AU2021103474A4

AU2021103474A4 - Digital error compensation of industrial energy measurement system

Info

Publication number: AU2021103474A4
Application number: AU2021103474A
Authority: AU
Inventors: Makarand Ballal; Manish Ganeshrao Wath; Hiralal Murlidhar Suryawanshi
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-06-19
Filing date: 2021-06-19
Publication date: 2022-03-24
Anticipated expiration: 2029-06-19

Abstract

The present disclosure relates to a method and system for development of a high accuracy class and cost-effective industrial energy measurement system (IEMS). For the development of required IEMS a unique Industrial Energy Measurement-Error Compensation Unit (IEM-ECU) is proposed. To achieve that three different accuracy classes (0.2, 0.5, and 1,0) are fabricated and their performances are measured in the laboratory and their characteristics are analyzed for various operating conditions. The proposed IEM-ECU system computes the voltage, load current, and power factor correction coefficient. The coefficients are used to compute the errors of CTs and PTs and then are used to compensate the error in measured value of voltages, current, and active power. 12 C Cp IC LDJ I it 42 - 0 CC -2 I r r_ -4 4

Description

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DIGITAL ERROR COMPENSATION OF INDUSTRIAL ENERGY MEASUREMENT SYSTEM FILED OF THE INVENTION

The present disclosure relates to a method and system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS).

BACKGROUND OF THE INVENTION

Current transformers (CTs) and potential transformers (PTs) are widely used in Industrial Energy Measurement System (IEMS). These transformers are used to measure the energy consumption by high-tension (HT) industrial customers. Due to the exciting current used to magnetize the core of the CTs and PTs ratio and phase angle errors occur often, they occur also because of the non-linear behavior of the core of CTs and PTs under different system conditions. The power distribution utilities have to face loss because, these errors affect the revenue directly by inaccurate measurements of energy consumed by industrial customers.

The existing solutions minimize the ratio and phase angle error of PTs and CTs but they do also have certain limitation and problems. Therefore, there is a method and system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS) by providing a digital error compensation.

SUMMARY OF THE INVENTION

The present disclosure relates to a method and system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS). For developing a high accuracy class and cost effective IEMS, a unique Industrial Energy Measurement-Error Compensation Unit (IEM-ECU) algorithm is proposed. First, three different accuracy classes (0.2, 0.5, and 1.0) IEMS are fabricated in laboratory. After fabrication the proposed digital error correction algorithm is implemented in real time to improve the ratio and phase angle errors of IEMS. Various tests have been performed and the results are validated by comparing the results obtained from digital storage oscilloscope. The results confirms that IEM-ECU convert the lower accuracy class to higher accuracy class i.e. having accuracy class 1.0 or 0.5 can be converted to accuracy class 0.2 just by mapping the errors under any operating conditions It compensate the errors and gives the results matching with higher accuracy class. The results confirms that it also gives flexibility to use any available class of CTs and PTs, if required in emergency which means that in case of failure of higher accuracy class of any unit i.e. CT or PT, it is possible to replace the failed unit by lower accuracy class. Because of these aforementioned benefits, cost saving can be achieved as the performance of both lower and higher accuracy class matches. These benefits also helps in avoiding the wrong assessment of electricity bill made by power distribution utility. This technique of compensating the errors required neither any CT/PT model nor they any additional hardware circuitry. The digital energy meter (DEM) which is connected to the secondary side of CTs and PTs is sufficient for the execution of proposed error compensation algorithm.

The present disclosure seeks to provide a method for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS). The method comprises: reading the RMS value of voltages and currents which are scaled down by PTs and CTs respectively; determining the respective values of percentage ratio and phase angle errors for each PT and CT respectively; computing the voltage, current and power factor correction coefficients; and compensating the errors in measurements of voltages, current, and active power using the correction coefficients.

The present disclosure also seeks to provide a system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS). The system comprises: a power supply, wherein the power supply is three-phase source feeding to three-phase load bank connected in Y configuration; IEMS of three different accuracy classes of 0.2, 0.5, and 1.0 which are designed and developed in the laboratory; a Digital Energy Meter (DEM) for measuring the voltages, current, and power factor of each IEMS; and IEM-ECU for compensating the errors in measurements of voltages, current, and power factor angle.

An objective of the present disclosure is to provide a method and system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS).

Another object of the present disclosure is to develop a unique industrial energy measurement-error compensation unit (IEM-ECU).

Another object of the present disclosure is to fabricate three different accuracy classes of 0.2, 0.5, and 1.0 IEMS.

Another object of the present disclosure is implementing the proposed IEM-ECU error correction algorithm to improve the error of IEMS.

Another object of the present disclosure is to compare the results of proposed algorithm with the results obtained from digital storage oscilloscope.

Another object of the present disclosure is to achieve cost saving by matching the performances of both lower accuracy class and higher accuracy class metering system.

Another object of the present disclosure is to improve the accuracy of the measurement of electrical energy consumption by high tension (HT) industrial consumers.

To further clarify advantages and features of the present disclosure, a more particular description of the invention will be rendered by reference to specific embodiments thereof, which is illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail with the accompanying drawings.

BRIEF DESCRIPTION OF FIGURES

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:

Figure 1 illustrates a flow chart of a method of digital error compensation for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS) in accordance with an embodiment of the present disclosure;

Figure 2 illustrates a block diagram of a digital error compensation system for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS) in accordance with an embodiment of the present disclosure;

Figure 3 illustrates the proposed IEM-ECU algorithm in accordance with an embodiment of the present disclosure;

Figure 4 illustrates functional diagram of digital error compensation of Industrial Energy Measurement System (IEMS) in accordance with an embodiment of the present disclosure;

Figure 5 illustrates three IEMS of accuracy classes of 0.2, 0.5, and 1.0 which are clubbed together and their corresponding PTs and CTs in accordance with an embodiment of the present disclosure;

Figure 6 illustrates the experimental setup in Maharashtra State Electricity Distribution Co. Ltd. (MSEDCL) laboratory in accordance with an embodiment of the present disclosure;

Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present disclosure. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present disclosure so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof.

Reference throughout this specification to "an aspect", "another aspect" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Thus, appearances of the phrase "in an embodiment", "in another embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises...a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.

Embodiments of the present disclosure will be described below in detail with reference to the accompanying drawings.

Figure 1 illustrates a flow chart of a method for developing a high accuracy class and cost-effective industrial energy measurement system (IEMS) in accordance with an embodiment of the present disclosure. At step 102 the method 100 includes, reading the RMS value of voltages and currents which are scaled down by PTs and CTs respectively.

At step 104 the method 100 includes, determining the respective values of percentage ratio and phase angle for each PT and CT respectively. The percentage ratio and phase angle are obtained by manufacturer's data sheet/test reports for both PT and CT.

At step 106 the method 100 includes, computing the voltage, current and power factor correction coefficients. The ratio and phase angle data are only required for the determination of correction coefficients. DEM is connected to the secondary side of CTs and PTs should have high accuracy class so that it displays accurate results. In this research, the characteristics of PTs i.e., plots between V 2 versus av and V 2versus pv and characteristics of CTs i.e., plots between I2 versus a, and I2 versus P1 are stored in the memory of IEM-ECU.

At step 108 the method 100 includes, compensating the errors in measurements of voltages, current, and active power using the correction coefficients. Once the correction coefficients are determined, they are applied to secondary side voltage, current and power factor to determine the correct value of PT secondary voltage, CT secondary current, and power factor for each phase and thereafter the calculation to determine the correct value of active power for each phase are performed and the results are displayed.

Figure 2 illustrates a block diagram of a cost-effective industrial energy measurement system (IEMS) in accordance with an embodiment of the present disclosure. The system 200 includes a power supply 202, wherein the power supply is three-phase source feeding to three phase load bank connected in Y configuration

In an embodiment, IEMS 204 of three different accuracy classes of 0.2, 0.5, and 1.0 are designed and developed in the laboratory. To design and develop these three IEMS of different accuracy classes, three sets of CTs and PTs are procured from M/s. Powerage India Private Limited, Nagpur, India.

In an embodiment, a Digital Energy Meter (DEM) 206 is used for measuring the voltages, current, and power factor of each IEMS. DEM is connected to the secondary side of CTs and PTs should have high accuracy class so that it displays accurate results.

In an embodiment, an IEM-ECU 208 is used for compensating the errors in measurements of voltages, current, and active power. The IEM-ECU algorithm reads the values of voltage and current scaled down by CTs and PTs respectively. Then the values of percentage ratio and phase angle are determined for CTs and PTs. From these values the voltage, current and power factor correction coefficient are computer. These correction coefficients are then used for the error compensation in measured value of voltages, currents, and active power.

Figure 3 illustrates the proposed IEM-ECU algorithm in accordance with an embodiment of the present disclosure. The proposed algorithm is used for the error correction of secondary side voltage, current, power factor based on the computation of various correction coefficients (y). Thus power and energy also get corrected. For the determination of rection coefficients the ratio and phase angle data is required. To display the accurate results, the DEM connected to the secondary side of CTs and PTs should have higher class. The characteristics of PTs and CTs are stored in IEM-ECU. The values of voltages and current are scaled down by PTs and CTs and to correct that the RMS values of voltages and current which are scaled down by PTs and CTs are read by the proposed algorithm and thereafter the respective values of av, Pva nd a,, P1 are determined. From these determined values the voltages, current and power factor correction coefficient are computed. These correction coefficients are used to compensate the error in measurement of value of voltages, current and active power.

Figure 4 illustrates functional diagram of Industrial Energy Measurement System (IEMS) in accordance with an embodiment of the present disclosure. This figure represents an IEMS which have higher accuracy and is cost-effective. This proposed IEMS consists of a power supply which is three-phase source feeding to three-phase load bank connected in Y configuration. Three different IEMS is used depending upon the accuracy class of PTs and CTs which are developed and designed in laboratory, and for the development of these three different IEMS, three sets of CTs and PTs are procured from M/s. Power age India Private Limited, Nagpur, India. A Digital Energy Meter (DEM) which is connected for the measurement of voltages, currents, power factor of each IEMS, the DEM not only measure power and energies of each phase but also measures cumulative energy. All these measured data by DEM are fed to IEM-ECU by RS 485 port with the help of connecting cable. The Lab VIEW setup and digital storage oscilloscope (DSP) are connected to measure the voltages, currents, and power factors from both side of PTs and CTs.

Figure 5 illustrates three IEMS of accuracy classes of 0.2, 0.5, and 1.0 which are clubbed together and their corresponding PTs and CTs in accordance with an embodiment of the present disclosure. The three IEMS of accuracy classes 0.2, 0.5, and 1.0 are clubbed together as shown in the figure (a) and the corresponding PTs and CTs are shown in the figure (b) & (c) respectively.

Figure 6 illustrates the experimental setup in Maharashtra State Electricity Distribution Co. Ltd. (MSEDCL) laboratory in accordance with an embodiment of the present disclosure. The calibration current and voltage were generated at frequency 50 Hz. The Tektronix DSO, TDS3054 series, 4 Channel, 500MHz, 2.5 GSPS is used for the measurement of CTs and PTs secondary side parameters. The CT and PT test system is obtained by the MSEDCL from Eltel Industries. The system consists of the appropriate reference CT and PT and a set of burdens to load the test CT and test PT. Burdens are designed according IEC-60044-2 standards. In the laboratory, all the control switches and connections for PT and CT under test are provided on the front panel. USB Port is also provided for multipurpose like data transfer, printout, etc.

The drawings and the forgoing description give examples of embodiments. Those skilled in the art will appreciate that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of processes described herein may be changed and are not limited to the manner described herein. Moreover, the actions of any flow diagram need not be implemented in the order shown; nor do all of the acts necessarily need to be performed. Also, those acts that are not dependent on other acts may be performed in parallel with the other acts. The scope of embodiments is by no means limited by these specific examples. Numerous variations, whether explicitly given in the specification or not, such as differences in structure, dimension, and use of material, are possible. The scope of embodiments is at least as broad as given by the following claims.

Benefits, other advantages, and solutions to problems have been described above with regard to specific embodiments. However, the benefits, advantages, solutions to problems, and any component(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential feature or component of any or all the claims.

Claims

WE CLAIM

1. A method for development of a high accuracy class and cost-effective industrial energy measurement system (IEMS), the method comprises:

reading the RMS value of voltages and currents which are scaled down by PTs and CTs respectively;

determining the respective values of percentage ratio and phase angle for each PT and CT respectively;

computing the voltage, current and power factor correction coefficients; and

compensating the errors in measurements of voltages, current, and active power using the correction coefficients;

2. The method as claimed in claim 1, wherein the percentage ratio (av) and phase angle (pv) for each PT is obtained by PT manufacturer data sheet/test reports for 80%-120% voltage condition and at defined burden.

3. The method as claimed in claim 1. Wherein the percentage ratio (av) and phase angle (pv) for each CT is obtained by CT manufacturer data sheet/test reports for 0%-120% load condition and at defined burden.

4. The method as claimed in claim 1, wherein computing the correction coefficient comprises:

entering the percentage ratio and phase angle errors data for each PT and CT repetitively; finding the secondary side voltage and current for each phase at a given value of percentage ratio and phase angle for PT and CT respectively; converting phase angle into radians from minute; developing the V 2 Vs av and V 2 Vs pv characteristics for each PT and I2 Vs ar and

I2 Vs P characteristics for each CT;

storing the developed characteristics in the memory of IEM-ECU;

reading online values of secondary side voltages and currents of each phase from the digital energy meter (DEM);

finding the corresponding av, pv and a,, P1 for measure value of secondary side voltage (V2 ) and secondary side current (12) from the stored characteristics; and

determining the correction coefficients for the measured values secondary side voltage, current and power factor;

5. The method as claimed in claim 1, wherein compensating the errors in measurements comprises:

applying the determined correction coefficients to secondary side voltage, current and power factor;

determining the correct value of PT secondary voltages, CT secondary currents and power factors for each phase; and

performing the calculations to determine the correct values of active power for each phase and display the results.

6. An industrial energy measurement system (IEMS), the system comprises:

a power supply, wherein the power supply is three-phase source feeding to three phase load bank connected in Y configuration;

IEMS of three different accuracy classes of 0.2, 0.5, and 1.0 are designed and developed in the laboratory;

a Digital Energy Meter (DEM) for measuring the voltages, current, and power factor of each IEMS; and

IEM-ECU used for compensating the errors in measurements of voltages, current, and active power;

7. The system as claimed in claim 6, wherein to design the IEMSs of three different accuracy classes, three sets of CTs and PTs are procured from M/s. Powerage India Private Limited, Nagpur, India;

8. The system as claimed in claim 7, wherein PTs and CTs have ratio of 230/63.5 V and 10/5 A respectively.

9. The system as claimed in claim 6, wherein the DEM not only measures power and energies of each phase but also measures cumulative energy.

10. The system as claimed in claim 6, wherein the IEM-ECU is connected through a RS 485 port by a connecting cable, wherein all the data are fed thorough this port.

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