DESC:Field of the invention:

The present invention relates to a field of numerical protection relays, power systems and switchgears and more particularly to a system and a method for measurement of sequence components into electrical networks.

Background of the invention:

In prior art method, computation of all sequence components is carried out after completing a cycle of power supply into electrical networks. In this method, a value of sequence component is updated after one cycle.

Also, a system requires trigonometric function to compute the value of sequence component. Hence, it is very difficult to update the value of sequence component and to issue a trip signal in quarter or half cycle.

Accordingly, there is a need develop a system and a method for fast measurement of sequence components to overcome above mentioned prior art problems thereby issuing a trip signal in quarter or half cycle.

Objects of the invention:

An object of the present invention is to provide fast measurement of sequence components.

Another object of the present invention is to issue a trip signal in quarter or half cycle.

Summary of the invention:

Accordingly, in one aspect, the present invention provides a system for measurement of sequence components. The system comprises of a three-phase input unit, a signal conditioning circuit, an analog to digital converter (ADC), a phase shifter, a zero sequence component block, a positive sequence component block and a negative sequence component block. The three-phase input unit sends a three phase signal to the signal conditioning circuit. The signal conditioning circuit converts the three phase signal into a three phase conditioned signal. Then, the signal conditioning circuit sends the three phase conditioned signal to the ADC. The ADC converts the three phase conditioned signal into a three phase instantaneous sample. Then, the ADC sends the three phase instantaneous sample to the phase shifter.

The phase shifter is a FIR Filter that is used to shift Y phase instantaneous sample and B phase instantaneous sample by a specific angle. For calculation of a positive sequence component value, Y phase instantaneous sample is shifted by 240 degree and B phase instantaneous sample is shifted by 120 degree. For calculation of a negative sequence component value, Y phase instantaneous sample is shifted by 120 degree and B phase instantaneous sample is shifted by 240 degree. A zero sequence component value is calculated and received by the zero sequence component block. The positive sequence component value is calculated and received by the positive sequence component block. The negative sequence component value is calculated and received at the negative sequence component block. The system provides fast measurement of all sequence components.

In another aspect, the present invention provides a method for measurement of sequence components. For computing a value of zero sequence component, the method involves taking an average of all three phase (Y phase, B phase, R phase) instantaneous samples to get a value of zero sequence sample and applying a Root-Mean-Square (RMS) method to the value of zero sequence sample. For computing a value of positive sequence component, the method involves calculating average of modified Y phase and modified B phase instantaneous samples along with a R phase instantaneous sample to get a value of positive sequence sample and applying the RMS method to the value of positive sequence sample. Further, the method involves calculating average of modified Y phase and modified B phase instantaneous samples along with the R phase instantaneous sample to get a value of negative sequence sample and applying the RMS method to the value of negative sequence sample for computing a value of negative sequence component. The method reduces trip time for sequence component and issues a trip signal in quarter or half cycle.

Brief description of the drawings:

Figure 1 shows a block diagram of a system for fast measurement of sequence components, in accordance with the present invention; and

Figure 2 shows a flow chart for performing a method for fast measurement of the sequence components, in accordance with the present invention.

Detailed description of the embodiments:

The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.

The present invention provides a system and a method for measurement of sequence components. The method provides fast measurement of sequence components. The system allows issuing a trip signal in quarter or half cycle.

The present invention is illustrated with reference to the accompanying drawings, throughout which reference numbers indicate corresponding parts in the various figures. These reference numbers are shown in bracket in the following description.

Referring to figure 1, in one aspect, a system for measurement of sequence components (100) (hereinafter referred as “the system (100)”) in accordance with the present invention is shown.

The system (100) comprises of a three-phase input unit (10), a signal conditioning circuit (20), an analog to digital converter (30) (hereinafter referred as, “the ADC (30)”), a phase shifter (40), a zero sequence component block (50), a positive sequence component block (60) and a negative sequence component block (70).

The three-phase input unit (10) generates a three phase signal (not numbered). In an embodiment, the three phase signal includes Y phase signal, B phase signal and R phase signal. The three-phase input unit (10) is electrically coupled to the signal conditioning circuit (20) for sending the three phase signal therefrom.

The signal conditioning circuit (20) receives the three phase signal from the three-phase input unit (10). The signal conditioning circuit (20) converts the three phase signal into a three phase conditioned signal. The signal conditioning circuit (20) is electrically coupled to the ADC (30) for sending the three phase conditioned signal therefrom.

The ADC (30) receives the three phase conditioned signal from the signal conditioning circuit (20). The three phase conditioned signal is converted into a three phase instantaneous sample using the ADC (30). The ADC (30) is electrically coupled to the phase shifter (40) for sending the three phase instantaneous sample therefrom. The ADC (30) is also electrically coupled to the zero sequence component block (50) for sending the three phase instantaneous sample therefrom.

The phase shifter (40) receives the three phase instantaneous sample from the ADC (30). In the embodiment, the phase shifter (40) is a FIR filter to shift Y phase instantaneous sample and B phase instantaneous sample of the three phase instantaneous sample by a specific angle. In a preferred embodiment, for calculation of a positive sequence component value, Y phase instantaneous sample is shifted by 240 degree and B phase instantaneous sample is shifted by 120 degree. In another preferred embodiment, for calculation of a negative sequence component value, Y phase instantaneous sample is shifted by 120 degree and B phase instantaneous sample is shifted by 240 degree. The phase shifter (40) is electrically coupled to the positive sequence component block (60) and the negative sequence component block (70).

The zero sequence component block (50) receives the three phase instantaneous sample from the ADC (30) to calculate a zero sequence component value.

The positive sequence component block (60) receives modified Y phase and modified B phase instantaneous samples from the phase shifter (40) to calculate the positive sequence component value.

The negative sequence component block (70) receives modified Y phase and modified B phase instantaneous samples from the phase shifter (40) to calculate the negative sequence component value.

Referring to figure 2, in another aspect, a method for measurement of sequence components (200) (hereinafter referred as “the method (200)”) in accordance with the present invention is shown. Specifically, the method (200) is illustrated in conjunction with the system (100) of the present invention. The method (200) starts at step (110).
At step (120), the method (200) involves calculating values of all sequence components by using three phase instantaneous sample and previous sample of three-phase.

At step (130), the method (200) involves taking an average of all three phase (Y phase, B phase, R phase) instantaneous samples to get a value of zero sequence sample.

At step (132), the method (200) involves applying a Root-Mean-Square (RMS) method to the value of zero sequence sample for computing a value of zero sequence component.

At step (140), the method (200) involves shifting a Y phase instantaneous sample by 240 degree to get a modified Y phase instantaneous sample.

At step (142), the method (200) involves shifting a B phase instantaneous sample by 120 degree to get a modified B phase instantaneous sample.

At step (144), the method (200) involves calculating average of the modified Y phase and the modified B phase instantaneous samples obtained at steps (140) and (142) along with a R phase instantaneous sample to get a value of positive sequence sample.

At step (146), the method (200) involves applying the Root-Mean-Square (RMS) method to the value of positive sequence sample for computing a value of positive sequence component.

At step (150), the method (200) involves shifting the Y phase instantaneous sample by 120 degree to get the modified Y phase instantaneous sample.

At step (152), the method (200) involves shifting a B phase instantaneous sample by 240 degree to get the modified B phase instantaneous sample.

At step (154), the method (200) involves calculating average of the modified Y phase and the modified B phase instantaneous samples obtained at steps (152) and (154) along with the R phase instantaneous sample to get a value of negative sequence sample.

At step (156), the method (200) involves applying the Root-Mean-Square (RMS) method to the value of negative sequence sample for computing a value of negative sequence component.

The method (200) ends at step (160).

In this way, the system (100) and the method (200) provide fast measurement of all sequence components (zero, positive and negative).

Advantages of the invention:

1. The system (100) and the method (200) provide fast measurement of all sequence components (zero, positive and negative).
2. The system (100) and the method (200) provide sequence component protection on signal basis.
3. The method (200) reduces trip time for sequence component.
4. The method (200) issues a trip signal in quarter or half cycle.
5. The system (100) leads to improvement in FCOMP relays.
6. The method (200) requires less flash memory as compare to prior art method.

The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:We Claim:

1. A system for measurement of sequence components (100), the system (100) comprising:
a three-phase input unit (10) generating a three phase signal;
a signal conditioning circuit (20) electrically coupled to the three-phase input unit (10) for receiving the three phase signal therefrom and converting the three phase signal into a three phase conditioned signal;
an analog to digital converter (ADC) (30) electrically coupled to the signal conditioning circuit (20) for receiving the three phase conditioned signal therefrom and converting the three phase conditioned signal into the three phase instantaneous sample;
a phase shifter (40) electrically coupled to the digital converter (30) for receiving the three phase instantaneous sample therefrom and for shifting of Y phase instantaneous sample and B phase instantaneous sample by a specific angle;
a zero sequence component block (50) electrically coupled to the ADC (30) for receiving the three phase instantaneous sample therefrom and calculating a zero sequence component value;
a positive sequence component block (60) electrically coupled to the phase shifter (40) for receiving modified Y phase and modified B phase samples therefrom and calculating a positive sequence component value; and
a negative sequence component block (70) electrically coupled to the phase shifter (40) for receiving modified Y phase and modified B phase instantaneous samples and calculating a negative sequence component value;
wherein, the system (100) provides fast measurement of all the values of the sequence components (zero, positive and negative).

2. The system (100) as claimed in claim 1, wherein the three phase signal includes Y phase signal, B phase signal and R phase signal.

3. The system (100) as claimed in claim 1, wherein the phase shifter (40) is a FIR filter.

4. The system (100) as claimed in claim 1, wherein the phase shifter (40) shifts the Y phase instantaneous sample by 240 degree and the B phase instantaneous sample by 120 degree for calculation of the positive sequence component value.

5. The system (100) as claimed in claim 1, wherein the phase shifter (40) shifts the Y phase instantaneous sample by 120 degree and the B phase instantaneous sample is by 240 degree for calculation of the negative sequence component value.

6. The system (100) as claimed in claim 1, wherein the zero sequence component block (50) calculates an average of all three phases (Y phase, B phase, R phase) instantaneous samples to get a value of zero sequence sample and applies a Root-Mean-Square (RMS) method thereto for computing the value of zero sequence component.

7. The system (100) as claimed in claim 1, wherein the positive sequence component block (60) calculates the average of modified Y phase and modified B phase samples along with a R phase instantaneous sample to get a value of positive sequence sample and applies the Root-Mean-Square (RMS) method thereto for computing the positive sequence component value.

8. The system (100) as claimed in claim 1, wherein the negative sequence component block (70) calculates the average of modified Y phase and modified B phase samples along with the R phase instantaneous sample to get a value of negative sequence sample and applies the Root-Mean-Square (RMS) method thereto for computing the negative sequence component value.

9. A method for measurement of sequence components (200), the method (200) comprising the steps of:
generating a three phase signal by a three-phase input unit (10);
receiving the three phase signal by a signal conditioning circuit (20) from the three-phase input unit (10) and converting the three phase signal into a three phase conditioned signal;
receiving the three phase conditioned signal by an analog to digital converter (ADC) (30) from the signal conditioning circuit (20) and converting the three phase conditioned signal into a three phase instantaneous sample;
receiving the three phase instantaneous sample by a phase shifter (40), shifting of Y phase instantaneous sample and B phase instantaneous sample by a specific angle and sending modified three phase instantaneous sample therefrom;
receiving the three phase instantaneous sample by a zero sequence component block (50) for calculating a zero sequence component value;
receiving modified Y phase instantaneous sample, modified B phase instantaneous sample and R phase instantaneous sample by a positive sequence component block (60) for calculating a positive sequence component value; and
receiving modified Y phase instantaneous sample, modified B phase instantaneous sample and R phase instantaneous sample by a negative sequence component block (70) for calculating a negative sequence component value;
wherein, the method (200) provides fast measurement of all the values of the sequence components (zero, positive and negative).

10. The method (200) as claimed in claim 9, wherein the phase shifter (40) shifts the Y phase instantaneous sample by 240 degree and the B phase instantaneous sample by 120 degree for calculation of the positive sequence component value.

11. The method (200) as claimed in claim 9, wherein the phase shifter (40) shifts the Y phase instantaneous sample by 120 degree and the B phase instantaneous sample is by 240 degree for calculation of the negative sequence component value.

12. The method (200) as claimed in claim 9, wherein the zero sequence component block (50) calculates an average of all three phases (Y phase, B phase, R phase) instantaneous samples to get a value of zero sequence sample and applies a Root-Mean-Square (RMS) method thereto for computing the value of zero sequence component.

13. The method (200) as claimed in claim 9, wherein the positive sequence component block (60) calculates the average of modified Y phase and modified B phase instantaneous samples along with a R phase instantaneous sample to get a value of positive sequence sample and applies the Root-Mean-Square (RMS) method thereto for computing the positive sequence component value.

14. The method (200) as claimed in claim 9, wherein the negative sequence component block (70) calculates the average of modified Y phase and modified B phase instantaneous samples along with the R phase instantaneous sample to get a value of negative sequence sample and applies the Root-Mean-Square (RMS) method thereto for computing the negative sequence component value.