Occupational exposure to electric and magnetic fields during tasks at ground or floor level at 110 kV substations in Finland

Effect of outer spherical shell opening structure on the sensitivity of double spherical shell electric field sensor

A double spherical shell (DSS) electric field sensor based on charge sensing has characteristics of small size and simple fabrication, which are appropriate for measuring complex electric field environments, but the sensitivity is low. To improve the sensitivity of the DSS electric field sensor, we theoretically analyze the effect of the diameter of the outer spherical shell opening on the sensitivity of the sensor. The sensors with outer spherical shell apertures of 2, 4, and 6 mm are designed and manufactured, and the sensor's sensitivity, linearity, hysteresis, and repeatability are tested. The relative error of the sensor is evaluated by measuring the rotational characteristics of the sensor. The experimental results show that the sensor sensitivity increases with the increase in hole diameter, while the sensor has good linearity, hysteresis, and repeatability after opening the hole. The rotational characteristics experiments' results show that the sensors' relative errors with different apertures are 18, 23, and 31%, respectively. The DSS open-hole structure is more suitable for electric field measurements than the conventional flat plate structure.

ASSESSMENT OF OCCUPATIONAL EXPOSURE LEVELS OF CLEANING PRODUCT MANUFACTURING FACTORY WORKERS TO ELECTROMAGNETIC FIELDS

Determination of the levels of the electromagnetic field of frequency between 0 Hz and 300 GHz bands in the working area and the evaluation of the results measured in terms of international standards is now essential according to the regulation of working safety and health. In this study, electromagnetic field measurements were performed in a cleaning product manufacturing factory with 400 workers. Electric and magnetic field measurements were performed at 10 different departments of the factory with extremely low-frequency and broadband (radiofrequency) frequencies. Obtained values are shown and analysed with graphs and compared by the International Commission on Non-Ionizing Radiation Protection and National Information Technology and Communication Authority (Turkey) limits. Also, an assessment is made for the occupational electromagnetic field levels in the factory and recommendations are suggested for the lowest risk occurrence and providing a healthier working environment for workers.

ESTIMATION OF THERMAL POWER PLANT WORKERS EXPOSURE TO MAGNETIC FIELDS AND SIMULATION OF HAZARD ZONES

Extremely low-frequency magnetic fields (ELF-MFs) have raised some concerns due to their possible effects on workers' health. In this study ELF-MFs were measured in different units of the thermal power plant based on gridding the indoor space. The exposure level was measured by spot measurement based on the IEEE Std C95.3.1 and then simulated in units with the highest magnetic field intensity by using ArcGIS software. The operators and balance of plant (BOP) technicians (12.64 ± 9.74 μT) and office workers (2.41 ± 1.22 μT) had the highest and lowest levels of both measured and estimated ELF-MFs exposure. The highest measured ELF-MFs were in the vicinity of the power transmission lines in the transformers' building (48.2 μT). Our simulation showed the high and low exposure areas and ranked exposure well; but, the actual measurements of ELF-MFs exposure were in all cases higher than the estimated values, which means we still need to improve our estimations.

A Power-Frequency Electric Field Sensor for Portable Measurement

In this paper, a new type of electric field sensor is proposed for the health and safety protection of inspection staff in high-voltage environments. Compared with the traditional power frequency electric field measurement instruments, the portable instrument has some special performance requirements and, thus, a new kind of double spherical shell sensor is presented. First, the mathematical relationships between the induced voltage of the sensor, the output voltage of the measurement circuit, and the original electric field in free space are deduced theoretically. These equations show the principle of the proposed sensor to measure the electric field and the effect factors of the measurement. Next, the characteristics of the sensor are analyzed through simulation. The simulation results are in good agreement with the theoretical analysis. The influencing rules of the size and material of the sensor on the measurement results are summarized. Then, the proposed sensor and the matching measurement system are used in a physical experiment. After calibration, the error of the measurement system is discussed. Lastly, the directional characteristic of the proposed sensor is experimentally tested.