Tower impedance

Bingeman, G. AM tower impedance matching, in Broadcast Engineering, Intertec Publishing, Overland Park, KS, July 1985. 

Gas contact is typically carried out in absorption towers over which the alkaline solutions are recirculated. Strict control over the conditions of absorption are required to efficiendy capture the NO and convert it predominantly to sodium nitrite according to the following reaction, thereby minimizing the formation of by-product sodium nitrate. Excessive amounts of nitrate can impede the separation of pure sodium nitrite from the process. 

Fig. C.2 By cascading two or more meander-line sheets, we may obtain broader bandwidth and tower refiecVon. The Smith charts show the input impedances at the various locations as indicated in the schematic.

The employer must use bonding cables to bond conductive objects, except for metallic objects bonded through metal-to-metal contact. The employer must ensure that metal-to-metal contacts are tight and free of contamination, such as oxidation, that can increase the impedance across the connection. For example, a bolted connection between metal lattice tower members is acceptable if the connection is tight and free of corrosion and other contamination. Figure 4 shows how to create an equipotential zone for metal lattice towers. 

For nonsoil conditions, tower anchor points should have their own radial systems or be encapsulated in concrete. Configure the encapsulation to provide at least 3 in. of concrete on all sides around the embedded conductor. The length will depend on the size of the embedded conductor. Rebar should extend as far as possible into the concrete. The dynamic ground impedance measurements of the anchor grounds should each be less than 25. ... 

A properly installed bulkhead panel will exhibit lower impedance and resistance to ground than any other equipment or cable grounding point at the facility [9]. Waveguide and coax line grounding kits should be installed at the bulkhead panel as well as at the tower. Dress the kit tails downward at a straight 45° angle using 3/8-in. stainless-steel hardware to the panel. Position the stainless-steel lug at the tail end, flat... 

Install a tower earth ground array by driving ground rods and laying radials as required to achieve a low earth ground impedance at the site. 

The azimuth pattern of each panel antenna is unidirectional, and three or four such panels are mounted on the sides of a triangular or square tower to achieve an omnidirectional pattern. The panels can be fed in-phase, with each one centered on the face of the tower, or fed in rotating phase with the proper mechanical offset. In the latter case, the input impedance match is considerably better. 

Antenna tuning unit (ATU). The tower s complex impedance at the feed point must be matched to the characteristic impedance of the transmission line so that maximum transfer of power may occur. Elements of inductive and capacitive reactance (coils and capacitors) are combined into a T or L network to accomplish this task. The ATU will also contain provisions for measuring base RF antenna current. 

Figure 20.27 shows comparative Nyquist plot impedance spectra of screen-printed Johnson Matthey based material shown above and (CCVC) NanoSpray " Combustion-based electrocatalyst layer. The resistances, Rp, associated with each spectrum show that the screen-printed sample has a polarization resistance of 0.78 ohms, white that of the NanoSpray Combustion sample is 0.812 ohms. A constant phase element fit factor (CPE-P) comparison shows that the NanoSpray Combustion-prepared sample exhibits a behavior closer to a capacitor than does the screen-printed counterpart (0.86 vs. 0.77), which is related to its more open pore structure. Deviation from capacitive behavior has been modeled [89, 90] as a measure of the pore sizes in electrode structures, whereby lower pore diameters and longer lengths represent greater deviation (and thus tower CPE fit values)... 

Figure 1.22 illustrates a 500 kV horizontal transmission line, and Table 1.1 shows the frequency dependence of its impedance. It should be noted that Figure 1.22 is only for one of the towers in the 500 kV line with length about 83 km. The geometrical configuration of one tower differs from other ones because of the geographical features along the line. For example, separation distance y varies from 22 m to 25 m, although only 25 m is specified in Figure 1.22. It is observed that the resistance increases nearly proportional to where f is...

There are a number of papers on nonuniform lines [30,31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48-49]. EMC-related transients or surges in a gas-insulated substation and on a tower involve nonuniform lines, such as short-line, nonparallel, and vertical conductors. Pollaczek s [7], Caron s [8], and Sunde s [50] impedance formulas for an overhead line are well known and have been widely used in the analysis of the transients mentioned earlier. However, it is not well known that these formulas were derived assuming an infinitely long and thin conductor, that is, a uniform and homogeneous line. Thus, impedance formulas are restricted to the uniform line where the concept of per-unit-length impedance is applicable. 

Sargent, M. A. and M. Darveniza. 1969. Tower surge impedance. IEEE Trans. Power Appl. Syst. 88 680-687. 

Okumura, K. and K. Kijima. 1985. AmeAod for coupling surge impedance of transmission tower by electromagnetic field theory. Trans. lEE Jpn. 105-B(9) 733-740 (in Japanese). 

Ametani, A., Y. Kasai, J. Sawada, A. Mochizuki, and T. Yamada. 1994. Frequency-dependent impedance of vertical conductor and multiconductor tower model. lEE Proc.-Gener. Transm. Distrib. 141(4) 339-345. 

System Voltage (kV) Lightning Current (kA) Tower Height/Geometry (m) Surge Impedance (i3) Footing Resistance... 

In Japan, modeling a tower footing impedance as a simple linear resistance Rf is recommended, although a current-dependent nonlinear resistance is recommended by the IEEE and the CIGRE [16,18,20]. The inductive and capacitive characteristics of the foot-ing impedance, as shown in Figure 2.40, are well known [10]. The recom-mended value of... 

Five towers are included in the model. The span distance of the transmission line between adjacent towers is 450 m, and that from tower No. 1 to the substation is 100 m. The end of the transmission line is terminated with the surge impedance matrix or, approximately, with matching resistances Rp = 350 Q for a PW and Rg = 560 Q for a GW. 

It is well known that tower surge impedance and footing impedance affect lightning surges significandy. Tower surge impedance is a function of the height and radius of the tower as... 

The tower-footing impedance is always represented as a resistance as in Table 2.4 recommended by guides on insulation design and coordination of transmission lines and substations [26]. However, it is not pure resistance, but shows an inductive or a capacitive nature (see Figure 2.40) as investigated by many authors [10,15,23,31]. 

Influence of a tower model on a tower top voltage, (a) Measured results, (b) Frequency-dependent tower model with a resistive-footing impedance, (c) Distributed line tower model with various footing impedances. 

Ip Vp Zp Xf are the tower current, voltage, surge impedance, and height (length)... 

Vf, Rfare the tower foot voltage and footing impedance... 

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