Arc Flash Hazard Analysis and Mitigation. J. C. Das

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      8 Chapter 8Figure 8.1. A 13.8-kV sectionalized bus with overlapping zones of differential...Figure 8.2. A 13.8-kV bus provided with only bus differential protection. The ...Figure 8.3. A cross-section through two high metal-clad switchgear, with bus d...Figure 8.4. (a) Overlapping zones of differential protection provided by prope...Figure 8.5. Concepts of differential protection. (a) A fault external to the p...Figure 8.6. (a) A differential protection using a simple overcurrent relay; (b...Figure 8.7. (a) Principle of a percent differential relay, (b) fixed percentage...Figure 8.8. Principle of a high impedance bus differential relay.Figure 8.9. Equivalent circuit of a bus differential relay for an external fau...Figure 8.10. Connections of a three-phase differential relay.Figure 8.11. Block circuit diagram of a modern multi-function, microprocessor ...Figure 8.12. Two-slope characteristics of the relay in Figure 8.11, with low a...Figure 8.13 (a) Directional operating principle during external faults; (b) di...Figure 8.14. Principle of CT saturation detection in Figure 8.11.Figure 8.15. Output logic of biased differential protection, Figure 8.11.Figure 8.16. Illustrates severe CT saturation of a CT during external fault.Figure 8.17. Differential protection of a 40-MVA, wye–delta connected, 138–13....Figure 8.18. A two-slope restraint characteristics of a modern transformer dif...Figure 8.19. (a) Phase shifts in two-winding transformers; (b) phase shifts in...Figure 8.20. Transformer winding phase-shift correction matrices, CTs on both ...Figure 8.21. A block circuit diagram of a modern transformer differential rela...Figure 8.22. A pilot wire scheme using metallic pilots and electromechanical r...Figure 8.23. The details of the equipment at one end of a pilot wire protectio...Figure 8.24. Simplified architecture of modern line current differential system...Figure 8.25. Alpha plane characteristics of a differential relay described by ...Figure 8.26. Characteristics of a new differential scheme in the alpha-plane.Figure 8.27. Typical operating times of differential and arc flash detection (A...

      9 Chapter 9Figure 9.1. Arc brightness verses time after a 20-kA arc flash event.Figure 9.2. Relative sensitivity of a lens sensor from different angles of lig...Figure 9.3. Sensitivity of sensors at various compensation settings. Source: C...Figure 9.4. (a) and (b) A lens or point sensor; (c) a fiber sensor.Figure 9.5. Layout of fiber sensor in switchgear, showing minimum bending radiu...Figure 9.6. (a and b) Routing of fibers through bus compartment, breaker compar...Figure 9.7. (a) Routing of fiber for nonselective AFD protection; (b) routing o...Figure 9.8. A logic circuit diagram of AFD system.Figure 9.9. AFD with current supervision, operating time of output 2.5 ms or l...Figure 9.10. Transfer of arc from the equipment to a remotely located location...Figure 9.11. A cross-section through the arc vault—arc containment device.Figure 9.12. Arc vault, sensing and control system for system protected with t...Figure 9.13. Arc vault located remotely in a separate cubicle. Source: Courtes...

      10 Chapter 10Figure 10.1. Settings on curve flexures, which can give increased fault clearan...Figure 10.2. Selectivity criteria based upon I²t let-through of current-limiti...Figure 10.3. I²t let-through curves of medium voltage power fuses, 4–40 A, of ...Figure 10.4. Peak let-through current of time-delay RK5 fuses of a manufacture...Figure 10.5. Coordination on instantaneous basis between an upstream LVPCB and...Figure 10.6. Graphical construction for determining the peak current setting o...Figure 10.7. Coordination on instantaneous basis between an upstream LVPCB and...Figure 10.8. To illustrate selective settings with various sensing methods: TC...Figure 10.9. Peak let-through current of current-limiting 100 A MCCB.Figure 10.10. An essential service system configuration for full selectivity an...Figure 10.11. Time–current coordination of the OCPDs in Figure 10.10.Figure 10.12. Time–current coordination of the OCPDs in Figure 10.10.Figure 10.13. Time–current coordination of the OCPDs in Figure 10.10.Figure 10.14. A medium voltage distribution system for selective overcurrent c...Figure 10.15. Time–current coordination in Figure 10.14, showing close spacing...Figure 10.16. Time–current coordination achieved by omitting the 5 MVA transfo...Figure 10.17. Time–current coordination for 25 MVA main transformer (Figure 10...

      11 Chapter 11Figure 11.1. Faults in the secondary zone shown in solid block cleared by prim...Figure 11.2. (a) A radial system of distribution, (b) primary selective system...Figure 11.3. ANSI through fault withstand curve, category I transformers, liqu...Figure 11.4. ANSI through fault withstand curve, category II transformers: (a)...Figure 11.5. ANSI through fault withstand curve, category III transformers: (a...Figure 11.6. ANSI through fault withstand curve, category IV transformers, liq...Figure 11.7. ANSI through fault withstand curve, category I, dry-type transfor...Figure 11.8. ANSI through fault withstand curve, category II, dry type transfo...Figure 11.9. Analytical construction of a through fault curve.Figure 11.10. Variations in the total clearing time–current characteristics of...Figure 11.11. Line and winding currents in transformers for various secondary ...Figure 11.12. Through fault withstand curve protection of a 2500-kVA, Z = 5.75...Figure 11.13. Through fault withstand curve protection of a 2500-kVA, Z = 5.75...Figure 11.14. Less flammable liquid-immersed transformers compliance to NEC sec...Figure 11.15. Less flammable liquid immersed transformers compliance to NEC sec...Figure 11.16. A low voltage and medium voltage distribution system for protect...Figure 11.17. Time–current coordination plot for 480-V, 2000-kVA transformer p...Figure 11.18. Time–current coordination plot for 2.4-kV, 7500-kVA transformer ...Figure 11.19. Modified distribution system of Figure 11.16, for arc flash reduct...Figure 11.20. Time–current coordination plot for 480-V, 2000-kVA transformer p...Figure 11.21. Time–current coordination plot for 2.4-kV, 7500-kVA transformer ...Figure 11.22. Time–current coordination plot for 480-V, 2000 kVA transformer p...Figure 11.23. Time–current coordination plot for 2.4-kV, 7500-kVA transformer ...Figure 11.24. A microprocessor based overcurrent relay connected through CTs o...

      12 Chapter 12Figure 12.1. Excitation characteristics of C-type current transformers, showin...Figure 12.2. Excitation characteristics of T-type current transformers.Figure 12.3. Construction of various CT types: (a) window-type CT, (b) a fully...Figure 12.4. Excitation characteristics of a 100/5 core balance CT. V_k is the ...Figure 12.5. Phase diagram of a class C current transformer.Figure 12.6. Illustrates the composite error according to IEC standards.Figure 12.7. Location of window type CTs in metal-clad draw-out switchgear. Tw...Figure 12.8. (a) Subtractive polarity and (b) additive polarity, shown by dark...Figure 12.9. (a) Residual connection of a GR fault relay through auxiliary wou...Figure 12.10. Connections of a product-type electromechanical ground fault rel...Figure 12.11. (a) Connection of a single 600/5 ratio CT, secondary voltage 162...Figure 12.12. Oscillogram showing progressive saturation of a CT.Figure 12.13. Hysteresis loop on magnetization of a magnetic material.Figure 12.14. Output of a 100/5 ratio C50 CT for a 40-kA fault current, severe...Figure 12.15. Improved response for 40 kA fault current, 200/5 ratio, C100 CT ...Figure 12.16. Adaptive overcurrent element block circuit diagram showing bipol...

      13 Chapter 13Figure 13.1. Time–current characteristics of four low voltage devices for anal...Figure 13.2. Calculated incident energy release versus three-phase bolted shor...Figure 13.3. A typical indicator frame used in arc-resistance testing.Figure 13.4. Pressure buildup after an arc flash event, with and without ventin...Figure 13.5. Flap plates on an arc-resistant equipment, normally closed.Figure 13.6. Hinged arc panels with inner shield.Figure 13.7. Pressure relief plate after an arc flash event.Figure 13.8. Typical arc-resistant medium voltage enclosure with arc chimneys....Figure 13.9. Typical arc-resistant medium voltage enclosure with plenum. Sourc...Figure 13.10. Inappropriate design of external arc venting system.

      14 Chapter 14Figure 14.1. Statistical data of arc flash hazard with respect to voltage level...Figure 14.2. Incident energy release verses percentage of buses, all voltages....Figure 14.3. Zone interlocking between feeder and main secondary circuit break...Figure 14.4. Zone interlocking between feeder and main secondary circuit break...Figure 14.5. A low voltage distribution system for study of zone interlocking.Figure 14.6. Time–current coordination of devices in Figure 14.5, with and wit...Figure 14.7. A low voltage distribution system, with considerable rotating mot...Figure 14.8. Time–current coordination of devices in Figure 14.7, showing moto...Figure 14.9. Zone interlocking in medium voltage system with two sources of po...Figure 14.10. Instantaneous values of short-circuit wave forms from three sour...Figure 14.11. (a) СКАЧАТЬ