Power System - Large Industries

Large industries require large amounts of power. To satisfy this need, the utility typically provides a higher service voltage to these industries than they do to smaller businesses. Service voltages ranging from 12 kV to 138 kV are common in heavy C/I facilities. This higher voltage changes the complexity of what goes on at the service entrance.

Instead of simply being the point of marriage between the utility and the facility, several sub-station type activities take place at the service entrance. Voltage regulation and power factor correction capacitor banks may be used to control the incoming voltage.

Large facilities commonly have two sets of distribution lines brought in from the utility. This enhances power reliability. Facility switchgear selects which line the building connects to. When these control systems are operated, momentary interruptions and transients are generated and sent into the building.

Due to this increased complexity, it is also common to find some form of power monitoring or control equipment at the service entrance. This equipment may range from simple strip chart voltage recorders, to advanced digital monitoring systems, to Supervisory Control And Data Acquisition systems, known as SCADA. While all of these may help prove the presence of power disturbances, they also require the expertise to know how to use them and their data effectively.

By the very nature of large industries, the larger the overall power system, the greater the risk for error and failure. Problems can easily arise from having so many conductors, panels, transformers, and even service drops. The hot conductor for a load may come from one panel while the neutral comes from another. Loads from different panels may all share the same neutral. Wires get crossed, panel schedules quickly become outdated, recommended color codes are ignored, and what is expedient usually replaces what is appropriate. The larger the facility, the more critical it is to comply with Code.