Gas Insulated Switchgear Substation Research Articles

Development and Experimental Research of VFTO Measuring Sensor

Very fast transient overvoltage (VFTO) generated by an operating disconnector is one of the main reasons for electromagnetic disturbance in gas-insulated switchgear (GIS) substations. Generally, the amplitude of VFTO can be used as one of the references for the insulation design of GIS primary electric power equipment, so it is necessary to obtain its accurate amplitude. In this study, a new VFTO measuring sensor is developed and its measurement performance is demonstrated through hundreds of operations by a disconnector in a 220 kV GIS test circuit. The validation shows that the low cut-off frequency of the new VFTO measuring sensor has been greatly expanded to 0.01 mHz, which is improved by about 50% compared with the old sensor. The measurement accuracy of amplitude of VFTO micro-pulse improves greatly by about 80% compared with the old one. Thus, the new VFTO measuring sensor can fully meet the measurement needs of trapped charge voltage, power frequency voltage, and high-frequency transient voltage in VFTO waveform. It can be used to provide more accurate data support for insulation design of GIS primary power electric equipment in extra-high voltage (EHV) and ultra-high voltage (UHV) GIS substations.

Frequency domain algorithm in the whole process simulation from VFTO to its conducted disturbance via voltage transformer in GIS substations

Simulation of very fast transient over-voltage (VFTO) and its conducted disturbance via voltage transformer (VT) is significant in guiding the insulation design and electromagnetic compatibility of gas-insulated switchgear (GIS) substations. However, the commonly used time-domain algorithms are difficult to deal with the complex frequency-dependent parameters in the VFTO simulation, and might introduce instability of conducted disturbance due to an active circuit synthesis of the VT in some cases. In this paper, a frequency-domain algorithm is proposed, which calculates the VFTO in the frequency domain and then directly uses the VFTO frequency spectrum and the VT transfer function to calculate the conducted disturbance without circuit synthesis. The proposed algorithm has been applied in the simulation of VFTO and its disturbance in the 1000 kV Wuhu substation. The calculated and measured VFTO waveforms are in good agreement, verifying the accuracy of the algorithm. The transfer functions of the 1000 kV GIS VT are obtained by the impulse test method, and the conducted disturbances are also calculated with their severity and suppression method analyzed. The proposed frequency-domain algorithm covers the whole calculation process from VFTO to its conducted disturbance and has good engineering application potential in the simulation, with better convenience and stability.

Interference to the Secondary Cable Caused by a Very Fast Transient Overvoltage in a Gas-Insulated Switchgear Substation

When a very fast transient overvoltage (VFTO) propagates in a high-voltage bus, the capacitive voltage transformer (CVT) causes considerable interference on its secondary side, which will affect the normal operation of the secondary equipment. In this article, a CVT equivalent calculation circuit model was established, and the disturbance voltage of the secondary cable was deduced and calculated. Using electromagnetic transient simulation software, a simulation model of the secondary cable disturbance caused by the VFTO in a 500 kV gas-insulated switchgear (GIS) substation was established, the disturbance voltage at the end of the secondary cable was simulated and analyzed, and the effects of the length of the secondary cable and the grounding mode of the shield on the disturbance were studied. Combined anti-interference measures are also suggested, which use a spiral tube damping busbar, grounding at both ends of the shield using multistrand conductors and installing filter capacitors, all of which greatly reduce the amplitude and harmonic components of the disturbance voltage of the secondary cable.

Influences on very fast transients induced on secondary cables of GIS substation

In order to protect the secondary equipment of gas insulated switchgear (GIS) substation, study on the very fast transients (VFTs) induced on secondary cables during the disconnector operations of GIS is developed. Based on the custom-designed experiment platform which can produce VFTs, the influences on VFTs including are discussed and some protections are proposed. The regularity of the influences is given through simulation including the GIS size, the soil resistivity and the loads. The measures to protect secondary equipment from the VFTs are suggested.

Modularization of High Voltage Gas Insulated Substations

Many existing petrochemical facilities are replacing outmoded high voltage (HV) air insulated switchyards (AISs) with new gas insulated switchgear (GIS) substations. Modularization or prefabrication has strategic advantages over site-built substations. While medium voltage (MV) and low voltage (LV) substations have been modularized for many years, the HV GIS substation modularization has not caught up with the construction industry. The modularized HV GIS substations are significantly different compared to other electrical MV or LV substations. This article addresses the modern philosophy and approach to modularization and how the end-user can benefit, in terms of design flexibility, cost-effectiveness, reduced lead times, premium quality, and accelerated site execution in a new or an operating facility. It describes the technological developments, design concepts, quality assurance, and environmental impact in delivering complete solutions based on site conditions.

Ferroresonance Analysis of 500kV GIS Substation during Commissioning Process

Ferroresonance is an important factor affecting the security and stability operation of Gas Insulated Switchgear (GIS) substation. The nonlinearity of excitation characteristic of inductance elements with iron cores is the fundamental cause for exciting ferroresonance. A 500kV GIS substation is taken into account in this paper, a variety of operating conditions which may excite ferroresonance during the commissioning process are analyzed by a numerical simulation method. The comparison with actual commissioning results shows that ferroresonance will be excited by opening circuit breakers to switch off no-load buses during the commissioning process. For single-phase electromagnetic potential transformer (PT), ferroresonance can be effectively suppressed by connecting damping resistance in parallel with residual winding temporarily.

A measurement system for very fast transients in GIS power substations

In order to acquire the very fast transients during the disconnector operations in GIS (gas insulated switchgear, GIS) of power substation, a novel measurement system is developed and tested. By using the high speed digitizer as an alternative of the oscilloscope with other auxiliary device, the system is an effective approach to acquire the characteristics of the disturbance voltage of VFTs, including the frequency domain and the time domain features. Several kinds of experiments are carried out in the lab and GIS substation. The results show the good performance of this measurement system.

Research and Experiments on an External Miniaturized VFTO Measurement System.

Disconnect switch and circuit breakers operations in gas insulated switchgear (GIS) systems may produce very fast transient overvoltage (VFTO). Detecting VFTO is the first step for researchers to reduce the damage to other equipment of the substation caused by VFTO. Most of the existing sensors used for VFTO are generally bulky, complex to install, and require modification of the GIS structure. In this paper, a miniaturized measurement system that uses capacitive voltage divider and differentiating–integrating circuit is proposed. A special sensor structure and optimized differentiating–integrating circuit components arrangement were designed to increase the bandwidth of the measurement system. The frequency-domain, time-domain and voltage divide calibration experiment was performed, and a comparison experiment with an internal VFTO sensor was conducted. The measurement system was applied in the 500 kV GIS substation, and the VFTO measurement under specific conditions was carried out. The measured time domain and frequency domain waveforms conformed to the definition of standard VFTO according to IEC 60,071. It was found that the proposed measurement system meets VFTO measurement requirements and can be applied to actual VFTO measurements.

Study on Coupling of Very Fast Transients to Secondary Cable via a Test Platform

Electromagnetic disturbance can be induced on the secondary cables by very fast transients generated during switching operation in the gas-insulated switchgear (GIS) substation. Usually, the secondary equipment that is fixed on GIS pipe or placed in the local control cabinet is connected by the cables. Disturbance voltages coupling to the terminal ports of the cable may cause malfunction of the equipment. To study the coupling mechanism of the disturbances, some experiments are carried out based on a test platform established in the laboratory. Through comparing the data that come from the lab experiments, the measurement of some GIS substations, and the IEC61000-4-18 standard, respectively, it is illustrated that the parameters of the disturbance generated on this platform are consistent with those measured in GIS. Then, an equivalent circuit model with transmission line network is proposed and the simulated waveforms are agreed with the experimental results.

Simulation and Test Study on Very Fast Transient Overvoltage in 1000kV GIS Substation

Disconnector switching in gas insulated switchgear (GIS) generates very fast transient overvoltage (VFTO). VFTO may damage the insulation of GIS equipment. This paper studies the VFTO of a 1000kV GIS substation. The simulation models are obtained according to the configuration of GIS. Operation modes of disconnector were summarized. The characteristics of VFTO were obtained. During the system commissioning test of the substation, VFTO were measured during disconnector switching. Comparison was made between the test and simulation results. The simulation results were in agreement with the test results. The accuracy of the simulation model is verified. Simulation and test study shows that it is safe to do switching operation of disconnector in this GIS substation without damping resistor.

Transient Electromagnetic Disturbance Induced on the Ports of Intelligent Component of Electronic Instrument Transformer Due to Switching Operations in 500 kV GIS Substations

Switching operations in gas-insulated switchgear (GIS) substations generate transient electromagnetic fields in the GIS pipes. These fields leak out discontinuities of the GIS and induce electromagnetic disturbance voltages on the cables and ports of secondary circuits. In smart GIS substations, secondary devices especially, such as the intelligent component of electronic instrument transformer, are vulnerable to electromagnetic interference. In this paper, the disturbance voltages induced on the ports of intelligent component of electronic instrument transformer had been measured in three 500-kV GIS substations, respectively. The disturbance was generated either during disconnector (DS) switching operations or circuit breaker (CB) operations. Then, the time-domain and frequency-domain characteristics of the disturbance waveforms have been analyzed. The micro-pulses of disturbance voltages have been extracted from the raw data. The waveform parameters, including peak voltage, rise-time, dominated frequency, and duration, have been calculated by the statistical analysis. The comparison between disturbance during DS switching operations and that of CB operations has been made. Also, the differences and similarities of disturbances between the three GIS substations have been displayed. Furthermore, the differences between measured waveforms and the IEC 61000-4-18 immunity test standard waveform have been discussed.

GIS 부분방전 신호와 도착 시간차 분석을 통한 PD발생 위치 추적

This paper analyzes of PD occurrence position through an analysis of the arrival time difference between the GIS partial discharge signal. Because of GIS (Gas Insulated Switchgear) is a facility very important power equipment and as part of the equipment that make up the power system, the stabilization of the power industry, which accounted for 88.5% share of GIS substation in the form of a substation is an important equipment for power supply. In the situation where we are gradually expanding the need for preventive diagnosis in order to improve the efficiency of equipment management and failure prevention for Preventive diagnosis. In this paper as a method for extracting pre-defect of failure of GIS Apply the average value method of calculating the 5 times each using a pulse of the first time of the second pulse (△t) with an oscilloscope generation position PD(Partial Discharge). the results of GIS internal inspection, the partial discharge of the actual the position of the partial discharge was confirmed with an accuracy of about 82% of positions. Arrival time difference in the most effective manner if the partial discharge of GIS internal occurs by applying the averaging method and TOA(Time of arrival) method, the partial discharge occurs you through the measurement and analysis of PD signal occurs was confirmed in the experiment are presented and diagnostic methods location tracking.

Grounding System Transient Characteristics of Underground GIS Substations

The transient grounding impedance of a gas-insulated switchgear (GIS) substation was investigated through measurements on a commercial 300-kV underground substation. Based on the results, the macroscopic transient impedance of the grounding grid was clarified to be the inductance component and estimated at approximately 0.2 μ H. In the low-frequency region where the frequency is almost zero or so, the impedance is shown to be lower than the general concrete resistance value by one digit due to the complexity of grounding systems specific to underground substations. Hence, the simple model of the grounding grid can be expressed mainly by inductance. The detailed model was expressed by using a π-type equivalent circuit, where each circuit constant was calculated using the specific low resistivity of concrete. In addition, the validity of both models was confirmed by comparing the measurement results. The proposal models are applicable to the Electromagnetic Transients Program analysis on the surge phenomena within the GIS grounding system.

Study of Wireless Secondary Connections in Gas Insulated Switchgear

The paper first discusses the feasibility of the wireless communication in GIS (Gas Insulated Switchgear) substation. The signals inside GIS according to ISA100 standard are first classified and then a scheme to transmit some of the signals by ZigBee wireless is given. A demo example is shown to verify the proposed scheme. In the end, some future modifications and conclusion are discussed.

Transient response of a grounding system in an underground GIS substation

AbstractThe transient grounding impedance of a gas‐insulated switchgear (GIS) substation was investigated through measurements on a commercial 300‐kV underground substation. Using the results, the transient impedance of the grounding grid was investigated. The attenuation factor of the propagation line composed of the outer surface of the GIS tank and the concrete floor was also evaluated. The validity of EMTP analysis of surge phenomena in the GIS grounding system was confirmed. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 146(1): 70–77, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10214

Suppression of Fast Transient Overvoltage during Gas Disconnector Switching in GIS

This paper describes the suppression of the transient overvoltage caused by gas disconnector switching of a small capacitive charging current in a gas insulated switchgear substation. The overvoltage is suppressed by the insertion of a resistor with an appropriate value during the switching. A scale model gas disconnector with the resistor is developed. The overvoltage suppression effect and the charging current breaking capability of the gas disconnector are experimentally confirmed. A prototype ultra high voltage gas disconnector is trial manufactured and tested.