Electrical study of a Canadian Coast Guard vessel
Techsol Marine, 2016
3E Eng. was mandated by Techsol Marine to produce and deliver an electrical study for a ship of the Canadian Coast Guard. This report included a short-circuit analysis, a protection coordination study and an Arc Flash hazard analysis. To carry out this study, the experts of 3E Eng. modeled the ship’s electrical distribution network with the software EasyPower. Subsequently, they proceeded to the simulation and analysis of different scenarios and then reconciled the whole in a complete report reporting the results of the electrical study.
The results of this electrical study allowed the client to obtain a complete diagnosis of the ship’s electrical network including, among others, the following results:
- The level of short circuit to main distribution panels, frequency converters and motor control centers.
- The study of the coordination of protections to allow an adequate adjustment of protective equipment.
- The level of energy released by arc flashes (Arc Flash) in the event of a short circuit in order to identify the personal protective equipment (PPE) required when working in online electrical panel.
About electrical protection study and Arc Flash hazard
An electrical study of this kind normally starts with the evaluation of short circuit currents. The calculation of this current with the help of EasyPower is based on CEI 60909 standard should also be considered for systems modeling and interpretation of results in the maritime domain.
Following this step, the results of the short circuit study are used to perform the protection coordination study. This study makes it possible to ensure that, as far as possible, the first protection upstream of a fault is that which interrupts the fault, thus limiting its extent. Depending on the protective equipment already in place, it can sometimes be difficult to obtain perfect coordination between them. In cases where coordination is impossible, recommendations are made to remedy the situation, if necessary. Of course, the more equipment is adjustable, the easier it is to coordinate with other equipment on the network. Special attention should be paid during coordination to minimize the hazards associated with electric arcs (Arc Flash). It is therefore necessary to adjust the equipment with sufficient margin to ensure proper operation for the passage of normal loads, without, however, unnecessarily passing too much energy in the event of a short circuit. The safety of the operators starts with an adequate coordination of the protection equipment and a limitation, as much as possible, of the energy released in the event of a short circuit.
The electrical study then addresses the question of the level of energy released by an electric Arc Flash in case of fault at a particular point on the network. As previously mentioned, good coordination helps keep this level of energy as low as possible. Arc intensity calculations are performed with EasyPower according to the specifications of the IEEE 1584 standard. Then, according to the results of these calculations, the CSA Z462 and NFPA 70E standards specify the appropriate PPE to wear when an operator has to work in a particular panel, kept energized. A label indicating, among other things, the arc intensity, the category of PPE to be worn and the clearance to be respected is then glued to each of the panels analyzed.
It should be noted that it will always be preferable for an operator to work in an electrical panel turned off. However, as this is not always possible, adherence to the recommendations of the labels attached to the panels (appropriate PPE, respect of clearances, etc.), will prevent the dangers associated with arc flashes and electric shocks. The CSA Z462 and NFPA 70E standards also indicate good safety practices to be adopted in this area.
Finally, to ensure that these new measures are properly implemented and to maximize the positive effects on safety, it is important to train the operators concerned in this respect. This will allow them to correctly interpret the new labels on the panels and then take the appropriate measures for their safety and that of others.