of the detection ability of dynamic simulation laboratory and high-voltage electrical laboratory is provided.

Abstract:With the continuous expansion of network scale, the probability of fault occurs in power system is increasing, the accident of power network will lead to the adjacent power plant electrical system in LVRT a short time. On the other hand, due to the energy saving effect is remarkable, the frequency converter is widely applied in power plants, and the LVRT may cause frequency converter tripping, resulting in power plant outage, such accidents have occurred more than. Based on power plant coal feeder frequency converter as an example, this paper analyses the causes and harm of LVRT, and combined with the experience in production field, measures to prevent from the security and economy analysis, to optimize the DCS control logic and the frequency converter control power is the best solution to prevent the accident of LVRT.

Abstract:With the rapid development of new energy technologies, the coordination control of reactive-power and voltage in the regional grid with new energy resources is attracting an increasing attention. In this paper, combining new energy resources and widely used automatic voltage control system, we propose a technical solution to coordinate reactive-power and voltage in the regional grid. The engineering application results show that the proposed technical solution and control strategy is effective.

Abstract:Taking the first 220 kV Suzhou smart substation-"Luzhi" substation as an example, this paper introduces the architecture of smart substation. The functions, devices and sequence controls of smart substation are also analyzed. Based on the analysis, advanced application functions of smart substation are studied. In addition, suggestions for the maintenance of relaying plate and switches are provided. This research is of certain reference significance for stable operation of smart substation.

Abstract:With the development of sensor, computer and communication technology and the higher requirement of power system reliability, the maintenance of oil insulation transformer has been improved from Time Based Monitoring (TBM) into Condition Based Monitoring (CBM). According to the technical characteristics of online monitoring, a new method with comprehensive application of vacuum degassing, classified impurity filtration and accurate control dehydration is introduced to satisfy the requirement of real-time, high efficiency and safety of the oil online processing. At the same time, modular design has been realized with the proposed technique and pertinence modular designs can be implemented for different transformers.

Abstract:The level controller of the low pressure heat-exchanger in cecodary loop is one of the most important controller of nuclear units. The process of optimization is described. Each statage of the optimiaztion and its effect is analyzed. Suggestions for furture optimization work are provided.

Abstract:With the popularization and application of the electronic transformer with small analog sample output, electricity meter with small analog sample input emerged. Different from the traditional electricity meter, this type of the meter has 6-channel voltage input. The traditional testing equipment is inappropriate for this type of meter. This paper developed a testing equipment for electricity meter with small analog input. The principle, hardware and software of the equipment are introduced. A detailed explanation to the anti-disturbance method is provided.

Abstract:The charging load calculation methods for EVs under normal charging mode and battery exchange mode are introduced. Firstly, key factors impacting charging are analyzed and modeled based on a set of proper assumptions. Secondly, the Monte Carlo method is adopted to calculate the charging load of EVs. Finally, the impacts of mixed-mode EVs on urban power system is studied.

Abstract:Massive and polymorphic data are produced during the process of electricity production. With the development of smart grid, the situation is becoming more obvious. This paper analyses the influence of massive data on information operation and thus proposes some countermeasures to change information operation to support big data platform's operation. In addition, a method using data mining to dig valuable information from operation and log data is proposed.

Abstract:The operation security of overhead transmission lines is threaten by the disconnection between strain clamp or splicing sleeve and conductor. Violation of related operating regulation is found to be the cause of the accident, and it also leads to abnormal operating conditions, such as overheat. To prevent such accidents and phenomenon, the detection method for the internal crimping state of compression type fittings is investigated. A ray detection method is proposed to detect the internal crimping quality directly. The developed detection device can be applied to detect the internal crimping state of strain clamp and splicing sleeve during construction and in air directly. Furthermore, the device has been applied in transmission lines of some projects successfully. Online crimping quality monitoring of strain clamp and splicing sleeve in overhead transmission lines is realized. The method can also play an important role in preventing related accidents in the power system.

Abstract:When a 630 MW supercritical boiler put into operation, it was found that exit gas temperature is much higher than design value, that will seriously affect the economic operation of the unit. In order to solve these problems, a lot of work such as combustion adjustment and technical renovation have been done, but still failed to completely solve the problem. Finally, by technical cooperation between the power plant and Harbin boiler company, a method of economizer heating surface modification have been confirmed to solve the problem. Finally, the technical renovation works have been finished during the overhaul period. After renovation, exit gas temperature of the boiler reached the design value, the thermal efficiency and the safety of boiler operation is improved.

Abstract:Along with the implementation of the new boiler emission standard, low NO_x burner alteration was generally carried out on coal-fired power plant boilers. After transforming, water wall transverse crack issues were encountered in many power plants. The main cause of transverse cracks is severe reducing atmosphere near the water wall tubes after reforming low NO_x burners. The operation technology measures and the low NO_x burner retrofit optimization method were put forward, which can provide valuable reference for related power plants.

Abstract:In this paper, the operating process of the heating unit is analyzed and thus its thermal system model is established. With the model, variable operating conditions of the unit can be calculated. Combined with the safety constraints, operating characteristic curve are mapped out for the cogeneration unit renovated from pure condensing unit. According to the diagram, the maximum and minimum capacity for electric load regulation of the cogeneration units satisfying the heating load can be obtained. The accuracy of the model is verified by field load performance test. The research makes large cogeneration units participating into depth peak load regulation of power grid possible, and provides a theoretical basis and technical support to enhance absorptive capacity of wind power and other renewable energy.

Abstract:Since unpredictable faults may be encountered, the first overhaul is especially important for newly installed plants, as compared with the plants in service. Through analyzing the large temperature difference between the internal and outer surface of the high and medium pressure cylinder, it was inferred before performing overhaul that the cylinder stator may deform seriously. Thus, preparation had already been made for returning the turbine components to the manufacturer. Besides, measures including optimizing the sealing, reducing steam leakage and strengthening the dummy plate within medium pressure cylinder were also implemented, and higher economy and reliability were achieved.

Abstract:At present, copper or copper-covered steel are usually utilized to construct the grounding grid in the transformer substations. Except the high cost for raw materials, copper or copper-covered-steel grounding grid is not suitable for all types of soils because of that copper accelerates the corrosion of the underground steel. From the start, this paper describes the current situation of grounding materials used in Jiangsu power grid. Then the comparisons of common-used grounding materials are discussed in conductivity, thermal stability and rotproofness and economic aspects. From the analysis, the conclusion can be obtained that copper or copper-covered-steel grounding grid cannot be utilized without the practical research. At last, some manufacture standards for copper-covered steel are recommend to Jiangsu power grid.