Development of a Hybridized Model for Detection of Voltage Collapse in Electrical Power Systems

Voltage collapse is an occurrence in power systems that are heavily loaded, faulted and have reactive power shortages. It is a system instability involving large disturbances (including rapid increase in load or power transfer) and usually associated with reactive power deficits. Numerous power system blackouts in the past indicates/shows that enough researches have not been done to solve the problem of voltage instability and the resultant voltage collapse. This research paper therefore develops a hybridized sensitivity based voltage collapse prediction index model for detection of voltage collapse in electrical power systems. Sensitivity based method and the voltage collapse prediction index method were hybridized using the linearized basic power flow equations. Newton-Rapson technique was employed to solve the linearized power flow equation to compute the changes in real and reactive powers with respect to change in voltage magnitudes and voltage phase angles. The stressed version of the standard IEEE 24 bus system was used as an input parameter for the computation.Load shedding technique was then embarked on to find the weak bus for load shedding and the required generation reduction to maintain power balancing while buses having an unstable voltage profile were selected using the developed model. Bus number 3 had the least voltage magnitude of 1.018 p.u before stressing while bus number 16 recorded the highest voltage magnitude of 1.082 p.u even though the voltage magnitudes of these two buses were 0.623 p.u and 0.4611 p.u respectively after being stressed. The least and highest loads after shedding with the sensitivity based method were 0.11925 p.u and 0.6214 p.u respectively while the least and highest loads after shedding with the VCPI method were 0.1368 p.u and 0.6148 p.u respectively. With the hybridized sensitivity based VCPI model, the least and highest loads after shedding were 0.2068 p.u and 0.6314 p.u respectively confirming the efficiency of the HSBVCPI model.The total load demand met by the system with the hybridized model was higher compared to that of the sensitivity based method and the VCPI method. The power generated after the multi-stage load shedding by the sensitivity based method, VCPI method and the hybridized model were 2.12 p.u, 3.05 p.u and 3.65 p.u respectively showing that the power balance equations were satisfied since the total generation was greater than the total demand. The hybridized model improves better the voltage profiles of many of the load buses as compared to the other two methods. Bus numbers 4, 5, 12 and 15 were selected for load shedding with the hybridized model since all the load buses had loads less or equal to their loadability margin, hence, all the buses have satisfied the loadability condition. Even though, the VCPI method perform better than the sensitivity based method in detecting voltage collapse, the hybridized model performs best in term of detection of power system voltage collapse and load shedding implementation. Keywords: Voltage Collapse, Sensitivity, Voltage Collapse Prediction Index (VCPI), Voltage Instability, Load Shedding, Power Balance, Newton-Raphson technique

Development of Top-Up And Bottom –Up Techniques for Assessment of Power Line Communication Channel Model

Power Line Communication (PLC) is the transfer of data and voice signals from one communication system to another over the electric power delivery network. However, with the advent of technology, human dependency on electricity and communication has grown beyond leaps and bounds. The power transmission line channel has not been designed with wired channel requirements for broadband applications and appears as a harsh environment for the low-power high-frequency communication signals. This study therefore evaluate the performance of PLC on power grid by simulating a practical multipath power line communication channel model using top-down and bottom-up approach. The statistical multipath parameters such as path arrival time, magnitude and interval for each category were analyzed. This is done over the frequency range of 100-300 kHz. The result shows that at 100 kHz, data can be transmitted up to 350 meters without signal distortions while for 300 kHz only 50 meters can be covered. In addition, signal attenuation with a distance of 2 km is about 0.2 of the original signal at 300 kHz and less at higher frequencies. The results in the time and frequency domains indicate that data transmission in PLC environment needs signal to be amplified at higher powers. Keywords: Power Line Communication, Power Grid, Transmission Line, Multipath Parameters, Channel Modelling, Top-Down Approach, Bottom-Up Approach. DOI: 10.7176/JNSR/9-16-03 Publication date: August 31st 201

Effects of Power Line Communication on Radio Communication Equipment

Radio communication is a wireless transfer of information via power cable by Power Line Communication (PLC) and its dissemination through radio communication equipment.. However, this information causes signal interference, noise and distortion with the power line communication. This work analyzed the effect of PLC on radio communication equipment by interconnecting two high-speed PLC modems communicating with a data rate of up to 250 Mbit/s using telephone distribution wiring for radio spectrum to reduce the interference radiation that emanates from a power line. The measurements were made using a reference antenna at a distance of 3 m from the power line. The peak field-strength values were measured and recorded in the 30-350 MHz frequency range in horizontal and vertical polarization. The result shows that interference radiation occurring at frequencies up to 305 MHz, includes the FM band as well as the Digital Audio Broadcasting (DAB) band. It is expected that as the data rate of high speed modems increases, a corresponding increase in the interference radiation occurs at frequencies above 300 MHz. To this regard, administrations should take all practicable and necessary steps to ensure that the operation of power and telecommunication distribution networks do not cause harmful interference to a radio communication service. Keywords: PLC, Radio Communication, Interference, Noise, Distortion, Communication Equipment, Field Strength, DAB DOI: 10.7176/JNSR/9-16-04 Publication date: August 31st 201

Impact of Automatic Circuit Reclosers and Distributed Generators on the Reliability Indices of Electrical Distribution Systems

Reliability is the ability of power system to perform its intended function as at when due. Parameters used to assess the level at which this is done are called reliability indices. Previous researches have not focused deeply on the effect of installing automatic circuit reclosers ACRs and distributed generators (DGs) on the assessment of reliability indices of electrical power distribution system, hence, the drive towards this research paper. Monte Carlo Simulation (MCS) was performed in MATLAB on the IEEE 34 test feeder. Under three different case studies- when one ACF was installed on the test system, when two ACRs were installed on the test system and when 1MW DG unit was installed on the test system.  Real system data were used as input parameters for the simulation. The overall distribution system reliability was evaluated using the load point and the system reliability indices such as System Average Interruption Frequency Index (SAIFI), System Average Interruption Duration Index (SAIDI) and Customer Average Interruption Duration Index (CAIDI).  (CAIDI), Average Service Availability Index (ASAI) and EUE.The results obtained with the MCS were compared with the results obtained previously for the same test system using analytical approach and was found to be in agreement. The results of the research paper showed that the installation of an automatic circuit recloser gave a reduction in SAIFI value from 17.33hours/year to 14.93 hours/year with the installation of ACR between nodes (800-802). The best improvement was noticed when ACR was installed between nodes (834-842) in the electrical feeder. The value of SAIDI obtained also decreased from 8.90hom/year to 7.99 hours/year with the installation ACR between nodes (800-802). When two ACR were installed in the test system between nodes (828-824) and (824-826), the values obtained for SAIFI were 10.74 hours/year and 11.20 hours/year respectively representing a level of improvement in the SAIFI index. Between these nodes, values of SAIFI were also 4.211 hours/year and 4.423 hours/year which also represents an improvement in SAIDI values.Installation of 1MW Distributed generator (DG) unit in the test system gave SAIFI and SAIDI values of 14.23 hours/year and 5.80 hours/year respectively representing an improvement in there two indices compared to when ACRs were installed at anywhere in the test system. The values obtained for ASAI for different locations of the 1MW DG unit fluctuate throughout the case descriptions. With the installation of the 1MW DG unit between nodes 834-842, 844-846, 834-860, 836-840, and 862-838, the values obtained for ASAI were 5.196, 5.101, 5.012, 6.141 and 6.128 respectively which represent appreciable level of improvement as compared to the base case. With the installation of one DG in the test system, the value obtained for the EUE was 17709kw. With the additional installation of ACR between nodes (846-848), (862-832), (888-890) and (854-856), the values obtained for EUE were 1152 kW, 11926 kW, 13146  kW and 14191 kW respectively indicating a level of reductions in the values of EUE. The ACRs, once installed optimally on the test system improves the reliability of the distribution system by isolating the healthy parts of the system automatically, which maintains the service to a substantial number of customers and reduce the repair time. The integration of DGs into the distribution test system provides the opportunity of operating the distribution system as a microgrid, allowing continuity of service in the network. It also forms a useful basis for evaluating the reliability of distribution feeders. Keywords: Automate circuit reclosers (ACRs), Distributed generators (DG), Reliability indices, Monte Carlo Simulation Power Distribution systems, SAIFI, SAIDI, CAIDI, ASAI

A Sensitivity Based Approach for Assessment of Reliability Indices of Electrical Distribution Systems.

In Nigeria, satisfactory degree of reliability has not been attained in the power system in recent times. The average duration of interruptions that customers experience is very high and the degree varies widely especially in urban and commercial cities of the country. This research paper therefore presents the sensitivity analysis of electrical distribution systems. Ten years of outage information from seven major distribution systems – Ibadan, Ilorin, Ikeja, Portharcourt, Kaduna, Kano and Benin were used as input data for computation of the mean and standard deviation for the system reliability indices using statistical analysis. The computed system reliability indices were used as input parameters in the analysis. A sensitivity analysis is performed to assess how the operation parameters could influence the numerical results. The results of the sensitivity studies indicate that Etete feeder of  Benin distribution system has the highest SAIDI sensitivity of 0.5478 because of prolonged customers‘ interruptions on the feeder while waterworks feeder of Ilorin distribution system has the least SAIDI sensitivity of 0.0019. Cocoa feeder of Ibadan distribution system has the highest SAIFI sensitivity of 1.0459 because of the frequent interruptions while waterworks feeder of Ilorin distribution system has the least SAIFI sensitivity of 0.0268. Ikpoba Dam of Benin distribution system recorded the highest CAIDI sensitivity of 0.8466 with waterworks feeder also recording the least CAIDI sensitivity of 0.0075. The results from this research paper provides baseline information for planning and managing distribution system on Nigeria national grid. Keywords: Sensitivity, Reliability indices, Distribution systems, SAIDI, SAIFI, CAIDI, Interruptions. DOI: 10.7176/APTA/77-07 Publication date:May 31st 201

Development of a Linear Optimization Model for Biogas Generation of Electrical Energy using Pig Dung

Biogas is a renewable energy source produced by the breakdown of organic matter in the absence of oxygen. It can be produced from raw materials such as agricultural wastes, manure, municipal wastes, plant materials, sewage, green wastes or food wastes. However, the production of biogas has not been commercialized and people are still depending on natural gas which is non renewable and depleting fast. This study develops a linear optimization model to optimally control pig dung for full-scale biogas power generation using computer simulation. The biogas digestion processes were simulated and a linear state space model was generated. The linear optimization model was implemented and validated by calculating the volume of digester, the volume of biogas and the daily energy generated by biogas. A linear optimization model with a coefficient term of 0.68 and a constant term of 0.77 was developed. The result showed that after retention time of 23 hours, the value of biogas electrical power output with linear optimization increased by 0.12 kWh which is 1.45% increase after optimization. The results show the applicability of the optimization model potential which can be exploited using optimal control scheme. The model developed forms a basis for optimal control of real full-scale biogas production. Keywords: Biogas, Computer Simulation, Renewable Energy, Linear Optimization, State State Model, Pig Dung

A Model for Assessment of Transient Stability of Electrical Power System

The stability of a system is its ability to return to normal or stable operation after having been subjected to some forms of disturbances. A disturbance in a power system is a sudden change or sequence of changes in one or more of the physical quantities. In this paper, the transient reactance of a synchronous machine, mechanical input power, kinetic energy of a rotating body, moment of inertia, angular acceleration, angular displacement and the rotor displacement angles were used as input parameters for the development of the Transient Stability model..The model is validated with a single machine system, a 2-machine system and a multi-machine system.  The results of the work showed that the single machine system supplying an infinite bus-bar fluctuates while the 2-machine system remains unstable throughout the period. Generator 3 of the multi-machine system experienced the most violent swing, pulled out of synchronism during the first swing thus making the system to be unstable. The Transient Stability Model developed can be used for effective planning and operation of power systems.DOI:http://dx.doi.org/10.11591/ijece.v4i4.585

Statistical Analysis of Reliability Indices of Ikeja and Port-Harcourt Distribution Systems

In the evaluation of the reliability levels of electrical power systems, reliability indices play a vital role.  These indicators are System Average Interruption Duration Index (SAIDI), System Average Interruption Frequency Index (SAIFI) and Customer Average Interruption Duration Index (CAIDI). Statistical analysis of reliability indices of Ikeja and Port-Harcourt distribution system was carried out in this research paper.. Ten years of outage data information from ten selected distribution feeders of Ikeja and Port-Harcourt distribution systems were used in this work. The mean and standard deviation of the basic reliability indices were computed using appropriate mathematical relations as input parameters. Olowu feeder of Ikeja distribution system recorded the highest mean SAIDI of 01040 compared to all other feeders in the selected distribution system. Customers on this feeder were interrupted for a prolonged time while fewer of the customers were adequately served. 7-UP feeder of Ikeja distribution system had the least mean SAIDI of 0.0693 because customers’ interruption was for a short period of time even though; more customers were being served by the feeder. Airport of Port-Harcourt distribution system recorded the highest mean SAIDI of 0.1050. More customers were interrupted compared to all other feeders on the distribution system while fewer of them were adequately served. Airport feeder of Port Harcourt distribution system had a least mean SAIFI of 0.1392 because fewer of the customers attached to this feeder were interrupted while many of them were adequately served. The result of the work will provide a background information for distribution system engineers for adequate planning and effective maintenance of Ikeja and Portharcourt distribution systems. Keywords: Statistical analysis, Mean SAIDI, Mean SAIFI, Mean CAIDI, SAIDI standard deviation, SAIFI standard deviation, CAIDI standard deviation. DOI: 10.7176/APTA/77-06 Publication date:May 31st 201

Impact of Prepaid Energy Metering System on the Electricity Consumption in Ogbomoso South Local Government Area of Oyo State

Electricity is one of the basic requirements for people and they are widely used for domestic, industrial and agricultural purposes. Every meter is a device that measures the amount of electrical energy consumed by a residence, business or an electrically powered device. This paper presents the impact of prepaid energy metering system on electricity consumption in Ogbomoso South Local Government Area of Oyo state. The results of the paper revealed that about 95% of the pre-paid meter users in the local government area are conscious of electricity management, about 74% of the post-paid meter users were just wasting the energy. The introduction of the pre-paid metering system has increased the revenue collection and hence, reduced the revenue generation of the local government area because of the reliability nature of the metering system. The pre-paid metering system has created a positive impact on the electricity consumption as well as the increment in the price tariff of the electricity. Keywords: Energy metering system, Electricity consumption, Post-paid metering system, Pre-paid metering system, Solid state electronic meters (SSEM)

INVESTIGATIVE STUDY OF VOICE AND DATA COMMUNICATION OVER POWER LINE COMMUNICATION SYSTEM

Communication is the transfer of information from one point to another over a channel. However, as technology is growing, more information is needed to be passed over large distances for the realization of the world being a global village. There is the need to place a reliable communication system that will transmit effortlessly both data and voice over a channel. Power Line Communication (PLC) also known as Broadband over Power Line (BPL) technology offers high speed and broadband communication services to homes connected to the power lines. This makes use of the electrical lines for transmission of data up to the last mile and there is no need of separating copper cables, short haul satellite systems, optical fibre cable and Wi-Fi. This work presented an overview of a voice and data communication over PLC in terms of the various types, equipment use, method of communication, application, regulatory activities on PLC and the challenges facing the implementation of power line for transmitting voice and data. Therefore, PLC is a viable alternative to all other methods of transmission as it is readily available and can be easily implemented in rural areas where other communication systems are not implemented for the transmission of voice and data communication. Keywords: Communication, Power Line Communication, Broadband over Power Line, Voice and Data Communication, Broadband over Power Line, Transmission, Electrical Line. DOI: 10.7176/MTM/9-8-03 Publication date: August 31st 201