of 2000 kVA/km2 and 0.9 lagging power factor. The 3-phase supply
from the substation is 11 kV (VLL) at 50 Hz. Two different plans
are being considered for serving the area. The plans are shown in
Figure 1. Plan-A proposes a pentagon shaped service area with 5
primary main feeders. Each feeder is 1 km long and connected to 10
laterals. The main feeders consist of 37/2.59 ACSR conductors while
the laterals are made of 7/2.11 ACSR conductors. Both the primary
main and laterals are constructed such that the geometric mean
distance for the three-phase wire is 0.6 m. Plan-B proposes a
square shaped service area. The service area is divided into four
triangular shaped areas as shown in the figure. Each area is served
by a 1 km primary main feeder and 10 laterals. The same conductor
sizes and geometric mean distance (as in Plan A) are used in this
plan.
(i) Calculate the K-constants for the primary main and laterals.
The characteristics of the ACSR conductors are given in Table
1.
(ii) Calculate the maximum percent voltage drop for the two
plans.
(iii) Explain the advantages and disadvantages of the two
plans.
For the calculation, assume that: 1). The laterals for both
plans are uniformly loaded. 2). The operating temperature of the
feeders is 20°C. 3). The area served by the last lateral has a
trapezoid shape as shown in the figure.
- A Substation Will Be Built To Serve The Area With Load Density Of 2000 Kva Km2 And 0 9 Lagging Power Factor The 3 Phase 1 (69.21 KiB) Viewed 26 times
Table 1: Characteristics of ACSR conductor TYPE CONDUCTOR APPROXIMATE CURRENT RESISTANCE AT 20°C (Ω/km) CARRYING AREA (mm) DIAMETER (mm) 6.33 1.40 ACSR 7/2.11 ACSR 7/3.55 MAX LOAD (BREAKING) (kN) 7.61 18.25 27.00 34.40 67.30 10.05 0.55 20 50 80 100 150 CAPACITY (A) 105 193 250 300 400 ACSR7/4.09 12.27 ACSR 7/4.72 ACSR 37/2.59 14.15 18.13 0.371 0.280 0.180