VA metering in delta-wired electrical service

1. An arrangement in a meter connected between a source and a load, comprising:

a) an A/D converter configured to generate digital samples of voltage and current waveforms in a polyphase electrical system;

b) a processing circuit operably coupled to receive the digital samples from the A/D converter, the processing circuit configured to:

i) obtain contemporaneous samples of V A , V B , V C , and at least three of I A , I B , I C , and I N , where I A is a current measurement signal of phase A, I B is a current measurement signal of phase B, I C is a current measurement signal of phase C, I N is a current measurement signal of a neutral connection, V A is a voltage measurement signal from phase A to neutral, V B is a voltage measurement signal from phase B to neutral, and V C is a voltage measurement signal from phase C to neutral;

ii) determine an I CB sample value based on contemporaneous samples of at least three of I A , I B , I C , and I N ;

iii) determine an I CA sample value based on contemporaneous samples of at least three of I A , I B , I C , and I N ;

iv) determine an I BN sample value based on contemporaneous samples of at least three of I A , I B , I C , and I N ;

v) determine an I AN sample value based on contemporaneous samples of at least three of I A , I B , I C , and I N ;

vi) determine a VA value based at least in part on I CB , I CA , I BN and I AN ; and

vii) provide information representative of the VA calculation to one of a group consisting of a display, a communication circuit, a memory and a billing calculation unit.

2. The arrangement of claim 1 , wherein the processing circuit is further configured to generate:

a) The I CB sample value based on the equation ⅙I A −⅙I B +½I C ;

b) The I CA sample value based on the equation ⅙I B −⅙I A +½I C ;

c) The I BN sample value based on the equation ⅚I B +⅙I A +½I C ; and

d) The I AN sample value based on the equation ⅚I A +⅙I B +½I C .

3. The arrangement of claim 1 , wherein the processing circuit is further configured to:

a) generate a plurality of each of the I CB , I CA , I BN and I AN sample values; and

b) generate a magnitude value for each of the plurality of the I CB , I CA , I BN and I AN sample values.

4. The arrangement of claim 3 , wherein the processing circuit is further configured to determine the VA value further based at least in part on the I CB magnitude value, the I CA magnitude value, the I BN magnitude value, and the I AN magnitude value.

5. The arrangement of claim 4 , wherein the processing circuit is further configured to determine the VA value further based in part on a magnitude of a voltage difference from phase C to phase B and a magnitude of a voltage difference from phase C to phase A.

6. The arrangement of claim 5 , wherein the processing circuit is further configured to determine the magnitude of the voltage from phase C to phase B and determine the magnitude of the voltage from phase C to phase A by:

a) generating a plurality of the V CB sample values, each V CB sample value comprising a difference between a phase C sample and a contemporaneous phase B sample; and

b) generating a V CB magnitude value using the plurality of the V CB sample values;

c) generating a plurality of the V CA sample values, each V CA sample value comprising a difference between a phase C sample and a contemporaneous phase A sample;

d) generating a V CA magnitude value using the plurality of the V CA sample values.

7. The arrangement of claim 5 , wherein the processing circuit is further configured to generate the VA value based on the equation:

V

⁢

⁢

A

=



V

CB

→



*



I

CB

→



+



V

CA

→



*



I

CA

→



+



V

B

→



*



I

BN

→



+



V

A

→



*



I

AN

→



wherein |{right arrow over (V CB )}| is the V CB magnitude value, |{right arrow over (I CB )}| is the I CB magnitude value, |{right arrow over (V CA )}| is the V CA magnitude value, |{right arrow over (I CA )}| is the I CA magnitude value, |{right arrow over (V B )}| is a magnitude of the voltage from phase B to neutral, |{right arrow over (I BN )}| is the I BN magnitude value, |{right arrow over (V A )}| is a magnitude of the voltage from phase A to neutral, and |{right arrow over (I AN )}| is a vector value representative of the current from phase A to neutral.

8. The arrangement of claim 1 , further comprising the display, and wherein the display is configured to display the information representative of the VA calculation.

9. An arrangement in a meter connected between a source and a load, comprising:

a) an A/D converter configured to generate digital samples of voltage and current waveforms in a polyphase electrical system;

b) a processing circuit operably coupled to receive the digital samples from the A/D converter, the processing circuit configured to:

i) obtain samples of V A , V B , V C , and at least three of I A , I B , I C , and I N , where I A is a current measurement signal of phase A, I B is a current measurement signal of phase B, I C is a current measurement signal of phase C, I N is a current measurement signal of a neutral connection, V A is a voltage measurement signal from phase A to neutral, V B is a voltage measurement signal from phase B to neutral, and V C is a voltage measurement signal from phase C to neutral;

ii) determine, based on the obtained samples, a magnitude value |{right arrow over (V CB )}| of a voltage from phase C to phase B, a magnitude value |{right arrow over (I CB )}| of a source current from phase C to phase B, a magnitude value |{right arrow over (V CA )}| of a voltage from phase C to phase A, a magnitude value |{right arrow over (I CA )}| of a source current from phase C to phase A, a magnitude value |{right arrow over (V B )}| of a voltage from phase B to neutral, a magnitude value |{right arrow over (I BN )}| of a source current from phase B to neutral, a magnitude value |{right arrow over (V A )}| of a voltage from phase A to neutral, and a magnitude value |{right arrow over (I AN )}| of a source current from phase A neutral;

iii) generate the VA value based on the equation

V

⁢

⁢

A

=



V

CB

→



*



I

CB

→



+



V

CA

→



*



I

CA

→



+



V

B

→



*



I

BN

→



+



V

A

→



*



I

AN

→



;

and

iv) provide information representative of the VA calculation to one of a group consisting of a display, a communication circuit, a memory and a billing calculation unit.

10. The arrangement of claim 9 , wherein the processing circuit is further configured to determine the value |{right arrow over (I CB )}| based on samples of at least three of I A , I B , I C , and I N .

11. The arrangement of claim 10 , wherein the processing circuit is further configured to determine the value |{right arrow over (I CA )}| based on samples of at least three of I A , I B , I C , and I N .

12. The arrangement of claim 9 , wherein the processing circuit is further configured to determine the value |{right arrow over (I BN )}| based on samples of at least three of I A , I B , I C , and I N .

13. The arrangement of claim 12 , wherein the processing circuit is further configured to determine the value |{right arrow over (I AN )}| based on samples of at least three of I A , I B , I C , and I N .

14. An arrangement in a meter connected between a source and a load, comprising:

a) an A/D converter configured to generate digital samples of voltage and current waveforms in a polyphase electrical system;

b) a processing circuit operably coupled to receive the digital samples from the A/D converter, the processing circuit configured to:

i) obtain contemporaneous samples of V A , V B , V C , and at least three of I A , I B , I C , and I N , where I A is a current measurement signal of phase A, I B is a current measurement signal of phase B, I C is a current measurement signal of phase C, I N is a current measurement signal of a neutral connection, V A is a voltage measurement signal from phase A to neutral, V B is a voltage measurement signal from phase B to neutral, and V C is a voltage measurement signal from phase C to neutral;

ii) determine a I CB sample value based on contemporaneous samples of the at least three of I A , I B , I C , and I N ;

iii) determine a VA value based at least in part on I CB ; and

iv) provide information representative of the VA calculation to one of a group consisting of a display, a communication circuit, a memory and a billing calculation unit.

15. The arrangement of claim 14 , wherein the processing circuit is further configured to generate the I CB sample value based on the equation ⅙I A −⅙I B +½I C .

16. The arrangement of claim 15 , wherein the processing circuit is further configured to:

generate a plurality of the I CB sample values;

generate a magnitude value of the plurality of the I CB sample values; and

determine the VA value based at least in part on the produce of the generated magnitude value and a magnitude of a voltage from phase C to phase B.