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

5 Chapter 5Figure 5.1. Decaying AC and DC components of the short-circuit current and the...Figure 5.2. Equivalent machine model for short-circuit calculations.Figure 5.3. Multiplying factors for E/X or E/Z amperes, three-phase faults, fo...Figure 5.4. (a) Typical computer-based calculation results, momentary (first cy...Figure 5.5. A low voltage distribution system for calculations of short-circui...Figure 5.6. Equivalent network for a fault at bus 3 (Figure 5.5 and Example 5....Figure 5.7. Equivalent network for a fault at bus 2 (see Figure 5.5 and Exampl...Figure 5.8. A multivoltage distribution system for hand calculations of short-...Figure 5.9. Equivalent network for a fault at 13.8 kV bus 2 (see Example 5.2).Figure 5.10. (a) Line-to-ground fault in a three-phase system, (b) line-to-gro...Figure 5.11. (a) Double line-to-ground fault in a three-phase system, (b) doub...Figure 5.12. (a) Two-phase fault in a three-phase system, (b) Two-phase fault-...Figure 5.13. Equivalent zero sequence circuit for a fault on bus 2 (Example 5....Figure 5.14. (a) Equivalent zero sequence circuit of a transformer with primar...Figure 5.15. Equivalent admittance diagram of the system in Figure 5.5.

6 Chapter 6Figure 6.1. Time constant of exponential DC decaying component of the short-ci...Figure 6.2. (a) Short-circuit current profile utility source only, no generator...Figure 6.3. Equivalent transformer circuits of a synchronous generator during ...Figure 6.4. Decaying AC component of the short-circuit current showing subtran...Figure 6.5. Calculated fault decrement curve of generator (DC component not sh...Figure 6.6. Calculated short-circuit currents for terminal fault of a 900 hp, ...Figure 6.7. A 13.8 kV bus with multiple sources of short-circuit currents.Figure 6.8. (a–c) Accumulation of incident energy profiles (see text).Figure 6.9. Calculation of short-circuit current decay profiles at 13.8 kV bus ...Figure 6.10. Crowbar arrangement.

7 Chapter 7Figure 7.1. Functionality of a MMPR (multifunction microprocessor-based relay)...Figure 7.2. An electromechanical overcurrent relay. Source : IEEE standard 141-...Figure 7.3. Time–current inverse characteristics of various overcurrent relay ...Figure 7.4. Instantaneous overcurrent function logic in an MMPR.Figure 7.5. Time–overcurrent characteristics of various overcurrent relay type...Figure 7.6. A low voltage system for illustration of selection of transformer ...Figure 7.7. Time–current coordination plot related to Figure 7.6, Example 7.2.Figure 7.8. A bimetallic thermal trip device. (a) Normal state and (b) tripped...Figure 7.9. A magnetic instantaneous trip device. (a) Normal state and (b) tri...Figure 7.10. (a) Current limitation, operation of a current limiting MCCB; (b)...Figure 7.11. Operation of a MCCB, not specifically designated as current limiti...Figure 7.12. Let-through characteristics of a current limiting MCCB.Figure 7.13. Time–current characteristics of a modern low voltage electronic t...Figure 7.14. Low arc flash circuit breaker design. Source : Arc-Flash Protection...Figure 7.15. Short-time bands of a low voltage trip programmer, to show coordi...Figure 7.16. A low voltage double-ended substation for calculations of arc flas...Figure 7.17. Let-through characteristics of a current-limiting fuse.Figure 7.18. Example of an installation where the motor contribution exceeds N...Figure 7.19. Current interruption by a current-limiting fuse.Figure 7.20. Arc voltage generated by a current limiting fuse during interrupt...Figure 7.21. Relation of X/R to rms and peak multiplying factors. Source : Base...Figure 7.22. Low voltage distribution system with integrally fused main second...Figure 7.23. Coordination in the distribution system of Figure 7.22. Current l...Figure 7.24. Coordination in the distribution system of Figure 7.22, modified b...Figure 7.25. Variations in the time–current characteristics of 150-A class E f...Figure 7.26. Thermal withstand curve of a 2.4-kV, 400-hp, SF = 1.15 motor.Figure 7.27. (a) and (b) Protection of thermal withstand curve of the motor in...Figure 7.28. Premature trip of 400-hp motor with overcurrent setting in Figure...Figure 7.29. A two-step overcurrent relay characteristics and motor starting c...Figure 7.30. Application of a zero-speed switch and an overcurrent element for...Figure 7.31. A practical time–current coordination of a 2.3-kV, 1000-hp motor ...Figure 7.32. A parallel running 10 MVA generator with a utility source for app...Figure 7.33. 51-V relay settings and coordination of the generator for the con...

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 I 2 t let-through of current-limiti...Figure 10.3. I 2 t 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...