Transcript Surge Arrester

Surge Arrester
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STANDARDS
• IEC 60099
Surge arresters —
Part 1 : Non-linear resistor type gapped surge
arresters for a.c. systems
Part 4 : Metal-oxide surge arresters without gaps for
a.c. systems
Part 5 : Selection and application recommendations
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Definition
‘‘A protective device for limiting surge voltages
on equipment by diverting surge current and
returning the device to its original status. It is
capable of repeating these functions as
specified.’’
[IEEE Standard C.62.11-2005]
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Metal-Oxide Arresters
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U-I-characteristic of a typical MO arrester in a solidly earthed
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neutral 420kV system
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Metal-Oxide Resistors
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Porcelain Housed Surge Arrester
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Polymer Housed Surge Arrester
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Two-Unit HV
Surge
Arrester
Components
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Surge Counter
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Surge Counter Installation
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Surge Arrester Calculation
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
Choosing the Continuous Operating Voltage and the Rated Voltage
U C ,min
1.05 U m


3
U
 m
U r1  1.25  U C ,min
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effectivel y earthed
non - effectivel y earthed

Choosing the Continuous Operating Voltage and the Rated Voltage
Ur2 
U m . L .Ce
3.Tr
C e : Earth Fault Factor
 L : Load Rejection Factor
Tr : Temporary Overvoltage Strength Factor
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
Choosing the Continuous Operating Voltage and the Rated Voltage
U r  max U r1 ,U r 2 
Ur2

U C  max 
, U C ,min 
1.25

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 Selecting the Nominal Discharge Current
IEC 60099-4 Table 1
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 Selecting the Line Discharge Class
IEC 60099-5 Table 1
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 Energy Absorption Capability due to Switching
2U res (30 / 60 s )
L
W
 [U L  U res (30 / 60 s )] 
Z0
v
U L : highest overvoltage
L : length of longest line
v  300 m/µs
W 
W
Ur
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IEC 60099-5 Table 1
Specific energy in kJ/kV of
rated voltage dependent
on the ratio of switching
impulse residual voltage
Ua to the r.m.s. value of
the rated voltage Ur the
arrester.
[Fig. E1 IEC 60099-4]
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 Energy Absorption Capability due to Lightning
[IEC 60099-5 ]
Tl
W  [2U f  NU pl (1  ln( 2U f / U pl ))]U pl 
Z
U pl : The lightningimpulse protectionlevel of the arrester
N : No. of lines connected to the arrester
Tl : The equivalentduration of of a lightningflash (300s)
U f : The negativeflashover voltageof the insulation
U f  700  d  k
d : Air gap
k : Altitudecorrection factor
W
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Ur
W 
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 Selecting the Housing
[IEC 60099-4]
1.
Insulation Characteristics
2.
Mechanical Characteristics
3.
Creepage distance
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 Selecting pressure relief class
Porcelain housed arrester
after pressure relief test
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Surge Arrester Calculation
 Protecting Distance
[IEC 60099-5 ]
N U rw
LP  (
 U pl )( Lsp  L f )
A 1.15
Urw :
Rated lightning impulse withstand voltage
Upl :
Lightning impulse protection level of surge arrester
Lf = Ra/r : Length of overhead line in front of the station, which gives a rate of lighting
events equal to the acceptable failure rate
Ra :
Acceptable failure rate (number of failures per unit time) for the protected
equipment (1/Year)
r:
Overhead line outage rate (1/100km.Year)
N:
Number of lines connected to the substation
Lsp:
Span length
Lp:
Protecting distance
A:
Voltage according to Table2 of IEC60099-5 describing the lighting performance
of the overhead line connected to the station
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 Protecting Distance
[IEC 60099-5 ]
IEC 60099-5 Table 2 : Factor A for various over head lines
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 Protecting Distance
[Ministry of Power Standard]
di
U p  U RES  2  S  D / V  LC  L 
dt
Up :
L:
Lc :
S:
voltage on the terminal of the protected equipment
Inductance Of The Conductor Between Line And Effective Earth
Maximum Length From Line Conductor To Effective Earth
Front Steepness Of Lightning Overvoltage (kV/µS)
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Catalogue
(TRIDELTA)
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