Apparatus and method for reducing neutral line current using load switching method

1. An apparatus for reducing a current flowing through a neutral line of a three-phase four-wire type two stage electric pole distribution system, comprising:

a phase current detection unit detecting phase currents in each of a top stage power line and a bottom stage power line;

a load switching unit changing an arrangement of loads connected to each phase of at least one among the top stage power line and the bottom stage power line; and

a control unit comparing strengths of the detected phase currents of the top stage power line and the bottom stage power line and controlling the load switching unit so as to change the arrangement of the loads connected to each phase of at least one among the top stage power line and the bottom stage power line according to the comparison result.

2. The apparatus as recited in claim 1 , wherein the control unit changes the arrangement of the loads such that an order of the phases of the top stage power line and an order of the phases of the bottom stage power line according to strength of phase currents are opposite from each other.

3. The apparatus as recited in claim 2 , further comprising a memory unit storing a condition table about the order of phases of the top stage power line and the bottom stage power line according to strength of phase currents, and the arrangement of the loads corresponding to the order according to the strength of the phase currents;

wherein the control unit searches the arrangement of the loads corresponding to the strength of the phase currents detected by the phase current detection unit from the condition table and changes the arrangement of the load according to the searched arrangement in case that phases having the same current strength to each other exist in one of the top stage power line and the bottom stage power line.

4. The apparatus as recited in claim 3 , wherein the control unit changes the arrangement of the loads connected to one of the top stage power line and the bottom stage power line with reference to the order according to the strength of the phase currents of each phases of the other of the top stage power line and the bottom stage power line.

5. The apparatus as recited in claim 1 , wherein the phase current detection unit is prepared at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

6. The apparatus as recited in claim 2 , wherein the phase current detection unit is prepared at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

7. The apparatus as recited in claim 3 , wherein the phase current detection unit is prepared at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

8. The apparatus as recited in claim 4 , wherein the phase current detection unit is prepared at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

9. The apparatus as recited in claim 5 , wherein the control unit converts the detected phase currents into effective values to compare the strength of the converted effective values.

10. The apparatus as recited in claim 6 , wherein the control unit converts the detected phase currents into effective values to compare the strength of the converted effective values.

11. The apparatus as recited in claim 7 , wherein the control unit converts the detected phase currents into effective values to compare the strength of the converted effective values.

12. The apparatus as recited in claim 8 , wherein the control unit converts the detected phase currents into effective values to compare the strength of the converted effective values.

13. The apparatus as recited in claim 9 , wherein the load switching units are prepared at each phase of any one power line among the top stage power line and the bottom stage power line, and each of the load switching units connects any one among loads connected to each phase of any one power line according to a control signal of the controlling unit.

14. The apparatus as recited in claim 10 , wherein the load switching units are prepared at each phase of any one power line among the top stage power line and the bottom stage power line, and each of the load switching units connects any one among loads connected to each phase of any one power line according to a control signal of the controlling unit.

15. The apparatus as recited in claim 11 , wherein the load switching units are prepared at each phase of any one power line among the top stage power line and the bottom stage power line, and each of the load switching units connects any one among loads connected to each phase of any one power line according to a control signal of the controlling unit.

16. The apparatus as recited in claim 12 , wherein the load switching units are prepared at each phase of any one power line among the top stage power line and the bottom stage power line, and each of the load switching units connects any one among loads connected to each phase of any one power line according to a control signal of the controlling unit.

17. The apparatus as recited in claim 13 , wherein each of the load switching units comprises a relay.

18. The apparatus as recited in claim 14 , wherein each of the load switching units comprises a relay.

19. The apparatus as recited in claim 15 , wherein each of the load switching units comprises a relay.

20. The apparatus as recited in claim 16 , wherein each of the load switching units comprises a relay.

21. A method for reducing a current flowing into a neutral line of a three-phase four-wire type two stage electric pole distribution system, comprising:

detecting phase currents in each of a top stage power line and a bottom stage power line; and

comparing the detected strengths of the phase currents of the top stage power line and the bottom stage power line; and

changing an arrangement of loads connected to each phase of any one of the top stage power line and the bottom stage power line according to the comparison result.

22. The method as recited in claim 21 , wherein the arrangement of the loads is changed in such a way that an order of the phases of the top stage power line and an order of the phases of the bottom stage power line according to strength of phase currents are opposite from each other in step of changing the arrangement of loads.

23. The method as recited in claim 22 , further comprising storing a condition table about the order for phases of the top stage power line and the bottom stage power line according to strength of phase currents, and the arrangement of the loads corresponding to the order according the strength of the phase currents in a memory unit;

wherein changing the arrangement of loads comprises searching the arrangement of the load corresponding to the strength of the phase currents detected by the phase current detection unit from the condition table and changing the arrangement of the loads according to the searched arrangement in case that phases having the same current strength to each other exist in one of the top stage power line and the bottom stage power line.

24. The method as recited in claim 23 , wherein changing the arrangement of loads is performed by changing the arrangement of the loads connected to one of the top stage power line and the bottom stage power line with reference to the order of the phases according to the strength of the phase currents of each phases of the other of the top stage power line and the bottom stage power line.

25. The method as recited in claim 21 , wherein detecting phase currents is performed by detecting the phase current at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

26. The method as recited in claim 22 , wherein detecting phase currents is performed by detecting the phase current at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

27. The method as recited in claim 23 , wherein detecting phase currents is performed by detecting the phase current at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

28. The method as recited in claim 24 , wherein detecting phase currents is performed by detecting the phase current at an input stage of the loads connected to each of the top stage power line and the bottom stage power line.

29. The method as recited in claim 25 , wherein comparing the detected strengths of the phase currents is performed by comparing effective values converted from the detected phase currents to compare the strength of the detected phase currents.

30. The method as recited in claim 26 , wherein comparing the detected strengths of the phase currents is performed by comparing effective values converted from the detected phase currents to compare the strength of the detected phase currents.

31. The method as recited in claim 27 , wherein comparing the detected strengths of the phase currents is performed by comparing effective values converted from the detected phase currents to compare the strength of the detected phase currents.

32. The method as recited in claim 28 , wherein comparing the detected strengths of the phase currents is performed by comparing effective values converted from the detected phase currents to compare the strength of the detected phase currents.

33. The method as recited in claim 24 , wherein changing the arrangement of loads is performed by changing the arrangement of each high voltage terminals of transformers connected to one of the top stage power line and the bottom stage power line with reference to the order of the phases according to the strength of the phase currents of each phases of the other of the top stage power line and the bottom stage power line.