Electrical Power

UNIT 63: ELECTRICAL POWERUnit 63: Electrical Power Unit code: H/601/1408 QCF level: 4 Credit value: 15 Aim This unit will develop learners’ understanding of electrical power systems and power distribution and the advantages and disadvantages of alternative energy sources. Unit abstract Our modern world increasingly relies upon electrical power to supply our industries, commercial centres and homes with a convenient, flexible and reliable source of energy. To meet the client’s expectations, electrical energy must be provided at a reasonable cost and transmitted to the point of need, at the appropriate voltage and current levels. The client’s utilisation of the energy source needs to be appropriate, without undue complexity, to facilitate energy generation and transmission. This unit takes the learner through the complex process of analysing three-phase systems with consideration being given to harmonics and their effects. The methods of power distribution through the National Grid are then discussed with final economic considerations taken into account to enhance generation, transmission and distribution, with acceptable costs to clients. Throughout their working careers, modern engineers will have to consider new technologies and be able to evaluate the options available to make appropriate selections. With our global resources of fossil energy reserves decreasing and concerns over protecting the environment growing, alternative sources of energy are considered. Evaluative considerations will be made to inform the engineer of the issues associated with this topic, which may need to be considered far more at local and regional levels. Additionally, self-generation of electrical energy is now possible for a broad range of users throughout the world, utilising local environmental facilities. Learning outcomes On successful completion of this unit a learner will: 1 Be able to analyse three-phase systems 2 Understand the sources and effects of harmonics in power systems 3 Understand methods of power distribution 4 Understand the economics of components, power systems and alternative energy. BH023332 – Edexcel BTEC Levels 4 and 5 Higher Nationals specification in Engineering – Issue 1 – May 2010 © Edexcel Limited 2010 291 permissible. triple-n currents trapped in delta transformers. open and closed rings. clock number and group. total harmonic distortion. power efficiency 292 BH023332 – Edexcel BTEC Levels 4 and 5 Higher Nationals specification in Engineering – Issue 1 – May 2010 © Edexcel Limited 2010 . inertia. voltage drop. zig-zag. loss of one line. passive and active filters. resonance Sources of harmonics: transformer magnetising current. acceleration time 2 Understand the sources and effects of harmonics in power systems Harmonics: pitch. steady state. connections eg terminal marking BS 171. voltage and current profiles. balanced delta loads. parallel feeders. radial feeders. triple-n neutral currents in star systems. ring. zero sequence. current. crawling. balanced star supply. direct current power supply units. circuit separation. reactive power. balanced delta supply. skin effect losses Mitigation of harmonics: methods of mitigation such as oversized neutral. harmonic resonance. shell and core type. K factor and factor K. harmonic series. wave theory. interconnector Operating parameters: load distribution eg radial. unbalanced delta loads Measurement of power: methods of determining power in three-phase balanced and unbalanced systems eg Blondel’s theorem. starting methods. de-rating. failure of power factor correction capacitors. operating point Load dynamics: eg dynamic stability. unbalanced 4 wire star loads. torque speed characteristics of motor and load. power losses. integrated three-phase wattmeters. star. reversed phase sequence Three-phase transformers: construction eg three single-phase transformers. friction. isolation transformers. unbalanced supply voltages. parallel operation Characteristics: methods of operation of a three-phase induction motor. overheating in neutral. 4 wire and 3 wire balanced star loads. standards G5/4 3 Understand methods of power distribution Topology: system integrity. apparent power Faulted three-phase systems: connection errors and faults eg loss of neutral. overheating in motors and transformers. parallel feeders. general non-linear loads Effects of harmonic: increased root-mean-square currents. natural frequencies. real power. torque and control techniques.UNIT 63: ELECTRICAL POWER Unit content 1 Be able to analyse three-phase systems Fault free three-phase systems: use of j-notation (complex numbers) in the analysis of unfaulted three-phase systems eg phase sequence. phasor diagrams. reversed supply phase. delta. wind. comparisons of single and three-phase systems. Kelvin’s law. biomass eg liquid biofuel. solid biomass. solar. efficiency. compact fluorescent lighting. power systems and alternative energy Economics: economic considerations eg power factor correction. high and low efficiency motors Alternative energy: geothermal. operating).UNIT 63: ELECTRICAL POWER 4 Understand the economics of components. energy tariffs. feasibility on large and small scale BH023332 – Edexcel BTEC Levels 4 and 5 Higher Nationals specification in Engineering – Issue 1 – May 2010 © Edexcel Limited 2010 293 . energy storage. biogas Evaluation: cost (capital. environmental impact. water. 6 assess the effect of load dynamics 2 Understand the sources and effects of harmonics in power systems 2.1 solve problems involving fault free three-phase systems Be able to analyse threephase systems 1. power systems and alternative energy 4.1 compare different power system topologies Understand the economics of components.1 identify typical sources of harmonics in a power system 2.UNIT 63: ELECTRICAL POWER Learning outcomes and assessment criteria Learning outcomes Assessment criteria for pass On successful completion of this unit a learner will: The learner can: 1 1.5 describe the characteristics of a three-phase induction motor 1.3 solve problems involving faulted three-phase systems 1.4 describe three-phase transformers 1.1 compare the economics of single-phase and threephase distribution 294 3.3 evaluate at least four different methods of mitigation of harmonics 3 4 Understand methods of power distribution 3.2 measure power in three-phase systems 1.2 explain the effects of harmonics in power systems 2.2 compare and evaluate the different forms of alternative energies. BH023332 – Edexcel BTEC Levels 4 and 5 Higher Nationals specification in Engineering – Issue 1 – May 2010 © Edexcel Limited 2010 .2 analyse the operating parameters of a radial and a ring distribution system 4. UNIT 63: ELECTRICAL POWER Guidance Links This unit may be linked with Unit 1: Analytical Methods for Engineers and Unit 5: Electrical and Electronic Principles. Employer engagement and vocational contexts Delivery of this unit would benefit from visits to a power station or wind farm or the attendance of guest speaker(s) with relevant experience of power generation and transmission. BH023332 – Edexcel BTEC Levels 4 and 5 Higher Nationals specification in Engineering – Issue 1 – May 2010 © Edexcel Limited 2010 295 . Unit 35: Further Analytical Methods for Engineers would support the use of j-notation (complex numbers) required in learning outcome 1. etc). transformer and loads. power analyser. Essential requirements Learners will need access to appropriate laboratory and test equipment (for example three-phase supply. three-phase induction motor and starters.