electric-power-quality-ppt ( Chất Lượng Điện Năng )

MHEC : LOSS CONTROL WORKSHOP Electric Power Quality Our Roadmap for this PQ Session • To arm you with some useful power quality design recommendations and ideas • Illustrate Power Quality solutions using case studies • Industry Trends • Questions and Answers What is Power Quality? • “The concept of powering and grounding sensitive equipment in a manner that is suitable to the operation of that equipment.”1 • “Within the industry, alternate definitions or interpretations of power quality have been used, reflecting different points of view.”2 • The definition of Power Quality cannot be limited to the characteristics of the supply power The definition must also include the requirements of the load 11 IEEE 1100-1992 22 IEEE 1159-1995 Power Quality Paradigms Key Services/Technologies in the “Power Quality” Industry Industry Trends Demand for Clean Power Fueled by 225% Growth in Microprocessors • Increased sensitivity to disturbances and poor grounding • Effects of harmonics on distribution systems • Increased problems from natural phenomenon Industry Trends Growth in Electronics = Growth in PQ Solutions Power Quality Solutions/Electronic Loads Surge Suppressors Power-Conditioning Equipment Electronic Ballasts Variable Speed Drives Energy Efficient Motors Solid-State Motor Controls Programmable Logic Controls Voice/Data Cable System Power-Monitoring System 00 10 10 20 20 30 30 40 40 50 50 60 60 70 70 EC&M Reader Survey (1995) Power Quality Solution Strategy Good Grounding Practices Harmonic Solutions Surge Solutions Voltage Variation Solutions Power Quality Design and Application Considerations • Ensure grounding system integrity • Limit creation of power quality problems • Attenuate power quality problems • Withstand poor power quality Grounding Equipment Grounding • Related to Over Half • Foundation of a of All Power Quality reliable electrical Problems distribution system • Proliferation of communication and computer network systems Good Grounding Practices Harmonic Solutions Surge Solutions Voltage Variation Solutions Grounding Equipment Grounding • Reasons for grounding • Personnel safety • Equipment protection • Power quality 10 Harmonics Sources of Harmonics • Harmonics are produced by the operation of nonlinear loads • General categories and common types of nonlinear loads are – Power electronic equipment – Arcing devices – Iron saturating devices – Rotating machines 19 Harmonics Sources of Harmonics Amps Variable Frequency Drive Fluorescent Lighting Amps 480V 480V - 3-Phase 480V Circuit #1 277V - 1-Phase THD = 15% Switch Mode - PCs Amps Amps 480V Secondary Amps THD = 7% THD = 104% THD = 9% Neutral 120V Current Amps 480V Primary Amps 120V - 1-Phase 120V - Neutral Source: IEEE 11001100-1992 THD = 30% 20 Harmonics Common Symptoms of Harmonics Harmonic voltage and current distortion cause: • Heating caused by higher frequency current components • Insulation stress caused by higher frequency voltage components • Circuit malfunction caused by voltage distortion 21 Harmonics Common Symptoms of Harmonics Specific symptoms include: • Transformer heating • Motor and generator heating and vibrations • Neutral heating • Nuisance fuse operations • Insulation deterioration • Electronic control malfunctioning • Inconsistent meter readings • Voltage regulator misoperations 22 Harmonics Harmonic Distortion Standards Harmonic Voltage Distortion Limits IEEE Standard 519 – 1992 Maximum Voltage Distortion in % at PCC* Below 69kV 69-138kV >138kV Maximum for Individual Harmonic 3.0 1.5 1.0 Total Harmonic Distortion (THD) 5.0 1.5 1.5 * % of Nominal Fundamental Frequency Voltage 23 Harmonics Harmonic Distortion Standards Maximum Harmonic Current Distortion IEEE Standard 519 – 1992 Harmonic Order (Odd Harmonics) /I Isc sc LL