This paper introduces an optical AC voltage sensor based on the transverse Pockels effect. The sensor utilizes a bulk Bi₄Ge₃O₁₂ (BGO) crystal as the sensing element. The measurement principle has been described and prototype of the sensor has been constructed and evaluated. Good linearity and accuracy performance was obtained for AC voltage measurement. The proposed sensor can be thus applied to high AC voltage measurements in the electric power industry.

Currently, in China’s power grid, the accounting of carbon emissions has shortcomings such as unclear accounting boundaries, slow updating of carbon emission factors (EFs), and a lack of spatiotemporal characteristics. In this study, a dynamic accounting model for carbon emission was constructed based on carbon flow theory and the QIO (Quasi-Input-Output) model using the transmission side, the substation side, and the distribution side as accounting nodes. By utilizing the electricity metering data and carbon EF on the input side of the node, the total carbon emissions flowing into the node could be calculated. Furthermore, based on the electricity metering data on the output side of the node, the carbon emissions and carbon EF flowing out of the node could be calculated. The accounting results of carbon emissions and carbon EF are characterized by flexibility and dynamicity in both spatial and temporal dimensions. Finally, the practicality of the method has been demonstrated through a substation node. The accounting model has a positive impact on accurate carbon emission accounting for the power grid, better tracing of carbon emissions, and effective user guidance on active carbon emission reduction.

The stability of the optical electric field sensor (OEFS) in actual operation is affected by environmental factors such as temperature and SF₆ (sulfur hexafluoride). To analyze the operational environment parameters affecting the optical properties of crystals, a thermodynamic model of the OEFS in which the optical properties of the crystal are changed by the first-order effects and the second-order effects was established. The intensity parameters such as electric, stress and temperature fields were introduced. The theoretical analysis results show that under temperature, stress and electric field conditions, the optical properties of the sensing crystals are no longer changed only by the electro-optic effect, but also by the temperature and the stress fields. Further synthesis suggests the expected optical property changes under the effect of the environment fields. OEFS tests show that the accuracy of OEFS is dependent on temperature with a ratio error of −0.8%~1.5% in the temperature range from −25 °C to +40 °C.

Facing a lack of high accuracy current standards in the calibration of AC (Alternating Current) + DC (Direct Current) measurement devices that function to measure DC and AC simultaneously, a measurement method with high accuracy is proposed based on zero-flux self-oscillating fluxgate. An iron core and two windings are added onto the single-iron-core double-winding structure of the traditional self-oscillating fluxgate. The added iron core and its upper winding are used to weaken the influence of ripple on the sensor’s accuracy. The other one of the added windings is used for the feedback from the AC+DC magnetic potential, allowing the sensor to work in a zero-flux state and to measure AC+DC simultaneously. An AC+DC transducer prototype with an AC ranging from 0–500 A and DC 0–300 A is developed by selecting the core parameters and an optimized design of the circuit. The test results of the prototype show that the prototype can measure the AC and DC simultaneously, and the measurement accuracy reaches class 0.05 level in the nominal current range. This transducer can be used as a calibration standard of measurement devices for AC only, DC only, or AC and DC simultaneously. Compared with the AC+DC current transducer with the same accuracy level, the proposed transducer has fewer cores and simpler measuring circuit.

In recent years, the Chinese government has focused on doing a good job of “peak carbon dioxide emissions” and “carbon neutrality” work. In order to answer the call for national green development and transformation, an accurate carbon measurement in power grid enterprises is the basic premise to accurately grasp the trend of the carbon emission and effectively carry out various carbon emission reduction work. In the power grid, substations, whose loss can account for 50% of the overall grid loss, have a wide range of operating equipment and some equipment also has emissions or leakages of sulfur hexafluoride gas. Therefore, in order to improve the carbon measurement of substations, the main work of this paper is as follows. The carbon emission mechanism of substations based on the composition of substations is analyzed in depth. We focus on the carbon emissions generated by various energy consumption of substations and the leakage of $SF_{6}$ gas based on the carbon emission accounting method of power grid enterprises issued by the National Development and Reform Commission and the relationship between the energy consumption and carbon emissions. Then, carbon measurement models of substations based on the measurement data are established. And we also calculate the carbon emissions of the substation, taking a 500kV GIS substation of China Southern Power Grid as an example. This paper provides a more comprehensive research on carbon measurement models of substations by analyzing the carbon emission generated by the energy consumption of substations and the leakage of gases. Therefore, it provides support for clarifying the distribution of substation carbon emissions, carrying out carbon emission reduction and promoting the transformation of the green development of power systems.

Optical voltage transformers (OVTs) have been applied in power systems. When performing accuracy performance tests of OVTs large differences exist between the electromagnetic environment and the temperature variation in the laboratory and on-site. Therefore, OVTs may display different error characteristics under different conditions. In this paper, OVT prototypes with typical structures were selected to be tested for the error characteristics with the same testing equipment and testing method. The basic accuracy, the additional error caused by temperature and the adjacent phase in the laboratory, the accuracy in the field off-line, and the real-time monitoring error during on-line operation were tested. The error characteristics under the three conditions—laboratory, in the field off-line and during on-site operation—were compared and analyzed. The results showed that the effect of the transportation process, electromagnetic environment and the adjacent phase on the accuracy of OVTs could be ignored for level 0.2, but the error characteristics of OVTs are dependent on the environmental temperature and are sensitive to the temperature gradient. The temperature characteristics during on-line operation were significantly superior to those observed in the laboratory.