Grounding practices ground resistance

Total ground resistance of power plant iirid switchyard aretis interconiieeied in parallel (recommended practice) where... 

Chemical analyses should be provided for all anodes used in the offshore and harbor area, together with results for current content in A h kg and current output in amperes [2,3]. The geometric shape and the number of anodes required is determined by these parameters. Expensive calculations for design based on grounding resistances are made only in exceptional cases because in practice there are too many uncertainties and the number and mass of the anodes have to be quoted with a corresponding safety factor. 

Cathodic protection, complete or partial (stem and bow), is arranged by the distribution of the anodes so that the desired current distribution is maintained correctly in the relevant areas. Galvanic anodes, depending on their dimensions and current output, deliver a certain maximum current which depends on the conductivity. The calculated maximum current from Eq. (6-12) based on the driving voltage and grounding resistance is reduced in practice on working anodes due to film for-... 

To apply these data and equations to the problem of ground resistance, the maximum anticipated current must first be estimated. For practical industrial situations, Iq varies in the range 0.01-100/rA. The upper value represents extreme cases such as microfiltration and the lower value to slow flow in pipe. Typical charging currents for tank tmck loading are of the order 1 /rA (5-3.1.1). As an example, consider a system such as a tank with a capacitance less than 1000 pF. First, consider the minimum ignition voltages in Table A-4-1.3b. From Eq. (2), f L = In the case of hydrogen the mini-... 

The solution to this problem is to make the connection to the true ground have practically no resistance (as shown by the short-dash line around the 150). Although there will always be some resistance, it should be low enough to avoid causing any malfunction of the other components. 

One of the reasons for developing the F-parameter approach to deal with cascaded connection of pipeline sections is to find effective grounding resistances and separation distance between them. Those become a significant subject in practice in Japanese gas pipelines. Based on the earlier approximate results, the characteristic of induced voltages and currents and the effect of grounding resistances can be discussed. 

AU ground glass joints should be constructed of a high resistance glass, such as Pyrex. The most common form is shown in Fig. II, 55, 1, and this is the type largely encountered in practice. Fig. II, 55, 2 is... 

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