Refinement of the mathematical model of electrical energy measurement uncertainty in reduced load mode

Kvasnikov

2022

EEJET

The object of the research is a measuring current transformer of the electromagnetic type, which is used as part of the electricity metering unit. The current transformers functioning in the mode of reduced primary current is accompanied by significant errors. The existence of such a regime for a long time due to downtime of production equipment leads to a significant underestimation of electricity. This leads to unjustified financial losses for energy supply companies as electricity in many countries has become more expensive. The static characteristic of the measuring current transformer at a reduced load of the metering unit is described by a linear statistical model. The parameters of the model are estimated on the basis of empirical data using methods of covariance analysis. The adequacy of the model is confirmed by analysis of regression residuals. The obtained statistical model of the static characteristic, unlike the known ones, is characterized by universality, as it describes current transformers with an arbitrary transformation ratio within the studied accuracy class of 0.5S. The uncertainty of the current error is estimated using the prediction intervals for the transformers secondary currents as a function of the primary currents, calculated on the basis of the obtained model. The prediction intervals for sample values of the current error were obtained through the application of the proposed approach for uncertainty estimation of such an error at a reduced load of the metering unit. It was found that the current error can reach −20 %. Taking into account the indicated intervals for measuring current transformers at a reduced load of the metering unit during billing will allow energy supply companies to increase the accuracy of commercial electricity metering.

Section: Discussion Of the Results Of Studying The Static Characteris...mentioning

confidence: 99%

Section: Literature Review and Problem Statementmentioning

confidence: 99%

Determining the static characteristic of a measuring current transformer at a reduced load of the metering unit

Kvasnikov

2022

EEJET

“…The accuracy of electricity measurement by the ζ={A, B, C} measuring channel of the accounting unit in the reduced load mode can be estimated by the relative deviation δWζ of the active energy measured for the time interval Δt between the readings of the transformer connected meter (PI1) and the direct connected meter (PI2), which is determined under the assumption of zero current in the other two channels [37]:…”

Section: Metrological Characteristics Identification Of the Accountin...mentioning

confidence: 99%

Increasing the accuracy of electricity accounting by digitalinformation-measuring systems

Vasylets¹,

Vasylets²

2023

AAIT

Significant non-technological losses of electricity are observed in 0.38 kV distribution networks, which lead to financial dam-ages of energy supply companies. The reason for their occurrence is the deficiencies in the accountingunits functioning inthe re-duced load mode, which occurs during the downtime of the main technological equipment. The purpose of the study is to increase the accuracy of electricity measurement by a commercial accountingunit in the reduced load mode based on mathematical modeling of measurement uncertainty. Evaluation of regression parameters for the static characteristics of measuring current transformersin the reduced load mode is carried out using the covariance analysis methods and analysis of regression residuals. Estimation of the non-random uncertainty of electricity measurementby one measuring channel of theaccountingunit was carried out using the fuzzy set theory. The polynomial approximation of the experimental values of the membership function for the measured quantity was carried out according to the maximum norm method. The least square method was used to approximate the boundaries of fuzzy functions. As a result of research, a universal static characteristic of a measuring current transformer of a certain accuracy class was obtained at a reduced primary current. It was established that the sample estimates uncertainty of the current transformer error of the 0.5 S accura-cy class changes from ±11.7% to ±1.7%. The uncertainty of electricity measurement by the commercial accountingunit in the re-duced load mode is proposed to be estimated by a fuzzy function. The developed mathematical model takes into account the depend-ence of the fuzzy interval boundaries, which characterizes the measurement result, on the phase currents asymmetric values. Compar-ison of the analytically obtained membership function for the relative deviations of the readings of the accountingunits with the em-pirically obtained value of such a deviation made it possible to establish the limitvalue of the confidence level, which was not less than 0.54 at the minimum permissible value of 0.4 of the adequacy criterion. This confirms the adequacy of the results of mathemati-cal modeling with experimental data. Estimating the electricity metering uncertainty with a fuzzy interval increases the accuracy of the measurement, as it allows clarifyingthe monthly electricity consumption by taking into account the energy that was consumed during the reduced load mode

“…Such a difference can reach two orders of magnitude, which makes it difficult to ensure the necessary accuracy of measurements. It was established in [8] that the current trans-formers characteristics have a decisive influence on the static conversion function of the measuring channel of the metering unit. In this work, such characteristics at reduced primary current were not determined.…”

Section: Introductionmentioning

confidence: 99%

Research on accuracy of electrical energy measurement in microgrid for mine dewatering

Vasylets¹,

Vasylets²,

Kylymchuk³

2022

TT: PhE

The object of the study is the current transformers of the electricity metering unit as part of the microgrid for mine dewatering, which includes a photovoltaic station. The need to pump mine waters is caused by the danger of flooding large areas. The introduction of a photovoltaic station to power underground pumps reduces electricity consumption from the central power grid. At the same time, it changes the operating conditions of the metering unit. There is a need to measure both the currents of the pumps in the absence of solar generation, as well as relatively small current flows in the case of commensurate capacities generated and consumed within the microgrid. A feature of electromagnetic current transformers is a decrease in the accuracy of operation if the primary current is several percent of the rated value. Based on the analysis of variance of the experimental data, it was established that there is a statistically significant connection between the secondary and primary currents of the measuring transformer at insignificant values of the primary current. Estimates of the values of the linear regression parameters that link the secondary and primary currents were determined. It was established that in the range of the transformer primary current from 0.22 % to 1.4 %, the current error reaches a value of 6.7 %. Taking into account the resulting dependence in the software of the electricity metering unit will make it possible to increase the accuracy of energy metering. Accordingly, the accuracy of financial calculations will be increased