This is a PPT on CORONA EFFECT(ELECTRICAL) Prepared By LAKSHYA PANDEY, 2nd Year Electrical Engineering Student of BIPIN TRIPATHI KUMAON INSTITUTE OF TECHNOLOGY, DWARAHAT, UTTARAKHAND...

1. POWER SYSTEM
PRESENTED BY: LAKSHYA PANDEY
(2ND YEAR, ELECTRICAL)
(190180105014)
TOPIC- CORONA PHENOMENON, FACTORS AFFECTING CORONA,
METHODS TO REDUCE CORONA.
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2. CONTENTS
Corona Phenomenon.
Reason for Violet Glow in Corona
Critical Disruptive Voltage
 Power Loss Due To Corona
Visual Critical Voltage
Factors Affecting Corona.
Methods to Reduce Corona.
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3. CORONA PHENOMENON
 Corona Phenomenon is the ionization of air surrounding the power conductor.
 In technical terms, we can say that a self sustained electric discharge in which the
intensified ionization is localized over a portion of the distance between the
electrodes.
 It produces violet light(can be observed through stroboscope ) , hissing sound.
 It also emits ozone gas and radio interference.
 It can be seen in both ac and dc transmission line.
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4. REASON FOR VOILET GLOW IN CORONA
 When an atom is energized , then the electrons present go
the higher energy levels and when they come back to lower
energy levels, they emit light.
 It depends how much is the gap between the energy levels&
and this energy gap determines how much frequency of light
will emit.
 And the highest frequency of light is equal to 𝟕. 𝟓𝑿𝟏𝟎𝟏𝟒
hz.
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5. CRITICAL DISRUPTIVE VOLTAGE(𝑣𝑐):
 Defined as the voltage at which corona initiates.
 It is given by:
𝐯𝐂 = 𝐦𝐫𝐠𝛅 𝐥𝐧
𝒅
𝒓
𝒌𝑽
here
m: 𝒊𝒓𝒓𝒆𝒈𝒖𝒍𝒂𝒓𝒊𝒕𝒚/𝒔𝒖𝒓𝒇𝒂𝒄𝒆 𝒇𝒂𝒄𝒕𝒐𝒓 & m= 1.0 for polished wires.
m= 0.98to 0.93 for roughened wires.
𝛿 : air density factor
𝒓 : radius of conductor
d : distance of conductor separation
g : dielectric strength of air
Air’s dielectric strength(g) = 30kV(MAX)/cm AT NTP( here P= 1atm , T=25°𝑪).
(g) = 21.1kV(rms)/cm at NTP
.
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6. VISUAL CRITICAL VOLTAGE(𝑣𝑣):
 It is the minimum phase-neutral voltage at which corona glow appears all along the line
conductors.
It is given by:
𝒗𝒗 = 𝒎𝒈𝜹𝒓 𝟏 +
𝟎. 𝟑
𝜹𝒓
𝒍𝒐𝒈𝒆
𝒅
𝒓
𝒌 𝑽/𝑷𝒉𝒂𝒔𝒆
POWER LOSS DUE TO CORONA(𝑷𝐿):
 Formation of corona is always accompanied by energy loss which is dissipated in the form of
light, heat, sound and chemical action. When disruptive voltage is exceeded, the power loss
due to corona is given by:
𝑃𝐿 = 𝟐𝟒𝟏
𝐟+𝟐𝟓
𝜹
𝒓
𝒅
𝒗 − 𝒗𝓛
𝟐 × 𝟏𝟎−𝟏𝟓 𝒌𝑾/𝒌𝒎/phase
f : supply frequency in hertz
v : phase neutral voltage/operating voltage (R.M.S)
𝒗𝒄 : disruptive voltage (R.M.S)per phase.
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7. FACTORS AFFECTING CORONA
1)Electrical Factors:
 Height of the Tower: The less is the Height the more is corona.
 Frequency and waveform supply: Power loss is the function of frequency.
2)Atmospheric factors:
 Pressure and Temperature Effect: For lower values of 𝛿, pressure will low and temp. high
 Dust, Rain & Snow: These Factors clog the conductor, so Low C.D.V.
3)Field Around the Conductor:
 Diameter of the conductor: Diameter is proportional to C.D.V.
 Number of conductors/ phase: For Operating voltage more then 380kV ,concept of
bundled conductor in which GMD Increases.
 Profile of the Conductor: It means shape of the conductor also effects corona.
 Surface Conditions of the Conductors: The conductors are exposed to atmospheric
conditions so low C.D.V.
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8. METHODS TO REDUCE CORONA
 Large Diameter Conductors.
 Hollow Conductors.
 Bundled Conductors, In case of bundled conductors the 𝒗𝑪𝜶𝒓 , if
effective radius (r) is high so C.D.V is high and it is used for reducing
corona effect.
 Transposition of transmission line.
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