Power transmission systems such as high-voltage power lines, substations, transformers and power distribution room and other facilities, these facilities will produce the alternating-frequency (50Hz) electric and magnetic fields. When they are close to the house, there will have a certain impact on the health of these residents if no certain protective measures are taken. Radiation protection for Power transmission system includes the electric field shielding and magnetic field shielding. The power transmission system shielding works mainly in the following three categories:
1. Outdoor substation shielding program
The implementation of outdoor substation shielding includes forest protection belts and protective devices. Shelterbelts generally involve the issue of trees in four seasons, involving multi-layered arrangement of trees. At the same time we should consider the extension of branches and leaves of the small density, and their impact on electric field, but also consider the height of the trees and the thickness of protection and so on.
Shelterbelt has a good shielding effect on the electric field. But it is no use to the magnetic field shielding. Special magnetic protection devices need to be installed in the middle of the forest shelterbelt. Magnetic field shielding facilities are mainly based on the magnetic field distribution of power transmission system in that region. And then using high permeability devices construct an open-type model structure with multi-layer, through which the magnetic field will be the guided and restricted.
2. Indoor substation shielding program
Indoor substation mainly includes 110 kV and 220 kV indoor distribution substations. Indoor substation is very close to the residential areas. In some cases the distance is only a few meters away. The electric field in general can be effectively shielded for indoor substation. Its magnetic field is always difficult to control. When the indoor substation is very near to the residential, it will pose a threat on the health of the neighboring residents.
We research the application of open-type model with multi-layer shielding system in indoor substations and its implementation. The layers of open-model structure will constraint the magnetic extension of power transmission equipment in the room effectively.
3. Residential shielding program
If the housing is very close to the power transmission facilities (such as high-voltage power lines, substations, power distribution room or transformer,) the active protection measures should be taken. According to the direction the radiation sources in the residential and the field distribution, multi-layered shielding structure can achieve good protection purpose.