Live Tank Circuit Breakers Application Guide

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6. Insulation requirements6.7.2 Environmental classes according to IECThe creepage distance is dependent on the degree of pollution. The original four pollutionlevels characterizing the site severity have, in the latest edition of IEC 60815,been replaced with five new levels that do not correspond directly to the previousnumber classes:abcdeVery lightLightMediumHeavyVery heavyNOTE! In the latest edition of IEC 60815, the creepage distance is specified as UnifiedSpecific Creepage Distance, (USCD). The definition is the creepage distance ofan insulator divided by the maximum operating voltage across the insulator, for ACsystems U m /√3. It is generally expressed in mm/kV.This definition differs from that of Specific Creepage Distance, where phase-tophasevalue of the highest voltage for the equipment is used. For phase-to-earthinsulation, this definition will result in a value that is √3 times that given by thedefinition of Specific Creepage Distance in IEC 60815 (1986). Table 6.2 shows theUnified Specific Creepage Distance in relation to the specific creepage distance.Pollution levelUnified SpecificCreepage Distance(phase-ground voltage)SpecificCreepage Distance(phase-phase voltage)mm/kVmm/kVa - Very light 22.0 -b - Light 27.8 (16)c - Medium 34.7 (20)d - Heavy 43.3 (25)e - Very heavy 53.7 (31)Table 6.2 USCD in relation to Specific Creepage Distance.To choose the correct creepage distance, the information gathered regarding thepollution at the site, Site Pollution Severity (SPS) class, can be used. Three differentapproaches for insulator selection are given in IEC 60815-1:−−Approach 1: Use past experience. Past experience from field or test station atthe same site, nearby site or a site with similar conditions.−−Approach 2: Measure and test. Measure or estimate the pollution level at site, selectappropriate candidate insulators, check for performed test results or completewith needed tests, if necessary adjust selection/size according to test results.−−Approach 3: Measure and design. Measure or estimate the pollution level at site,use guidance from IEC 60815-1 to get input to design an appropriate insulator.90 Application Guide | ABB Circuit Breakers
In nature, the change from one class to another is gradual; hence if measurementsare available, the actual Site Pollution Severity (SPS) value, rather than the class, canbe taken into account when determining insulator dimensions. Figure 6.6 shows theSPS classes and curve in relation to the Unified Specific Creepage Distance.USCD (mm/kV)605553.7504543.34035302522.027.834.720a b c d eSPS ClassFigure 6.6 The SPS classes and curve in relation to the Unified Specific Creepage Distance.6.7.3 Environmental classes according to IEEEThe IEEE requirements regarding creepage distances are stated in IEEE C37.010.The requirements are basically the same as for IEC, with the exception that fourclasses still are used. The values are given in Table 6.3.Pollution levelMinimum nominal specific creepage distancemm/kV (line-to-ground voltage)Light 28Medium 35Heavy 44Very heavy 54Table 6.3 Creepage distance according to IEEEABB Circuit Breakers | Application Guide 91
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Live Tank Circuit BreakersApplicati
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Table of contents3.6.2 Recovery vol
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Table of contents8. Standards and t
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1. Introduction1.1 What is a circui
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1. IntroductionThe different types
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2. Live tank circuit breaker design
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Page 59 and 60: Figure 3.28 Reignition overvoltages
Page 61 and 62: The rated static terminal loads, F
Page 63 and 64: Example:For a 245 kV circuit breake
Page 65 and 66: Example:Forces at three-phase short
Page 67 and 68: 4.1.3.1 Measures to increase seismi
Page 69 and 70: connected anti-condensation heater.
Page 71 and 72: 4.5 Sound effects of circuit breake
Page 73 and 74: This is higher than the highest all
Page 75 and 76: Combining these two equations gives
Page 77 and 78: This compensation is generally unne
Page 79 and 80: The shape of the lightning impulse
Page 81 and 82: Figure 6.3 Full switching impulseT
Page 83 and 84: For most of the rated voltages, IEC
Page 85 and 86: ONABA Power frequency voltage appli
Page 87 and 88: 6.5 Atmospheric correction factorTh
Page 89: Example:A 170 kV circuit breaker is
Page 93 and 94: 6.9 Insulating materialPorcelain is
Page 95 and 96: across the contact gap. If multiple
Page 97 and 98: As the number of faults per km tran
Page 99 and 100: 7.2.3 SynchronizationIn power stati
Page 101 and 102: If a fault (short-circuit) occurs o
Page 103 and 104: properties in combination with the
Page 105 and 106: In many cases however, the existing
Page 107 and 108: In addition, the high amount of har
Page 109 and 110: 8. Standards and tests8.1 Standards
Page 111 and 112: 8.1.2 ANSI/IEEEThe standardization
Page 113 and 114: 8.3.2 Radio Interference Voltage (R
Page 115 and 116: The resistance of the main current
Page 117 and 118: Figure 8.4 Test sequence for high t
Page 119 and 120: 8.3.7.3 Unit test/full pole testOwi
Page 121 and 122: In order for the synthetic test to
Page 123 and 124: 8.3.7.11 Shunt reactor current swit
Page 125 and 126: This organization is named STL, whi
Page 127 and 128: For each circuit breaker type, the
Page 129 and 130: 9.5 Life Cycle CostsFor a user, a c
Page 131 and 132: Selection of circuit breakersTo get
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