Switching Impulse Research Articles

On reachable set problem for impulse switched singular systems with mixed delays

AbstractThis paper focuses on the reachable set problem for impulse switched singular (ISS) systems with mixed time‐varying delays via the Lyapunov theory. To solve the state boundary of system, a real‐bounded lemma is developed by analyzing the impulse switching point under bounded disturbance input and initial function. Based on real‐bounded lemma and integral inequality technology, a sufficient condition for reachable set of ISS system is established in the form of linear matrix inequalities (LMIs) to ensure that the reachable state of system is limited to a closed bounded set. Simulation results are given to verify the validity of the obtained theoretical results for the reachable state criterion.

Multiple discharges before leader inception in long air gaps under positive switching impulses

Multiple discharges before leader inception in long air gaps under positive switching impulses

A machine learning‐based approach for dielectric strength prediction of long air gaps with engineering configurations

It is a long-term goal in external insulation studies to determine the discharge voltages of complicated engineering gaps by simulation methods. Based on the one-to-one correspondence between air gap structure and the static electric field (EF) distribution, this paper characterizes the transmission tower gap configuration by spatial EF features, which were used for machine learning to achieve switching impulse discharge voltage prediction. An interelectrode path and a conical zone between the energized sub-conductor and the crossarm or the tower window were considered as EF regions strongly associated with gap breakdown, where 73 parameters were extracted to construct a feature set. Taking 15 extra-high voltage (EHV) transmission tower gaps as training samples, with different gap distances and tower configurations, their EF features were input to a support vector machine (SVM) for model training to establish the relationships with discharge voltages. The trained SVM model was used to predict the impulse discharge voltages of 20 EHV and ultra-high voltage (UHV) transmission tower gaps. The prediction results with different feature dimensions and various sizes of conical zones were compared to the experimental values, which demonstrate similar variation trends and acceptable errors. This study contributes to realize insulation strength calculation of engineering gaps.

Breakdown Characteristics of a Long Air Gap Containing a Floating Conductor Under Positive Switching Impulse

Experiments on the breakdown characteristics of a long air gap containing a floating conductor under switching impulse are carried out to address issues in live-line work engineering. The effects of gap distance, floating conductor structure, wavefront time, and high altitude on breakdown voltage are investigated, respectively. The results show that a floating conductor with sharp protrusions reduces the breakdown voltage and produces the lowest breakdown voltage area (LBA). The maximum reduction rate of the breakdown voltage and the position of the LBA vary with the gap distance. The position of the LBA is also related to the floating conductor structure. The results indicate that different floating conductor structures with similar electric field distortions have a similar effect on the breakdown voltage. For the effect of wavefront time on breakdown characteristics, the results show that the breakdown voltage under switching impulse with a long wavefront time is higher than that under a standard switching impulse. For the effect of high altitude, the results show that the LBA at high altitude is different from that at low altitude, and the high-altitude breakdown voltage corrected using the International Electrotechnical Commission (IEC) altitude correction method is not exactly the same as the actual experimental results.

Asynchronous Nonfragile Guaranteed Cost Control for Impulsive Switched Fuzzy Systems With Quantizations and Its Applications

This article investigates the nonfragile guaranteed cost (GC) control problem of discrete-time impulsive switched Takagi–Sugeno (T–S) fuzzy systems with input quantization and asynchronous switching. The model-dependent dynamic quantizers are applied to obtain the quantized input signal. To deeply study the GC performance analysis and GC control problems in the presence of quantization, asynchronous switching, and impulses, a novel piecewise cost function containing the quantized input instead of normal input is applied in this article. By using the mode-dependent average dwell time approach and introducing a class of Lyapunov-like functions allowing to increase during the asynchronous period, new sufficient conditions are established to guarantee the asymptotical stability with the GC performance index for the impulsive switched T–S fuzzy systems with quantized control input and asynchronous switching. Then, new design conditions about the nonfragile GC controllers and dynamic quantizers of impulsive switched T–S fuzzy systems are obtained in the form of linear matrix inequalities. Finally, a numerical example and a practical example are provided.

Experimental Investigation of Discharge Path Selectivity of a Long Air Gap Containing a Floating Conductor

Live-line maintenance is an effective means to ensure the reliability of the power system. When linemen float between the high-voltage conductors and the ground potential towers, the discharge characteristics of air gaps are significantly affected. In this article, simplified experiments are carried out to simulate the linemen by a floating conductor. The discharge characteristics of air gaps when the floating conductor is in different positions are studied. An experimental platform with a long air gap containing a floating conductor is used to obtain the breakdown voltage and the discharge path of air gaps under a positive switching impulse. The experimental results show that the existence of a floating electrode affects the air gap breakdown voltage and the discharge path. When the transverse displacement is 80 cm, almost all the discharge paths directly connect the high voltage electrode and plane electrode. Furthermore, the influencing factors of discharge path and breakdown voltage are analyzed, and the fitting equations of breakdown voltage and discharge path probability considering spatial position coordinates are established. Finally, the easy breakdown region considering discharge path is proposed, which provides a theoretical reference for quantitative analysis of the path of linemen entering high potential safely, and to improve the working efficiency of live-line maintenance.

Stability of neutral stochastic delayed systems with switching and distributed-delay dependent impulses

This paper is devoted to discuss the exponential stability in mean square of neutral stochastic delayed systems (NSDDs) with switching and distributed-delay dependent impulses. By using multiple Lyapunov functions and average dwell time (ADT), we provide some sufficient conditions for the exponential stability in mean square for NSDDs with switching and distributed-delay dependent impulses. Compared with the existing related works, we consider not only the influences of switches and neutral type on the stability of NSDDs with switching and distributed-delay dependent impulses but also the influences of both the stable continuous dynamics case and the stable discrete dynamics case. Finally, we provide two examples to illustrate the effectiveness of the theory.

Surface Dielectric Characteristics of GFRP and PTFE in Cryogenic Environment Under the Switching Impulse Superimposed on DC Voltage

For insulation materials utilized in DC superconducting fault current limiter, surface discharge along the interface is more damaging to the insulation relative to penetration breakdown. Therefore, for the reliable and economical insulation design of DC superconducting fault current limiter, it is very important to investigate an insulation materials and study the surface dielectric characteristics. Additionally, DC superimposed switching impulse can cause critical stress to the insulation of DC superconducting fault current limiter and can potentially result in breakdown. Therefore, the insulation materials of DC superconducting fault current limiter must have sufficient surface distance to prevent surface discharge under DC superimposed switching impulse. In this paper, the surface breakdown tests were performed by applying DC superimposed switching impulse to glass fiber reinforced polymer (GFRP) and polytetrafluoroethylene (PTFE) specimen in cryogenic environment. Surface dielectric characteristics according to positive and negative polarities of DC and switching impulse were analyzed. In addition, the surface dielectric characteristics were analyzed by selecting the gap distance. From the experimental results, the surface dielectric strength of GFRP was higher than that of PTFE, but the difference in surface dielectric strength between GFRP and PTFE decreased as the gap distance increased. The surface breakdown voltage of PTFE was lowest at the superposition of positive DC and positive switching impulse. However, GFRP has the lowest surface breakdown voltage when negative DC superimposed positive switching impulse. Consequently, it is possible to design the optimal surface distance of solid insulation materials in DC superconducting current limiter by considering the superposition of DC and switching impulse polarity.

Fault diagnosis technologies for power transformers during the on‐site inductive oscillating switching impulse voltage withstand test

Although oscillating switching impulse (OSI) voltage is recommended for the transformer field test, the lack of corresponding fault diagnosis technologies limits its application in the field. In this study, the inductive OSI test technology and diagnostic methods are investigated. The front time and the oscillation frequency of the OSI are altered by changing the additional inductance, whereas the tail time is affected by both the front and tail resistance. The OSI voltage withstand test is carried out on a 110 kV three-phase double-winding transformer on site. Furthermore, transfer function (TF) analysis is used for the diagnosis of transformer insulation with high sensitivity during the OSI test. The fault winding is distinguished by comparing the change in the voltage TF and current TF at different voltage levels. The partial discharge (PD) detection method has the highest sensitivity, which realizes the early diagnosis of insulation faults. The insulation status of the windings is ascertained based on the number and amplitude of PDs. The test results prove that the inductive OSI voltage withstand test is easy to perform on site and can successfully diagnose the insulation faults of the transformer in more detail compared with other routine insulation tests.

The Usage of High Voltage Amplifiers to Set up Reference Calibrators for Combined and Impulse Voltages up to 1 kV

An approach to set up reference calibrators to generate combined voltages, using voltage amplifiers, has been demonstrated. Four high voltage amplifiers were tested and studied. Measurements and experiments have shown that this approach could be used to set up calibrators for combined voltages, at least up to 1 kV. The advantage is the flexibility to generate separate or combined wave shapes (combination of AC, DC, distorted shapes, double exponential impulses such as lightening and switching impulses). This method could be beneficial to the fields where impulses, combined or not with DC or AC voltages, need a reference calibrator to calibrate digitizers. This method, relatively cheaper and simple to develop, reaches high metrological performance. For example, for lightning impulses up to 900 V, the uncertainties are lower than 0.2 % for the peak voltage, 1 % for the front time and 0.5 % for the time to half value . The traceability to the international system of units can be ensured by characterizing the gain using a step response, followed by the convolution technique.

Design and Verification of a Calculable Composite Voltage Calibrator

Components used in the power grid need to be tested to verify they can withstand specified voltage stresses. Composite voltage test according to IEC 60060-1:2010 is a test method where impulse voltage is applied simultaneously with AC or DC voltage to the same terminal of the test object. To provide traceability to instruments used for composite voltage measurements, low-voltage calibrator based on combining existing calibrators was developed. The developed composite voltage calibrator can generate lightning and switching impulses together with DC and AC. The calibrator design is based on a series connection of a DC/AC calibrator and a calculable impulse voltage calibrator. Maximum impulse voltage peak is 330 V whereas the DC/AC voltage can be within 1000 V. Reference parameters for composite waveshape are calculated based on the applied voltage, charging voltage of the impulse calibrator, internal impedance of the impulse calibrator, and the input impedance of the device under calibration. The main uncertainty components of this composite voltage calibrator are the uncertainties related to the separate calibrators and the uncertainty of the load impedance needed for the parameter calculation.

Pushing the boundaries of inductive voltage transformer design

Designing inductive voltage transformers for the highest voltage levels (550 kV and above) is a true challenge indeed. The main reason for this is their complex internal R-L-C structure, including an insulating system which needs to be resistant to all types of overvoltages and consequent dielectric stress it can encounter during its lifetime. This is why it is necessary to verify behavior of such transformers during the design process, and under four sets of standard test overvoltage types; the Power Frequency Withstand Voltage (PFWV), the Lightning Impulse Withstand Voltage (LIWV, i.e. BIL), Chopped Impulse Withstand Voltage (CIWV) and the Switching Impulse Withstand Voltage (SIWV). The main idea of the paper is to demonstrate that by understanding the influence of crucial parameters of the appropriate equivalent diagram on the voltage distribution across the active part of the transformer, it is possible to define the overall design of inductive voltage transformers so that they can satisfy even the most rigorous insulation requirements, thus pushing the boundaries of design even further.

Input-to-State Stability Criteria of Discrete-Time Time-Varying Impulsive Switched Delayed Systems With Applications to Multi-Agent Systems

This paper considers weakly and strongly input-to-state stability (ISS) of a discrete-time time-varying delayed system with synchronous impulses and switches. By employing the uniformly asymptotically stable function and mode-dependent dwell time conditions, ISS criteria are derived using the Krasovskii and Razumikhin techniques. The time differences of the Krasovskii functionals or the Razumikhin functions can be mode-dependent and time-varying, which release constraints of some existing results. As subsequent results, we apply the derived ISS criteria to the multi-agent systems (MASs). Finally, two examples considering the quasi-consensus of MASs are given to verify the established results.

An Accurate Evaluation of Switching Impulse Voltages for High-Voltage Tests

For assessment of the insulation performance of high-voltage (HV) equipment installed in extra-high-voltage (EHV) systems, switching impulse voltage tests are performed in an HV testing laboratory. The waveform parameters of the switching impulse voltages are defined by peak voltage (Up), time to crest (Tp), and time to half (T2) according to IEC 60060-1. In this paper, a new, simplified, and accurate approach used for determination of the waveform parameters of the switching impulse voltages is presented. The formula used in the evaluation of Tp was derived from analytically simulated two-exponential waveforms, where Tp and T2 are in the ranges of 20 μs to 300 μs and 1000 μs to 4000 μs, respectively. The accuracy of the proposed approach was validated by the waveforms collected from the test waveform data generator (TDG) provided by IEC 61083-2, simulations, and experiments. It is found that the accuracy of the proposed approach is relatively higher than the expressions provided by IEC 60060-1 and previously developed. The proposed method is an alternative and useful approach for evaluating the waveform parameters of the standard switching impulse voltage.

Assessment of the Effect the Height and Relative Position of Support Insulation Components Have on the Insulation Electrical Strength

The article presents the results from studies of the effect the height and relative position of extra high voltage class support insulation components have on the insulation electrical strength when subjected to positive polarity switching impulses, at which the insulation minimum permissible overall dimensions are determined. It is shown that the highest values of the insulation flashover voltage are achieved when a leader discharge develops along purely air trajectories: screen--pedestal or screen-- plane. A similar result is obtained in the case of cascade flashovers from the screen over the column elements if the upper insulator structural height is significantly larger than that of the lower one. The reverse mutual arrangement of these insulators leads to a significant drop in the insulation flashover voltage during cascade flashovers. It is shown that at the final jump onset moment, the main contribution to the insulation flashover voltage value is introduced by the voltage drop across positive streamers, which is directly proportional to the length of these streamers. Hence it follows that the ambiguous effect of the height and mutual arrangement of the support insulation components on the insulation electrical strength during cascade flashovers is mainly due a significant difference in the lengths of the positive streamer zones at the final jump onset. With the upper insulator height equal to 2.7 m, the length of positive streamers at this moment is commensurable with the length of streamers when the flashover develops along purely air trajectories, whereas decreasing the upper insulator height by almost a half entails a significant decrease in the streamer lengths. Measures to eliminate undesirable cascade flashovers and ensure the highest electrical strength of support insulation are proposed.

Breakdown Characteristics of Eco-Friendly Gas C5F10O/CO2 Under Switching Impulse in Nonuniform Electric Field

In this article, an experimental study was carried out on the switching impulse (SI) breakdown characteristics of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O/CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> mixture, and the effects of pressure and mixing ratio on its breakdown characteristics were analyzed. The results show that there is a polarity effect between positive and negative breakdown voltages, and the polarity effect becomes stronger with the pressure increased, and a polarity reversal occurred at 0.15 MPa. Increasing the gas pressure and the content of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O can improve the SI breakdown voltage of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O/CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , but it can only reach 60%–70% of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> under the same conditions. The positive breakdown voltage has a “hump” phenomenon as the pressure increases. With the increase in C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O content, the “hump” tends to shift toward low pressure. The “hump” is explained from the improving effect of positive space charge on electric field, and the influence of the applied voltage, pressure, and C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O content on the positive charge layer is comprehensively considered. The results of this article can provide reference for the engineering application of C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sub> F <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> O gas insulating medium.

Input‐to‐state stability of discrete‐time switched delayed systems with delay‐dependent impulses: Admissible edge‐dependent average impulsive interval

AbstractThis article addresses the input‐to‐state stability (ISS) problem for general discrete‐time impulsive and switched delayed systems coupled by delay‐dependent impulses. In our studied systems, the impulsive signal has a large degree of freedom, that is, the impulse effect can occur simultaneously with or different from the switching effect. A new Lyapunov–Krasovskii functional is proposed to deal with the delay effect of switching signal and impulsive jump, which is divided into the delay‐independent part and delay‐dependent part. A new concept named admissible edge‐dependent average impulsive interval (AED‐AII) is set up to characterize the impulse sequence relative to the admissible edge‐dependent average dwell time (AED‐ADT) concept of the switching signal. Based on AED‐ADT approach and AED‐AII technique, some improved sufficient outcomes guaranteeing ISS of discrete‐time impulsive and switched delayed systems are presented, respectively, for stabilizing and destabilizing delay‐dependent impulses. Meanwhile, the relationship among AED‐AII, AED‐ADT, the jump amplitude of switching signal and impulse signal at their respective discrete points, the decay rate of Lyapunov functional for system dynamics is connected to pursue ISS of the whole system. Compared with previous works, our setups enjoy the following characteristics: it thoroughly digs the influence of time delay existing in impulses and system dynamics on the function part of L‐K functional, which are less conservative relative to other works; the proposed AED‐ADT switching signals and AED‐AII jump signals cover a large set of hybrid systems. Two numerical examples are given to illustrate the effectiveness and less conservativeness of the obtained results.

Investigation of the corona discharge activity in liquid nitrogen under transient voltage conditions using fluorescent fiber sensor

In the present study, corona inception voltage in liquid nitrogen under standard lightning impulse voltage (SLIV) and oscillatory impulse voltages were studied using fluorescent fiber sensor. A single discharge signal is observed near the peak of the applied SLIV. The amplitude of the fluorescent signal is high with positive polarity than under negative polarity. At higher voltages, the magnitude of the fluorescence signal increases and it shifts towards the rising edge of the applied voltage. Under unidirectional oscillatory impulse voltage (UOIV) and sinusoidal bidirectional oscillatory impulse voltage (SBOIV) conditions, Corona discharge occurs around the peak of the first cycle. When the applied voltage is increased, the discharges occur in the subsequent cycles. Under switching impulse voltage (SIV), corona discharge is noticed at the rising edge in positive polarity, whereas in negative polarity, it is observed at the falling edge. The corona discharge inception voltage (CDIV) is determined to be highest under Unidirectional Oscillating Lightning Impulse (UOLI) and lowest under SI. The negative polarity exhibits more temporal spread than the positive polarity under oscillating impulse voltages.

Electric field control by permittivity functionally graded and superficially non‐linear conductivity materials for DC‐GIS spacer

This paper offers a simulation study on the application of a novel approach to control the electric field around a basin-type spacer by combining permittivity functionally graded materials (ε-FGM) and superficially non-linear conductivity materials (SNCM), namely multi-dimensional functional materials (MDFM). The permittivity distribution of the ε-FGM spacer is designed by the iteration optimization algorithm, and the epoxy/SiC composites with 30 and 60 phr doping contents are assigned as the coating materials of two SNCM spacers, namely SNCM30 and SNCM60. The MDFM spacer combines ε-FGM in its bulk and SNCM60 on its surface. The electric field regulation effect of each functional spacer is investigated under variable conditions, that is, DC steady state (DC-steady), DC turn-on state (DC-on), DC polarity reversal (DC-PR), and DC superimposed with switching impulse voltage (DC-SI). Results show that the applicability of ε-FGM and SNCM is limited to transient and stationary conditions, respectively. The MDFM spacer combines the advantages of ε-FGM and SNCM for adaptively relaxing the electric field under all the above conditions. It is hoped that this research will be beneficial to the development and application of spacers for the direct current gas-insulated switchgear (DC-GIS).

Intelligent computing and analysis of breakdown voltage of rod-rod long air gap

The discharge characteristics of air gap is one of the important factors to determine the insulation level which is crucial for electrical engineering construction. In order to calculate the 50% breakdown voltage of rod-rod air gap under different meteorological conditions and different gap distances, we take the positive standard switching impulse test data of rod-rod air gap under different meteorological conditions as samples. Based on training set, a breakdown voltage prediction model of rod-rod air gap under different meteorological conditions was established by cuckoo search optimized weighted support vector regression (CS-ω-SVR). The results show that the average absolute percentage error of the test set is 3.6%, which verifies the validity of this computing method. The method can provide reference for the computation of air gap breakdown voltage under different altitudes and extreme meteorological conditions.