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Induction motors are becoming crucial components in numerous industries. The daily usage of induction motors creates the demand for proper maintenance and slight fault detection to avoid serious damage to the induction motor and the shutdown of industries. Among the various kinds of faults in induction motors, bearing faults, broken rotor bar faults, and short-circuit insulation faults are the most common. Thus, detection and classification of these faults in initial stage are attracting great attention. There are conventional methods for detecting such faults, such as the vibration method for bearing faults, the self-organizing map in the case of broken rotor bar faults, and motor current signature analysis for short-circuit insulation faults. From an industrial point of view, diagnosis methods that can classify all these major faults are required. However, reports on the detection and classification of these faults in initial stage using common diagnosis methods are scarce. In this paper, all three kinds of notable faults in an induction motor were artificially induced, and diagnoses using motor stator current spectral features and the rotation speed of the motor were performed. The diagnosis was accomplished using an auto-tunable and arbitrary featured support vector machine algorithm. Although the faults were minor, a high accuracy rate was obtained. The capability to classify the faults and the high diagnosis accuracy prove the robustness and high sensitivity of the method, enabling its practical applications in industries.

Cable termination fault is one of the most important problems for high voltage underground cable lines (HVUCL). Harmonic current (HC) and the sheath current (SC) are causes of cable termination faults of HVUCL. The sheath voltage (SV) of cable increases due to SC and HC also. So, the electroshock risk for human occurs. In this study, cable termination faults are examined for long HVUCL that is connected to electric network with high harmonic distortion rate. In literature, solid bonding (SB) and sectional solid bonding (SSB) methods are used to reduce harmonic distortion rate and SC effect in HVUCL. However, when SB and SSB methods are used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are exceeded. Therefore, the modified SSB (MSSB) method is developed for bonding of long HVUCL. SV of HVUCL should be known to use MSSB for bonding of long HVUCL. Then SV of HVUCL is forecasted by using artificial neural network and hybrid artificial neural networks (HANN) before the long HVUCL is installed. MSSB parameters should be optimized, so that optimization methods are used for optimization of MSSB and HANN. When MSSB method is used for bonding of long HVUCL, harmonic distortion limit and touch voltage limit are not exceeded under high harmonic distortion conditions.

In the unbalanced loading (UL) and phase to ground fault (PGF) cases, zero sequence current (ZC) flows on neutral point of power transformer, and the sheath current (SC) and the sheath voltage (SV) increase due to ZC. Thus, overvoltage (OV) and high harmonic distortion (HD) occur in cable termination (CT). OV causes high and imbalanced electric field, and high HD causes increasing of insulation temperature in CT, so CT faults occur. In the literature, bonding methods are used to prevent SC and SV effects, but these methods are not sufficient to prevent ZC effects, so the modified sectional solid bonding (MSSB) is suggested to prevent ZC effects. The aims of this study are minimizations of SV and HD on CT to prevent CT faults, so MSSB parameters are optimized by optimization method. In optimization algorithms of MSSB, the forecasting methods (FM) and optimization methods (OM) are used to optimize MSSB parameters. The best FM is selected according to training and forecasting errors, and the selected FM is used as an objective function of OM. Training and forecasting errors of hybrid ANN are less than the other methods, so hybrid ANN methods are used as FM. When bonding methods that are in literature are simulated under UL and PGF cases, SV and HD values exceed the limits. When the optimized MSSB method is used, HD and SV do not exceed the limits. Therefore, the optimized MSSB is suggested to prevent CT faults for the unbalanced cases. [ABSTRACT FROM AUTHOR]

Cable termination fault is one of the most important problems for high voltage underground cable lines (HVUCL). Harmonic current (HC) and the sheath current (SC) are causes of cable termination faults of HVUCL. The sheath voltage (SV) of cable increases due to SC and HC also. So, the electroshock risk for human occurs. In this study, cable termination faults are examined for long HVUCL. In literature, solid bonding (SB) and sectional solid bonding (SSB) methods are used to reduce harmonic distortion rate and SC effect in HVUCL. However, when bonding of long HVUCL is made with SB and SSB, the limits of touch voltage and harmonic distortion are exceeded. Therefore, bonding of long HVUCL is made by the modified SSB (MSSB). In MSSB, SV of HVUCL should be known. Thus SV of HVUCL is forecasted by using artificial neural network and hybrid artificial neural networks (HANN) before the long HVUCL is installed. MSSB parameters and HANN are optimized by optimization method. The limits of touch voltage and harmonic distortion are restricted by using MSSB in long HVUCL under high harmonic distortion conditions. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) detection is one of the most effective methods for electrical equipment insulation fault diagnosis. Most existing PD detection methods are based on the processing of PD waveforms. However, the PD waveforms can be severely disturbed by the complex environment noise in substations, which can lead to great drop in detection accuracy. In this paper, we propose a PD detection method based on power maximum likelihood estimation. This method does not rely on the PD waveforms but utilizes a statistical approach of maximum likelihood estimation to analyze the distribution characteristic of PD signals, transferring the traditional method of waveform processing to a new perspective of statistical analysis. Eventually, the direction of arrival of the PD source can be derived. The proposed method has greatly improved the PD detection accuracy, especially in low signal to noise ratio (SNR) conditions. In simulation tests, it shows a better capability of noise immunity with signal SNR in [–5 dB, 5 dB] range. Field tests performed in a 110-kV substation (SNR around 5 dB) showed that the PD detection accuracy can be improved by up to 70% compared to the traditional methods. Our results may further promote the practical application of substation PD detection system. [ABSTRACT FROM AUTHOR]

This article describes faults that occur in the core wire of metallic cables and the methods used to locate them. This is the forty-first article in a series on telecommunication technologies. This contribution is from the Access Engineering Group, Technical Assistance and Support Center, Maintenance and Service Operations Department, Network Business Headquarters, NTT EAST. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) is an early manifestation of insulation fault that occurs in electrical equipment, which holds rich feature information used to insulation assessment. In this study, step voltage method was applied to investigate the PD development process of typical protrusion defects in gas‐insulated switchgear. Nine features were extracted to represent the deterioration degree of internal insulation. Fuzzy C means clustering was applied to solve the state centres. PD severity was divided into four states based on the PD developing process, and the harmfulness of each state was illustrated. Finally, adaptive objective weight technology based on the theory of maximising deviation was adopted, and two‐level fuzzy comprehensive evaluation (TL‐FCE) model was established to address the problem of the weight allocation of different features on the evaluation result. The experimental test has been conducted to test the validity and effectiveness of the model. It is proved that TL‐FCE owns good performance to assess PD severity, and it is more suitable to handle fuzzy boundary problems than support vector machine. [ABSTRACT FROM AUTHOR]

In series compensation stations of the UHV AC demonstration project in China, capacitive voltage transformers (CVTs) failed several times during the operation of disconnecting switches (DSs). The reasons for this failure are analyzed in this paper. The stray inductor, the stray capacitor between the platform and ground and the capacitor of the CVT forms a resonant circuit in series compensation stations, causing repeated oscillating overvoltage and impulse current acting on the CVTs during DS operation. A full-scale experiment indicates that the oscillating frequency is approximately 200 Hz and the repeating frequency is approximately 0.5 MHz. The simulation experiment in the laboratory indicates that the partial welding mode and the partial high electric field are the main causes of damage to the CVT element insulation. A mechanism of the insulation damage is proposed, and some suggestions are given based on our results. [ABSTRACT FROM AUTHOR]

Abstract: This paper proposes a tool of assistance to prelocate insulation faults affecting electrical single-phase cables by using measurements of voltage and current available in source substation. An equivalent network modeling faults to the ground is analyzed by employing the distributed parameters approach. The per-unit length values of these parameters are calculated according to the geometrical data of the cable. The specificity of this tool is the introduction of a resistance to model sheath-ground insulation what allows studying various types of short-circuits to the ground (frank and resistive). Scenarios of fault are applied to the underground cable 150kV, connecting high voltage (HTB) sub-stations of Tyna–Taparoura–Sidimansour in Sfax city of Tunisia. A study of validation is approved by the software Simulink–SimPowerSystems of Matlab. [Copyright &y& Elsevier]

• High zero sequence current (ZC) and high current harmonic distortion (THDI) cause the cable termination faults. • Various bonding methods are used to prevent cable termination faults in IEEE 575-1988 standard, but these methods are not sufficient to prevent cable termination faults. • In this study, LSSB method is developed as a new bonding method. • Simulations of the optimized LSSB and solid bonding (SB) that is suggested in IEEE 575-1988 standard are made under high ZC and high THDI situations in PSCAD/EMTDC. • It is seen that the sheath voltage (SV), ZC and THDI are at very high level in SB results, and SV, ZC and THDI on the metallic sheath are at very low level in LSSB. Cable termination fault (CTF) is a major problem for high voltage cable lines (HVCL). Increasing of the sheath voltage (SV), zero sequence current (ZC) and current harmonic distortion (THDI) on metallic sheath (MS) of HVC are major factors for CTF. MS is grounded according to IEEE 575-1988 standard to reduce SV. However, these methods are not sufficient to prevent CTF based on ZC and THDI. The aims of this paper are minimization of SV, ZC and THDI to prevent CTF based on ZC and THDI. Thus, LSSB method is developed as a new bonding method. Also, LSSB parameters should be optimized to make the most economical and practical bonding. GA, DEA, PSO and iPSO are used optimization methods for optimization of LSSB. SV and THDI should be known for optimization of LSSB, so the forecasting methods (FM) are used as fitness function of optimization methods in LSSB optimization. The regression and hybrid artificial neural network methods are compared to determine the most suitable FM. When the optimized LSSB is used for bonding of long HVCL, SV reduces approximately 90%, ZC reduces approximately 93%, and THDI reduces approximately 70%. Thus CTF risk is minimized by using the optimized LSSB in HVCL. [ABSTRACT FROM AUTHOR]