Circuit Breaker Contacts Research Articles

Research on measures suppressing high frequency transient overvoltage in offshore wind farms

A large number of different types of cables, wind turbines, transformers and vacuum circuit breakers (VCBs) are used in power collecting system of offshore wind farms (OWFs). Due to the phenomenon of traveling wave refraction and reflection in cable collector system, transient overvoltage with high amplitude and high steepness will be generated when reignition phenomenon occurs in frequent operation of vacuum circuit breakers on wind turbines, which will cause serious damage to transformers, the problem of overcurrent is also becoming more and more serious. Therefore, through the electromagnetic transient simulation software of ATP-EMTP, a single-phase model of VCB switching-off transformer in offshore wind farm is built to study the influence of the separation speed of contacts of vacuum circuit breaker, high-frequency arc quenching capability and arching time on overvoltage. Then, the medium voltage cable collector system of OWF is built. Installing ferrite ring near the VCB or on the high-voltage side of transformer can suppress high frequency transient overvoltage. The results show that the high frequency transient overvoltage generated by offshore wind farm can be well suppressed after the installation of overvoltage protection device.

Determination Method of Contact Ablation Degree of Power System Circuit Breaker Based on Power Load Property

In the field of electrical engineering, the stable operation of circuit breaker is one of the important indexes to ensure the safety and stability of power system. Because the influence of load property on electromagnetic wave waveform is not considered, the method to determine the ablation degree of circuit breaker by using the characteristics of radiated electromagnetic wave is not completely accurate. Therefore, this paper proposes a method to determine the ablation degree of circuit breaker considering the load properties. By adding load factor, the ablation degree of circuit breaker contact can be determined more accurately. When the load is resistive load, the load factor is 1, when the load is inductive load, the load factor is 2.5, when the load is capacitive load, the load factor is 3. When the duration of the radiated electromagnetic wave exceeds the corresponding time, it can be judged that the contact is seriously ablated. The method proposed in this paper mainly uses electrical detection means to realize the rapid determination of the ablation degree of the circuit breaker contact and avoid the misjudgment caused by not considering the nature of the load.

Determination Method of Contact Ablation Degree of Circuit Breaker in Power System Based on Radiated Electromagnetic Wave Detection

Power is the most important energy in the current society, so it is very important to ensure the stable operation of the power system. In order to determine the state of the circuit breaker in the power system effectively, the power supply is stable. This paper presents a method to determine the ablation degree of the contact of the circuit breaker based on the radiation electromagnetic wave detection. The method adopts the means of electrical measurement and waveform observation to realize the rapid diagnosis of the contact ablation degree of the circuit breaker. The antenna is used to receive the radiated electromagnetic wave generated in the opening process of the circuit breaker, and the common oscilloscope is used to monitor the waveform. The number of electromagnetic wave pulses per unit time is analyzed to determine the ablation degree of the circuit breaker contact. If the number of pulses found by oscilloscope is large, it can be judged that the contact ablation is serious. The method mentioned in this paper belongs to the field of electrical engineering, which is mainly used to determine the ablation degree of the contact of the circuit breaker by means of electrical detection. This method has the advantages of simplicity, rapidity and efficiency.

Generate Various Parameters Of Trv Envelope Synthetic Test Circuit

The most basic transient a circuit breaker needs to suffer during its activity is the transient recovery voltage (TRV), started by the electric force system as a characteristic response on flow interference. To test high voltage CBs, direct testing utilizing the force system or short out alternators are not practical. The testing of high voltage Circuit Breakers (CBs) of bigger limit requires huge limit of testing station. An equal infusion of short out current and transient voltage to medium and high voltage circuit breaker (CB) by a synthetic model is examined. Transient recovery voltage is made by a capacitor bank and is applied to CB. An optical set off spark gap has been utilized to interrupt short circuit and to introduce of transient recovery voltage that is applied across the contacts of circuit breaker. Transient recovery voltage examination can never be done totally, as the advancement of circuit breaker development and organization configuration goes on. The most widely recognized way to deal with TRV examination is concerning the supposed planned TRV, in which a suspicion of dismissing association between circuit breaker itself and the innate system recovery voltage is being made. Notwithstanding, it actually is by all accounts qualified to examine what circuit breaker means for transient recovery voltage. An ideal grouping to open/close of reinforcement test article and helper circuit breakers inside suitable chance to infuse of recovery voltage. The impact of reactance of inductive flaw current limiter just as distance to blame in short line issue condition on pace of ascent of recovery voltage. A 4-boundaries TRV synthetic test circuit dependent on equal current infusion technique is planned and mimicked for testing 145kV rating circuit-breakers according to new TRV prerequisites given in IEC 62271-100.

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.

Fault Diagnosis of Conventional Circuit Breaker Contact System Based on Time–Frequency Analysis and Improved AlexNet

In order to eliminate the influence of parameter predefined caused by manual feature extraction, achieve fast feature extraction, and improve the recognition rate of fault diagnosis, a 2-D convolution neural network (CNN) method for fault diagnosis of conventional circuit breaker contact system is proposed. First, by introducing the data preprocessing method of continuous wavelet transform (CWT), the nonlinear and nonstationary original vibration signal is transformed into a time–frequency image to extract the transformed image features. Second, the convolutional layer module in the AlexNet model is combined with the network in network (NIN) module, and the global average pooling (GAP) layer is adopted to replace the fully connected (FC) layer, which realizes the improvement of the traditional AlexNet model. Then, an improved Adam optimization algorithm, namely, AMSGrad, is adopted to solve the problem that the Adam optimization algorithm may not converge or produce local optimization during model training. Finally, the preprocessed time–frequency image is taken as the input of the improved AlexNet model and through the supervised adjustment of network parameters, the fault diagnosis of the contact system for the conventional circuit breaker is realized accurately.

Tungsten-Copper Composites for Arcing Contact Applications

The study presents the research findings on electrical contact materials based on tungsten-copper (W-Cu) composites containing 72 ± 3 wt.% W, rest Cu, and up to 1.5 wt.% Ni. Cylindrical sintered parts with 57 ± 0.5 mm in diameter and 12 ± 0.5 mm in height were manufactured by pressing, sintering, and liquid infiltration route, then were mechanically polished and processed as complex shape protection rings used as arcing contacts in high voltage circuit breakers (HVCBs). The surface elemental composition of the sintered parts was determined by wavelength dispersive X-ray fluorescence spectrometry. The density was determined by hydrostatic weighing in ethanol. The arithmetic mean surface roughness was measured by contact profilometry. The microstructure was studied by scanning electron microscopy. The electrical conductivity was measured by eddy current method. The thermal diffusivity and specific heat were determined by laser flash analysis. Instrumented indentation testing and two computational methods (Oliver & Pharr, and Martens hardness) were employed to study the mechanical properties under quadratic loading and continuous multi cycle (CMC) indentation mode. The functional behavior of the arcing contacts was assessed in terms of static and dynamic contact resistance in operation in minimum oil HVCBs of 110 kV. The properties investigation revealed highly dense contact parts with homogeneous microstructure, Vickers hardness of 260-374, elastic modulus of 185-311 GPa, as well as good electrical and thermal conductivity. The arcing contacts proved a good functional behavior. in service, too. The results endorse the developed sintered contact materials for implementation in practical applications.

Thermal Plasma of Electric Arc Discharge Between Composite Cu-Cr Electrsodes: Optical Emission and Electrode Surface Interaction

This work deals with investigations of thermal plasma of electric arc discharge between sintered composite Cu-Cr electrodes, which can be used in electrical contacts of vacuum circuit breakers. Breaking arcs between composite Cu-Cr as well as single-component copper electrodes were used to study the electrical properties, plasma optical emission and electrodes surface modification behavior. In particular, the temporal evolution of plasma emission spectra of electric breaking arcs in air atmosphere was investigated by Optical Emission Spectroscopy (OES). Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray Spectroscopy (EDXS) were applied to analyze the cross-section of working layer of electrodes surface modified by the heat flux from the discharge.

Numerical Simulation and Analysis of Arc Anode Erosion Process with Electrode Rotation

A three-dimensional geometric model of anode contact of vacuum circuit breaker is established. Considering the influence of electrode rotation on vacuum arc and anode thermal process, a physical model of phase transformation process is established for the melting and evaporation of anode surface. The solid-liquid mixing area is treated by the description method of porous media, and the numerical simulation of anode thermal process is carried out. The conclusion is that with the increase of time, the anode surface temperature increases, molten pool development, molten pool depth deepening, in addition, with the increase of electrode speed, the highest temperature on the surface of the contact and the size of the molten pool were reduced, the temperature distribution more uniform. It provides theoretical basis for evaluating the breaking capacity of vacuum circuit breaker.

170㎸ 가스절연개폐기용 차단 접점 마모에 따른 기계적 열화 특성 분석

This paper deals with the effect of mechanical wear on the contact of circuit breaker applied to the 170㎸ Gas Insulated Switchgear (GIS). The arc occurrence was ignored to verify the pure effect of mechanical wear on the contact of circuit breaker. Since only the effect of the mechanical wear was considered, the experiment was carried out under no-load state. The accelerated test method was adopted and the specimens were operated until the lifetime same as actual 170㎸ GIS contact. The specimens were tripped and closed up to 20,000 times and the its electrical resistances and weights were measured at regular intervals. Based on the test results, the correlation between mechanical wear of contact and trip/close coil current was analyzed. The analysis result showed that, even the slight mechanical wear of contact can cause delays in the trop/close operation of the GIS.

Theoretical study of the decomposition mechanism of C5F10O in the presence of Cu vapor

C5F10O is one of the promising SF6 replacements in power switchgears due to its low global warm potential and high dielectric strength. As Cu metal evaporated by discharges and overheat faults in power switchgears will change the decomposition mechanism and products of C5F10O, the interaction between C5F10O and Cu vapor is important to evaluate the arc-quenching behavior but seldom reported yet. Therefore, this paper is focused on the impacts of Cu vapor, mainly released from the contacts in circuit breakers, on the decomposition mechanism and products of C5F10O. The molecular geometries, harmonic vibrational frequencies, and energetic information of products, reactants, and transition states in C5F10O + Cu decomposition pathways including 19 reactions were calculated by density functional theory. The main decomposition reactions and products were selected based on the analysis of rate constants. This work is hopeful to evaluate the arc-quenching behavior of C5F10O-insulated power equipment considering the evaporation from Cu contacts.

Circuit Breaker Performance Analysis

The problem of circuit breaking becomes complicated when voltages and currents in the range of kilovolt and kiloampere are involved. Circuit breaker (CB) is used in performing switching operations, and is a switch that can open live circuits. Circuit breakers are especially important in protective schemes where they have to interrupt fault currents, and isolate faulty section of the network. When the circuit breaker opens under fault condition many thousands of amperes pass through the contacts and the extinction of the arc and hence effective opening of the contacts of the CB are major engineering problems. When a circuit breaker opens, a high-frequency voltage, superimposed on the normal system voltage appears across the CB contacts. This voltage is known as transient recovery voltage (TRV) or restriking voltage, constituting a switching surge. Restriking delays arc quenching, and so it is detrimental to the circuit breaker as well as the entire system, since fault clearing may be delayed. This paper shows how resistance switching can be used to damp this surge and enable the CB to open before the magnitude of the voltage across the CB contacts reaches peak level, to prevent possible restriking of the arc.

Convection effect on an arc plasma evolution process in a two parallel contact system

A low voltage circuit breaker (LVCB) is an important piece of protection equipment which will switch off the fault current in a power system. The moving contact of a low voltage circuit breaker with a higher rated current consists of two parallel contacts. Therefore, the convection effect on the air arc evolution process in a two parallel contact system is analyzed. A three-dimensional (3D) magneto–hydro–dynamic (MHD) model of arc simulation is built. In this model, the anode consists of two parallel contacts and a bonding conductor. A nonlinear voltage–current density characteristic is employed to represent the near-anode and near-cathode voltage. The current density, arc voltage and currents through every contact are obtained. The influence of convection and conduction on the arc evolution process are quantitatively calculated. The displacements of the arc roots are obtained and the asymmetry of the arc root motion is analyzed. The arc evolution process of a two parallel contact system is preliminarily revealed.

Numerical simulation of heat transfer processes of the circuit breaker contact system

The article is devoted to the study of heat transfer processes of the high-current AC circuit breaker contact system. The creation of a mathematical model is based on the application of well-known physical laws such as the Joule-Lenz and Fourier laws, which describe physical processes in the form of partial differential equations. Cooper-Mikic-Yovanovich correlation is used for evaluation of thermal and electrical contact conductance. The developed mathematical model is verified by the results of experimental studies. The calculation of the composite material properties for numerical simulation of heat transfer processes is presented. The calculation is presented for the actual design and materials of the circuit breaker.

A New Algorithm for Detecting Failure to Clear Mode of Circuit Breakers Using Fundamental Frequency Component of Voltage Signals

This paper introduces a new algorithm for the early detection of abnormal arcing conditions of circuit breakers (CBs). Any interruption with a higher arcing time compared to maximum permissible arcing time of CB is defined as a CB failure to clear mode. Measuring CB arcing time is not easy because there is no control on the mechanical opening and closing instants of CB contacts. Nevertheless, there is a correlation between the spectral energy densities of CB arcing voltages and arcing times of CB. This correlation is used by calculating the spectral energy densities of the instantaneous system voltage and the instantaneous CB voltage across its terminals utilizing discrete Fourier transform for two periods of the system frequency. The difference between the spectral energy densities at the fundamental frequency is defined as a criterion for identifying a failure to clear mode. Whenever this criterion exceeds a predefined trip level, it indicates the occurrence of a failure to clear mode. In this situation, a trip signal is initiated for adjacent CBs to isolate the faulted CB and the fault. The results obtained from computer simulations and measurements show that the algorithm discriminates between normal and abnormal arcing conditions of CB.

Synthesis of Mo-Cu Nanoalloys and Computer Aided Thermal Analysis of Mo-Cu Nanoalloys Based Heat Sink

Mo-Cu alloys are used as heat sinks, microwave absorbers in microelectronic devices and as electric contacts in circuit breakers. Mo-Cu nanoalloys with average sizes below 200 nm were prepared using molybdenum powder and copper nitrate. Compositional characterization of Mo-Cu alloys was carried out using portable XRF. The developed material i.e. Mo-Cu is used as heat sink application in which the heat sink is modeled and thermally analyzed for evaluation of heat flux. The heat flux obtained was compared with heat sink made of aluminum. It was observed that the Mo-Cu heat sink exhibited superiority in withstanding higher temperature whereas, heat sink designed from aluminum was limited with their parameter which is thermal conductivity.

Analysis of alternative parameters of dynamic resistance measurement in high voltage circuit breakers

Throughout its lifetime, high-voltage circuit breaker (HVCB) contacts suffer from inevitable degradation processes, especially during the formation of electric arcs. Highly degraded contacts can reduce the current interruption capacity and increase the chances of operational faults, which might lead to considerable financial losses. Therefore, the use of efficient evaluating techniques is a key factor to achieve systems reliability. The dynamic resistance measurement (DRM) is a technique that can be used to evaluate the degradation level of HVCB' contacts. It stands out from the usual technique, static resistance measurement, by allowing the assessment of both the main contacts and the arcing contacts (ACs). Usually, the mean resistance or the area under the DRM curve is used to estimate the AC degradation. However, DRM is a non-standardised technique and there are no specified parameters to evaluate the real wear conditions. Therefore, an analysis of alternative parameters extractible from the DRM technique is presented in this study, such as amplitude and variance of the DRM curve. The results attest the possible use of more than one parameter for the continuous evaluation of HVCB ACs, characterising the DRM as a more complete and precise diagnosis tool.

Arrester Thermal Stability Control: Implementing a Combination of Countermeasures During Power System Restoration: A Real Case Study

Power outage, also known as blackout, is inevitable despite all operator efforts. Accordingly, an exhaustive restoration plan should be prepared beforehand. Considering all the static and dynamic constraints of power systems during system restoration leads to a comprehensive restoration plan which, in turn, results in the alleviation of its negative impacts. One of the challenges in developing the restoration plan is switching transients in energizing no-load or lightly loaded transformers and its effect on other power system equipment, arresters in particular. In this article, a restoration plan in the Iran power system is studied, focusing on switching transients. First, the flux–current curve is plotted applying three different methods, utilizing the real standard test data of a transformer; then, the thermal effect of switching transients on an arrester existing in Iran electric grid is studied. Results yielded that the arrester may be damaged in the absence of preventive actions; therefore, a proper countermeasure which takes into consideration the frequency and voltage constraints, as well as the asynchronous operation of circuit breaker contacts, is proposed. The simulation shows that the proposed countermeasure guarantees arrester safety.

On Calculation of Forces in a Contact Device with Electromagnetic Compensation

Compensators of the repulsive electrodynamic forces of electrical contacts provide stable operation of automatic switches during the flow of short-circuit currents. This paper presents a contact device with electrodynamic compensation and its design model. The electrodynamically interacting parts of the compensator structure are the U-shaped bent ends of the current-carrying output tire and slow-moving contacts parallel to each other. The formula for calculating the repulsive electrodynamic force of electrical contacts is given. On the basis of the calculation model, the formulas for the electrodynamic effort of the compensator and expressions for contour coefficient of electrodynamic forces of compensator have been obtained. The condition of complete compensation of the repulsive electrodynamic force of contacts is presented. Calculations of the electrodynamic effort of the compensator of the breaker for a rated current of 630 А with a rated short-time withstand current of 40 kA have been performed. The compensator with the proposed configuration fully compensates for the electrodynamic repulsive force of contacts of circuit breaker, confirming the validity of relations obtained in the work.

A Novel Arcing Power-Based Algorithm for Condition Monitoring of Electrical Wear of Circuit Breaker Contacts

This paper introduces a condition monitoring (CM) algorithm based on the circuit breaker (CB) arcing power and its related energy to estimate the electrical wear of arcing contacts. There is an electric arc occurring between the CB arcing contacts mainly during opening operations. Instantaneous voltage across the terminals of the CB and instantaneous current going through the CB are measured to calculate the arcing power and its related energy, which only exist under arcing events. Therefore, the power-based algorithm does not require the time synchronization to the power system frequency for measuring the CB arcing powers. The cumulative arcing energy of the CB is a good indication of the degradation level of arcing contacts and it is used to estimate the CB contact wear. Unlike the current-based CM method, the proposed power-based algorithm detects arc restrikes that produce more arcing energies and cause a greater contact wear. Thus, it allocates a higher amount of contact wear for interruptions with arc restrikes that makes it a more reliable and accurate technique. The outcomes of computer simulation and real-time test studies demonstrate that the power-based method can estimate the electrical wear of arcing contacts accurately, and thus, provides accurate inspection or maintenance times of CB's arcing contacts.