Ultra-high Voltage Substation Research Articles

Study on Control Cabinet of Automatic Filtration System for Insulating Oil of UHV Substation

Ultra-high voltage substation has a large demand for insulating oil, but the impurities in the oil are required to be regularly filtered out before and during use. However, the existing insulating oil is operated by manpower and it has some defects. For example, it needs a large amount of labor but with low efficiency, and it is difficult to precise control temperature and quality of the oil. This paper introduces a control cabinet for transformer oil filter. It is mainly used in the process of transformer oil filter to achieve the monitoring of liquid level, oil temperature and flow rate, at the same time, to achieve the automatic control of oil filter.

超特高压变电站开关设备精益运检工作探析

超特高压变电站开关设备精益运检工作探析

Time and frequency characteristics of very fast transient overvoltage in ultra high voltage substation

Most work about the measurement of very fast transient overvoltage (VFTO) was carried out in the laboratory and test base. Because of the different GIS arrangement and power capacity, the time and frequency characteristics of VFTO in ultra high voltage (UHV) substation could be different with that obtained in the laboratory and test base. A series of VFTO measurements were carried out in two 1100 kV GIS substations to investigate the characteristics of on-site VFTO. The port-hole sensor based on surface-mounted device was chosen to measure the VFTO for its reliability and wide band-width. The whole measurement system was introduced and the schematic layout of each experiment was given. Measurement results of different switch conditions and measure points were presented for comprehensive understanding of the VFTO characteristics on site. The results indicated that the striking number during one operation was 16 (closing) and 14 (opening), similar to that obtained from test base result. Besides, single strike with front time 5.3 ns and voltage steepness 186.1 kV/ns was recorded, and the steepness was relatively higher than that gained in the test base. Moreover, the spectral analysis based on S transform was investigated to get the duration of different frequency components of VFTO waveform. Compared with the data obtained from the test base, the high frequency components of VFTO were reduced, while the lower frequency components lasted longer. The results provided references for the investigation of the electromagnetic interfere, the insulation coordination, and VFTO mitigation methods.

Feasibility of Using One-Column-Varistor Arresters in 1000-kV UHV Substations

With the application of ultra-high-voltage (UHV) technology, how to reduce the construction cost of the UHV substations is becoming an important and emergent issue. In this paper, two kinds of one-column-varistor arresters are used to replace conventional four-column-varistor arresters for busbars or transformers or both of them. The switching overvoltage and lightning intruding overvoltage are calculated to evaluate the feasibility of using one-column-varistor arresters in UHV substations. At the same time, the energy absorbed by and current flowing through the arresters, and the thermal stability of these one-column-varistor arresters are analyzed to ensure their safe operations. It is shown that conventional one-column-varistor arresters can be used for busbars and transformers in UHV substations to replace conventional four-column-varistor arresters and could highly reduce the construction cost of the UHV substation, but the safety of the substation will remain the same.

A Comparison of Ground Grid Mesh Design and Optimization for 500kv substation using IEEE 80-2000 and Finite Element Methods

An Air Insulated substation is chosen for the analysis located in Pakistan. The protective scheme installed in any substation should be fully active to ensure its proper and accurate operation in case of any fault. Ground Grid mesh used under substation ground consist of horizontal conductors connected with vertical rods. The function of mesh is to dissipate extremely high current generated in any scenario related to fault. In this regard, firstly 500KV substation is chosen for analysis of protection scheme with focus especially on Ground Grid mesh. The analysis of mesh is carried out using both IEEE 80-2000 and Finite Element Methods for the evaluation of important ground grid mesh parameters. A Software is used for analysis i.e. ETAP -12 having more enhanced features than previous versions. The problems regarding existing functioning ground grid mesh are brought to light in one case study. In second Case study, the remedies for the rectification of mesh are provided. In third, case study a new ground mesh is designed for the existing substation considering new methodologies and latest analysis techniques. In fourth case study, a new ground mesh for Ultra High Voltage Substation is designed for 750KV substation. Finally, a inter comparison is done between mesh designed using IEEE 80-2000 and FEM methods to effectively establish the efficiency and effectiveness of each method by each Case study. A recommendation is given regarding the best method to be used for the future designing of ground grid mesh of all AIS substations.

Application of On-Line Ultrasonic and UHF Partial Discharge Detection in 1000kV GIS

This paper introduces the detecting principle、range of application and interferencerejection of Ultrasonic And UHF Partial Discharge Detection In GIS(Gas Insulated Switchgear).In view of the advantages and disadvantages of ultrasonic and UHF detection,this paper proposesa quick joint detection method, which uses UHF (Ultra High Frequency) method to online detectthe suspected discharge range in real time, adopts ultrasonic method to determine the specificdischarge points, finally through a concrete instance in a 1000KV UHV(Ultra High Voltage)Substation verified the feasibility of the joint detection method.

Influence of Potential Difference Within Large Grounding Grid on Fault Current Division Factor

The fault current division factor describes the shunting ability of the ground wires of the transmission lines or that of the neutral conductors connected to a substation ground. As the power system capacity grows rapidly in China, more substations with higher voltage classes are constructed, and the grounding grid is becoming larger and larger in area. As a result, the potential difference within the grounding grid may become more obvious and, hence, its influence on the fault current division factor cannot be ignored. This paper proposes a multiport circuit model for grounding grids with multiple grounding points to take into account the potential difference. With the help of commercially available tools for power system simulation, the model can be easily used to calculate the fault current distribution and the fault current division factor. The main factors that affect the potential difference within the grounding grid as well as the fault current division factor are analyzed. As an application, the fault current division factor of a 1000-kV ultra-high voltage substation is further calculated.

Impacts of UHV on Short Circuit Currents in China's Central 500kV Grid and Its Countermeasures

Ultra-high voltage (UHV) projects are making power system growing lager and resulting in sharp increase of short circuit currents in some area especially in the vicinity of UHV access points. The paper presented the damage of short circuit current increases and common methods to limit fault current. Taking the construction and development of UHV grid in a province of central China as background, the over short circuit currents in 500kV Grid within UHV were showed and several countermeasures including choosing proper UHV access scheme, implementing UHV substation lower voltage bus partition running, installing reactors, optimizing power grid network based on UHV connection point were proposed and then verified by PSASP simulation. The results show those measures are useful to reduce the short circuit current to a reasonable level.

Measurement of Electric Fields Around a 1000-kV UHV Substation

This paper investigates the power frequency electric fields around a 1000-kV ultra-high voltage (UHV) substation which is located in Jingmen, China. Detailed field measurements around this substation as well as numerical results in a 1000-kV area are provided. Most values observed are below the reference level indicated in the relevant national design guideline. Therefore, we can conclude that the power frequency electric fields around this UHV substation are safer for working personnel.

Power-Frequency Electric Field Calculation of Ultra-High Voltage Substation

To ensure the normal operation, calculation of electric field in ultra-high voltage substation is particularly important. A line model is proposed to simplify current model and improve computational efficiency. Combining this model with boundary element method, this article described a method to calculate the electric field at the vicinity of complex equipment of ultra-high voltage substation. An actual substation environment is also simulated, with detailed analysis of simulation results, proposed model and method are verified as valid and effective.

The Influence on Lightning Invasion Waves from UHV Substation Bus Arresters

Ultra high voltage (UHV) AC transmission is a trend in the modern transmission technology development, the UHV substation is the center in the power system. The lightning invasion waves pose a serious threat to the safety of the substation, therefore it is very important to improve the features of the substation anti-lightning. The arresters of UHV substation bus sides, the role of restraining the lighting invasion waves on main transformer have been researched. Applying ATP-EMTP, a simulation model of the lightning over-voltage invasion substation along the double-circuit self-reliance transmission line was built. Whether and how the number of arresters influences the lightning waves were analyzed comparatively. The maximum amplitude of the lightning current can be reduced when the arresters installed in the bus side, and the protective effect of the transformer can be improved effectively.

Investigation of occupational exposure to power frequency electromagnetic fields in workers of power grid

To measure and assess the levels of occupational exposure to power frequency electromagnetic fields in workers of power grid. PMM8053 electromagnetic fields measuring system with EHP-50 probe was used to measure the levels of electromagnetic fields at working place. Personal dosimeters (EMDEX LITE) were utilized to measure the individual exposure levels of power frequency magnetic field. The results were evaluated with the limitation criteria of GBZ2.2 and ICNIRP. In the 500 kV ultra high voltage substation, the intensity at 90% measure points of power electric field was more than 5 kV/m. The magnetic field intensity in the areas nearby reactors and capacitors was often higher than 100 µT, even several hundreds µT. The mean daily exposure levels of workers in power grid were between 0.04 and 5.0 µT, and the exposure levels of 70% workers were higher than 0.4 µT. In the areas of ultra high voltage and nearby the reactors and capacitors are the key control points for occupational health in power grid. There is acute health risk of workers exposed to high accumulative exposure levels.

Potential calculation and grading ring design for ceramic insulators in 1000 kV UHV substations

The electromagnetic environment of insulators in substations is more complicated than that in transmission lines, this difference gets more prominent as the system voltage increases. Considering all the influencing factors, this paper presents the calculation results of the potential and electric field distribution of the ceramic insulator strings in 1000 kV ultra-high voltage (UHV) substations, using a three-dimensional (3-D) finiteelement method (FEM) software. Factors that affect the potential distribution such as grading ring, jumper, string structure, mounting location and drop conductors have been analyzed. The structural parameters of grading ring were optimized. A use of double ring was proposed for terminal tension insulators. A true-type test was carried out to verify the reliability of the FEM calculation method and results. The optimized grading ring configuration was successfully applied on the 1000 kV UHV pilot project in China and it was proved very effective by field observations with an ultraviolet camera.

Important technologies applied for UHV AC substations in Japan

SUMMARYThe Tokyo Electric Power Company, Inc (TEPCO) plans 1100 kV power network system in Japan in order to meet the steady increasing demand for electricity. Four‐hundred kilometer 1100‐kV‐designed double‐circuit transmission lines have already been constructed and are now operated at 550 kV. 1100‐kV substation equipment has also been developed.To realize the best design technically and economically throughout the transmission line and the substation, important technical solutions for network problems peculiar to the ultra high voltage (UHV) system have been introduced. They include insulation coordination, overvoltage countermeasures, and fast multi‐phase reclosing systems with high speed earthing switches (HSESs). The overvoltage countermeasures are realized by high performance metal oxide surge arresters (MOSAs), gas circuit breakers (GCBs) with closing/opening resistor, and disconnectors (DSs) with resistor. These sophisticated technologies realize highly reliable and economical UHV substations and transmission lines.This paper describes important, fundamental, and specific requirements for UHV substations such as their compactness, economical view, and environmental harmony. There are many technical/economical aspects to be considered on UHV substation and based on those considerations: (a) compactness, (b) less impacts to the environment, (c) optimizing cost, could be fulfilled.This paper also describes the technologies addressed to UHV class components such as the introduction of new concept “on‐site assembly transformer,” VFTO reduction countermeasure and the necessity of full‐scale seismic qualification test. Copyright © 2011 John Wiley & Sons, Ltd.

Lightning Surge Overvoltages at Substations Due to Backflashover With Assumed Lightning Current Waveforms Based on Observations

Recent lightning current observations have suggested that a front duration of 1.7 s is more appropriate than the conventional 1.0 s for the lightning protection design of ultra-high voltage (UHV) systems in Japan. This study examined overvoltages at gas-insulated subsystems (GIS) and transformers in a UHV (the rated voltage of 1100 kV) substation during backflashovers, with the front duration of lightning stroke current waveforms taken as a parameter. The dependence of overvoltages on the front duration of the lightning stroke current is significant at GIS and relatively small at the transformer. Generally speaking, the shorter the front duration is, the higher the voltage will be. The transformer capacitance, ranging from 0 to 1000 pF, equivalently increases the distance to the surge arrester, and a voltage increase was observed at the transformer terminal. However, the steepness of the intruding surge waveform is reduced and the voltage increase suppressed at 1000 pF and over. The effect of overvoltages on insulation design was also evaluated and the results thereof indicated the possibility of reducing the lighting impulse withstand voltage.

Suitable configuration of switchgear for UHV AC substation and its environmental consideration

AbstractThis paper describes some environmental considerations, a suitable configuration of switchgear, and their site test considerations for ultra‐high‐voltage (UHV) alternating current (AC) substations based on experiences gained in planning, development, and field tests conducted in China and Japan.Due to high voltage levels, the size and weight of UHV equipment is invariably greater than normal EHV equipment, which has impact on the UHV substation design for environment. On the other hand, it is also important to reduce the size of the UHV equipment so that the cost of the UHV substation is not increased drastically. Reduction of the installtion space and improvement of the environmental and seismic qualification may be achieved by selecting full GIS and MTS (hybrid GIS) solutions. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Technical requirements for UHV substation equipment

AbstractCIGRE Study Committee A3 established WG A3.22 ‘Technical requirements for substation equipment exceeding 800 kV’ to review the state‐of‐the‐art technical specifications for substation equipment exceeding 800kV in accordance with a request from IEC SC 17A. WG A3.22 conducted the initial surveys and submitted the first Technical Brochure on technical specifications for substation equipment such as gas circuit breaker (GCB), disconnecting switches (DS), earthing switches (ES), high‐speed grounding switches (HSGS) and metal oxide surge arrester (MOSA) applied to 800 kV and 1100/1200 kV networks. The investigations include the insulation level, first‐pole‐to‐clear factor, DC time constants, transient recovery voltage (TRV), line surge impedance and secondary arc extinction time. WG A3.22 will provide the technical background of all aspects of the available specifications with the intention of identifying the best practice for ultra high voltage (UHV) transmission systems. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Development of 1200-kV Compressed-Gas-Insulated Transmission and Substation Equipment in the United States

Major research and development (R&D) programs for the development of sulfur hexafluoride (SF6) compressed-gas-insulated (CGI) equipment for ultrahigh-voltage (UHV) application at 1100-1200 kV have been under way independently in both the United States and Japan. The CGI transmission and substation equipment under study and development in these countries has included the surge arrester, circuit breaker, CGI transmission bus, disconnect and ground switches, and an air-SF6 termination. The U.S. CGI program has also included development of a power transformer, shunt reactor, voltageand current-sensing instrumentation, and a line trap, all for 1200-kV application. This paper presents the overall status of development of CGI substation equipment for UHV application in the United States. It describes the major CGI components developed, highlights their key design aspects, indicates the present status of development and testing, and addresses the work remaining to establish final design concepts. The paper also includes 23 references, a number of which have not been widely distributed or included in any of the recently published bibliographies of UHV substation equipment.

Development of 1200-kV Compressed-Gas-Insulated Transmission and Substation Equipment in the United States

Major research and development (R&D) programs for the development of sulfur hexafluoride (SF6) compressed-gas-insulated (CGI) equipment for ultrahigh-voltage (UHV) application at 1100-1200 kV have been under way independently in both the United States and Japan. The CGI transmission and substation equipment under study and development in these countries has included the surge arrester, circuit breaker, CGI transmission bus, disconnect and ground switches, and an air-SF6 termination. The U.S. CGI program has also included development of a power transformer, shunt reactor, voltageand current-sensing instrumentation, and a line trap, all for 1200-kV application. This paper presents the overall status of development of CGI substation equipment for UHV application in the United States. It describes the major CGI components developed, highlights their key design aspects, indicates the present status of development and testing, and addresses the work remaining to establish final design concepts. The paper also includes 23 references, a number of which have not been widely distributed or included in any of the recently published bibliographies of UHV substation equipment.

Testing Facilities for Developing UHV Equipments

The testing facilities of UHV (Ultra High Voltage) laboratory are described in this paper. The voltage rating of testing facilities and dimensions of the laboratory for developing UHV substation equipments, especially transformers and gas insulated equipments, are discussed on the basis of research and development experiencies of UHV equipment manufacture.