Momentary Interruptions Research Articles

A new multi-objective-stochastic framework for reconfiguration and wind energy resource allocation in distribution network incorporating improved dandelion optimizer and uncertainty

Improving the reliability and power quality of unbalanced distribution networks is crucial for ensuring consistent and reliable electricity supply. In this research, multi-objective optimization of unbalanced distribution networks reconfiguration integrated with wind turbine allocation (MORWTA) is implemented considering uncertainties of networks load, and also wind power incorporating a stochastic framework. The multi-objective function is defined by the minimization of power loss, voltage sag (VS), total harmonic distortion (THD), voltage unbalance (VU), energy not-supplied (ENS), system average interruption frequency index (SAIFI), system average interruption duration index (SAIDI), and momentary average interruption frequency (MAIFI). A new improved dandelion optimizer (IDO) with adaptive inertia weight is recommended to counteract premature convergence to identify decision variables, including the optimal network configuration through opened switches and the best location and size of wind turbines in the networks. The stochastic problem is modeled using the 2m + 1 point estimate method (PEM) combined with K-means clustering, taking into account the mentioned uncertainties. The proposed stochastic methodology is implemented on three modified 33-bus, and unbalanced 25-, and 37-bus distribution networks. The results demonstrated that the MORWTA enhanced all study objectives in comparison to the base networks. The results also demonstrated that the IDO had superior capability to solve the deterministic- and stochastic-MORWTA in comparison to the conventional DO, grey wolf optimizer (GWO), particle swarm optimization (PSO), and arithmetic optimization algorithm (AOA) in terms of achieving greater objective value. Moreover, the results demonstrated that when the stochastic-MORWTA model is considered, the power loss, VS, THD, VU, ENS, SAIFI, SAIDI, and MAIFI are increased by 18.35%, 9.07%, 10.43%, 12.46%, 11.90%, 9.28%, 12.16% and 14.36%, respectively for 25-bus network, and also these objectives are increased by 12.21%, 10.64%, 12.37%, 9.82%, 14.30%, 12.65%, 12.63% and 13.89%, respectively for 37-bus network compared to the deterministic-MORWTA model, which is related to the defined uncertainty patterns.

Analysis of Electrical Signal Disturbances. A New Strategy.

A joint treatment for signal analysis based in both Fourier and Wavelet theory is presented. Distinguishing from harmonics and transient disturbance components present on an electrical signal, the former part is extracted by means of Fourier methods, while the latter is subjected to multiresolution treatment in order to split disturbance low frequency components with high frequency components. Numerical experiments are performed over a variety of signals with a given harmonic content, which are classified according to the kind of low frequency disturbance (voltage sag, swell and momentary interruption) and high frequency disturbance (oscillatory transient) present. In every case, a good compression rate is achieved and disturbance components in an efficient way are extracted. Finally, characteristic plots of the low frequency disturbances are obtained for classification purposes.

Optimized Allocation of Fault Transmitters for Improving the Recloser-Fuse Coordination

New technologies are currently delivering protective devices that can enhance the design of protection coordination in modern distribution systems. This paper proposes an integer linear programming (IP) model to find the optimal location of a Fault Transmitter (FT) in the distribution system. The proposed IP model provides the optimal FT allocation considering the minimization of sustained interruption frequency and momentary interruption duration. A study of the appropriate number of FT reveals the best alternative in the proposed adaptive protection scheme. A Monte Carlo simulation with a richer representation of stochastic fault scenarios is used for further evaluation of the solutions obtained with the proposed IP model. The combined strategies allow full-scale studies of the optimal allocation of FT in distribution systems. The results of studies using two test systems certify the benefits of the proposed strategy in fuse-saving coordination and in reducing the total duration of the momentary interruption, which can cause power quality problems.

The effect of electricity reliability on the sustainability of SMEs in Fako Division of Cameroon

Purpose: To investigate the effects of the reliability of electricity supply on the sustainability of SMEs in Cameroon. Research Methodology: This study investigates the effects of the reliability of electricity supply on the sustainability of SMEs in Cameroon. The study used a quantitative approach with the philosophical underpinnings of objectivist ontology and positivist epistemology. Primary data were obtained through closed-ended questionnaires that were responded to by 54 purposively sampled participants in the Fako division. The data were analyzed by Structural Equation Modeling (SEM) using SPSS 23 and SPSS Amos 24 software. Results: The study revealed that sporadic electricity supply interruptions, chronic electricity supply interruptions, and momentary electricity supply interruptions have no significant positive impact on the sustainability of SMEs in the Fako Division of the Southwest Region of Cameroon. Limitations: This study had a limitation in methodology, as it used a quantitative approach only. A better understanding of this study’s phenomenon can be achieved by adopting a mixed research method, where the qualitative aspect will provide a deeper understanding of the effects of other variables that affect SME sustainability. Contribution: Based on the results of this study, business managers will come to the understanding that the sustainability of their businesses is not dependent on the reliability of the electricity supply. This means that other variables responsible for the sustainability of businesses can be studied qualitatively.

An Improved Human-Inspired Algorithm for Distribution Network Stochastic Reconfiguration Using a Multi-Objective Intelligent Framework and Unscented Transformation

In this paper, a stochastic multi-objective intelligent framework (MOIF) is performed for distribution network reconfiguration to minimize power losses, the number of voltage sags, the system’s average RMS fluctuation, the average system interruption frequency (ASIFI), the momentary average interruption frequency (MAIFI), and the system average interruption frequency (SAIFI) considering the network uncertainty. The unscented transformation (UT) approach is applied to model the demand uncertainty due to its being simple to implement and requiring no assumptions to simplify it. A human-inspired intelligent method named improved mountaineering team-based optimization (IMTBO) is used to find the decision variables defined as the network’s optimal configuration. The conventional MTBO is improved using a quasi-opposition-based learning strategy to overcome premature convergence and achieve the optimal solution. The simulation results showed that in single- and double-objective optimization some objectives are weakened compared to their base value, while the results of the MOIF indicate a fair compromise between different objectives, and all objectives are enhanced. The results of the MOIF based on the IMTBO clearly showed that the losses are reduced by 30.94%, the voltage sag numbers and average RMS fluctuation are reduced by 33.68% and 33.65%, and also ASIFI, MAIFI, and SAIFI are improved by 6.80%, 44.61%, and 0.73%, respectively. Also, the superior capability of the MOIF based on the IMTBO is confirmed compared to the conventional MTBO, particle swarm optimization, and the artificial electric field algorithm. Moreover, the results of the stochastic MOIF based on the UT showed the power loss increased by 7.62%, voltage sag and SARFI increased by 5.39% and 5.31%, and ASIFI, MAIFI, and SAIFI weakened by 2.28%, 6.61%, and 1.48%, respectively, compared to the deterministic MOIF model.

Cost Effective Reliability Improvements in 33kV/11kV Electricity Distribution Networks – A Case Study in Western Province South 1, CEB, Sri Lanka

Electricity Distribution system in Sri Lanka consists of 33 kV, 11 kV and LV (400V/230 V) networks. Providing reliable supply to the end user is a challenging task to any utility. Therefore, utility is committed to develop its network to provide reliable supply to electricity users by investing in system developments. In this research, a methodology is introduced for selecting cost-effective solutions to improve the reliability of the 33 kV and 11 kV distribution systems among different proposals. Improvement of conductor, its insulation and protection of short duration faults are focused to develop the system in this research. Part of the method developed includes a software tool (named as DisFeeRIA) to analyse the reliability indices and economic parameters for the relevant proposal. Database of the DisFeeRIA software tool includes failure rate improvement, mean time to repair and costing of each option under consideration. Medium Voltage Underground Cable (MVUGC), Medium Voltage Aerial Bundle Conductor (MVABC), Medium Voltage Covered Conductor (MVCC), Room Temperature Vulcanizing (RTV) Si-R coating on existing bare overhead line ceramic insulators are considered as options for improving conductor and its insulation. One of the latest and innovative technologies used in distribution network, Pulse Closing Technology, is used to reduce short duration faults (momentary interruptions) and enhance the lifetime of the equipment used in distribution networks. Developed tool and method were tested by a case study done for distribution network in Western Province South – 01 of Ceylon Electricity Board (CEB). Three (03) feeders were selected in different areas from Urban, Coastal and Rural for this purpose. MVCC and RTV Si-R coating for existing Medium Voltage Bare Overhead lines can be used for improving the reliability of Coastal, Urban and Rural distribution feeders in a cost-effective manner after proper analysis, based on technical and economic aspects. However, depending on the safety concerns, MVUGC or MVABC can be used irrespective of the economical aspect. Intelirrupter pulse closers can be used to replace traditional auto recloses, especially with MVUGC, MVABC and MVCC in rural feeders. It helps to reduce momentary interruption failures and enhance the equipment lifetime by reducing thermal and mechanical stress on all distribution equipment and cables. Furthermore, it improves the power quality of the system.

Efficacy of Closed and Open Endotracheal Suction on Prevention of Ventilator-Associated Pneumonia on Patients Admitted to Critical Care Unit at Tertiary Care Hospital

Background: Endotracheal suctioning is a method commonly used to clean airway secretions in patients under mechanical ventilation. This study aimed to compare the effects of open and closed suction methods on the occurrence of ventilator-associated pneumonia (VAP). In the open endotracheal suction, the approach necessitates the participation of two nurses and may result in a momentary interruption of ventilation and oxygen supply due to the patient’s disconnection from the ventilation device during suctioning. In the closed endotracheal suction, the approach can be performed through connections in a closed suction set while the patient is ventilated without separating the patient from the ventilator. Objective: (1). To compare the close endotracheal suction with open endotracheal suction for the prevention of VAP. (2) To assess the incidence of VAP among intubated patients. Materials and Methods: The study was conducted among 60 patients who are on mechanical ventilator in the critical care unit in tertiary care hospital. For the study, simple random sampling technique is used for the selection of sample. Using a lottery method of sampling, one in the experimental group and one in the control group on the basis of inclusion criteria. Results: The study was done on patients who are on mechanical ventilators in the critical care unit in tertiary care hospitals. The data analysis was done using descriptive and inferential statistics. The study finding revealed that in VAP scoring of the patient’s 1st and 2nd day in open endotracheal suction, there are no significant changes in open endotracheal suction then null hypothesis was accepted (t = 0.9, P = 0.37). VAP scoring of the patient’s 2nd and 3rd day and 3rd and 1st day in open endotracheal suction, there are significant changes in open endotracheal suction method in null hypothesis was rejected (P < 0.05). VAP scoring of the patient’s 1st and 2nd day and 2nd and 3rd day and 3rd and 1st day in closed endotracheal suction, there are significant changes in closed endotracheal suction then null hypothesis was rejected (P < 0.05). Conclusion: The study assessed the efficacy of open endotracheal suction versus closed endotracheal suction on age, sex, duration of hospital stays, return of mechanical ventilation, and mode of ventilation are not significant but the duration of mechanical ventilation is significant. The nurses play a vital role in assessing the cardiac monitor while doing suctioning to prevent cardiorespiratory complications.

Power-Loss Ride-Through with Reduced Number of Voltage Sensors in a Cascaded H-Bridge Inverter fed Vector Controlled Induction Motor Drive

Cascaded H-Bridge (CHB) inverter-fed drives are quite popular in high-power industrial applications. However, these drives are extremely sensitive to power supply disturbances on the input grid side, such as voltage sags or short-duration power interruptions that cause the drive to trip on under-voltage protection resulting in production losses. Therefore, it is necessary to employ techniques that improve the resilience of the drive by enabling it to smoothly ‘ride-through’ such short-duration disturbances. The traditional ride-through solutions in CHB drives typically necessitate additional hardware or multiple DC link voltage sensors, which increase the cost and complexity of the system. This paper proposes a simple and cost-effective approach for power-loss ride-through in CHB inverter based vector-controlled induction motor drives. In this method, the kinetic energy stored in the rotating mass is recovered and fed back to the DC-link capacitors to keep all the DC link voltages constant during momentary supply interruptions or voltage sags. The proposed technique works by controlling the voltage space phasor without the need for extra hardware and voltage sensors at the CHB cells. The proposed scheme is experimentally validated on a 30 kW, 7-level CHB inverter based vector controlled induction motor drive.

Ensuring the Continuity of Power Supply to the On-Board Auxiliary Devices of the Trolleybus through the Recuperation of Kinetic Energy

When a trolleybus travels through insulated sections of the overhead contact line, it experiences momentary power interruptions, which adversely affect the vehicle’s on-board auxiliary subassemblies. To reduce these negative effects, one can harness energy recovered via regenerative braking. A model power supply circuit diagram for structural systems of the trolleybus is proposed. Simulation tests were carried out to develop a method for analyzing power supply to trolleybus auxiliary devices and verify it in a real-life example. The results allow determination of the limit power that can be generated by the trolleybus drive system to feed auxiliary devices during interruptions in power supply from the overhead contact line. The possibility of powering the on-board auxiliary equipment of a trolleybus using energy from recuperation with a traction motor is presented.

Power Quality Improvement Using Unified Power Quality compensator

Power quality has become an important factor in power systems, for consumer and household appliances with proliferation of various electric/ electronic equipment and computer systems. The main causes of a poor power quality are harmonic currents, poor power factor, supply voltage variations, etc. In recent years the demand for the quality of electric power has been increased rapidly. Power quality problems have received a great attention nowadays because of their impacts on both utilities and customers. Voltage sag, swell, momentary interruption, under voltages, over voltages, noise and harmonics are the most common power quality disturbances.It proposes a new connection for a unified power quality compensator (UPQC) to improve the power quality of two feeders in a distribution system. It illustrates how UPQC can improve the power quality by mitigating all these PQ disturbances. The proposed configuration of the UPQC is developed and verified for various power quality disturbances by simulating the mode using MATLAB.

A transformerless active voltage quality regulator with the novel three‐leg circuit

AbstractVoltage sags and momentary interruptions of power are the most severe voltage disturbances. Here, a tansformerless active voltage quality regulator with the novel three‐leg circuit is proposed to mitigate long duration and deep voltage sags. The shunt rectifier and series inverter of this novel three‐leg circuit are all full‐bridge structures, so it has lower DC bus voltage and smaller filter parameters than the conventional half‐bridge topologies. The totem‐pole bridgeless boost circuit is formed among the three bridge arms and the DC bus voltage will be charged to exceed the peak value of the supply voltage. It can compensate for deep voltage sags (that may be more than 50% of the nominal voltage). Compared to the conventional transformerless series‐connected topology, the proposed topology has the merits of higher efficiency, smaller volume and lower cost. The validity and feasibility of the proposed topology are verified by theoretical analysis, simulation and experiment.

Recognition of complex and multiple power quality disturbances using wavelet packet-based fast kurtogram and ruled decision tree algorithm

This paper introduces an algorithm based on wavelet packet supported fast kurtogram and decision rules for the identification and classification of complex power quality (PQ) disturbances. Features are extracted from the signals using fast kurtogram, envelope of filtered voltage signal and amplitude spectrum of squared envelop. Proposed algorithm can be implemented for the recognition of the complex PQ disturbances, which include the combination of voltage sag and harmonics, voltage momentary interruption (MI) and oscillatory transient (OT), voltage MI and harmonics, voltage sag and impulsive transient (IT), voltage sag, OT, IT and harmonics. Proposed work has been performed using the MATLAB software. Performance of the algorithm is compared with performance of algorithm supported by discrete wavelet transform (DWT) and fuzzy C-means clustering (FCM).

Role of angiotensin II in chronic intermittent hypoxia-induced hypertension and cognitive decline.

Sleep apnea is characterized by momentary interruptions in normal respiration and leads to periods of decreased oxygen, or intermittent hypoxia. Chronic intermittent hypoxia is a model of the hypoxemia associated with sleep apnea and results in a sustained hypertension that is maintained during normoxia. Adaptations of the carotid body and activation of the renin-angiotensin system may contribute to the development of hypertension associated with chronic intermittent hypoxia. The subsequent activation of the brain renin-angiotensin system may produce changes in sympathetic regulatory neural networks that support the maintenance of the hypertension associated with intermittent hypoxia. Hypertension and sleep apnea not only increase risk for cardiovascular disease but are also risk factors for cognitive decline and Alzheimer's disease. Activation of the angiotensin system could be a common mechanism that links these disorders.

Smart Anti-jamming Mobile Communication for Cloud and Edge-Aided UAV Network

The Unmanned Aerial Vehicles (UAV) networks consisting of low-cost UAVs are very vulnerable to smart jammers that can choose their jamming policies based on the ongoing communication policies accordingly. In this article, we propose a novel cloud and edge-aided mobile communication scheme for low-cost UAV network against smart jamming. The challenge of this problem is to design a communication scheme that not only meets the requirements of defending against smart jamming attack, but also can be deployed on low-cost UAV platforms. In addition, related studies neglect the problem of decision-making algorithm failure caused by intermittent ground-to-air communication. In this scheme, we use the policy network deployed on the cloud and edge servers to generate an emergency policy tables, and regularly update the generated policy table to the UAVs to solve the decision-making problem when communications are interrupted. In the operation of this communication scheme, UAVs need to offload massive computing tasks to the cloud or the edge servers. In order to prevent these computing tasks from being offloaded to a single computing resource, we deployed a lightweight game algorithm to ensure that the three types of computing resources, namely local, edge and cloud, can maximize their effectiveness. The simulation results show that our communication scheme has only a small decrease in the SINR of UAVs network in the case of momentary communication interruption, and the SINR performance of our algorithm is higher than that of the original Q-learning algorithm.

A Restart Strategy of a Rotating Induction Machine for Inrush Current Elimination

In the application of electric railway traction, induction machines may suffer momentary power interruptions. Restarting control while machine running is a critical part of such applications, but residual flux in the free-running rotor deteriorates conventional controller performances, leading to inrush current and torque impact. Thus, this article proposes an improved feed-forward current controller that compensates voltage variations in the restart process. The residual rotor flux, as well as the induced back electromotive force, is estimated only with the measured speed in the free-running stage. The exact electromotive force is compensated at the restart moment, and the following current re-establishing stage. Based on the feed-forward compensation, the restart impact is eliminated and the restart current is controlled accurately in the predefined trajectories. Verified by experiments, the restart controller provides flexible restart manipulations.

Valuation of Reliability Index in Distribution Network 13.8 kV

This study is proposed to calculate and analyze the level of reliability of the 13.8 kV distribution system. To calculate the reliability index based on the reliability index of the value of the failure that occurred. The method used throughout this study is the Reliability Index Assessment (RIA) when this method takes into account momentary interruption. The distribution network is considered as the object of this study has six feeders. Based on blackout data obtained, the reliability index becomes smaller and can be distinguished between permanent and temporary disruptions. The calculation results show the reliability index of SAIDI, SAIDI, and MAIFI based on the type of disturbance; the results of this calculation will be compared with SPLN and IEEE. A comparison of the results of the calculation of SAIFI values from the six feeders analyzed all meet the SPLN and IEEE rules. However, in one of the feeders, the SAIDI index exceeds the established standard, which is 24 hours/year/customer, with the SPLN regulation being 21 hours/year/customer, and the IEEE standard is 2.3 hours/customer/year. And finally, the results of an analysis of the MAIFI index for all feeders meet the IEEE standard of 5 times/year/customers.

Development and Integration of Momentary Event Models in Active Distribution System Reliability Assessment

The random failures in a distribution network lead to different reliability events, such as voltage sags, momentary interruptions, and sustained interruptions. Even momentary reliability events i.e., voltage sags and momentary interruptions cause significant financial losses to many customers. This paper develops a novel aggregated reliability event model for the reliability studies of distribution systems integrating the momentary reliability events in addition to sustained interruptions. The developed model incorporates the impacts of temporary and permanent failures on the customers considering different reliability events. A graph theory-based search algorithm is utilized to efficiently recognize different protection settings, alternate supplies, and presence of Distributed Energy Resources (DERs)/microgrids in the network. Furthermore, the proposed model incorporates the possible mitigation measures brought by the DERs/microgrids while quantifying the reliability profile of load points and the overall system. The case studies conducted on a practical test system show the effectiveness of the proposed model to evaluate the reliability and to carry out system upgrades in the context of active distribution systems.

Recognition of Complex Power Quality Disturbances Using S-Transform Based Ruled Decision Tree

Deteriorated quality of power leads to problems, such as equipment failure, automatic device resets, data errors, failure of circuit boards, loss of memory, power supply issues, uninterrupted power supply (UPS) systems generate alarm, corruption of software, and heating of wires in distribution network. These problems become more severe when complex (multiple) power quality (PQ) disturbances appear. Hence, this manuscript introduces an algorithm for identification of the complex nature PQ events in which it is supported by Stockwell’s transform (ST) and decision tree (DT) using rules. PQ events with complex nature are generated in view of IEEE-1159 standard. Eighteen different types of complex PQ issues are considered and studied which include second, third, and fourth order disturbances. These are obtained by combining the single stage PQ events such as sag & swell in voltage, momentary interruption (MI), spike, flicker, harmonics, notch, impulsive transient (IT), and oscillatory transient (OT). The ST supported frequency contour and proposed plots such as amplitude, summing absolute values, phase and frequency-amplitude obtained by multi-resolution analysis (MRA) of signals are used to identify the complex PQ events. The statistical features such as sum factor, Skewness, amplitude factor, and Kurtosis extracted from these plots are utilized to classify the complex PQ events using rule-based DT. This is established that proposed approach effectively identifies a number of complex nature PQ events with accuracy above 98%. Performance of the proposed method is tested successfully even with noise level of 20 dB signal to noise ratio (SNR). Effectiveness of the proposed algorithm is established by comparing it with the methods reported in literature such as fuzzy c-means clustering (FCM) & adaptive particle swarm optimization (APSO), Wavelet transform (WT) & neural network (NN), spline WT & ST, ST & NN, and ST & fuzzy expert system (FES). Results of simulations are validated by comparing them with real time results computed by Real Time Digital Simulator (RTDS). Different stages for design of complex PQ monitoring device using the proposed approach are also described. It is verified that the proposed approach can effectively be employed for design of the online complex PQ monitoring devices.

Reliability Analysis of Distribution Network Based on Reliability Index Assessment Method: A Case Study.

A primary requirement of a modern electric power system is reasonable ability to satisfy the customer load requirements. Electric utilities involve generation, transmission, and distribution facilities each one of which contributes its own inherent difficulties to the problem of satisfying customer requirement. A power system should be designed and expanded the facilities in order to perform its intended function with a reasonable risk. With increasing the electrical energy demand and the potential of disruption that may occur in the system, the distribution system must have high reliability and continues supply to customer. In this case, the reliability of the distribution system needs to be evaluated by monitoring and analyzing the level of distribution system failure in a certain period of time. A study on a practical distribution system with application of automatic circuit reclosers (ACRs) which plays an important role in enhancing the reliability index of system is presented. The reliability index assessment analyze the reliability index of the existing system before and after application of ACRs. From the simulation point of view, the system average interruption frequency index (SAIFI) is about 19.43% or decreased the failure frequent event from 11.4 failure/ customer.year to 9.25 failure/customer.year); while the momentary average interruption frequency index (MAIFI) has decreased from 6.72 failure/customer.year to 5.05 failure/ customer.year, or increase the reliability index of about 24.85%.

Wavelet based performance analysis of AC transmission systems with unified power flow controller under power quality issues

The developments in power quality are fast and difficult to predict. The majority of power quality issues experienced by industrial customers can be attributed to momentary interruptions, voltage sags or swells, transients, harmonic distortion, electrical noise, and flickering lights, among others. A new device may be invented tomorrow solving power quality problems. The FACTS devices could provide fast control of active and reactive power through a transmission line. The unified power-flow controller (UPFC) is a member of the FACTS family with very attractive features. This device can independently control many parameters, so it is the combination of the properties of a static synchronous compensator (STATCOM) and static synchronous series compensator (SSSC).The performance of AC Transmission system with Unified power flow controller under various power quality problems analysis described. The proposed system is formulated and research work is done by wavelet multi resolution analysis using Bior1.5 mother wavelet with MATLAB/SIMULINK software. It is observed that the effectiveness of AC power transmission through Unified power flow controller under power quality problems of sag, swell, transient, temporary faults and capacitive switching.