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Surge Arrester [email protected] All rights reserved 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 [email protected] All rights reserved 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] [email protected] All rights reserved Metal-Oxide Arresters [email protected] All rights reserved U-I-characteristic of a typical MO arrester in a solidly earthed [email protected] neutral 420kV system All rights reserved Metal-Oxide Resistors [email protected] All rights reserved Porcelain Housed Surge Arrester [email protected] All rights reserved Polymer Housed Surge Arrester [email protected] All rights reserved Two-Unit HV Surge Arrester Components [email protected] All rights reserved Surge Counter [email protected] All rights reserved Surge Counter Installation [email protected] All rights reserved Surge Arrester Calculation [email protected] All rights reserved 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 [email protected] All rights reserved 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 [email protected] All rights reserved 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 [email protected] All rights reserved Selecting the Nominal Discharge Current IEC 60099-4 Table 1 [email protected] All rights reserved Selecting the Line Discharge Class IEC 60099-5 Table 1 [email protected] All rights reserved 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 longestline v 300 m/µs W W Ur [email protected] All rights reserved 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] [email protected] All rights reserved 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 (300s) U f : The negativeflashover voltageof the insulation U f 700 d k d : Air gap k : Altitudecorrection factor W [email protected] Ur W All rights reserved Selecting the Housing [IEC 60099-4] 1. Insulation Characteristics 2. Mechanical Characteristics 3. Creepage distance [email protected] All rights reserved Selecting pressure relief class Porcelain housed arrester after pressure relief test [email protected] All rights reserved 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 [email protected] All rights reserved Protecting Distance [IEC 60099-5 ] IEC 60099-5 Table 2 : Factor A for various over head lines [email protected] All rights reserved 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) [email protected] All rights reserved Catalogue (TRIDELTA) [email protected] All rights reserved [email protected] All rights reserved [email protected] All rights reserved [email protected] All rights reserved [email protected] All rights reserved [email protected] All rights reserved