Industrial Plant Design/System Planning

System Planning

An industrial plant is only as good as its electric distribution system. For this reason, careful system planning for an industrial power system is very important. This wiki outlines the procedures of system planning and presents a guide which will make the details of Electric Power Distribution Design for Industrial Plant more understandable.

A standard electric distribution system is not adaptable to all industrial plants because no two plants have identical requirements. Methods must be used to analyze the specific requirements of the industrial plant qualitatively and quantitatively, and design the system which will most adequately meet the electrical requirements of the particular plant, with consideration given to both present and future operating conditions.

Basic Design Consideration

Any approach to the problems must include several basic considerations which will affect the overall design. These are

Safety

Safety takes two forms; safety to personnel and safety to property. The safety of personnel involves no compromise; only the safest system can be considered.

Safety to property may involve some compromise where safety to personnel is not jeopardized.

Reliability

The continuity of service required is dependent on the type of manufacturing or process operation of the plant. Some plants can easily tolerate momentary outages while others require a very high degree of service continuity. In view of this, the system should designed to isolate faults with a minimum disturbance to the system and should have features to give the maximum dependability consistent with the plant requirements.

First Cost

While the first cost is important, it is often minimized if the system is reliable and its operation is satisfactory. It should not be the determining factor in the design of the plant since distribution cost represents only 2 to 10 percent of the plant investment.

Simplicity of Operation

Simplicity of operation is a big factor in the safe and reliable operation of a plant. Avoid complicated and dangerous switching operations under emergency conditions.

Voltage Regulation

For some plant power systems, voltage spread may be the determining factor of the distribution design. Poor regulation is detrimental to the life and operation of electrical equipment.

Maintenance

A well-designed distribution system with properly chosen equipment will reduce emergency maintenance. In planning the system, the accessibility and availability for inspection and repairs should be given careful consideration.

Plant Expansion

Plant loads generally increase. Consideration of the plant voltages, ratings of equipment, pace for additional equipment and capacity for increased load must be given serious study.

Planning Guide for Distribution Design

With the above factors in mind, the following procedure is given to guide the Electrical Engineer in the design of an electric distribution system for any industrial plant.

1. Obtain a general layout and mark it with the major loads at various locations and determine the approximate total plant load in kilowatts, and kilovolt-amperes.
2. Estimate the lighting, air-conditioning, and other loads from known data and the system load preliminary information.
3. Determine the total connected load and calculate the maximum demand by using demand and diversity factors.
4. Investigate unusual loads, such as the starting of large motors, operation of arc furnaces or welders, and operating conditions such as boiler auxiliary motors, loads that must be kept in operation under all conditions, and loads that have a special duty cycle.
5. Investigate the various types of distribution systems and select the system or systems best suited to the requirement of the plant. Make a preliminary single line diagram of the power system.
6. If power is to be purchased from the utility, obtain such information concerning the supply system or systems as
   1. voltage available, voltage spread,
   2. type of systems available,
   3. method of system neutral grounding, and
   4. other data such as
      1. relaying,
      2. metering and
      3. the physical requirements of the equipment.
   5. The interrupting rating and momentary ratings of power circuit breakers should be obtained as well as the present and future short-circuit capabilities of the utility system at thepoint of service to the plant.
   6. Investigate the utility’s power contract to determine if off-peak power at lower rates is available, and any other requirements, such as power factor and demand clauses, that can influence power cost.