ABSTRACT
OBJECTIVE: To analyze the current status of occupational exposure to power frequency electromagnetic field in converter stations. METHODS: Eight converter stations with voltage levels of ±500 kV and ±800 kV within normal operation were selected as the research subjects using the typical sampling method. Power frequency electric field and power frequency magnetic field strengths were measured and calculated according to the GBZ/T 189.3-2018 Measurement of Physical Agents in Workplace--Part 3: Electric Field and Magnetic Field between 1 Hz and 100 kHz. The GBZ 2.2-2007 Occupational Exposure Limits for Hazardous Factors in the Workplace--Part 2: Physical Factors were used to evaluate whether the power frequency electric field strength exceeds the regulatory limit(the occupational exposure limit of power frequency electric field in 8 hours workplace is 5.000 kV/m). Meanwhile, the test results were evaluated according to the short-term occupational exposure limit of 50 Hz electric field and magnetic field recommended by the International Committee on Nonionizing Radiation Protection in 2010 that are 10.000 kV/m and 1 000.00 μT. RESULTS: The power frequency electric field and magnetic field strengths of 582 working environment detection points were measured. The median and 0-100 th percentile of power frequency electric field and power frequency magnetic field strength were 4.342(0.001-12.003) kV/m and 5.51(0.10-186.90) μT, respectively.The exceeding standard rate of power frequency electric field strength in converter station workplaces was 37.8%(220/582), which concentrated in 500 kV alternating current filter area and 500 kV alternating current field area. Among them, 5 detection points had power frequency electric field strength exceeding 10.000 kV/m. The magnetic flux density of all the detection points did not exceed 1 000.00 μT. The power frequency electric field strength in ultra-high voltage region was higher than that in high voltage region(P<0.01). There was no significant difference in power frequency magnetic field strength(P>0.05). There was no significant difference in power frequency electric field and magnetic field between rectifier stations and inverter stations(P>0.05). The 8 hours time weighted average(TWA) value of power frequency electric field strength of 8 converter station operators was 1.044-2.335 kV/m, which did not exceed the occupational exposure limit. CONCLUSION: The converter station operators might be exposed to excessive power frequency electric fields for a short time, but the 8 hours TWA value of the power frequency electric field meets the requirements of standards, and the power frequency magnetic field exposure strength also meets the requirements of the relevant standards.
ABSTRACT
OBJECTIVE: To evaluate the major influence factors affecting the quality and accuracy of measuring instruments for power frequency electromagnetic fields in occupational hygiene technical service organizations by developing interlaboratory comparison in workplaces. METHODS: Six measuring instruments for power electromagnetic fields from 6occupational hygiene technical service organizations in Guangdong Province were selected by typical sampling method. A high-voltage substation was selected as a standard source. We set measurement sites underneath it as inter-laboratory comparison spots for power frequency electromagnetic fields. The stability of the standard source was evaluated by pairedsamples t-test and measure results were analyzed by z-score evaluation method based on quartile robust statistical technology. RESULTS: During and after the inter-laboratory comparison,the intensity of electric field and magnetic field of the standard source showed no significant difference [( 555. 03 ± 2. 94) vs( 555. 68 ± 3. 20) V / m,( 2. 30 ± 0. 06) vs( 2. 29 ± 0. 07) μT,P > 0. 05],which met the demand of stability of inter-laboratory comparison. The data of electric field measured by 2 measuring instruments without remote-reading system were found to be high because of proximity effect from its handheld status. The z-score of inter-laboratory( zB) of other 4 measuring instruments with remote-reading system ranged from- 0. 52 to 1. 10,while the z-score of within-laboratory( zW) ranged from- 1. 28 to 0. 37,and both results of| zB| and | zW| were satisfactory( < 2. 00). The zBof power frequency magnetic field measured by the 6 measuring instruments ranged from- 0. 67 to 1. 26,while zWranged from- 0. 59 to 0. 90,and both | zB| and | zW| were also satisfactory( < 2. 00). CONCLUSION: It is feasible that the inter-laboratory comparison of measuring instruments of power frequency electromagnetic fields could be implemented by a high-voltage substation as a standard source. The measuring instruments without remote-reading system could be used to measure the intensity of magnetic field but not the electric field. The measuring instruments with remote-reading system could be used to measure the intensity of either the electric field or the magnetic field,and the measurement results are satisfactory.