Line impedance

It would also add to the line impedance to contain the severity of the fault conditions. 

Series capacitor - connected in series at the far end of a long transmission or FTP distribution line to offset the reactive component of the line impedance, contain the voltage drop and enhance the receiving-end voltage. It can support a transmission or distribution system in the following ways ... 

To alter the circuit parameters L and C, reduce the line impedance and hence the voltage drop, and itiso to enhance utilizatioti. i.e. the power ti ansfei capability of the line. 

Since the line impedance, R + J (Xl - Xc), will reduce with a series compensation, the fault level of the system will rise. It should not matter if the fault level of the system is determined by the impedance of the source of supply, ignoring any other impedance of the circuit (Section 13.4.1 (5)). Moreover, such a situation is automatically averted through the protection of the series capacitors, as discussed below, by which the capacitors are bypassed during a line fault, the line restoring its original impedance, hence the original fault level. Nevertheless, when it is required to limit the system fault level, inductive coupling circuits may be provided to reduce the fault to the desired level. This is also discussed below ... 

That the line impedances have been ignored, which would further dampen the capacitor charge on every switch-off. 

A CT is provided in series with the spark gap to sense its operation during a line fault. As soon as there is arcing, it provides an instantaneous command to a short-circuit relay. The relay, in turn, closes the bypass breaker, within 3 to 5 cycles, leaving only the natural line impedance in the faulty eircuit. Now = 0, which limits the fault current to the natural level of the system, as if the capacitors were not connected. The shorting device is restored to its original status as soon as the fault condition is cleared. The device must be capable of interrupting the line fault... 

A three-phase fault somewhere in the bus system, without reactive compensation and ignoring the line impedance, can reach a level of... 

Assume that a damping factor of 0.707 or greater is good and provides a -3dB attenuation at the corner frequency and does not produce noise due to ringing. Also assume that the input line impedance is 50 ohms since the regulatory agencies use an TISN test which make the line impedance equal this value. Calculate the values needed in the common-mode inductor and Y capacitors ... 

One assumes that the line impedance is 50ohms (because that is what the LISN test s impedance is). This impedance is then the damping element within the reactive filter circuit. 

Figure 42. Impedance characteristics of porous LSM electrodes on YSZ, measured at zero bias and 945 °C in air, as a function of polarization history and processing conditions. U-11, U-12, and U-13 correspond to firing temperatures of 1100, 1200, and 1300 °C, respectively. Bold line initial impedance. Thin line impedance measured 2 min following cathodic polarization at 100 mA/cm for 30— 90 min. Dashed line impedance measured 30 min following cathodic polarization. (Reprinted with permission from ref 209. Copyright 1997 The Electrochemical Society, Inc.)...

The following may be used as a rule of thumb for dimensioning vacuum lines The lines should be as short and as wide as possible. They must exhibit at least the same aoss-section as the intake port at the pump. If particular circumstances prevent shortening the suction line, then it is advisable, whenever this is justifiable from the engineering and economic points of view, to include a roots pump in the suction line. This then acts as a gas entrainment pump vi/hich reduces line impedance. 

FIGURE 6.9 Schematic and phasor diagram showing voltage rise due to capacitive current flowing through line impedance. 

Whatever you get for the fore pump speed from Eq. (7.11), it s a good idea to use a pump with at least double that figure to accommodate pressure fluctuations and make up for line impedance within the vacuum system. 

Figure 14. Faradaic (dashed line) and total (continuous line) impedance for a reversible reaction under conditions of semiinfinite cylindrical diffusion. Rs= 10 fl.

For measuring EMI, we need to use an ISN ( Impedance Stabilization Network ). In off-line power supplies, this becomes a LISN (Line Impedance Stabilization Network) — also called an AMN (Artificial Mains Network). See Figure 9-2 for a simplified schematic. Note that the LISN, as recommended for CISPR-22 compliance, is detailed in CISPR 16. 

And we know that that is inherently common mode in nature. However, since radiative pickup is not necessarily the main (or only) source of common mode noise in a switching converter, we should be prepared for surprises. For example, we recall that unequal line impedances can convert a (high-frequency) common mode noise into a (high-frequency) differential mode noise. 

In Figure 10-1, we have shown both the CM and DM filter stages as being symmetrical (balanced). So for example, we have placed identical DM chokes on each of the L and N lines. In Fig. 10-1 we see that in fact the DM choke is also a part of the CM equivalent circuit (and vice versa). And since line impedance imbalance can cause CM noise to get converted into DM noise, it is always advisable to keep both the CM and DM stages symmetrical (balanced). 

The line impedance is calculated for each frequency using the equation below ... 

Having fonnd K and Ki it is now possible to find the mesh voltage Em as follows. The resistance Rep is substitnted into the fanlt cnrrent eqnations (H.1.1) and (H.1.2), to give the total fault current If. The earth retnm circnit between the pole at point A in Fignre 13.12 and the earthing connection at point B at the sonrce is a parallel circnit of the resistances to earth en and Rgp and the overhead earth retnm line impedance Zgoh- The parallel combination is -... 

Stepped transmission line transformer (TR2) with a frequency range 40-220 MHz is shown in Fig. 3. The rf power is fed from this broadband transformer through a symmetrical 100 Q cable to the coil in a modified E235 Varian large sample cavity and from the latter to two 50 Q loads. The four rods in the cavity are connected to form a Lecher type cable with a line impedance Z == 100 Q. With this anangement a VSWR of 1/1.2 between the rf transmitter and the loop in the cavity is achieved in the frequency range 70-220 MHz. The rf field at the sample position was measured to be 0.03 mT t. 

Figure 9 Equivalent circuit accounting for the electrode-polarization effect. Fq(0 is a rapidly increasing voltage step I(i) is a current Zq is the coaxial line impedance Cp is the capacitance of electrode polarization Cq is an empty cell capacitance filled with a dielectric sample of permittivity e and conductivity 1/R Vp(t) and Fg(i) are the voltages at the appropriate parts of the circuit. (From Ref. 72. With permission from Elsevier Science B.V.)...

Bisquert, J., Gratzel, M., Wang, Q., Fabregat-Santiago, F. Three-channel transmission line impedance model for mesoscopic oxide electrodes functitmalized with a conductive coating. J. Phys. Chem. B 110, 11284-11290 (2006)... 

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