Selection of Distribution System Parameters

The next step in design is to establish the distribution system parameters. The parameters include: 

· Environmental Specifications

· Voltage Levels in the Distribution System and its Frequency

· Acceptable Variations in System Parameters

· Fault Interrupting/Withstanding Capacity 

Environmental

Environmental specifications depend on facility location for the distribution system design and equipment purchasing. Temperature and humidity are defining factors to determine distribution system equipment selection. Other considerations include understanding lightning flash density for protection, presence of dust, possible combustible gases, and chemical pollutants. These will help in determining the appropriate location for distribution system placement.

Distribution System Voltage and Frequency

Determining distribution system voltage and frequency values to use is the next step. Frequency is usually determined by standards in the region. Voltage selection tends to be a little more complicated. The equipment must match the external utility system for the distribution system in the facility. This is usually determined based on the total load anticipated.   

Acceptable Variation in Distribution System Parameters

Frequency and voltage are mainly controlled by systems within a certain limit. Normally, variations keep happening depending on system operating condition and facility load draw. As long as it is within acceptable limits there is no need for concern. Abnormal conditions such as shorts or faults can cause voltage/frequency surges beyond the limiting values.

        Equipment are designed to withstand some variations. But, if equipment can be expected to exceed design limitations the following options are available: 

· Control Variation Extent (Components to Minimize Voltage Drop)

· Automated Interfaces to Limit Variations (Regulate Voltage and Reduce Fluctuations)

· Certain Equipment to Enhance Variation Levels (Satisfactory Operation Over Larger Voltage Band) 

Capacity to Withstand Faults

Equipment subjected to high fault currents must be  able to withstand the thermal and mechanical stresses associated with it. Equipment developed for the purpose of interrupting faults always have a limit. Equipment selection must have ratings that are higher than short circuit currents where this could occur. 

Planning Distribution System Configuration

Up until now we have discussed the important considerations for planning a distribution system project. Once the proper configurations are understood, detailed finalization is next for the following: 

· Overall Configuration

· Number of Incoming Feeders

· Incoming and Distribution Voltage Levels

· Major Equipment Ratings

· Type of Distribution

· Integration of Emergency Standby Equipment

· Protective System Earthing 

        These details lead to the overall single line distribution schematic for facility planning. Optimizing the configurations now will require little revision later on. 

Rating/Sizing for Equipment

The next step in the distribution system is deciding equipment ratings. Selecting the appropriate rating requires finalization of the following: 

· Rated Voltage, Current, and Frequency

· Voltage and Frequency Variation

· Fault Withstanding Current and Time

· Fault Breaking Capacity

· Clearance and Creepage 

All equipment will arrive using the distribution system parameters previously discussed. Permissible voltage and frequency variation tolerance is equipment specific and limitations need to be matched with power system parameters. Specific measures will have to be planned for sag correctors and uninterrupted power supply system.

        Market availability constraints can make selection difficult for planning configuration. Ratings of swithgears, transformers, and circuit breaker interrupting capacity can become a limiting factor and can introduce unintended additional equipment to maintain the projected distribution system parameters. 

Designing and Planning Summarized

Power distribution systems require large amounts of funds for investments in any industry and a sizeable amount for operational costs. Proper planning for designing a distribution system with optimum performance requires several steps from collecting data, selecting proper configurations, and selecting appropriate equipment using planning tools, and software for modeling and documenting important aspects of the distribution system. 

Designing and Planning with E3.Series

Planning distribution systems requires great attention to detail. Designing, documenting, and selecting equipment already require a great deal of time. E3.series offers great tools to make this process easier for the designers. 

E3.Schematic

Offers a platform for designing and documenting electrical controls from fuses to transformers. Having ratings and sizes from intelligent component based libraries from multiple manufacturers. This helps in providing information and specifications based on distribution system parameters and requirements. It also offers: 

· Short Circuit Prevention

· Reuseable Centrally Stored Sub-Circuits

· Automatic and Parallel Connections

· Component Driven Parts Libraries

· Ensures on Valid Parts are Used

· Online Cross Referencing of Connections and Devices

· Terminal Configuration

· PLC Integration

· Automatic Wire Numbering

        E3.schematic manages all design data and affiliated documentation, such as bill of materials and connection list or assembly instructions and datasheets. 

E3.Panel

E3.Panel allows engineers to layout components within panel enclosures. Easy component snapping placement, component clash prevention, and integrated with E3.schematic where design work can begin either in of the tools. Easily see how electrical and mechanical aspects merge into one cohesive CAD. Also provides wire routing so wires can be automatically connected from schematic and generating the shortest route possible for the configuration. It also provides: 

· Complete Component Definitions

· Slots and Mount Functionality

· Restricted Area Support

· Breakout and Cutting Details

· Shortest Path Algorithm for Wiring

· Wire Segregation

· 3D Visualization

· Integration with Automatic Wiring, Drilling, and Milling Machines