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Typical Time-Current Coordination Curves for Electronic Circuit Breakers

High Efficiency Furnace

Typical Electrical Switchboard and Motor Control Center


Boiler Replacement Project

4.16KV Power Switchgear, Automatic Paralleling, for Distributed Generation


J.W. Sims & Associates Engineering Company Inc. is an independent professional engineering private practice established in 1987, specializing in electrical engineering and related services for industrial, institutional, and commercial facility projects.

Engineering services include preparation of short circuit, protective device coordination, and arc flash studies for new and existing facilities using SKM Power Tools for WindowsTM software.

Completing a study involves three phases of work: Data Gathering, Modeling, and Analysis.

Data Gathering involves obtaining make and model number of protective devices and trip units, ratings and data for switchboards, panels, motor control centers, and similar electrical equipment; and length and type of feeder circuits and conduits.

Modeling involves entering the data for each device and modeling the power system one-line diagram on the SKM software.

The Analysis phase is where calculations and comparisons are made using the SKM software, and for different operating scenarios if applicable. Equipment ratings are compared against calculated available fault currents; arc flash energy and hazard levels are calculated at major points in the power system; and adjustable circuit breaker set-points are determined for best coordination.

Any concerns such as inadequate short circuit equipment ratings or unprotected feeder circuits are noted.

All of the above information is compiled into a report format, including calculation results, analysis results, tables of circuit breaker settings, coordination time-current curves, and AutoCAD one-line diagram drawings; and arc flash hazard labels are printed.


Arc Flash Electrical Safety Training Services are available.

Harmonic Analysis and Power System Quality Engineering Studies are available.

AutoCAD Drafting and Asset Management Services are available.

Automatic Paralleling Switchgear

Typical Arc Flash Warning Label