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Training Session on Energy Equipment Electrical Systems Presentation to Energy Efficiency Guide for Industry in Asia Chapter 1 1 © UNEP GERIAP Training Agenda: Electricity Introduction 2 © UNEP 2005 Electricity General Electricity Scenario • Development can be measured by a nation’s electricity consumption • Electricity usage is divided into: a) Industrial b) Commercial and residential c) Agriculture and irrigation • Electricity is one of the most important inputs for the industrial sector 3 © UNEP 2005 Electricity General Electricity Scenario • Electrification in developing countries will reach 78% of the population by 2030 (World Energy Outlook) • Electricity supply must increase by 1,000 tWh to satisfy the world’s electricity demand by the year 2030 (World Energy Outlook) • The world’s poorest and remote will gain more electricity access (World Energy Outlook) 4 © UNEP 2005 Electricity General Electricity Scenario • How can the challenge of the growing gap between electricity demand and supply be solved? a) Renovation and modernization of plants, transmission and distribution systems b) Demand side management c) Awareness raising among energy users 5 © UNEP 2005 Electricity Generation & Distribution • Most of the world's electricity is generated using non-renewable energy sources such as fossil fuels (coal, gas and oil) and radioactive substances such as uranium • Renewable energy technologies is widely researched to make it better and cheaper World electricity generation by energy Renewable 21% Nuclear 16% Fossil fuels 63% Figure: World electricity generation 6 Source: EIA © UNEP 2005 Electricity Generation & Distribution • Electricity is generally generated by AC generators known as “alternators” in thermal, hydro or nuclear plants • Electricity is typically generated at 9-13 KV and the power generated is in the range of 67.5 MW, 110 MW, 220 MW, 500 MW • Generated power is transmitted to the user end through a transmission & distribution network 7 © UNEP 2005 Electricity Generation & Distribution Transmission system Power plant Generator GT 10.6 KV Distribution system 220 KV Distribution Step down transformer Figure: Single line diagram of generation and transmission system • All power stations have generating transformers (GTs) that step up the voltage level 132400 KV • Conversely, sub-stations have step-down transformers to reduce voltage before distribution 8 © UNEP 2005 Electricity Phase of Electricity A single phase AC circuit: • Has two wires connected to the electricity source • The direction of the current changes many times per second Figure: 3-phases of electric system Source: Wikipedia Three phase systems: • Have 3 waveforms that are that are 2/3π radians (120 degrees,1/3 of a cycle) offset in time • The cycle in the figure above will repeat itself 9 50-60 times per second © UNEP 2005 Electricity Active and Reactive Power • Active power (kW) is the real power used by any load to perform a task • Reactive power (kVAR) is virtual in nature and decides the load/demand on an electrical system • The utility has to pay for the total power (kVA) kVA = (KW)2 + (KVAR)2 Figure: Representation of power triangle Source: OIT 10 © UNEP 2005 Electricity Power Factor Correlation • Power factor is the ratio of active power (kW) to the apparent power (kVA) = Cosine of the angle Figure: Power factor of electric circuit • The undesirable component (kVAR) demand should be as low as possible for the same kW output Figure: Capacitor as kVAR generator 11 © UNEP 2005 Electricity Improving Power Factor • Correction capacitors act as reactive power generators and accomplish kW of work • This reduces the amount of total power that has to be generated by the utilities Figure: Fixed capacitor banks Source: Ecatalog 12 © UNEP 2005 Electricity Improving Power Factor Advantages with capacitor addition: • Reactive component of the network is reduced and also the total current in the system from the source end • I2R power losses are reduced in the system because of reduction in current. • Voltage level at the load end is increased • kVA loading on the source generators as also on the transformers and lines up to the capacitors reduces giving capacity relief 13 © UNEP 2005 Electricity Improving Power Factor Cost benefits of power factor improvement: • Reduced kVA (maximum demand) charges in utility bill • Reduced distribution losses (kWH) within the plant network • Better voltage at motor terminals and improved performance of motors • A high power factor eliminates penalty charges imposed when operating with a low power factor 14 © UNEP 2005 Electricity Electrical Load Management • A load curve is useful for integrated load management by predicting patterns of drawl, peaks and valleys in demand KVA • The goal of peak load management is to reduce the maximum electricity demand to lower the electricity costs Hours Figure: Daily load curve of an 15 engineering industry © UNEP 2005 Electricity Electricity Billing Mechanism • Maximum Demand Charges • Energy Charges • Fuel cost adjustment charges • Electricity duty charges • Meter rentals • Lighting and fan power consumption • Time Of Day (TOD) rates • Penalty for exceeding contract demand 16 © UNEP 2005 Electricity 1) Shifting Non-Critical and Non-Continuous Process Loads to Off-Peak time Rescheduling of large electric loads and equipment operations in different shifts, these can be planned and implemented to minimize the simultaneous maximum demand. 2) Shedding of NonEssential Loads during Peak Time It is possible to install direct demand monitoring systems, which will switch off non-essential loads when a preset demand is reached. 3) Operating In-House Generation or Diesel Generator (DG) Sets during Peak Time Connect the DG sets for durations when demand reaches the peak value in order to reduce the load demand to a considerable extent and minimize the demand charges. 4) Operating Air Conditioning units during off-peak times and utilizing cool thermal storage Reduce the maximum demand by building up storage capacity of products/ materials, water, chilled water / hot water, using electricity during off peak periods. 5) Installation of Power Factor Correction Equipments The maximum demand can also be reduced at the plant level by using capacitor banks and maintaining the 17 optimum power factor. Table: Peak load management strategies Peak Load Management Strategies © UNEP 2005 Electricity Peak Load Management Strategies • The demand varies from time to time • Maximum demand is the time integrated demand over the predefined recording cycle • Trend analysis can help identify key areas for electricity cost reduction Figure: Typical demand curve 18 © UNEP 2005 Electricity Transformer • A static electrical device that transforms electrical energy from one voltage level to another • Consists of two or more coils that are electrically insulated but linked magnetically • Figure: 3 phase core&coil assembly of a transformer Source: Kuhlman The number of turns on the 2nd coil (connected to the load) to the turns on the 1st coil (connected to the power source) is the 19 turn’s ratio © UNEP 2005 Electricity Types of transformer Table: Classification of transformers Types Criteria Based voltage on Input Step Up Transforms LV to HV Step Down Transforms HV to LV Power Transformer Located at Power Stations to Step up the voltage & handles large power. Typical voltage ratings are 400 kV, 220kV, 132KV, 66 kV, 33kV etc. Distribution Transformer Located at Sub-Stations of a distribution network and handles low power. Typical voltage ratings are 11kV, 6.6 kV, 3.3 kV, 440V, 230V etc. Instrument Transformer Used for measuring high voltage and current in measuring instruments Outdoor Located outside on a concrete structure or iron pole structure Indoor Located inside a shed on concrete structure Three Phase Input & output supply are of three phases (R/Y/B) with or without neutral Single Phase Input & output supply are of single phase Based on Operation Based on Location Based Connection on Remark 20 © UNEP 2005 Electricity Transformer Losses & Efficiency PTOTAL = PNO-LOAD+ (% Load/100)2 x PLOAD PTOTAL = PNO-LOAD+ (Load KVA/Rated KVA)2 x PLOAD Figure: Transformer loss vs. % loading • The transformer losses are due to constant and variable losses • The best efficiency occurs at the load 21 where constant loss and variable loss ©are UNEP 2005 Training Session on Energy Equipment Electrical Systems THANK YOU FOR YOUR ATTENTION 22 © UNEP GERIAP