SF6 Circuit Breaker Research Articles

Research on operation and fault diagnosis technology for EHV/UHV SF6 circuit breakers pre-insertion resistors

Pre-insertion resistors (PIR) are critical components for suppressing the closing inrush current and operating overvoltage during the closing process of the circuit breaker. And it is widely adopted in 800kV and above transmission lines and alternating current filters of converter substations. These special application environments lead to higher failure rates than other electrical components. However, in the daily operation and fault diagnosis of PIR, there is no systematic method to analyze whether there are defects in PIR and the cause of failure after the PIR fails. Based on two PIR failure in series and parallel structures, this paper proposes methods such as dynamic resistance fitting, acoustic and vibration signal detection, insulation performance test, and heat capacity test during operation. In the aspect of fault diagnosis, methods such as PIR splicing based on Iterative Closest Point , stress analysis, and electric field simulation are proposed. Finally, proposed methods can be adjusted to estimate the operating state of PIR through the disassembly inspection to avoid the GIS breakdown accident during the operation of the circuit breaker.

БЕЗПЕЧНЕ ВИМКНЕННЯ ЕЛЕГАЗОВИХ ВИМИКАЧІВ У ПОВІТРЯНИХ ЛІНІЯХ ЕЛЕКТРОПЕРЕСИЛАННЯ

The paper analyses the transient currents during the energisation of a 750 kV overhead transmission line (OTL). The safety of OTL state after symmetrical and asymmetrical closing of the circuit breakers and technical feasibility of SF6 circuit breakers opening with time delay after their closing is substantiated. The necessity of transient processes simulation for analysing the characteristics of periodic and direct components of currents is shown. A method for determining of SF6 circuit breaker opening time delay for a set of the states that may arise after the energisation of OTL is developed. References 13, tables 2, figures 5.

Operation of Circuit Breakers: Data and Analysis

An attempt has been made for the analysis on Circuit breakers (CBs) this paper. First, the types and arcing phenomenon of Oil and SF6 Circuit breakers were briefly discussed. However, various CBs were analyzed in terms of certain outage frequencies and reliability indices to ascertain the most reliable CB. This was possible using data collected from the 33kV Transmission Company of Nigeria (TCN) New Haven, Enugu. After the analysis, Emene Industrial CB had the highest value of availability of 0.9999 and the lowest tripping report while Ezillo had the highest failure rate of 0.1032.

Study of Shock Wave Development in Cold Flow of Gas Circuit Breaker for Improving Capacitive Current Switching

Abstract Capacitive current switching performance of SF6 circuit breaker is determined by combined action of gas flow and electric field in interruption chamber. Computational fluid dynamics method is used to study the development of shock waves inside a SF6 circuit breaker under the condition of capacitive current switching. It was found that a shock wave exists and travels with the pin contact during the contact opening. Existence of shock waves reduces the local gas density around contact head, while the contact head is also stressed by high electric field at the same time. If the region of low gas density coincides with the region with high electric strength, local dielectric performance will be significantly reduced. Using E/ρ as the dielectric performance index, when the local value of E/ρ exceeds the gas breakdown criterion, it will result in restrike to the capacitive current switching. The causes of high E/ρ are studied by analyzing the shock waves during the sequential periods of contact travel. Since the gap between the pin contact and nozzle throat strongly affects the strength of shock wave, the behavior of gap is studied with the calculation of E/ρ to find its influence on capacitive current switching.

Averting Failure of Pre-Insertion Resistor in Circuit Breaker Through Preventive Maintenance

Pre-insertion resistor (PIR) is an important component of circuit breaker. The healthiness of the circuit breaker (CB) depends upon that of PIR contact. With the increasing demand of uninterrupted power supply, failure in major equipment like CB may incur huge loss to the utility. The existing study reveals that mechanical failures are more dominant than other types of failures. Thus, many industries prefer to undertake preventive maintenance of equipment rather than break down maintenance. This paper describes the actual problem detected in PIR contact of North Eastern Regional Transmission System, having a 400 kV, 3000 A, SF6 CB through testing and rectification thereafter. The results obtained from the graph helped in detecting mechanical dis-alignment of the connecting link in the link arm and the tubular contact of the PIR. Furthermore, a model has been developed to show the possible threat that would have occurred, had the problem been not rectified. This paper will help the utilities to emphasize on detecting the problem by undergoing preventive maintenance and thereby saving unprecedented failure of equipment.

Investigation of the impacts of the refill valve diameter on prestrike occurrence in gas circuit breakers

In puffer type Sulfur Hexafluoride (SF6) Circuit Breakers (CBs), the refill valve is the main inlet duct for the SF6 gas to enter the puffer volume. When the CB is closing and moving contacts and the nozzle are moving toward fixed contacts, the SF6 gas enters the puffer volume via the refill valve. Since changing the refill valve diameter can alter the direction of the SF6 gas motion in the closing operation of CBs, understanding its effects on CBs' function and performance may help to improve the CB design. This paper has focused on the effects of refill valve diameter on prestrike occurrence in the closing operation of puffer type SF6 CBs. In order to accurately study these effects, some equations are used in the developed multiphysics model, including the Navier–Stokes equations and standard K–ε turbulent model for modeling the motion of the SF6 gas, heat equation for calculation of the gas temperature, Maxwell equations for electromagnetic fields modeling, and gas state equation for taking into account the severe dependence of the SF6 gas properties on temperature. Numerical studies have been performed on a 72.5 kV CB. Performance and functionality of this CB have been investigated for four different refill valves from several physical aspects. Numerical studies show that the refill valve diameter has a considerable influence on the prestrike occurrence instant.

Comparative Analysis of Measures and Technical Means for Suppressing the Aperiodic Current Component in Circuit Breaker

Electromagnetic transients are considered in the implementation of three-phase automatic reclose on the transmission line of extra high voltage 750 kV. The influence of automatic shunting of phases and pre-insertion active resistance for limiting the characteristics of the aperiodic component of the current, which obstructs the transition of full current through zero, is evaluated. The paper analyses measures taking into account the effect of changing the degree of compensation of charging power and the angles of switching on an SF6 circuit breaker. Sub-schemes of disconnected undamaged phases of the extra high voltage transmission line for the investigation of the aperiodic current component have been developed. The values of the pre-insertion active resistances of different connection and automatic shunting of the phases are determined at which there is an effective reduction of the characteristics of the aperiodic component of the current. In the software environment, a model was developed and switching transient processes were simulated in the 750 kV transmission line. Operating modes that are potentially dangerous for SF6 circuit breakers are determined and recommendations are given to avoid them. Currently the technical and economic requirements for power transmission lines designed for the transport of electricity from large power plants and for the communication of powerful energy systems are increasing. Today there is the importance of reducing specific investment in the construction of new and reconstruction of existing lines. The solution of these issues is associated with the maximum use of power lines by increasing their power transfer capability and controlling modes, especially in operating emergency conditions and post-emergency operation of power systems.

REDUCTION OF ENERGY LOSSES ON HEATING OIL CIRCUIT BREAKERS 35–110 KV IN JSC «CHERNIGIVOBLENREGO»

The analysis of the state of 35–110 kV circuit breakers in the Chernihiv region, which are on the balance sheet of the operator of the distribution system JSC «Chernigivoblenergo», has been carried out. It was shown that the number of circuit breakers that satisfy regulatory documents is only 18.9 % in 35 kV and 2 % in 110 kV power networks. Unfortunately, most of the 35–110 kV circuit breakers in the Chernihiv region are low-oil and bulk-oil type, which required heating during cold meteorological conditions. The article assess the duration of the circuit breakers heating and their drives, depending on the selected set point of the temperature and the averaging interval of the ambient temperature, and the value of technological energy losses. The article considers following ways to reduce technological costs for heating: optimization of the heating control system, replacement of oil circuit breakers with modern vacuum and SF6 circuit breakers, which require lower costs on heating, and applied both above ways. The effectiveness of the above ways was done with apply Net Present Value, which includes not only investments and Net Profit Margin, but also operating costs and Discount Rates. It has been shown that all of the above ways are effective. In particular, the least costly is the modernization of the heating control system, which has payback period is low three years. The payback period for second way to replace all 35–110 kV oil circuit breakers with modern ones at JSC «Chernigivoblenrego» is about 6.5 years, but this way requires large investments. However, this way cannot be done in one year. Therefore effectiveness will be less due to energy losses to operated oil circuit breakers.

An arc contacts life assessment method based on dynamic resistance measurement and bp neural network

Arc contacts ablation of high voltage SF6 circuit breaker will cause potential problems for safe operation of the grid. In view of the difficulty of predicting arc contacts life by existing methods, an arc contacts life assessment method based on dynamic contact resistance and BP neural network is proposed. The dynamic contact resistance-travel curve is obtained from the high-current ablation experiments, from which the data characterizing the arc contacts state is extracted as samples to train the neural model. The model is optimized by k-fold cross-validation method, which is finally validated by experimental results. The results show that the arc contacts life prediction value agrees well with the experimental value, which means that the BP neural network can effectively predict the arc contacts life and provide a basis for decision making for arc contacts overhaul and replacement.

First principles analysis of SO2, H2S adsorbed on Fe-ZnS surface

In order to solve the threat of SO2 and H2S, decomposition by SF6 circuit breaker to the environment, staff safety and equipment operation, a Fe-doped ZnS nanomaterial adsorbent was proposed. In this paper, the adsorption behavior of Fe-ZnS was studied by the first principles theory. The adsorption ability of Fe-ZnS for the different orientations of SO2 and H2S was analyzed from the density of states, adsorption energy, charge transfer, Charge density difference and electron localization function. The results show that the adsorption ability of Fe-doped ZnS is significantly higher than that of pure ZnS, and the adsorption order of Fe-ZnS for two gases is SO2 (Eads=-3.299 eV,Qt=-0.67e)> H2S(Eads=-2.749 eV, Qt=-0.55e). In addition, the results are verified by the competitive adsorption of mixed gas. Therefore, Fe-ZnS may be a promising gas adsorbent, which can greatly eliminate the influence of two toxic gases on SF6 circuit breakers and play a key role in improving the safe operation of SF6 circuit breakers.

Research Based on Modeling and Simulation of the Transient Regime in Controlled Switching with High Power Switches

This paper addresses one of the current areas of interest in electrical engineering, which is controlled switching of high voltage circuit breakers. During their operation, the problem of controlled switching of high voltage circuit breakers in commutation regimes was studied. Several types of switching were analyzed, considered representative of the transient regime, depending on the type of load, on the defect that may occur on the power supply lines, as well as depending on the position of this defect (near or far). The study carried out in the paper includes simulations of the controlled connection/disconnection operations in a transient regime, assuming the existence of different kinds of defects. To perform the study and simulations in the transient regime, a model, implemented in Matlab, was used for a time interval located around the origin of the time axis. The study included the dependence of the SF6 circuit breaker switching process on the following parameters: the DC voltage supply, ambient temperature and oil pressure in the circuit breaker actuator. The validity of the theory presented in this paper, in addition to being validated by simulations, is proven by the fact that the protection system currently in use at the power station of an 800 MW power plant, at the 400 kV power line, is based on the principles presented in this paper. The theory presented in the paper has been implemented in industry for nearly two years, and the results confirm that the theory presented in the paper is fully applicable in high voltage power stations.

Predominant reaction products and dielectric breakdown properties of gas mixtures consisting of SF6 and ablation products of C2F4/BN in the temperature range of 300–3000 K

For a high voltage SF6 circuit breaker equipped with a boron nitride (BN)-filled polytetrafluoroethylene ((C2F4)) nozzle, the predominant reaction products in a high-temperature SF6 mixture with vapor decomposition of C2F4 and BN at temperatures of 300–3000 K are determined based on calculations of equilibrium composition. The calculation is performed by considering the molecular products obtained by chemical reactions with boron atoms (e.g. BN, BS, BC, BF, BF2 and BF3), nitrogen atoms (e.g. N2, N3, CN, NS, NF, NF2 and NF3) and carbon atoms (e.g. CS, CS2, C2F4, CF2, CF3 and CF4). The results obtained for the C2F4–BN molar fraction of 20%–80% reveal that BF3, N2 and CF4, the molecules originating from the nozzle material, are produced at high molar fractions over a range of 300–3000 K. Such an evaluation of the gas composition allows the derivation of a reduced collision ionization coefficient α/N and a reduced electron attachment coefficient η/N of the gas, considering various electron impact processes such as BF3 + e BF2 + F− and CF4 + e CF3 + F−. The evaluation subsequently enables us to determine a critical reduced electric field strength causing . The results suggest that the decomposed C2F4–BN mixture at of 80% causes the reduction of to 110 Td in the range of 1000–2000 K at a gas pressure of 1.0 MPa. This strength is 20 Td lower than that determined separately for the SF6 gas mixture with only 80% C2F4 vapor decomposition, because of the CF4 molar fraction reduction in the SF6/C2F4–BN mixture.

ЗАСТОСУВАННЯ КЕРОВАНИХ ПРИСТРОЇВ КОМПЕНСАЦІЇ ЗАРЯДНОЇ ПОТУЖНОСТІ ЛЕП НВН В ЕЛЕКТРИЧНИХ МЕРЕЖАХ

It is shown that the use of controlled shunt reactors allows you to create FACTS-controlled power lines based on extra-high voltage power lines that meet the necessary requirements of modern energy systems to control normal conditions. The typical modes of operation of an ultra-high voltage power line with installed controlled shunt reactors are analyzed. The efficiency of using controlled shunt reactors to increase the reliability of single-phase auto-reclosing is shown. The issues of the appearance of an aperiodic component in the current when disconnecting the line of SF6 circuit breakers are considered. It is shown that the presence of a ferromagnetic core in controlled shunt reactors causes the appearance of transition resonance, which must be taken into account when designing the FACTS. References 10, figures 1, tables 1.

Decomposition Characteristics of SF6 under Arc Discharge and the Effects of Trace H2O, O2, and PTFE Vapour on Its By-Products

The research on decomposition characteristics of SF6 and its by-products have great significance to the operation, maintenance, condition assessment and fault diagnosis of power equipment. In this paper, the particle composition models of SF6, SF6/polytetrafluoroethylene (PTFE), SF6/PTFE/O2, SF6/PTFE/H2O, and SF6/PTFE/O2/H2O were established by using Gibbs free energy minimization method, and the effects of trace H2O and O2 impurities and PTFE vapour on SF6 by-products were studied by the models. In order to verify the correctness of the simulation results, a series of breaking experiments were carried out on a 40.5 kV SF6 circuit breaker, and a gas chromatograph was used to detect and analyse the SF6 by-products. It was found that when PTFE vapour is involved in the arc plasma, the main by-product after arc quenching is CF4, and the molar fractions of C2F6 and C3F8 are very low. When O2 is involved, the main by-products are SOF2, SO2 and SO2F2, and a small amount of CO and CO2 was also produced. When H2O is involved, the main by-products in simulation are SOF2, SO2 and HF, and a small amount of SO2, CO2, CO, SO2F2 and H2 was also produced. The experimental results are in good agreement with the above results.

Инновационная технология рентгенографического контроля технического состояния высоковольтных выключателей в эксплуатации

The paper displays the results of the practical application of an instrumentation and analytical system (IAS) for X-ray control of minimum oil and SF6 circuit breakers. The capabilities of IAS are described and the technology for its implementation is given. The paper shows that the proposed technology makes it possible to control the contact group (moving and fixed contacts) and elements of the moving contact control system of circuit breakers without bus bar dismantling, oil drain, and disassembly of the circuit breaker poles. The paper also presents the assessment of the reliability indicators of high-voltage circuit breakers, which confirms the prospects for introducing the developed X-ray control technology.

Особливості експлуатації високовольтних електричних вимикачів

The paper draws attention to the fact that nowadays there are many high-voltage switches in operation of different manufacturers and designs, which differ in arc-quenching environment, principle of operation, features of operation. This requires from the maintenance and repair staff additional knowledge and skills agreed with the representatives of enterprises - manufacturers of switches of new designs. Based on the analysis of the statistics of damage to high-altitude switches, it is proved that there is not only damage to obsolete oil or air switches, but also new SF6 switches. the number of damaged SF6 circuit breakers in the total number of damaged high-voltage circuit breakers is 7.1%, while air circuit breakers - 22.3%, and oil circuit breakers - 70.6%. In order to improve the quality of operation of high-voltage switchgear equipment, it is necessary to have information about the technical, preferably current, condition of high-voltage switches. After all, these switches, by disconnecting damaged electrical equipment, significantly reduce the time of leakage of short-circuit overcurrents, and therefore reduce the likelihood of spreading damage to adjacent to the damaged equipment. To reduce errors of the first and second kind when forming conclusions about the technical condition of the diagnosed switch, it is desirable to use modern methods and tools of diagnosis. Conclusions based on the results of diagnosing circuit breakers should take into account the determination of risks during operation of the diagnosed circuit breakers. The following risk components are considered in the article: risk component of damage to living beings as a result of electric shock as a result of non-operation or destruction of the switch; component of the risk of physical damage to high-voltage equipment adjacent to the switch caused by failure of the switch, which could lead to explosion or fire, leakage of SF6 and endanger the environment, component of the risk of failure of internal switch systems due to deterioration main contacts, reduction of SF6 pressure, etc.) during switching on / off of rated currents; components of risk for electrical equipment of the switchgear in case of short circuit near the switchgear, component of risk of failure of internal circuit breaker systems caused by disconnection of short-circuit currents in the cycle of unsuccessful APV; Risk components for switchgear and switchgear equipment in the event of a short circuit in or near switchgear equipment, namely: component of risk of damage to living beings due to electric shock or step voltage during short circuits in switchgear equipment and switch failure , component of risk of physical damage to switchgear equipment (fire or explosion caused by short circuits and overloads of electrical equipment of switchgear and failure of appropriate switches due to unsatisfactory technical condition of the switch; component of risk of failure of the switch caused by damage to the source coil on and off coils, risk components for the circuit breaker during a short circuit in the operating DC line, namely the component of the risk of failure of internal circuit breaker systems caused by breakage or short circuit in the operating DC or voltage lines.

Research on the wear and life of copper tungsten alloy contacts of high voltage SF6 circuit breakers

Three phase short circuit and two phase short circuit grounding fault of power system have a significant influence on the electrical life of circuit breaker contact. In this paper, the mathematical model of each component is established by Power System Analysis Software Package (PSASP), and the simulation model is built to simulate the dynamic state of the circuit breaker after different short-circuit faults. The simulated result confirms that contact electrical wear quantity related to the type of short circuit fault and the position of short circuit point. The size of short circuit current will directly impact electrical wear quantity and electrical life of circuit breaker contact.

Measures and technical means for increasing efficiency and reliability of extra high voltage transmission lines

Electromagnetic transients are considered in the implementation of three-phase automatic reclose on the transmission line of extra high voltage 750 kV. The influence of automatic shunting of phases and pre-insertion active resistance for limiting the characteristics of the aperiodic component of the current, which obstructs the transition of full current through zero, is evaluated. The paper analyses measures taking into account the effect of changing the degree of compensation of charging power and the angles of switching on an SF6 circuit breaker. Sub-schemes of disconnected undamaged phases of the extra high voltage transmission line for the investigation of the aperiodic current component have been devel oped. The values of the pre-insertion active resistances of different connection and automatic shunting of the phases are determined at which there is an effective reduction of the characteristics of the aperiodic component of the current. In the software environment, a model was developed and switching transient processes were simulated in the 750 kV transmission line. Operating modes that are potentially dangerous for SF6 circuit breakers are determined and recommendations are given to avoid them. Currently the technical and economic requirements for power transmission lines designed for the transport of electricity from large power plants and for the communication of powerful energy systems are increasing. Today there is importance of reducing specific investment in the construction of new and reconstruction of existing lines. The solution to these issues is associated with the maximum use of power lines by increasing their power transfer capability and controlling modes, especially in operating emergency conditions and post-emergency operation of power systems.

Coupling model of AC filter branch in SF6 circuit breaker during the break process

In this paper, a coupling model of the AC filter branch circuit with the arc plasma in the circuit breaker was built to investigate the arcing process considering the harmonic current. The comparisons among the current at power frequency (50 Hz), power frequency combining the 11th harmonic and power frequency combining the 24th harmonic show that the high-order harmonic current would lead to higher decreasing rate of current before current-zero period. In addition, the influence of arc on the amplitude of high-order harmonic current is not negligible. Thus, the coupling of arc with AC filter branch circuit is quite necessary in the numerical modeling of the circuit breaker in the AC filter branch at the high voltage direct current converter station.

Adsorption mechanism of decomposition gas of SF6 circuit breaker on MOF-505 analogue

The decomposition gas of SF6 circuit breaker adsorbed on MOF-505 analogue had been analyzed and studied in this paper by using the first principles of density functional theory (DFT) to analyze adsorption mechanism. The adsorption structures of organic ligands and metal sites were established and optimized. Through analyzing the adsorption energy, adsorption distance difference, charge transfer, density of states, Charge density difference and electron localization function, the results show that organic ligands and metal sites have excellent adsorption effect on H2S and SO2, belonging to chemical adsorbent, and the adsorption capacity is far greater than that of SF6. The MOF-505 analogue will be a potential adsorbent for the fault recovery of SF6 circuit breaker.