S. THONGSUK, A. NGAOPITAKKUL 1041

Table 6. The comparison of electrical line losses and per-

centage change between base case (no DG) and 2 DG that 8

MVA DG is installed at bus 4.

2 MVA 4 MVA 6 MVA 8 MVA

Loss % Loss Loss % LossLoss % Loss Loss%Loss

Bus (MW) (MW) (MW) (MW)

1 0.451 25.63 0.483 34.540.531 47.91 0.59465.46

2 0.437 21.73 0.525 46.240.648 80.50 0.807124.79

3 0.454 26.46 0.504 40.390.581 61.84 0.68791.36

4 0.806 124.51 1.503 318.662.277 534.26 3.283814.48

5 0.804 123.96 1.451 304.182.218 517.83 3.141774.93

6 0.84 133.98 1.528 325.632.567 615.04 3.652917.27

7 0.815 127.02 1.51 320.612.269 532.03 3.257807.24

8 0.451 25.63 0.483 34.540.531 47.91 0.59465.46

On the other hand, when the capacity of DG at bus 4 is

varied and th e capacity of other DG does not change, it is

noticed that the electrical line losses at each bus are

slightly increased more than the base case (no DG). This

also indicates the slight mismatch between DG capacity

and size of load.

Considering the load at bus 7 and bus 8 that is less

than 1 MW and load is installed at the end of the distri-

bution system, it can be seen that the electrical line losses

tend to increase, when the capacity of DG is increased.

However, if the DG capacity is not too large (less than 4

MVA), the electrical line losses also decrease. This also

indicates the slight mismatch between DG capacity and

size of load. From the Figure 5(d) and Table 6, it is

clearly seen that as the DG capacity increases, the elec-

trical line losses also increases.

5. Conclusions

This paper presented the impact of electrical line losses

when multi-distributed generation is connected to distri-

bution system. In order to evaluate the impact of multi-

DG for electrical line losses, the line losses of the case of

no DG and with DG are compared. The results show that

when DG is installed close to the substation, the electri-

cal line losses are reduced. However, if DG capacity be-

comes larger and the distance between DG and load is

longer, the electrical line losses tend to increase. The

results indicate that the capacity of DG, location of DG,

location of load and size of load play an important role

for electrical line losses as shown in Figures 4 and 5.

6. Acknowledgements

The authors wish to gratefully acknowledge financial

support for this research from the King Mongkut’s Insti-

tute of Technology Ladkrabang Research fund. And en-

ergy policy and planning office (EPPO), Ministry of En-

ergy, Thailand. They would like also to thank for the

DIgSILENT presented in this paper which is supported

by Provincial Electricity Authority (PEA).

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