Transformers - Capacity, voltages, impedance, connection, and grounding method.

Metering and Relaying - Meter types, relay types, CT and PT ratios.

Power Sources - Generators, transformers (rating, winding connection and grounding means), voltages available short-circuit current, and grounding methods of separately derived sources should be included.

Efficient maintenance planning and executionĪ typical package of single line diagram can include:.

Motor Control Center schedules & schematicsĮlectrical studies and project activities affected by the one line are:.

Some of the engineering and design documents directly affected by a one line are: Additionally, having an up-to-date single line diagram is a requirement to NFPA 70E (Standard for Electrical Safety in the Workplace). Similar to a piping and instrumentation diagram, as changes are made to the facility, it must be kept up to date. Like any drawing, the single-line diagram is a snapshot of the facility at a moment in time. Whether it is in a new or existing facility, the single-line diagram is a roadmap for electrical engineering drawings and documents, future testing, service and maintenance activities. Some of the more common symbols can be found here.

Like any schematic drawing, an electrical one line diagram should include a legend which details the various symbols being used. On an SLD, standard symbols are used to represent components of power systems, such as transformers, circuit breakers, generators, fuses and switches. As equipment is finalized or updated, the one line should be updated. In order to create the single line diagram, the P&ID should be fairly well established and an electrical load study should be completed. Just like Piping and Instrumentation Diagrams, the one line diagram reflects electrical relationships and sequences relative to each-other and does not represent geographic relationships. Single line or one-line diagrams get their name from the fact only one phase of three phase system is shown and only one line is used to represent any number of current carrying conductors.ĭuring the design process, the SLD is extremely important as nearly every electrical engineering and design document relies on the one line to accurately depict how the system will function. The purpose of single line diagram is to diagrammatically show sources of power, electrical equipment loads, electrical drives, system details and fault levels.

An electrical one line diagram (or single line diagram, SLD) is a simplified drawing used to represent the power system in a plant.

Electrical one line diagram