Medium Voltage Application Guide

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SWITCHGEAR Causes of internal arc There are many potential causes for internal arcing within metal enclosed switchgear. Some of the more common causes are: foreign matter in the enclosure (eg vermin, metal swarf, tools) contamination and general degradation of insulation material inadequate insulation of cable terminations overheating of termination points due to inadequate preparation and tightening system overvoltage incorrect protection settings and coordination Locations, causes and examples of measures to decrease the probability of internal faults Locations where internal faults are most likely to occur Possible causes of internal faults Examples of possible preventive measures Cable compartments Inadequate design Selection of adequate dimensions. Use of appropriate materials. Faulty installation Avoidance of crossed cables connections. Checking of workmanship on site. Correct torque Failure of solid or liquid insulation (defective or missing) Checking of workmanship and/or dielectric test on site. Regular checking of liquid levels, where applicable Disconnectors Switches Earthing switches Bolted connections and contacts Maloperation Corrosion Interlocks. Delayed reopening. Independent manual operation. Making capacity for switches and earthing switches. Instructions to personnel. Use of corrosion inhibiting coating and/or greases. Use of plating. Encapsulation, where possible. Faulty assembly Checking of workmanship by suitable means. Correct torque. Adequate locking means. Instrument transformers Ferro-resonance Avoidance of these electrical influences by suitable design of the circuit. Short circuit on LV side for VTs Avoid short circuit by proper means for example, protection cover, LV fuses. Circuit breakers Insufficient maintenance Regular programmed maintenance. Instructions to personnel. All locations Error by personnel Limitation of access by compartmentation. Insulation embedded live parts. Instructions to personnel. Ageing under electric stresses Partial discharge routine tests. Pollution, moisture, ingress of dust, Measures to ensure that the specified service vermin, etc conditions are achieved. Use of gasfilled compartments. Overvoltages Surge protection. Adequate insulation co-ordination. Dielectric tests on site. Source: IEC 62271-200 Page 86 Medium Voltage Application Guide 710-12280-00A
SWITCHGEAR Minimising the effects Certain design techniques are used to provide a high level of safety to personnel, by minimising the effects of internal arcing: compartmenting of enclosure pressure relief methods double skin panels arc venting away from access areas remote control of switchgear rapid fault clearance Rapid fault clearance requires fast detection and isolation of the arc. This can be achieved using: light, heat or pressure sensors combined with a relay to trip a fast acting circuit breaker pressure operated earth switch capable of diverting the internal arc to ground (arc eliminator) fast acting, current limiting line supply fuses 710-12280-00A Medium Voltage Application Guide Page 87
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Medium Voltage Application Guide
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CONTENTS 4 Switchgear .............
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INTRODUCTION 1 Introduction This re
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03340.B Current Torque MOTORS magne
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Torque Current MOTORS Typical start
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03340.B Current Torque MOTORS 2.2 M
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13190.A Current Torque 13193.A Curr
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MOTORS How does soft start compare
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MOTORS Soft starters Electronic sof
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MOTORS Bypassed VFD installation 1
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13473.A SOFT STARTERS Open loop sof
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SOFT STARTERS 3.2 Benefits Electric
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13490.A 13489.A SOFT STARTERS Snubb
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SOFT STARTERS Enclosed soft starter
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12996.A SOFT STARTERS Local control
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SOFT STARTERS Key Features MVS soft
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SOFT STARTERS Vibration ...........
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SOFT STARTERS MVX Soft Starter Over
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Page 84 and 85: SWITCHGEAR Resonant frequency The b
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Page 90 and 91: 13716.A Current 13680.A SWITCHGEAR
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Page 104 and 105: SWITCHGEAR IEC Ratings Disconnector
Page 106 and 107: Pre-arcing time (seconds or minutes
Page 108 and 109: SWITCHGEAR Nominal current, In (A)
Page 110 and 111: 13745.A Fuse rating (A) 13697.A Fus
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Page 114 and 115: Flux () SWITCHGEAR Exercises 1. A C
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13807.A 13808.A SWITCHGEAR Power Fa
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SWITCHGEAR Exercise Calculate the t
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13812.A SWITCHGEAR Calculations: pe
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SWITCHGEAR Step 3: Calculate the eq
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13847.A SWITCHGEAR The calculated s
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SWITCHGEAR Transformer internal imp
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SWITCHGEAR Exercise For a motor run
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SWITCHGEAR The total coefficient fa
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SWITCHGEAR Short-time withstand cur
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14009.A SWITCHGEAR Mechanical stren
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SWITCHGEAR Resonant frequency The b
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Current 13850.A SWITCHGEAR Synchron
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13854.A 13852.A 13853.A SWITCHGEAR
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SWITCHGEAR 4.6 Switchgear Inspectio
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SWITCHGEAR Commissioning Tools and
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SWITCHGEAR 62271-302 High voltage s
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13856.A 13855.A SWITCHGEAR 4.9 IEC
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SWITCHGEAR 4.10 Protection index IP
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SCHEMATIC DIAGRAMS 5 Schematic Diag
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14043.A 14042.A SCHEMATIC DIAGRAMS
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14046.A 14045.A SCHEMATIC DIAGRAMS
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14049.A SCHEMATIC DIAGRAMS 5.5 MVS
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14051.A SCHEMATIC DIAGRAMS 5.6 MVX
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RESOURCES 6 Resources 6.1 Equipment
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CONTENTS Contents Introduction ....
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2. ENVIRONMENTAL SPECIFICATIONS Env
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LOGIC CONTROL CONFIGURATION 3.2 Ope
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LOGIC CONTROL CONFIGURATION 3.6 Met
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SPECIFICATION: MVX Solid State Redu
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1. 1. INTRODUCTION Introduction 1.1
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ENVIRONMENTAL SPECIFICATIONS The eq
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LOGIC CONTROL CONFIGURATION 3.2 Ope
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LOGIC CONTROL CONFIGURATION 3.6 Met
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SPECIFICATION: Power factor Correct
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1 INTRODUCTION Introduction 1.1 Sco
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3 SUPPORT AND SERVICES Support and
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CONTENTS Contents Introduction ....
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2. DOCUMENTATION Documentation 2.1
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3.2.2 MV Equipment a) Circuit break
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ELECTRICAL SUPPLY 9. Circuit breake
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RESOURCES 6.2 Metric/Imperial Conve
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RESOURCES 6.4 Incoterms Internation
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RESOURCES kW Active power unit LRC
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