Welcome to this module on layout engineering for outdoor substations, guidelines for outdoor air insulated substation up to 33kV. This topic explains guidelines, requirements for outdoor substation, layout considerations, site location, design considerations, amenities, normal service conditions and legends for outdoor equipment. Before starting our discussion on the outdoor substation layout concept, let us recall what we have learned so far. By now, you would have understood the concept of the single line diagram. Also, you have been highlighted the processes involved in developing SLD. Further, you learned about various outdoor equipment such as outdoor CB, isolators, instrument transformers and their functionalities. You are also familiar with their physical general arrangement. Having understood all of the above, let us discuss how they lay out plan and section are being developed for an outdoor envy substation. Normally at 33 by 11 kV, primary distribution substation is provided with a single bus configuration. Further bus sectionaliser is provided to improve operational flexibility. If sufficient land is available for construction of substation with less obstacle from the surrounding, 33kV and 11kV equipment are located outdoors. In the outskirt of city limits, 33kV equipment may be located outdoor while 11kV equipment is located indoor. Within the city limits, both 33kV and 11kV equipment are located indoors. In this chapter, we will focus on the 33 by 11 kV outdoor air insulated substation. The first and foremost thing is the SLD of 33 by11 kV substation shall be available before proceeding with layout design. When you want to construct your own house you decide on the number of rooms and type of rooms based on affordability and land availability. Similarly, the requirements for a substation will be dictated by the number and rating of each feeder and the maximum demand, which is expected to be catered to by the substation. Number of bays are to be determined at each voltage level. At 33 kV Level for incoming line feeders, outgoing line feeders, transformer feeders, say 33 by 11 kV and bus sectionaliser. At 11kV level say incoming transformer feeders, outgoing cable feeders capacitor feeders, 11 by 0.415 kV auxiliary transformer feeders and bus sectionaliser. Level of redundancy and security required in respect of outgoing feeders, transformer feeders and incoming feeders. Preparation of layout shall consider, present load requirements and future load growth, plot area availability, outgoing power distribution whether by means of cables or overhead lines to the lower centers, incoming power supply whether by means of cables or overhead lines, level of redundancy and security required, finalised power distribution arrangement or SLD, future bay extensions and requirements. Ideal site location, shall be as close to load center for distribution of power. Shall be accessible to nearby roads, approach roads etcetera, for the transport of materials. Uniformly levelled site, shall be away from municipal garbage dumping grounds and burial grounds. Shall be away from army areas where practices are held normally. As far as possible, rectangular or square plot. Shall avoid waterlogged area ponds, lakes and river bed. The design shall consider, soil bearing capacity data for civil design to consider the type of foundations, soil resistivity for earth mad design purposes, wind speed and seismic zone for the design of buildings and structures, flood level data of that area. Assess the need for amenities to be provided, administrative and office buildings or rooms, pantry, rest rooms, stores, security room, fire pumps, DG rooms, housing quarters wherever required. Design of substation and equipment shall consider normal and abnormal service conditions. Design ambient temperature, maximum and minimum, site altitude above MSL, pollution level, solar radiation, wind speed, maximum, flood level, snowfall, seismic zone, contour of land flat or undulated, nearby accessible road, water source availability. The gender legends for the substation equipment and SLD are shown on screen. This can be customized based on the type of equipment being used, for example, center rotating double break type isolator, outdoor type vacuum circuit breaker, current transformer etcetera can be shown according to their actual plan. This will help the user to visualize it correctly when he reads the layout plan. In layout, the representation of the equipment shall be scaled to indicate physical dimension and shape wherever necessary. Here is a quick recap of what you have learned thus far, preparation of a substation layout shall consider the plot area availability, present load requirements and future load growth. The type of outgoing and incoming feeders, that is cables or overhead lines and the level of redundancy or security required also dictates the preparation of layout. The site location should be close to load centre ,should be of uniformly levelled terrain with access to nearby roads in a rectangular or square shaped plot. The site location should be away from municipal garbage dumping grounds, burial grounds, army areas and waterlogged area including ponds, lakes, etcetera. The substation design should consider, soil bearing capacity for foundation design, soil resistivity for earth mat design, wind speed and seismic zone for building and structure design, flood level data of the area.
