Pagtantiya sa Kaba sa Pagsukod sa Grid Electronic Voltage Transformer

1. Paghulagway

Ang mga grid electronic voltage transformers, isip mga indispensable nga pagsukol komponente sa mga sistema sa kuryente, ang ilang kasiguraduhan sa pagkuha direkta nga gisikdohan sa stable nga operasyon ug efficient nga pamahalaan sa mga sistema sa kuryente. Subalit, sa praktikal, tungod sa inherent nga katangian sa mga electronic komponente, environmental nga mga factor, ug mga limitasyon sa mga paraan sa pagkuha, ang mga resulta sa pagkuha sa mga voltage transformers karon naglakip og uncertainty. Kini nga uncertainty dili lamang nakaimpluwensya sa kasiguraduhan sa mga datos sa kuryente apan usab misala sa dispatching, control, ug protection strategies sa mga sistema sa kuryente. Busa, ang in-depth nga pananaliksik sa mga paraan sa pag-evaluate sa uncertainty alang sa verification ug measurement results sa grid electronic voltage transformers importante kaayo aron mapataas ang kasiguraduhan sa pagkuha sa mga sistema sa kuryente.

Ang studya kini nagnatiling sistemahan nga analisis sa mga factor nga nakaimpluwensya sa measurement uncertainty sa mga voltage transformers, kasama ang temperature drift, aging, ug noise interference sa mga electronic komponente, sama sa mga pagbag-o sa temperature, humidity, ug electromagnetic fields sa measurement environment. Pinaagi niining, ang scientific ug reasonable nga mga paraan sa pag-evaluate sa uncertainty magpakita. Sa pagbuhat og mathematical models gawas sa statistical principles ug metrology knowledge, ang research kini mahimong comprehensive nga assess ang measurement uncertainty sa grid electronic voltage transformers sa uban nga working conditions, naghatag og teyoretikal nga basehan ug teknikal nga support aron mas precise ang mga regulation sa verification ug mapataas ang product quality sa mga voltage transformers.

2. Experiment for Evaluating Uncertainty of Measurement Results
2.1 Experimental Object

Para sa uncertainty evaluation sa mga grid electronic voltage transformers, napili ang precision voltage calibration device nga may accuracy level sa 0.001, na-cover ang measurement range sa 1–1000 V. Ang voltage transformer nga atong i-verify designed para sa scenarios nga primary voltage 10 kV–50 kV ug secondary voltage 100 V, may accuracy level sa 0.02. Ang structure sa grid electronic voltage transformer makita sa Figure 1.

Ang experimental environment gihatagan og constant temperature sa 20 ± 2 °C, ang relative humidity gihimo nga below 60%, eliminando ang potential nga environmental impacts sa mga resulta sa pagkuha.

2.2 Verification and Measurement Method for Grid Electronic Voltage Transformers

Sa panahon sa verification sa mga grid electronic voltage transformers, kinahanglan ang scientific nga paraan sa pag-evaluate sa uncertainty aron siguro ang measurement accuracy. Gamiton ang grid electronic voltage transformer nga makita sa Figure 1 isip standard device, adunay comparison-based circuit connection. Kini nag-enable sa seamless alignment sa tested electronic voltage transformer ug standard device, makita sa Figure 2.

Subsequently, usa ka high-accuracy digital measurement system direktang gibasa ug gicalculate ang error sa electronic voltage transformer under test. Ang standard device model DHBV - 110/0.02, may excellent accuracy nga underpinning sa verification. Para sa transformer under test, rated voltage points sa 0.5%, 2%, 10%, 50%, ug 110% gihatagan aron cover ang operating range. Noteworthily, bagama ang maximum allowable error limits sa kini nga mga points sama sa full- ug light-load conditions, ang temperature drift ug aging sa mga electronic components mao ang significant nga stability differences across conditions. Busa, kinahanglan independent nga evaluate ang stability sa kada point aron kontrolon ang verification result uncertainty, meeting power grid operation's strict requirements for high-accuracy measurement technology.

3. Mathematical Model

Sa experiment for evaluating the uncertainty of verification and measurement results of grid electronic voltage transformers, when verifying the accuracy of the device under test, its uncertainty is often quantified through multiple dimensions, such as accuracy deviation and phase lag. These two indicators reflect the amplitude difference and phase deviation between the measured value and the true value, respectively. Thus, independent mathematical models can be constructed to accurately describe these sources of uncertainty. For the accuracy deviation Y, a linear regression model can be used, expressed as:

Where β0 and β1 are model parameters; $X$ is the input signal of the grid electronic voltage transformer; $\ε$ is the random error term. For the phase lag $\φ$, it can be expressed by a trigonometric function model as

Where α represents the fixed phase shift;θ(X) is a phase function that varies with the input signal. For more detailed analysis, nonlinear terms or polynomial approximations can be introduced to enhance the model’s accuracy. The establishment of these mathematical models provides a solid theoretical basis and quantitative tools for comprehensively and systematically evaluating the uncertainty of measurement results.

4.Results of the Uncertainty Component Evaluation Experiment

In the verification of grid electronic voltage transformers, multiple sets of voltage levels are set for uncertainty assessment. The rated voltage points of 0.5%, 2%, 10%, 50%, and 110% are selected and measured using the comparison method. The average values of the amplitude difference and phase deviation are recorded and calculated as the reference values at the corresponding voltage levels, so as to accurately evaluate the performance uncertainty of the tested transformer.

4.1 Type A Uncertainty Evaluation

Type A uncertainty reflects the degree of dispersion among the results obtained during repeated measurements of the same object. Its calculation formula is:

Where n is the number of measurements; x_i is the i-th measured value;xˉ  is the arithmetic mean of the measured values.

Then, for the rated voltage points of 0.5%, 2%, 10%, 50%, and 110%, the evaluation results of Type A uncertainty are shown in Table 1.

As can be seen from Table 1, as the rated voltage point increases, the Type A uncertainty of both the amplitude difference and the phase deviation shows an increasing trend. This is because at lower voltage levels, the voltage transformer is more stable, resulting in less dispersion in the measurement results. However, at higher voltage levels, the voltage transformer is affected by more factors, thus leading to greater dispersion in the measurement results.

4.2 Evaluation of Type B Uncertainty

Under JJF 1059.1—2022 Evaluation and Expression of Measurement Uncertainty, Type B uncertainty comes from reasonably inferring known relevant information to estimate its standard deviation. This information may involve equipment specifications from manufacturers, data of industry-recognized calibration methods, or statistical analysis of historical measurement data. The core of Type B uncertainty is to define the possible variation range of the measured value based on experience or professional knowledge, with its half-width being half the range width.

Then, select an appropriate coverage factor k for quantification according to the probability distribution characteristics and required confidence level. Usually, if measured values are uniformly distributed within the preset interval (each value has equal probability), the uniform distribution model is used, and k can be taken as an approximation of √3
 to ensure evaluation accuracy and rigor. The calculation formula for Type B uncertainty is

Where a is the half-width of the measurement variation interval.

For the rated voltage points of 0.5%, 2%, 10%, 50%, and 110%, the evaluation results of Type B uncertainty are shown in Table 2.

As can be seen from Table 2, at different rated voltage points, whether for amplitude difference or phase deviation, the uncertainty shows an increasing trend as the voltage level rises. Compared with Type A uncertainty, the evaluation of Type B uncertainty relies more on the accuracy and completeness of known information, reflecting a prior estimate of the performance of the voltage transformer under measurement. Therefore, in practical applications, comprehensively considering Type A and Type B uncertainties allows for a more comprehensive grasp of the accuracy and reliability of measurement results.

4.3 Evaluation of Combined Standard Uncertainty

When evaluating the combined standard uncertainty, if the verification and measurement results of each grid electronic voltage transformer are independent and uncorrelated (i.e., their correlation coefficients are all 0), the uncertainties follow the principle of linear combination for accumulation. Based on this, the evaluation of the combined standard uncertainty can be expressed by the following formula

Then, for the rated voltage points of 0.5%, 2%, 10%, 50%, and 110%, the evaluation results of the combined standard uncertainty are shown in Figure 3.

From Figure 3’s results, as rated voltage rises from 0.5% to 110%, combined standard uncertainties of amplitude difference and phase deviation show steady growth. Specifically, amplitude difference uncertainty increases from 0.008% to 0.085% (≈10-fold), and phase deviation uncertainty rises from 0.05° to 0.35° (≈7-fold). This trend implies higher voltage increases the transformer’s susceptibility to external interference, expanding measurement uncertainty. Yet, no extreme data changes occur, indicating the evaluation process is stable and reliable.

5.Conclusion

In the research on the uncertainty evaluation method for the verification and measurement results of grid electronic voltage transformers, multiple factors affecting measurement accuracy are analyzed, and scientific and effective evaluation methods are explored. Through theoretical analysis and experimental verification, it not only improves the reliability of the measurement results of voltage transformers but also provides a solid guarantee for the stable operation of the power system.