Calculating linetoneutral voltage without connecting system neutral or ground
Calculating linetoneutral voltage without connecting system neutral or ground
 CN 105,044,426 B
 Filed: 04/24/2015
 Issued: 01/31/2020
 Est. Priority Date: 04/28/2014
 Status: Active Grant
First Claim
1. , a method for determining a voltage, the method comprising:
 measuring three linetoline voltages of phases in a threephase power system, each linetoline voltage comprising a voltage magnitude;
constructing a phasor triangle including the three linetoline voltages expressed as phasors on a twodimensional coordinate system having an origin, wherein the th phasor V_{ab}Originating at point and extending in the direction of the horizontal axis of the coordinate system to the origin, a second phasor V_{bc}Extending between said origin and a second point, said second point being in a vertical and horizontal direction with respect to said origin, and a third phase quantity V_{ca}Extending between said second point and said point ;
adding th line segment, the th line segment is selected from the second phasor V_{bc}The point of bisection is perpendicular to the second phasor V_{bc}And extends away from the direction of the phasor triangle, the th line segment terminating at a third point;
adding a second line segment that follows the third phasor V_{ca}The point of bisection is perpendicular to the third phasor V_{ca}And extending away from the direction of the phasor triangle, the second line segment terminating at a fourth point;
adding a third line segment from the third point to the th point;
adding a fourth line segment from the fourth point to the origin;
wherein the third line segment intersects the fourth line segment at a neutral point; and
determining a linetoneutral voltage, the linetoneutral voltage comprising a line from the neutral point to a vertex of the phasor triangle.
Chinese PRB Reexamination
Abstract
The invention relates to calculating linetoneutral voltage without connecting the system neutral or ground. The invention provides a method, an apparatus and a computer program product for determining a voltage. The method measures three linetoline voltages and constructs a phasor triangle with voltage phasors. V_{ab}Extending horizontally from point to the origin V_{bc}Extending between the origin and the second point. V_{ca}Extending between the second point and the point the method includes adding the th line segment, the th line segment from the V_{bc}The bisected point is perpendicular to V_{bc}Extends to the third point. The method adds a second line segment, the second line segment is selected from V_{ca}The bisected point is perpendicular to V_{ca}The method adds a third line segment from the third point to a th point and a fourth line segment from the fourth point to the origin.
32 Claims

1. , a method for determining a voltage, the method comprising:

measuring three linetoline voltages of phases in a threephase power system, each linetoline voltage comprising a voltage magnitude; constructing a phasor triangle including the three linetoline voltages expressed as phasors on a twodimensional coordinate system having an origin, wherein the th phasor V_{ab}Originating at point and extending in the direction of the horizontal axis of the coordinate system to the origin, a second phasor V_{bc}Extending between said origin and a second point, said second point being in a vertical and horizontal direction with respect to said origin, and a third phase quantity V_{ca}Extending between said second point and said point ; adding th line segment, the th line segment is selected from the second phasor V_{bc}The point of bisection is perpendicular to the second phasor V_{bc}And extends away from the direction of the phasor triangle, the th line segment terminating at a third point; adding a second line segment that follows the third phasor V_{ca}The point of bisection is perpendicular to the third phasor V_{ca}And extending away from the direction of the phasor triangle, the second line segment terminating at a fourth point; adding a third line segment from the third point to the th point; adding a fourth line segment from the fourth point to the origin;
wherein the third line segment intersects the fourth line segment at a neutral point; anddetermining a linetoneutral voltage, the linetoneutral voltage comprising a line from the neutral point to a vertex of the phasor triangle.


2. The method of claim 1, wherein determining the linetoneutral voltage comprises or more of:

determining phasor V of phase A_{an}The linetoneutral voltage of (a), comprising determining a line from the neutral point to the th point; determining phasor V of phase B_{bn}The linetoneutral voltage of (a), including determining a line from the neutral point to the origin; and determining phasor V of phase C_{cn}Including determining a voltage from said neutralA line dotted to the second point.


3. The method of claim 2, further comprising or more of:
determining phasor V_{an}The size of (A) is as follows;

4. the method of claim 1, wherein the th point comprises a coordinate (x)_{a}，
 y_{a}) The second point comprising coordinates (x)_{c}，
y_{c}) And the origin comprises coordinates (x)_{b}，
y_{b}) Wherein;x_{a}said V_{ab}Magnitude of phasor, and y_{a}＝
0；x_{b}0 and y_{b}0; and and isWherein, V_{ab}Is said th phasor V_{ab}Size of (V)_{bc}Is said second phase quantity V_{bc}A size of (2), and V_{ca}Is said third phase quantity V_{ca}The size of (2).
 y_{a}) The second point comprising coordinates (x)_{c}，

5. The method of claim 1 wherein the length of said th line segment comprises said third phasor V_{ca}Is divided by the square root of 3 and multiplied by the square root of the sum of 1 and the square of the slope of the th line segment, and wherein the length of the second line segment comprises the second phasor V_{bc}Is divided by the square root of 3 and multiplied by the square root of the sum of 1 and the square of the slope of said second line segment.

6. The method of claim 5, wherein the length of the th line segment comprises:

7. the method of claim 5, wherein the third point comprises a coordinate (x)_{pbc}，
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，
y_{pca}) Wherein, in the step (A),
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，

8. the method of claim 7, wherein the neutral point comprises a coordinate (x)_{n}，
 y_{n}) And wherein;
and
 y_{n}) And wherein;

9. the method of claim 8, wherein if y is_{n}Less than 0, then y_{n}0;
 and if y_{n}Greater than or equal to 0 and greater than y_{c}Then y is_{n}＝
y_{c}。
 and if y_{n}Greater than or equal to 0 and greater than y_{c}Then y is_{n}＝

10. The method of claim 9, wherein if x_{n}Less than 0, then x_{n}0;
 if x_{n}Greater than or equal to 0 and greater than x_{a}Then x_{n}＝
x_{a}(ii) a And if x_{n}Greater than or equal to 0 and less than or equal to x_{a}And y is_{c}＝
y_{n}Then x_{n}＝
x_{c}。
 if x_{n}Greater than or equal to 0 and greater than x_{a}Then x_{n}＝

11. The method of claim 1, wherein the length of the th line segment includes the second phase quantity V_{bc}Is multiplied by the square root of 3 and then divided by 2, and the length of the th line segment represents the second phasor V_{bc}The height of the th equilateral triangle constructed above and extending away from the phasor triangle, and wherein the length of the second line segment includes the third phasor V_{ca}Is multiplied by the square root of 3 and then divided by 2, the length of the second line segment represents the magnitude of the third phase quantity V_{ca}The height of a second equilateral triangle constructed above and extending away from the phasor triangle.

12. The method of claim 11, wherein the third point comprises a coordinate (x)_{pbc}，
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，
y_{pca}) Wherein, in the step (A),
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，

13. the method of claim 12, wherein the neutral point comprises a coordinate (x)_{n}，
 y_{n}) And wherein;
and
 y_{n}) And wherein;

14. the method of claim 1, wherein the linetoline voltage is measured at a location in the threephase power system where a neutralless connection is available for measurement.

15. The method of claim 1, wherein the threephase power system comprises an ungrounded power system.

16. The method of claim 1, wherein the threephase power system includes an unbalanced voltage.

17. The method of claim 1, wherein the th phasor V_{ab}The second phase amount V_{bc}And said third phasor V_{ca}Spaced 120 apart.

18. , an apparatus for determining voltage, comprising:

a measurement module that measures three linetoline voltages of phases in a threephase power system, each linetoline voltage comprising a voltage magnitude; a triangle module constructing a phasor triangle including the three linetoline voltages expressed as phasors on a twodimensional coordinate system having an origin, wherein th phasor V_{ab}Originating at point and extending in the direction of the horizontal axis of the coordinate system to the origin, a second phasor V_{bc}Extending between said origin and a second point, said second point being in a vertical and horizontal direction with respect to said origin, and a third phase quantity V_{ca}Extending between said second point and said point ; a th line module, the th line module adding a th line segment, the th line segment from the second phasor V_{bc}The point of bisection is perpendicular to the second phasor V_{bc}And extends away from the direction of the phasor triangle, the th line segment terminating at a third point; a second line module that adds a second line segment that follows the third phasor V_{ca}The point of bisection is perpendicular to the third phasor V_{ca}And extending away from the direction of the phasor triangle, the second line segment terminating at a fourth point; a third line module that adds a third line segment from the third point to the th point; a fourth line module that adds a fourth line segment from the fourth point to the origin, wherein the third line segment intersects the fourth line segment at a neutral point; and a linetoneutral module that determines a linetoneutral voltage, the linetoneutral voltage comprising a line from the neutral point to a vertex of the phasor triangle, wherein at least portions of the modules include or more of hardware and executable code stored on or more computerreadable storage media.


19. The apparatus of claim 18, wherein the linetoneutral module determines the linetoneutral voltage by:

determining phasor V of phase A_{an}The linetoneutral voltage of (a), comprising determining a line from the neutral point to the th point; determining phasor V of phase B_{bn}The linetoneutral voltage of (a), including determining a line from the neutral point to the origin; and determining phasor V of phase C_{cn}The linetoneutral voltage of (a), comprising determining a line from the neutral point to the second point.


20. The apparatus of claim 19, further comprising a linetoneutral size module that performs or more of:
determining phasor V_{an}The size of (A) is as follows;

21. the apparatus of claim 18, wherein the th point comprises a coordinate (x)_{a}，
 y_{a}) The second point comprising coordinates (x)_{c}，
y_{c}) And the origin comprises coordinates (x)_{b}，
y_{b}) Wherein;x_{a}said V_{ab}Magnitude of phasor, and y_{a}＝
0；x_{b}0 and y_{b}0; and and isWherein, V_{ab}Is said th phasor V_{ab}Size of (V)_{bc}Is said second phase quantity V_{bc}A size of (2), and V_{ca}Is said third phase quantity V_{ca}The size of (2).
 y_{a}) The second point comprising coordinates (x)_{c}，

22. The apparatus of claim 21 wherein the length of said th line segment comprises said third phasor V_{ca}Is divided by the square root of 3 and multiplied by the square root of the sum of 1 and the square of the slope of the th line segment, and wherein the length of the second line segment comprises the second phasor V_{bc}Is divided by the square root of 3 and multiplied by the square root of the sum of 1 and the square of the slope of said second line segment.

23. The apparatus of claim 21, wherein the third point comprises a coordinate (x)_{pbc}，
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，
y_{pca}) Wherein, in the step (A),
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，

24. the apparatus of claim 23, wherein the neutral point comprises a coordinate (x)_{n}，
 y_{n}) And wherein;
and
 y_{n}) And wherein;

25. the apparatus of claim 24, wherein if y is_{n}Less than 0, then y_{n}0;
 and if y_{n}Greater than or equal to 0 and greater than y_{c}Then y is_{n}＝
y_{c}。
 and if y_{n}Greater than or equal to 0 and greater than y_{c}Then y is_{n}＝

26. The apparatus of claim 25, wherein if x_{n}Less than 0, then x_{n}0;
 if x_{n}Greater than or equal to 0 and greater than x_{a}Then x_{n}＝
x_{a}(ii) a And if x_{n}Greater than or equal to 0 and less than or equal to x_{a}And y is_{c}＝
y_{n}Then x_{n}＝
x_{c}。
 if x_{n}Greater than or equal to 0 and greater than x_{a}Then x_{n}＝

27. The apparatus of claim 18 wherein the length of said th line segmentIncluding the second phase quantity V_{bc}Is multiplied by the square root of 3 and then divided by 2, and the length of the th line segment represents the second phasor V_{bc}The height of the th equilateral triangle constructed above and extending away from the phasor triangle, and wherein the length of the second line segment includes the third phasor V_{ca}Is multiplied by the square root of 3 and then divided by 2, the length of the second line segment represents the magnitude of the third phase quantity V_{ca}The height of a second equilateral triangle constructed above and extending away from the phasor triangle.

28. The apparatus of claim 27, wherein the third point comprises a coordinate (x)_{pbc}，
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，
y_{pca}) And wherein the first and second end portions of the first and second,
 y_{pbc}) And the fourth point comprises coordinates (x)_{pca}，

29. the apparatus of claim 28, wherein the neutral point comprises a coordinate (x)_{n}，
 y_{n}) And wherein;
and
 y_{n}) And wherein;

30. the apparatus of claim 18, further comprising a meter comprising the measurement module.

31. The apparatus of claim 18, further comprising a processor executing executable code of or more of the measurement module, the triangle module, the line module, the second line module, the third line module, the fourth line module, and the linetoneutral module.

32. , computer readable storage medium containing program code readable/executable by a processor to:

measuring three linetoline voltages of phases in a threephase power system, each linetoline voltage comprising a voltage magnitude; constructing a phasor triangle including the three linetoline voltages expressed as phasors on a twodimensional coordinate system having an origin, wherein the th phasor V_{ab}Originating at point and extending in the direction of the horizontal axis of the coordinate system to the origin, a second phasor V_{bc}Extending between said origin and a second point, said second point being in a vertical and horizontal direction with respect to said origin, and a third phase quantity V_{ca}Extending between said second point and said point ; determining a third point by adding an th line segment, the th line segment from the second phasor V_{bc}The point of bisection is perpendicular to the second phasor V_{bc}And extends away from the direction of the phasor triangle, the th line segment terminating at the third point; determining a fourth point by adding a second line segment, the second line segment being derived from the third phasor V_{ca}The point of bisection is perpendicular to the third phasor V_{ca}And extends away from the direction of the phasor triangle, the second line segment terminating at the fourth point; determining a neutral point by adding a third line segment from the third point to the th point and adding a fourth line segment from the fourth point to the origin, wherein the third line segment intersects the fourth line segment at the neutral point, and determining a linetoneutral voltage, the linetoneutral voltage comprising a line from the neutral point to a vertex of the phasor triangle.

Specification(s)