Electromagnetic Fields Monitoring
QCVN has announced the conditions for environmental testing in accordance with Decree 44/2016 / ND-CP effective July 1, 2016.
1. Why need to measure electromagnetic fields
Evaluate activities that cause or suffer from industrial frequency electromagnetic fields in the working environment.
2. What are electromagnetic fields
– Electromagnetic: is a form of matter characterized by interaction between charged particles, generated by charged particles and a uniform field of electric and magnetic fields.
– Industrial Frequency Electromagnetic Fields (Industrial Frequency Electromagnetic Fields): are electromagnetic waves with frequencies from 50Hz to 60Hz arising from electrostatic induction and electromagnetic fields from power sources, transmission lines and used devices electricity.
– Electric field intensity: is the effective magnitude of the electric field vector (E) at a point, determined by the force (F) acting on a unit of charge (q) at a point in the field. , in volts per meter (V / m), ie.
– Magnetic field intensity: is the effective magnitude of the magnetic field vector.
– The magnetic field strength is denoted by H, unit of amperes per meter (A / m).
- Exposure allows the electric field
– When workers have no equipment to prevent the impact of electric fields, the working time at the place of electric field is specified in Table 1.
Table 1. Permissible exposure to electric fields at work
|The electric field intensity E (kV / m)||<5||5≤ E≤ 20||20<E<25||≥25|
|Exposure time allows (Minute)||Unlimited||(50/E-2).60||10||Not exposed|
– When workers use protective equipment to prevent the impact of electric fields, the working time at the place of electric field shall be implemented according to separate regulations for each type of equipment.
2. Permissible exposure levels to magnetic fields
The allowable exposure level for magnetic fields is specified in Table 2.
Table 2. The allowable exposure level from the school at work
|Exposure time allows (hours)|
Magnetic field – H (A/m)
Industrial frequency electromagnetic field measurement method is as follows:
– Measuring and evaluating electromagnetic fields in areas with sources of generation and areas of workers working under the influence of industrial frequency electromagnetic fields.
– Measure at times: When new equipment is put into operation, when organizing a new workplace, when there is a change in equipment structure and periodic measurement.
– When measuring, it must strictly comply with the electric safety rules.
– Measuring equipment must meet the provisions of the law on measurement and the industrial frequency magnetic field measuring device must have an antenna head to receive electromagnetic fields of frequency 50-60Hz.
– Limits of measurement:
+ Electric field: 0.1 V / m – minimum 30 kV / m
+ Magnetic field: 0.1 mA / m – minimum 5000 A / m
– Minimum sensitivity: Electric field 0.01 V / m; Magnetic field: 0.01 mA / m.
3. Measurement techniques
– Measuring electromagnetic fields at electrical equipment: Generators, transformers placed on the ground, working floor: Measure across the chest of the worker (if standing), horizontal head (if seated); If at other positions measured at the position of the body closest to the source.
– Measuring electromagnetic fields at high-voltage equipment, transmission lines:
+ For power transmission lines measured under lines or distances 1; 2; 5m etc. … from the heart of the line or at the working position of the magnetic field from the line.
+ For transformer stations: Measure at positions in the station according to technical titles.
+ At each measuring position, it is necessary to measure 3 points at a height of 0.5m; 0.8m and 1.6m from the ground or working floor and 0.5m from the grounding component, taking the average result.
– Conduct measurement: Place the device on a rack or handheld. Turn on the device, measure the electric and magnetic fields at the points above. When the screen displays stable measurement results, read and write the results to the field measurement record.
- Establishments having workers exposed to industrial electromagnetic fields must periodically measure and evaluate the electromagnetic field of the industrial frequency at least once a year and according to the provisions of the Labor Code and the Law of Security Labor safety and hygiene.
- Employers must provide adequate means of labor protection for employees in accordance with the working environment in accordance with the Law on Safety and Occupational Hygiene.
- If the industrial frequency electromagnetic field at the workplace exceeds the permitted limit, the employer must immediately implement measures to improve working conditions and protect workers’ health
- This regulation applies in place of the Standard from the low frequency field and the standard of low frequency electric field strength in the Occupational Hygiene Standards issued under Decision No. 3733/2002 / QD-BYT October 10 2002 of the Minister of Health.
- The Department of Health Environmental Management – Ministry of Health presides and coordinates with relevant authorities to guide, implement and organize the implementation of this regulation.
- Based on the practical requirements of management, the Department of Health Environmental Management is responsible for proposing the Ministry of Health to amend and supplement accordingly.
- In case the national standards for industrial frequency electromagnetic fields cited in this Regulation are amended, supplemented or replaced, the provisions of the new documents shall apply.
Refer to the standards for measuring labor environment:
– National technical regulation QCVN 21: 2016 / BYT on high frequency electromagnetic fields – Exposure level allows high frequency electromagnetic fields at work
– National Technical Regulation QCVN 23: 2016 / BYT on Ultraviolet Radiation – Exposure level allows ultraviolet radiation at work
– National technical regulation QCVN 24: 2016 / BYT on Noise – Noise permissible exposure level at the workplace
– National technical regulation QCVN 26: 2016 / BYT on Microclimate – Value for microclimate at workplace
– National technical regulation QCVN 27: 2016 / BYT on Forest – Allowable value at the workplace
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