Study on the Grounding Line of the Standard Transformer Stage

This paper's aiming at the standard transformer stage that they don’t have the obvious position for hanging a grounding line. For solving the problem, and develop a kind of special grounding line for the standard transformer stage. The grounding line is the copper mesh structure of three layer hollow circle, and it achieved the whole weight of a grounding line is less than the normal regulations grounding line. This paper also expounds the method of use for the special grounding line for the standard transformer stage. It proved that the special grounding line for the standard transformer stage not only solved the problem that could not hang a grounding line causing the range of power outages, also proved that the use of the special grounding line can shorten the operation time, achieving the purpose of saving time and effort. Introduction A grounding method by grounding the shell of electric equipments is called protective grounding. Its purpose is to ensure personal safety. When shell of electrical equipment is charged by insulation damage, it will produce the distributed capacitance between power lines and ground. At this point, if one person is standing on the ground with his hand touch the shell, current will go through the person body which causes electrical shock. If we use the device to take protective grounding measures, the shell will contact the earth through wiring. It is the equal of a human body resistance in parallel beside the protective grounding line. As to "human body resistance" is much greater than grounding resistance, therefore the current through the human body is very small, so we avoid the electric shock accidents[1, 2]. The purpose of taking the grounding line when we working on power cut equipments are to protect workers. It is the reliable security measures in the work place to prevent coming electricity suddenly. At the same time, equipment cut off parts of the residual charge is gone with the grounding, which prevents the induced voltage. When we installing grounding line, we must install the earthing terminal, followed by the conductor[3]. The contacting Must be well. The order of destuffing grounding line is contrast, to ensure the safety of grounding line installation personnel. We must use insulation rod and wear insulating gloves when we install or destuffing the grounding line. Fig.1 The red turn part is an insulator 4th International Conference on Machinery, Materials and Computing Technology (ICMMCT 2016) © 2016. The authors Published by Atlantis Press 1339 Fig.2 The red turn part is bare part of high voltage line The safe regulations provisions: When the transformer maintenance, it must hang a ground line in two sides .On account of the standard transformer stage didn't have the obvious position for hanging a ground line, it didn't hang a ground line, as shown in the figure below. Figure 1 is the red turn part is an insulator; it can't hang a ground line. Figure 2 is the red turn part is bare part of high voltage line which is very thin, and it can not bear the weight of the normal regulations ground line. So we develop a kind of special ground line for the standard transformer stage for the transformer maintenance work[4, 5]. Design scheme According to the surface effect, most of the current go through the conductor by the external surface, thus we develop a dedicated grounding line of the standard transformer stage. Grounding line is a three layer hollow round made by copper mesh structure, Based on the test, we choose the layer, which make it equal to the current capacity of the routine grounding line. It is shown in figure 3.At the point of contacting wiring of the low voltage side in the transformer, we install the grounding ring. Installation location (red circle) as shown in figure 1.At the arrester on the high voltage side of the transformer, we install a homemade ground lug. Installation location (red circle) as shown in figure 2.When we use it, we contact the bottom of the dedicated grounding line of the standard transformer stage with the ground strip, and then we use wire clip to clip a set of dedicated grounding line of the standard transformer stage to the ground lug which is on the high voltage side of the transformer, another group of clip on the grounding ring of the low voltage side the transformer. Fig.3 A sketch of the dedicated grounding line used on the standard transformer stage Note: 1--wire clip(length of 0.1 m) 2--a dedicated net grounding line(length of 1.5 m) 3--the end of grounding line(length of 8 m) The effect and advantages of the development The dedicated grounding line of the standard transformer stage is developed successfully on March 11, 2014.Figure 4 is the cross-sectional view of the dedicated grounding line used on the standard transformer stage and figure 5 is the dedicated grounding line of the standard transformer stage. From the figure 4 and figure 5, special grounding line adopts three layer hollow round copper mesh structure, compare with the same length, same cross-sectional with the conventional