Electrical Isolation Diagrams
Engineers get excited about a new design opportunity to solve a real world problem. We tend to jump into the possible solutions and trying out new and interesting technologies. However, the excitement can cause engineers to jump over very critical steps in the design process that, if not taken, will lead to a disastrous project. This happens even in the medical device industry where there are QMS systems to follow.
One important step commonly overlooked in the design process is Electrical Isolation Safety. In the medical device base standard (IEC 60601-1), section 8 details the requirements regarding protection against electrical hazards from medical equipment (ME). Essentially, there needs to be two means of patient protection (MOPP) and two means of operator protection (MOOP) from voltages that can cause excessive leakage current to the body (i.e. Mains voltage). IEC 60601-1 details the requirements for creepage (as the ant crawls) and clearance (as the crow flies) between conductors of an applied / accessible part to said voltages. Based on the level of protection, pollution degree of the environment, category of material used in the design, and voltages within the system, one determines the required barrier construction. Insulating materials can be (and most often are) used as a means of protection.
An Electrical Insulation Diagram should be produced in early system definition phase when a basic system architecture is drafted. The diagram identifies the isolation barriers within a system in a simplified schematic form. The diagram includes a table listing each isolation barrier, the means of protection (1 or 2), the creepage and clearance requirements, and dielectric voltage withstand limit. Your product might fall into a particular standard within the IEC 60601-1 standard family, which might call out special isolation barriers needed within the design. Also defibrillation proof has requirements for creepage, clearance, and a particular defib proof electrical discharge test.
If your company is in need of creating an Electrical Insulation Diagram, feel free to reach out to my email joe.young@upliftinginnovations.com to discuss your needs.