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Corona effect presentation
- 1. 1 KINGDOM OF SAUDI ARABIA MINSTRY OF HIGHER EDUCATION JAZAN UNIVERSITY College of Engineering Electrical Engineering department
- 2. 2 Subject Page No. Introduction 3 Factors and causes 6 Power loss 18 Methods of reducing corona effect 21 Advantages and disadvantages of corona effect 26 Advantages 27 Disadvantages 28 Application 31 conclusion 33 The end 34
- 4. 4 Fig-2
- 5. 5 Fig-3
- 6. Causes and factors of Corona effect 6 Atmospheric Conditions like Pressure and Temperature. The Inception Corona Voltage and the Disruptive Critical Voltage. Spacing Between Conductors. The Supply Frequency. Stormy and Fair- Weather Conditions.
- 8. 8
- 9. What is critical disruptive voltage? 9
- 10. Calculation of critical disruptive voltage 10
- 11. Calculation of critical disruptive voltage 11
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- 13. 13 Value of Surface Irregularity Factor µ Surface Condition 1 Polished Surface 0.92 to 0.98 Conductor with dust deposit 0.8 to 0.87 Stranded Conductor
- 14. 14 Visual voltage and disruptive critical voltage Visual Critical Voltage:At disruptivevoltage Vc, the glow of corona does not appear along the conductorsbut at a higher voltage Vv, termed as Visual critical voltage. The phase- neutral effective value of visual critical voltage can be determined by the following formula: Where m v is another irregularity factor. Its value is 1 when conductors' surface is polished, and 0.72 to 0.82 for rough conductors.
- 15. 15 Fig-5 spacing between conductors versus power loss
- 16. 16 Fig-6 power loss versus frequency
- 17. 17 Fig-7 power loss versus disruptive critical voltag
- 18. 18 The formation of corona is always accompanied by the loss of energy which is dissipated in the form of light, heat, sound and chemical action. When disruptive voltage is exceeded, according to F.W. peek, the corona loss under Fairweather conditions is given by: Where, f = supply frequency in Hz Vθ = phase-neutral voltage (r.m.s.) Vc = disruptive voltage (r.m.s.) per phase PC = corona power loss d = spacing ( or equivalent spacing) between conductors (meters) r = radius of the conductor (meters) 𝛽 = air density factor
- 19. 19 It also noted that for a single-phase line Vθ = VL 2 And for three phase line Vθ = VL 3 Peek’s formula for corona loss is valid when the ratio of Vθ Vc >1.8, but when Vθ Vc <1.8 the following formula known as Peterson’s formula, gives better results: Pc = 2.1f Vθ log D r 2 × 10−5 × F KW/phase/Km Where P𝑐 = corona loss in KW/phase/Km f = supply frequency Hz Vθ= rms phase voltage in KV r = radius of conductor in meters D = spacing ( or equivalent spacing) between conductors in meters F = factor of corona loss function. It varies with the ratio Vθ Vc and is given in table-2
- 20. 20 D = spacing ( or equivalent spacing) between conductors in meters F = factor of corona loss function. It varies with the ratio 𝑉𝜃 𝑉𝑐 and is given in table-2 𝑉𝜃 𝑉 𝑐 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 F 0.012 0.018 0.05 0.08 0.30 1.0 3.5 6.0 8.0 Table-2
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- 23. 23 d d d
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- 30. 30 Corona discharge has a beautiful form that can damage the insulators: Fig-13 Fig-14 Fig-15 Fig-16
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- 33. 33 The corona effect is phenomenonthat occur in high voltage that cause power losses in transmission line that we show how to calculate previously, and corona could damage the insulators, but it has a useful benefits that we use today.
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