Study On The Distributions Of The Electromagnetic Fields In220kV And Above Substation

With the wide application of high-voltage transmission technology, a large number of high-voltage substations have been put into operation. There are many primary and secondary equipments in a substation, and the electromagnetic environment is more complex. Therefore, it is of significance to obtain knowledge of the characteristics of the electromagnetic environment in a high-voltage substation and the level of the corresponding electromagnetic field intensity, not only for the reliable operation of the secondary equipments but also for the protection against harmful electromagnetic radiation.In this paper, according to the characteristics of the equipment layout in the substations and the patrol route of the electric power staff in daily maintenance, an electromagnetic data acquisition scheme has been designed, and the database structure has been presented for fast handling a large number of the monitoring data. In order to know the electromagnetic environment well, this paper divides the measurement areas based on the voltage levels which present in a substation and determines the measurement points with the equal step length. Especially, the measurement points are taken into account around the main power transformers, capacitors, and shunt reactors. On the basis of the above, the distributions of the electromagnetic fields for the four typical220kV substations and the four typical500kV substations have been monitored.Based on the measured data, for the four220kV substations the following characteristics are shown. The overall level of the electromagnetic field intensity is low, but it is evidently affected by the type of the power distribution unit. The electromagnetic field strength level is highest in the power distribution area of outdoor AIS type and lowest in the power distribution area of indoor GIS type. In a substation, the electromagnetic field strength is higher in the region with220kV equipments than in the region with110kV equipments. The electromagnetic field strength is relevant to the voltage level, especially for high and low voltage side of main power transformers. At boundary of the power distribution area, the electromagnetic field strength is obviously low, indicating that the electromagnetic field strength will decay rapidly with the increase of distance between the source and the monitoring point.For all the four500kV substations the electromagnetic field strength is dominated directly by type of power distribution unit. The electromagnetic field strength level in the power distribution area of outdoor AIS type is highest. In addition, there are evident high electromagnetic field strength at some monitoring points due to the influences of both the altitude of equipments relative to the ground and the interaction between the resources. The electromagnetic field strength in the power distribution area with220kV equipments in500kV substations presents the distribution similar to that in220kV substations, and the corresponding electric field strength is weaker than that in the power distribution area with500kV equipments. But, the corresponding magnetic strength is higher. In500kV substations, there are a few reactive compensation devices, such as capacitor and shunt reactor. Around these devices, the electric field strength is low, but the magnetic strength changes in a large range because of the influences of the operating conditions, and there is the positive correlation between it and the operating power.