Arc Flash is the result of a rapid release of energy due to an arcing fault between multiple phases, a single phase and ground, and multiple phases and ground. An arc fault is often caused by 1) Human mistake (e.g., dropping a tool, accidental contact with live part), 2) Environment (e.g., water vapor), 3) Equipment failure (e.g., insufficient insulation, deteriorated insulation, corrosion), 4) Overvoltage conditions, and 5) A combination of the any of these. The energy released in the form of pressure is of concern for worker safety since the pressure wave can directly injure the worker or can destroy objects resulting in shrapnel that can injure the worker. In the context of an arc fault hazard analysis, the burn hazard during an arc fault is the main concern for worker safety. The incident energy (specified in cal/cm2) is the energy that is impressed on a surface located at some distance from a source and is used as a measure to quantify the burn hazard from arc flash.
Modern wind turbines generate power at various output voltage levels (generally range from 480V to 1000V). This voltage is further stepped up to an industry standard collector system voltage of 34.5 kV (typical in North America). The collector system is a network of underground cables and comprises multiple stings of turbines called feeders. All these feeder strings terminate at main 34.5 kV bus at the substation yard where voltage is further stepped up to the local utility’s transmission voltage level. Wind plants are potentially exposed to variety of arc flashes and shock hazards and can cause serious injuries to workers. The main safety concern is inside wind turbines due to the limited area in the base of the tower and nacelle, as well as when operating pad mount transformers. The Occupational Safety & Health Administration (OSHA) requires all the wind plants to implement the safe working practices and training requirements. Therefore wind plants are required to comply with National Fire Protection Association (NFPA) 70E standard.
EnerNex’s qualified power system consulting (PSC) group has performed many arc flash studies for wind plants that include analysis at main substation equipments, collection system equipments, and equipments inside the turbine tower. For the arc flash hazard assessment, EnerNex uses the IEEE 1584 empirical model for voltages below 15 kV, which is widely accepted and for voltages above 15 kV, ArcPro model, which is a model that is compliant with NFPA 70E. The ArcPro model gives reasonable incident energy levels for high voltage levels. EnerNex has developed its own arc flash program in Matlab for incident energy calculations. The program offers many special features such as calculations of arc flash parameters using conventional arc flash models, plotting of output results as well as export feature files as a figure or data files. This program has been successfully tested against some industry standard software’s such as Computer Aided Protection Engineer (CAPE) and EDSA.
In summary EnerNex’s arc flash hazard analysis services include:
- Short circuit analysis
- Arc flash hazard calculations using IEEE 1584 and ArcPro models
- Recommendations on appropriate personal protective equipment (PPE)
- Recommendation on safe flash protection boundary
- Recommendation on safe working distances
- Mitigation techniques for reducing arc flash hazards
- Arc flash labels printing