The best grading is grading that give where does searching line out, from 1 line out to the other line out, smoothest progression and line out load is equal. In figure 5.6 showed a system with beginning condition: k = 10, n = 31 line and total group = 6.
Figure 5.6 System with 31 line out (a, b, c, and d).
Assumed grading with N = 31 line out (server) not yet optimum and be looked for best grading form. When assumed best grading is achieved in N = 27 line out, so grading form looked for in the following way:
Make equation based on system condition in the beginning situation:
a + b + c + d = 10
6a + 3b + 2c + d = 27
From both above equation will get:
5a + 2b + c = 17
Do predictions (approximately) from a, b, c, d, values and so on, and these values must fit if putted into to all above equation. then count the absolute difference value (NSM) that is total from difference (absolute value) a, b, c, d, value in a series with equation:
NSM = S ( |a-b| + |b-c| + |c-d| )
Do predictions and calculation several times, example 10 times, and the result table likes in table 5.1.
Individual a 3 3 2 2 2 2 1 1 1 0 0
Pairs b 1 0 0 1 2 3 4 5 6 8 6
Three c 0 2 7 5 3 1 4 2 0 1 3
Common d 6 5 1 2 3 4 1 2 3 1 0
NSM 9 8 15 8 1 6 6 7 14 1 14
Table 5.1 best grading calculation table.
Based on calculation data result, take values a, b, c, and d, that gives minimum NSM. From calculation, got value a, b, c, and d, that give minimum NSM and fulfill equation: a = 2, b = 2, c = 3, d = 3.
Got final configuration as best grading:
Figure 5.7 The Best grading configuration.
