Ultra-high Voltage Substation Research Articles

Response and fragility of long-span truss structures in ultra-high voltage substation subjected to near-fault pulse-like and far-field ground motions

This study numerically investigates the seismic responses, bearing capacities, and fragilities of long-span truss structures (LSTSs) in ultra-high voltage substations subjected to near-fault pulse-like (NFP) and far-field (FF) earthquakes. The finite element model established in ABAQUS software considers the tower-line dynamic coupling effect, and it is excited by 20 NFP and 20 FF earthquakes. The seismic responses and bearing capacities are analyzed to generate the design recommendations for LSTS. According to five performance levels, the fragility curves are developed by performing a fragility method based on intensity measure. The peak displacement, acceleration amplification factor, bearing capacity, and fragility results significantly indicate that the seismic risk of LSTS under FF earthquakes is much higher than that under NFP earthquakes. Moreover, there are three typical failure modes (i.e., I – III) of LSTS under strong earthquakes. Mode I is a brittle failure while mode III is a ductile failure. Furthermore, the bearing capacity basically obeys a lognormal distribution, and the distributions subjected to NFP and FF ground motions are very close.

Binary Tree Algorithm-based Fault Location Method for Tripping in Ultra-high Voltage Substations

The current conventional method for fault location in substations involves using a mathematical model to convert the problem into a parameter identification problem. However, this approach often yields poor results due to the lack of characterization of fault features. To address this, a new fault location method for tripping faults in Extra High Voltage (EHV) substations is proposed. This method utilizes a binary tree algorithm to construct a fault binary tree and encode the nodes to accurately characterize the fault characteristics. Using this information, a fault location model is developed. Experimental verification confirms the effectiveness of the proposed method, with analysis showing its ability to successfully locate tripping faults in EHV substations with high convergence and superior accuracy.

Autonomous Inspection Method of UHV Substation Robot Based on Deep Learning in Cloud Computing Environment

Aiming at the problem that substation robots cannot automatically find and analyze the fault equipment and carry out patrol inspection, a method of autonomous patrol inspection for ultra-high voltage (UHV) substation robots based on deep learning in cloud computing environment is proposed. Firstly, based on the cloud computing environment, an autonomous patrol system is designed to upload the data obtained by robots to the cloud platform for processing, so as to complete data analysis quickly and with high quality. Then, the deep learning algorithm (DL) is used for fault diagnosis, and the FP-growth algorithm is combined to realize the association mining of fault data, so as to clarify the patrol order of fault-related nodes. Finally, the improved ant colony algorithm (IAC) is used to optimize the path of the robot to complete the reliable inspection of the substation in the shortest time. Based on the selected UHV substation, the experimental analysis of the proposed method shows that the fault diagnosis error rate and time are about 4.3% and 14.2[Formula: see text]s, respectively, and the patrol path is only 180.351[Formula: see text]m, and the patrol time is 19.708[Formula: see text]s, which can realize the optimal patrol of the robot.

Structural performance of long-span truss structures in ultrahigh voltage substations under multi-hazard action of earthquake and icing

The transmission line is a vulnerable lifeline system when subjected to extreme loads, such as earthquakes and heavy ice loads. This study numerically investigates the structural performance of ultrahigh voltage long-span truss structures (LSTSs) under the multi-hazard action of earthquake and icing to mitigate disaster losses. A typical LSTS-3-tower-3-line system was selected as an analytical model. Its finite element model was established using a simplified spring model to simulate an ice-covered transmission conductor; it was excited by seven multi-component far-field ground motions. The natural vibration characteristics, structural responses, earthquake failure modes, and bearing capacities of LSTS affected by icing were comprehensively analyzed. The results showed that the seismic response of LSTS decreased, and its total response (induced by the tension of the conductor, ice load, and earthquake) increased with an increase in ice thickness. In addition, icing severely reduced the bearing capacity of LSTS with average reductions of 11.7% and 39.1% when the ice thicknesses were 15 and 50 mm, respectively. Moreover, the influence mechanism of icing on LSTS seismic responses and the failure mechanism of LSTS under the multi-hazard action of earthquake and icing were revealed. Specifically, the failure modes of LSTS, namely flexural (mode 1), mixed (mode 2), and shear failures (mode 3), were determined by the ice condition. Finally, prediction models for the structural responses and bearing capacity of LSTS were developed to facilitate the design of electrical equipment and LSTS and improve design efficiency.

Linear Quadratic Gaussian Control for Wireless Communication Reliability for a Mobile Monitoring Robot in a UHV Power Substation

In ultrahigh-voltage (UHV) power substations, mobile robots equipped with sensors and cameras have been adopted for patrolling and inspecting the operational status of devices. The robots connect with a management system via wireless communication. However, environmental factors, such as distance to the wireless access point, surrounding structures, or electromagnetic interference, affect the reliability of wireless communication and, therefore, impact robot operation. To meet the reliability requirement specified by the smart grid communication standard, we propose a linear quadratic Gaussian (LQG) control on the wireless link to ensure its reliability. First, a state-space model of wireless links is constructed based on a path loss model, in which the signal-to-interference-plus-noise ratio (SNIR) is chosen as the state of the system. Then, an improved Kalman filter and a linear quadratic regulator control are adopted to estimate the state and obtain the optimal transmitting power, respectively. In addition, the confidence interval of the SNIR is estimated to compensate for the filtered random factors on the SNIR. Finally, to evaluate the proposed LQG controller, we compare it with state-of-the-art methods through simulation and verify its effectiveness in a real-world UHV substation.

Directionality effect in the seismic fragility of long-span supporting frames in ultrahigh-voltage substation

A 1000 kV outgoing line frame (OLF1000), which is an important and long-span supporting frame in ultrahigh-voltage substations (UHVSs), is prone to damage or collapse under strong earthquakes, resulting in serious power system outage. This study numerically investigates the seismic fragility of OLF1000, which has complex and multiple interactions with transmission towers and lines, subjected to earthquakes with multiple angles of seismic incidence (multi-ASI). A new multi-ASI seismic fragility analysis method (N-MASI-SFAM) considering the orientation layout of the structure and strike of the fault zone is proposed; it fully reflects record-to-record, structure-to-structure, and direction-to-direction uncertainties. The samples of structure-record-ASI pairs and structure-record pairs are generated using Latin hypercube sampling to develop probabilistic seismic capacity models and probabilistic seismic demand models for OLF1000. In addition, fragility planes of OLF1000 for different limit states are generated by performing the N-MASI-SFAM, which provide suggestions for the orientation layout of OLF1000-tower-line coupling system outside the UHVSs. Further, the results obtained by N-MASI-SFAM and seismic fragility analysis method based on the traditional excitation method (TEM-SFAM) are compared, and they demonstrate that the TEM-SFAM cannot identify the maximum seismic risk of the OLF1000; the guarantee rates of TEM-SFAM are 51% and 45% under far-field and near-fault pulse-like earthquakes, respectively, indicating that its reliability in the seismic fragility analysis of OLF1000 is very low. Finally, a seismic risk assessment method based on the epicenter position is proposed, and the seismic risk of built engineering structures is quantitatively evaluated.

Cause Analysis of Abnormal Condition in Partial Discharge Test of 220kV GIS

With the continuous development and construction of the power grid system, 220kV GIS equipment has been widely used in ultra-high voltage substations. Before leaving the factory, GIS equipment needs to be tested for lightning impact, partial discharge, etc. to check whether there are problems in the manufacturing, assembly and other links of the equipment. This paper analyzes a 220kV GIS when the partial discharge test (factory test) occurs when the partial discharge exceeds the standard. By using the directional elimination method, the equipment fault range is determined, and the fault structure is disassembled. Analysis, X-ray flaw detection results found that the insulation There are tiny bubbles in the base, indicating that the assembly workshop has problems of technical control or lack of cleanliness. At the same time, after the insulation base has been subjected to multiple lightning strikes, due to the cumulative effect, the equipment has exceeded the standard in the partial discharge test. Finally, through the analysis of the cause of the failure, the targeted rectification measures are put forward to improve the technical management and control level of the assembly workshop.

A MultiModal Detection Method for UHV Substation Faults Based on Robot Inspection and Deep Learning

Aiming at the problem of multi-modal fault detection of different equipment in ultrahigh voltage (UHV) substations, a method for based on robot inspection and deep learning is proposed. First, the inspection robot is used to collect the image data of different devices in the station and the source data is preprocessed by standard image augmentation and image aliasing augmentation. Then, the HSV color space model based on saliency area detection is used to extract equipment defect areas, which improves the accuracy of defect image classification. Finally, the traditional YOLOv3 network is improved by combining the residual network and the K-means clustering algorithm, and the detailed flow of the corresponding detection method is proposed. The proposed detection method and the other three methods were compared and analyzed under the same conditions through simulation experiments. The results show that the detection accuracy and recall rate of the method proposed in this study are the largest, which are 95.9% and 91.3%, respectively. The average detection accuracy under multiple intersection ratio thresholds is also the highest, and the performance is better than the other three comparison algorithms.

A broadband optical fiber transmission-based time domain measurement system for nanosecond-level transient electric field.

A novel nanosecond transient electric field (E-field) measurement system is developed in this paper to measure the E-field pulse caused by the operation of the high-voltage switch (switching E-field pulse) in the substation. An electrically small rod antenna is used as the receiving antenna and is matched by the operational amplifier with high input impedance to achieve broadband frequency response and stable working performance. A broadband analogoptical fiber transmission system is further designed based on the high-frequency circuit model of the electronic components. Unlike the traditional frequency domain E-field measurement methods, the developed measurement system can directly output the time domain waveform of the switching E-field pulse. It also has the advantages of adjustable sensitivity, portability, and anti-electromagnetic interference. The calibrated measurement bandwidth ranges from 200Hz to 680MHz. Furthermore, the switching E-field pulse in an ultra-high voltage substation is measured and analyzed to verify the effectiveness of the fabricated measurement system.

Investigation of GIS enclosure circulating current in UHV substation with hybrid reactive power compensation

There are typically large circulating current losses when such a current is produced in a gas-insulated switchgear (GIS). An excessive circulating current also causes a heating phenomenon and insulation aging, as well as hidden dangers and adverse effects on the normal operations of power systems. In addition, the installation of hybrid reactive power compensation (HRPC) may increase the complexity of the circulating current. Thus, a detailed investigation of GIS enclosure circulating current on an ultra-high-voltage (UHV) substation with HRPC is imperative. Here, the mechanism of the enclosure circulating current is thoroughly discussed, and models of the GIS busbar, and enclosure are established based on the partial element equivalent circuit (PEEC) method. Combined with HRPC equivalent circuit model, the equivalent calculation model for the GIS enclosure circulating current with HRPC equipment is established. The influence of the structural parameters on the circulating current, such as the inlet capacitance of the stepped controlled shunt reactor (SCSR), enclosure radius, enclosure height from the earth, and distance between earthing points, are considered in terms of the simulation model as built using transient simulation software. The factors that influence the enclosure circulating current and their associated rules are used to develop suppression measures.

Effect of incident directionality on seismic responses and bearing capacity of OLF1000

As a typical and important supporting structure in ultra-high voltage substations, the 1000 kV outgoing line frame (OLF1000) bears the role of supporting electrical equipment and long-span transmission lines. The interaction between transmission towers, lines and OLF1000 makes it exhibit asymmetric stress and deformation states in normal use. For this kind of irregular coupling system (i.e., OLF1000-tower-line coupling system), the seismic incident directionality effect (SIDE) with high uncertainty may be a disadvantage. To investigate the effect of incident directionality on the seismic responses and ultimate bearing capacity of the OLF1000, and provide a reference for its seismic design, this study numerically evaluated the seismic responses of the OLF1000 by considering the dynamic coupling effect between a tower-line system and OLF1000 (DCE-TLS-OLF1000) under 40 multi-direction ground motions. According to our results, the seismic incident directionality significantly affects seismic responses, participation of vibration modes, plastic development law, failure modes, and ultimate bearing capacity of the OLF1000. In contrast, traditional approaches (i.e., 0° directional excitations) cannot ensure the seismic safety of the OLF1000 in arbitrary incident direction as the guarantee rate is less than 50%. Furthermore, the direction-to-direction (DTD) and record-to-record (RTR) uncertainties were theoretically derived; moreover, 95% guarantee models based on the two uncertainties and prediction models by considering the DCE-TLS-OLF1000 and SIDE were proposed to ensure the seismic safety of the OLF1000 under excitations exhibiting arbitrary incident direction and provide a helpful seismic design method for designers.

Nanocrystalline based Mitigation Technique for Very Fast Transient over Voltages in Gas Insulated Substations

: in gas insulated substations, issue of very fast transient over voltages is very familiar problem because of its effects on live ultra-high voltage equipment. During switching events of disconnectors and circuit breakers prestrikes and restrikes occur due to which voltage transients propagate through gas insulated switchgear. Reflection retraction of these transients increases voltage magnitude and generates very high frequency oscillations. Mitigation or suppression of these voltage transients is important to protect equipment and their dielectric strength and insulation. Due to very high frequency stress, they wield on the apparatus and their magnitude (up to 3.5pu), they create an important problem in the design of ultra-high voltage Gas Insulated Substations. In this paper nanocrystalline based mitigation technique for VFTOs is presented. Nanocrystalline rings can be placed around inner conductor of GIS switchgear. This method of mitigation technique is investigated with four ultra-high voltage substations simulation test setup. Simulation results are presented in MATLAB/SIMULINK

Application and Design of Inspection Robot System Based on Multi-parameter Hierarchical Inspection of UHV Substation

In this paper, a new substation inspection robot system is introduced, to meet the application requirements of multi-parameter full-station automatic hierarchical inspection of the insulation status of power equipment in UHV ( Ultra-High Voltage ) substation. The system is designed to control the inspection of substation robots, including identifying the number of meters on the cabinet, measuring partial discharge, measuring temperature and humidity and so on . The system is divided into two parts. One part runs in the robot body ,which is called the body control system , and it contains web server, robot ground control system and database. The other part runs on external industrial computer, which is called station control service system. The function of the body control system is more specific, mainly for controlling its own motor driver, in order to complete its own motion. The station control service system achieves important logic control, including configuring inspection plan, visual recognition, robot walking path planning, and writing inspection results into the database.

Electromagnetic Interference of Partial Discharge in Ultra High Voltage Substation

In order to block the electromagnetic interference source of partial discharge in UHV substation and improve the actual power generation efficiency, in this study, the experimental method of partial discharge in ultra high voltage (UHV) substation is first introduced. Secondly, the types of PD EMI are described in detail. Finally, the principle of blocking electromagnetic source is introduced and the blocking measures of each electromagnetic interference source are analyzed in detail. The results show that the actual equipment test of UHV substation is complex, and there are many factors affecting the test accuracy. Therefore, the field test of UHV substation is the most complex and precise test item at present. The time of noise interference of pulse signal is short and the distribution of signal is wide. This kind of interference is also repetitive, but the orientation of the display is relatively stable, and the waveform also has certain rules. Thyristors use relatively weak current to grasp relatively strong current, and the process is very short. At the same time, the period of application is very long and the stability is very strong. Recursive filters are used. The workload of calculation is greatly reduced, but there are many disadvantages. In practical UHV substation, the sources of PD are closely arranged, so it is suitable to use recursive filter. After using wavelet transform to disperse EMI sources, it can block the sources in different regions.

Analysis of Monitoring System of Partial Discharge Electromagnetic Interference in Ultra-high Voltage Substation Environment

In order to solve the existing noise reduction measures in substation is not comprehensive, and the lack of substation on-site interference measures, the monitoring system of partial discharge electromagnetic interference in ultrahigh voltage (UHV) substation environment is studied. First of all, the ultrahigh frequency (UFH) interference information in substation is analyzed. Then signal suppression measures are adopted according to the interference signals in the substation. Finally, the UFH monitoring system is established based on the random pulse interference signal elimination method based on fuzzy clustering analysis. The results show that the electromagnetic interference monitoring system of partial discharge in the environment of UHV substation studied in this research can significantly improve the detection and localization of partial discharge, and can have more choices in determining the frequency band, which is helpful to improve the accuracy of time delay measurement so as to improve the accuracy of localization. The result of this research provides a good guidance for solving electromagnetic interference problems in UHV substations in China.

Analysis of wind-induced response of down lead transmission line-connection fitting systems in ultrahigh-voltage substations

Based on a certain 1,000-kV ultrahigh-voltage substation, a finite element model is established for the down lead transmission line (DLTL)-connection fitting system using the ABAQUS software. The mechanical properties of the bushing terminal and the connection fitting under equivalent static loads corresponding to various wind speeds are analyzed. The analytical results are compared with experimental results to verify the correctness of the model. On this basis, the effects of the connection fitting type, the DLTL system type and the suspension location of the DLTL system on the mechanical properties of the bushing terminal are discussed. The dynamic response of the DLTL-connection fitting system to various wind speeds is investigated through simulation. The results are as follows. From a mechanical perspective, the bushing terminal with an “I”-shaped connection fitting is notably superior to that with a “U”-shaped connection fitting; however, the “I”-shaped connection fitting system must be strengthened. Compared to the “λ”-shaped DLTL system that is currently and commonly used, the “π”-shaped DLTL system is more reasonable, but the offset of its suspension point must be controlled (0–3 m is recommended). When considering the vibration caused by pulsating winds, the maximum stress on the bushing terminal increases significantly, and premature failure is risked. In engineering design, a dynamic amplification factor no less than 2.0 is recommended for use to consider this adverse effect.

Low voltage and large current DC superconducting power cable designs for 10 km to 100km transmission line using experimental data of Ishikari project

Main merit of the DC superconducting power transmission line is low loss even in low voltage power transmission. It should be realized when the transmission length is long. Therefore, we discuss and analyse an aspect of thermo-hydrodynamic performance of Ishikari project, and show one design of 100 km transmission line. At the same time, we also discuss the cable design and the rated voltage of the cable is lower than 50 kV for 500MW transmission. This is one of the most important advantages to make the DC power grid because we can omit an ultra-high voltage substation, the primary and the secondary substations and we can connect the power stations to the distribution stations directly. Finally, we may be able to reduce the construction and operation costs of the power grid.

Diagnostic analysis and protective measures of transient ground potential rise in a 1000 kv UHV substation

With the continuous expansion of power grid capacity and growth of voltage levels, the transient ground potential rise (GPR) caused by the switchgear operation has become great threaten to the safety of the grid. In the startup operation of 500 kV part of Taizhou 1000 kV ultra-high voltage (UHV) substation, the electromagnetic lock installed in the switchgear filed was broken by the GPR in case of switchgear operation. There are two possible transmission paths of the GPR, one is the ground copper bar connecting the ground and the other is the control cable connecting the control cabinet and electromagnetic lock. In order to find out the transmission path of the electromagnetic disturbance, the experiment is carried out to distinguish the two possible paths. The waveform of the GPR in case of switchgear operation from different measuring points are recorded and compared, the results are analysed by comparing the signal characteristics and the transmission path is eventually diagnosed. Finally, the protective measures are proposed by wrapping the control wires with the conductive metal cube to reduce the influences of GPR. The outcomes in the study provide beneficial methods to analyse the GPR disturbance and positive guidance for the protection of locally installed equipment.

Characteristics of very fast transient currents in ultra high-voltage power system with Hybrid reactive power compensation

Hybrid reactive power compensation (HRPC) consists of a stepped controlled shunt reactor (SCSR) and a series compensation (SC), which will find applications in future ultra high-voltage (UHV) power grids to resolve the problems due to the frequent change of reactive power and bulk power transmission. However, very fast transient currents (VFTCs) are inevitably generated during switching, which would lead to insulation breakdown. In the present work, we first develop the equivalent model for HRPC, following which we deduce the expression of VFTCs in the time domain by using an inverse Laplace transform. The analysis indicates that the amplitude and frequency of VFTCs are both affected by the capacitance of the SCSR and of the SC, as well as the line length, stray capacitance, etc. The oscillating frequency, peak, and amplitude of the main frequency of the VFTCs in the substation can be modified by adjusting the silicon-controlled rectifiers in the SCSR when the disconnecting switch in gas-insulated switchgear is switched on. When the disconnecting switch in the SC is switched on, the VFTC oscillation frequency in SCSR decreases with increasing stray capacitance of SC, but the frequency and peak of the VFTC remains quite large. Increasing the line length between the SC and the SCSR suppresses the VFTC in UHV power systems. These results lay the foundation for developing HRPC methods to suppress VFTCs in UHV substations.

Compact system for onsite calibration of 1000 kV voltage transformers

This study describes the development and evaluation of a compact system for onsite calibration of 1000 kV voltage transformers in ultra-high-voltage (UHV) AC power transmission projects. The proposed compact system consists of a 1000 kV electromagnetic voltage transformer as a standard, a high-voltage resonant power supply, and a voltage transformer test set, which are assembled and mounted on a calibration truck. The developed system accuracy is 0.05% in ratio and 0.058 mrad in phase angle, respectively. Also, the total basic uncertainty is about ±0.028% and ±0.03 mrad under field conditions. The compact system can be automatically set up and taken down quickly on site requiring no substation cranes or utility operating crews. It has successfully undergone complete field tests and calibrated 63 1000 kV voltage transformers in total at 5 UHV substations. The feasibility of an automatic and efficient approach to calibrating UHV voltage transformers on site has been demonstrated.