Page 10 - Handbook of Electrical Engineering

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10.5 Types of Protection for Hazardous Areas 254
10.5.1 Type of protection ‘d’ 255
10.5.2 Type of protection ‘e’ 256
10.5.3 Type of protection ‘i’ 256
10.5.4 Type of protection ‘m’ 257
10.5.5 Type of protection ‘n’ and ‘n’ 257
10.5.6 Type of protection ‘o’ 258
10.5.7 Type of protection ‘p’ 258
10.5.8 Type of protection ‘q’ 259
10.5.9 Type of protection ‘s’ 259
10.5.10 Type of protection ‘de’ 259
10.6 Types of Protection for Ingress of Water and Solid Particles 260
10.6.1 European practice 260
10.6.2 American practice 261
10.7 Certification of Hazardous Area Equipment 265
10.8 Marking of Equipment Nameplates 266
References 266
Further Reading 266

11 Fault Calculations and Stability Studies 269
11.1 Introduction 269
11.2 Constant Voltage Source – High Voltage 269
11.3 Constant Voltage Source – Low Voltage 271
11.4 Non-Constant Voltage Sources – All Voltage Levels 273
11.5 Calculation of Fault Current due to Faults at the Terminals of a Generator 274
11.5.1 Pre-fault or initial conditions 274
11.5.2 Calculation of fault current – rms symmetrical values 276
11.6 Calculate the Sub-Transient symmetrical RMS Fault Current Contributions 279
11.6.1 Calculate the sub-transient peak fault current contributions 281
11.7 Application of the Doubling Factor to Fault Current I found in 11.6 287
frms
11.7.1 Worked example 288
11.7.2 Breaking duty current 291
11.8 Computer Programs for Calculating Fault Currents 292
11.8.1 Calculation of fault current – rms and peak asymmetrical values 292
11.8.2 Simplest case 293
11.8.3 The circuit x-to-r ratio is known 293
11.8.4 Detailed generator data is available 293
11.8.5 Motor contribution to fault currents 293
11.9 The use of Reactors 294
11.9.1 Worked example 297
11.10 Some Comments on the Application of IEC60363 and IEC60909 300
11.11 Stability Studies 300
11.11.1 Steady state stability 301
11.11.2 Transient stability 303