LOCATION AND SIZING SUBSTATION SUBSTATION LOCATION THE RATING

LOCATION AND SIZING SUBSTATION • SUBSTATION LOCATION • THE RATING OF A SUBSTATION SQUARE SHAPE HEXAGONALLY SHAPE • SUBSTATION SERVICE AREA WITH N PRIMARY FEEDRS • VOLTAGE DROP CALCULATION 1

SELECTING LOCATION FOR SUBSTATION • As much as feasible close to the load center of its service area, • Proper voltage regulation can be obtainable without taking extensive measures. • Provides proper access for incoming subs-transmission lines and outgoing primary feeder. • Provide enough space for the future substation expansion. • The selected substation should not be opposed by land use regulations, local ordinances, and neighbors. • The selected substation location should help to minimize the number of customers affected by any service discontinuity. • Other considerations, such as adaptability, emergency. 2

Steps of The rule to a service area map 1. Draw a straight line between a proposed substation site and each of its neighbors 2. Perpendicularly bisect each of those line 3. The set of all the perpendicular bisectors a round a substation defines its service territory. 4. The target load for this substation will be the sum of all loads in its service territory. 3

The perpendicular bisector rule for planning expansion 4

The Rating of a Substation The additional capacity requirements of a system with increasing load density can be met by: • Either holding the service area of a given substation constant and increasing its capacity • Developing new substations and thereby holding the rating of the given substations constant. 5

. Square Shaped Distribution Substation Service Area The percent voltage drop % VDac = % VDab + % VDbc 6

Serves total load of each feeder is, S 4 = A 4 x D k. VA Where, S 4 : k. VA load served by one of four feeder emanating from a feed point. A 4 : area served by one of four feeders emanating from a feed point, mi 2 D : load density, k. VA/mi 2 S 4 = l 42 x D k. VA Since A 4 = l 42 7

For a hexagonally shaped service area supplied 8

A 6 = area served by one of six feeders emanating from a feed point, mi 2 l 6 = linear dimensions of a primary feeder service area, mi Each feeder serves a total load S 6 = A 6 x D k. VA or S 6 = 0. 587 x D x l 62 9

Substation Service Area served by n primary feeder The total k. VA load served by one of n feeders 10

Voltage Drop Calculation or % VDn = percent voltage drop in primary feeder circuit 2/3 x ln = effective length of primary feeder K = % VD/(A. mi) of the feeder (the value of K is obtained from Slide 12) An = Area served by one feeder n = number of primary feeders D = Load density. TSn = n x D x An = total k. VA supplied from feed point 11

The K constant for conductors 12