Arc Flash Study Principles & Procedures for below 15 kv AC Systems Xuan Wu, Dennis Hoffman, Ronald Wellman, and Manish Thakur
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
OSHA Requirements Requirement 1: employer must make a reasonable estimate Requirement 2: outer layer must be flame resistant (FR) Requirement 3: rating of arc-rated clothing must be greater than the estimated incident energy
Incident Energy Variations Incident energy values can vary significantly between stations, and between equipment inside the same station due to various system configuration, high-side/ low-side clearing devices, fuse amperage ratings and their timings, transformer impedance, cable length/material, etc.
Require appropriate PPE for a possible Arc Flash Event, e.g. Class 2 PPE is necessary for 4.1~8 cal/cm 2 and Class 3 PPE is necessary for 8.1~20 cal/cm 2. Relationship to PPEs
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
What is Arc Flash Arc flash from electrical faults on the low-side of distribution (< 15 kv) or station AC service circuits ( 480 V) are possible safety hazards that drive safe work practices, personal protective equipment requirements for substation workers, and relay and other overcurrent protection settings and practices. Manikin test arc flash hazard demonstration [3]
How & When to Analyze Arc Flash ASPEN using the IEEE-1584 method is the main tool to calculate the incident energy values. The incident energy threshold: 8 cal/cm 2 for open air; 4 cal/cm 2 for switchgear. In AEP, the arc flash study is triggered by a transmission project to build a brand-new substation or modify an existing substation.
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
Distribution Station High-Side Clearing Devices Arc Duration (s) Incident Energy (cal/cm 2 ) Fuse SMD-2C (119-152-300) 4.0404 30.533 Circuit Switcher 0.2 1.511
Station AC Service
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
Engineering Flowchart
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
Original Model
Arc Flash Model
Incident Energy Calculator
Results Incident Energy (cal/cm 2 ) Risk Locations FRN-R-400 350MCM KTN-R-400 350MCM FRN-R-200 350MCM FRN-R-400 1000MCM Safety Switch Cabinet 281.3 281.3 281.3 281.3 Transfer Switch Cabinet 2.99 0.365 0.49 2.99 Control Building Panels 6.03 0.95 0.58 4.49 Power Transformer Panels 11.87 1.83 0.68 7.02
Agenda Arc Flash Study Purposes Introduction of Arc Flash Arc Flash Risk Locations & Mitigation Plans Arc Flash Study Methodology Case Study Conclusions
Conclusions This paper describes AEP s principles and procedures of conducting arc flash analysis for both distribution and station AC service applications. IEEE-1584 method, which is built inside ASPEN software, is mainly used to calculate risk location incident energy values for below 15 kv systems.
Conclusions (Cont.) If the calculated incident energy value is above the corresponding threshold, changing the high-side clearing device for the distribution systems and the low-side fuse for the station AC service systems are typically recommended. The calculated incident energy values will also be used to determine corresponding safe work practices, personal protective equipment requirements, protective relaying settings, and other practices.