Enhancement of Soil Discharge Channels on Potential Surrounding Buried Cables Under Impulsive Currents

Substations have a large number of signal transmission cables beneath the ground.Both the insulation safety and signal reliability of the cables are affected severely by the electromagnetic field.Under high-amplitude impulsive currents,the dispersion of currents can cause soil discharge and thus cause unexpected distortions in an electromagnetic field.This paper focuses on the distortions of the electric field.In general,soil discharge channels occur in the vicinity of the independent rod.Closer development of the channel might enhance the electric field distribution and the potential surrounding the outer insulation of the cables(i.e.the surface potential on the cable).Therefore,this paper establishes a platform for observing the soil discharge channel and measuring the surface potential.Direction characteristic of the channel is extracted from the captured image of soil discharge channels and the surface potential is obtained by the measured coupling capacitive current on the shield experimentally.This paper also presents an improved model considering a dynamic growing discharge channel for the transient analysis of the grounding electrode.Study results show the surface potential increases as the discharge channel approaches the cable.To quantify this enhancement effect,the ratio of the highest to the lowest value of surface potential in different directions is taken as the multiple of the surface potential increase.The calculated multiples of the surface potential increase are in the range of 1 to 1.64 times under different conditions by the improved model.Therefore,taking the soil discharge channel into account is helpful to accurately analyze the impulsive interference of buried cables.

Assessment of agri-spillways as a soil erosion protection measure in Mediterranean sloping vineyards

Suitable vineyard soils enhance soil stability and biodiversity which in turn protects roots against erosion and nutrient losses. There is a lack of information related to inexpensive and suitable methods and tools to protect the soil in Mediterranean sloping vineyards(>25° of slope inclination). In the vineyards of the Montes de Málaga(southern Spain), a sustainable land management practice that controls soil erosion is actually achieved by tilling rills in the down-slope direction to canalize water and sediments. Because of their design and use, we call them agri-spillways. In this research, we assessed two agri-spillways(between 10 m and 15 m length, and slopes between 25.8° and 35°) by performing runoff experiments under extreme conditions(a motor driven pump that discharged water flows up to 1.33 l s^(-1) for 12 to 15 minutes: ≈1000 l). The final results showed: i) a great capacity by these rills to canalize large amounts of water and sediments; and, ii) higher water flow speeds(between 0.16 m s-1 and 0.28 m s^(-1)) and sediment concentrationrates(up to 1538.6 g l^(-1)) than typically found in other Mediterranean areas and land uses(such as badlands, rangelands or extensive crops of olives and almonds). The speed of water flow and the sediment concentration were much higher in the shorter and steeper rill. We concluded that agri-spillways, given correct planning and maintenance, can be a potential solution as an inexpensive method to protect the soil in sloping Mediterranean vineyards.