Electrical design basis
- Posted by: Martín Torres
- Category: Electrical Engineering
Electrical designs -from small cables to big networks- must follow the guidelines provided by local and/or international standards and should contemplate particularities of the electrical network and client preferences.
Becoming an expert on local standards is not an easy task; regulations tend to change from place to place. However, becoming knowledgeable on international standards is easily achievable and could significantly enhance the toolbox of an engineer. Contemplating the standards issued by IEC, ANSI, IEEE, NFPA, NEMA and NEC in any electrical design is fundamental, thus learning how to back up electrical designs with solid foundations should be a must for any engineer.
But the electrical network design is not only a function of what standards dictate. There are other factors that must be considered and analyzed case by case, such as:
- Short circuit current
It is defined as a higher-than-normal current that flows through the network due to a failure in the system. It can generate degradation or destruction of the materials and equipment, and even result in serious injuries or death of the operators.
Knowing the prospective level of short-circuit current that could be present in a network allows to properly size the equipment and materials and, to define the “energy level” that is available in the network for a correct load functionality.
A correct selection of the voltage levels that should be used in the plant can lead to a substantial economy of energy and material costs. Even more, a proper study of the network voltage drops can guarantee a correct operation of the final loads and the complete electrical system.
When the temperature of the equipment surrounding air is high, the heat dissipation generated by the electrical equipment or material will be compromised and, therefore, the equipment temperature will be increased above its rated value.
A continuous temperature excess in the equipment or material will progressively decompose the material insulation and will drive to an overcurrent, producing overheat in the machine, and again to higher decomposes, until reaching the complete failure or a short-circuit.
When the temperature of the air surrounding the equipment is high, the dissipation of the heat generated by the electrical equipment or material can be compromised and, therefore, the temperature of the equipment could increase above its rated value. A continuous overheating of the equipment will progressively decompose the material insulation and will drive to an overcurrent. Therefore, more heat will be generated in the machine, which in turn will generate further deterioration, ending, eventually, in a complete failure or short-circuit.
- Network configuration
Selecting an adequate electrical network configuration (mesh, radial, simple, double, redundant) as well as phases system (three-phases or single-phase) allows improving the plant functionality,reducing electrical loss, and enhancing the network reliability, which can be translated into economic benefits, even when certain parts of the plant electrical-network need to be duplicated.
- Earthing system
A proper earthing system should be selected based on the desired electrical network behavior against ground faults (phase-to-ground short-circuits). This system will establish the network short-circuit levels and will be directly bounded to the protection of the equipment, materials, and human beings.
When an electrical network needs to be fully designed or partially modified, knowing the regulations, and understanding the concepts that will deeply impact the design is mandatory. Based on that, we are developing the course “Electrical Engineering in Industrial Plants” through which the tools that will allow understanding and acquiring this and many other theoretical and practical concepts of the electrical world will be provided, supporting Engineers around the world in the creation of well-founded, rounded and effective electrical networks.