Abstract:With the DSA system, Jiangsu Electric Power Dispatching and Control Center implemented an after-fault analysis. Compared PMU-recorded data with simulation curve, it is discovered that random noise in the PMU data, introduced during the process of measuring, transmission and conversion etc., may significantly affect the precision of Prony analysis. This paper proposes a noise characteristic based EMD which can be used as a pre-filter algorithm in Prony analysis. This algorithm reduces the power of noise through random sort iterations, and thus increases the signal-noise-ratio of the reconstructed signal. Therefore, the noise in the signal can be filtered effectively within several loops. The comparison between a test signal and a real fault in of Jiangsu power grid proved the effectiveness and practicability of the proposed algorithm.

Abstract:Offshore wind farms are always connected to the power grid through VSC-HVDC. In this paper, the mathematical model and control strategy of VSC-HVDC system are studied. For an asymmetric fault, delay method is used to obtain the positive and negative sequence currents. Hence, with the sequence currents, a control strategy for damping negative current is proposed. Simulations have been implemented in PSCAD, and the results show that the proposed strategy is effective in damping negative current.

Abstract:Research on the mechanical fault diagnosis of high voltage breakers is carried out in this paper. By monitoring the vibration signal of high voltage circuit breakers at the instant of closing operation, an intelligent diagnosis method for mechanical faults with wavelet decomposition and support vector machine is proposed. Firstly, wavelet decomposition is used to decompose the vibration signal, and then the reconstruction signal energy of low frequency and high frequency signals is extracted from the vibration signal and selected as the fault indicator. Finally, the mechanical faults of high voltage breakers is classified by using support vector machine. In order to validate the proposed method, the hardware and software of mechanical fault diagnosis system for high voltage breakers has been built, and the experiments on high voltage circuit breaker have been implemented. The experimental results show that the proposed method can effectively diagnose mechanical failure of high voltage circuit breaker.

Abstract:In transformer trials, the capacity and tgδ are important references for determining the status of transformer. For studying the excessive low-voltage winding electrical capacity and tgδ of a 10 kV transformer due to poor grounding, we established the transformer insulation equivalent capacitance map and analyzed the causes of abnormal data. The study shows that the calculation based on the transformer insulation equivalent capacitance map is accurate for analyzing the causes of excessive capacity, which provides the basis for the investigation of defects. Finally, the paper compared the transformer frequency response curves in the conditions of transformer well-grounded and poor-grounded and found that the two curves are significantly different. The test has some instructive meanings for future transformer grounding fault detection.

Abstract:During the operation of the fixed series compensator of Shanbao-to-Dongming extra high voltage transmission lines of East China, the spark gap would trigger itself unexpectedly, which may result in bypass of the series compensator, in some cases even cause the trip-out of the transmission lines. In this paper, the structure of the fixed series compensator is firstly illustrated. Then a statistics analysis of the actions of the spark gap in the last 6 years is carried out. Afterwards, a three-dimensional model of the main gap is established in the ANSYS. The dispersion of the discharge with various spark gap is investigated. The experimental system for the discharge is build up with the main gap scale as same as the real one. The test results show that the dispersion of the discharge voltage is small, which is in agreement with the experimental date afforded by the supplier.

Abstract:When HVDC transmission system has a system failure or outage because of equipment insulation withstand transient overvoltage threat, the recorder in nowadays can only record the pole line voltage and current, it can't provide the high frequency fault waveform information related to identify the fault in a short time, so the time of trouble shooting and restoring power supply will be delayed. In order to monitor the transient traveling wave and lighting invasion wave through the HVDC transmission line, this paper designed a transient fault monitoring device for ±500 kV DC transmission line, including suitable new power supply system, the high frequency sensor, data collecting and transmission unit. Based on the design, the prototype of the device is used and the lighting waveform data is monitored and showed its validity and reliability. This paper provides technical means to monitor, identify and reproduce a transient fault of HVDC transmission system.

Abstract:Estimating short circuit capacity of bus is important for evaluating system robustness and is essence to setting and coordinating relaying protections. The short circuit capacity calculation for operating bus is not convenient. In this paper, the Thevenin's theory is applied to construct a two-port network for operating bus with different loading conditions. Then, the relationships among power increment, voltage regulation and short circuit capacity is obtained. Considering power increment and voltage change rate are easy to measure, the short circuit capacity calculation for operating bus can be obtained.

Abstract:Targeting at the disadvantages of current modelling methods, a vector diagram is adopted to construct and analyze TV error mathematical model in this paper. With the model established using vector diagram, the errors of TV are analyzed systematically and comprehensively. Also, the influence of the TV error on the electric power energy metering is elaborated. It helps technicians of the electric energy metering to know more about TV error theory.

Abstract:Photovoltaic (PV) generation is widely accepted as an alternative energy for its gradually reducing cost. The increasing number of PV stations integrated into distribution grid brings a challenge to the grid operation. In this paper, based on the control strategy and the circuit topology of PV inverter, electromagnetic transient characteristic of the PV inverter short-circuit was studied theoretically. The short current changing trend under different switching states was studied. Besides, three short current experiments have been done under different output power, voltage drop depth and voltage angel. The experimental results show that the inverter inner closed loop controls can inhibit rush current. Moreover, the inverter self-protection action would block driving signal so as the bypassing trip accident wouldn't be caused.

Abstract:With the continuous improvement of industrial technology, intelligent electric meter is running in an increasingly complex environment. The reliability and accuracy of meter is facing more and more challenges. Small metering error has been observed in some meters in practice. In this paper, we analyzed the causes of small metering error, and provided a suppression method from the point of view of hardware, software and field installation. Test results show that the suppression method is effective and feasible.

Abstract:Line loss rate is an important synthetic indicator for power enterprise, which reflects the level of network planning and design, production technology and operation management. In order to promote the management of loss, Jiangsu electric power company has carried out the research on the potential loss reduction and its realization method from 2013 to 2015. This paper analyzed the grid structure, loss management level, technology line loss, problems in loss management, factors for line loss reduction, factors of power losses, and causes for large line loss and so on. At the same time, based on the theoretical calculation and analysis of line loss, a three-year loss reduction target, along with its implementation method and some suggestions are proposed.

Abstract:For the 500 kV transmission lines with series reactors, high transient recovery voltages (TRVs) may be caused between the contacts of the breakers when they are dropping out short circuit currents. A serious TRV may result in a restrike, which makes cutting short circuit current off different. In his paper, a TRV simulation model for the 500 kV grid in Jiangsu province is constructed. There are two series reactors installed on the line between Shipai substation and Changshu South substation in the model. The TRVs are calculated when a single-phase earth fault occurred at different positions in the line. A protection scheme is proposed and verified by calculations. The results show that the TRVs are too high to meet the requirements in the standard when there are series reactors on the line without protections. The TRVs can be suppressed effectively by installing a parallel capacitor with reactor. The capacitance should be greater than 35 nF. This work provides a reference for the practical application of series reactor and protections against TRV in projects.

Abstract:Our country has been long-term facing the regional, seasonal, periodical and structural shortage of power. Orderly power utilization is a tool to keep balance in supply and demand of power and so as to ensure the power supply to residential and important demanders. However, currently choosing demanders to participate into orderly power utilization program is mostly subjectively decided by the operator, which is lacking of scientific basis, unreasonable and injustice. This paper proposes a load characteristic analysis method for orderly power utilization demanders based on fine management object. Through clustering the historical load of the demanders, typical daily load curve of demanders are figured out. Then through combining the sampling points clusters of typical daily load curve, power utilization pattern and power utilization interval of demanders are obtained. The peak load shifting and holiday staggering plan value of the demanders are calculated. Rules and strategies for orderly power utilization demander selection are constituted based on the analysis of load property, which is public to the community, makes the orderly power utilization work more scientifically and orderly.

Abstract:The new operation mode in the State Grid requires the operator to control substation equipment remotely. In the current dispatching support system, the IEC 60870-5-104 protocol only checks control point number during remote control command transmission and verification process. This may result in mal-operation of remote control because wrong corresponding relation between control point number and device. By extending the IEC 60870-5-104 protocol, double check among device ID, control point number, and device IP is achieved. It greatly reduce the possibility of mal-operation of remote control caused by wrong corresponding relation between control point number and device.

Abstract:In this paper, some kinds of factors affecting line losses are analyzed, and some indexes for line losses evaluation are proposed. A method for line losses index evaluation based on partition similar area is proposed. It shows that there is a positive correlation between index evaluation result and real line losses. Therefore, the grids which have similar index evaluation results can be defined as similar grids in terms of line losses.

Abstract:This paper introduces a kind of general tool for live work insulator replacement for 500 kV suspension angle tower considering the character of multiple hanging points of towers in Jiangsu province. Also, the analysis on the mechanical property of this general tool is provided. Then using the finite element method the precise force model of the general tool is build, and the stress distribution of its each part is investigated. Calculation results show that the general tool meets mechanical strength requirement.

Abstract:In this paper, the structure and the operational principle of cascaded high voltage inverter based on different carrier phase-shifted angle are first introduced. Simulations on the inverter verified its superiority. Based on this, the constant U/F control method is applied to the 6 kV high-voltage and variable frequency speed-regulating system. The simulation results show that the control strategy in this paper performs well and can be used in industrial control.

Abstract:Optical voltage transformer is susceptible to temperature. Therefore, the error characteristic of optical voltage transformer has been attracting many attentions. This paper introduced several typical optical voltage transformer, established the test platform and programs for optical voltage transformers. Temperature impact tests have been carried out for two kinds of optical voltage transformers which are used in practice. Based on the tests, we found that optical voltage transformer based on capacitive voltage divider principle performances better in terms of temperature impacts.

Abstract:This paper introduces the application experience of applying high frequency power supplies (HFPS) technique into the optimization of the operation of electrostatic precipitator (ESP) in No.1 power generating unit in the Guodian Taizhou Power Generation Co.Ltd., and also addresses the characteristic of HFPS in energy saving. Through improving high frequency power supplies (HFPS) technique, along with numerous practical field tests, the HFPS significantly increases dust collection efficiency in Taizhou Power Generation Co.Ltd,. which brings remarkable economic benefits as well as social benefits. The successful application provides a practical experience for prompting HFPS-based energy saving and emission reduction techniques for ESP.

Abstract:In order to solve the problem of some embedded devices cannot be maintained remotely due to system trouble during the process of operation and maintenance, this paper proposes a solution to control equipment's power supply by adopting Raspberry Pi programming, which can realize remote power-off and restart. A detailed introduction to the configuration method of Raspberry Pi web server and the key points on GPIO and Web programming by using python programming language is provided. Compared to the method using Intelligent PDU, the proposed method has advantages of low cost and strong expansion ability.

Abstract:Reliable and stable operation of 1000 MW coal-fired power units is especially important for not only themselves but also the whole electric power grid. Based on the statistical data of the unscheduled shut-down accidents encountered in the 1000 MW power units of Jiangsu power grid, this paper analyzed the main factors influencing the operation of the units and subsequently proposed several solution measures to improve the reliability of the 1000 MW power units.

Abstract:This paper introduces the retrofit of the four corner tangential low NO_x 480 t/h combustor of #10 boiler in Yancheng Power Generation Company. After transformation, all the key parameters including the content of NO_x, carbon content in the fly ash, the temperature of the exhaust gas and the boiler efficiency can meet the design requirements. For the significant steam temperature fluctuations encountered during initial stages after putting the unit into operation, optimization adjustments were implemented and satisfactory effects were finally obtained. This work can provide valuable reference for similar power units performing combustor retrofit and operation optimization.

Abstract:With the increasing coal price, in coal-fired power plants, more and more attention is currently put on energy saving. Due to the high pressure difference across the valves of draining system, leakage accidents induced by high-speed flushing during the shut-down and restart processes were frequently encountered. Through analyzing the function of each valve, solution measures, such as removing redundant valves and merging pipes transporting waters with similar pressures into one single pipe, were adopted to reduce leakage. Taking the draining system of one 330 MW steam turbine as an example, the influence of draining system on economy was analyzed. The results can provide valuable reference for other similar power units.

Abstract:With the development of big data mining, visualization analysis has been becoming an important tool. This paper introduced the meanings of big data mining visualization technology and its applications. Targeting at the three types data of grid enterprises, namely grid operating data, customer data, and data of management, this paper presented an idea for the visualization of big data mining analysis, and provided suggestions to visualization platform construction for enterprises.