Depending on the configuration of impedance an electrical network can be specified into six different sections. These sections are described as follow:
When a network section looks like a “T”, it is known as T-Section Figure 1 (a) and (b) represent unsymmetrical and symmetrical T-sections.
The figure indicates that in a symmetrical section, the series arm impedance is equal in both the sides of the shunt arm impedance, it may be observed that in unsymmetrical section, the impedances Z1 and Z3 are not equal to each other. The net series arm impedance of the unsymmetrical section is (Z1 + Z3) ohm while that for the symmetrical section is (2Z1) ohm. The shunt arm impedance in both the cases is given by Z2 ohm.
Balanced and Unbalanced configuration of a T-section has been shown in figure 2. The balanced T-section has also been termed as H-section.
Through the figure 1 represents the balanced and unbalanced configuration of a symmetrical T-section, asymmetrical T-section can also be similarly configurated. It may also be noted that both the balanced and unbalanced T-section have identical transmission characteristics under identical mode of connection and hence there is exact equivalence between balanced and unbalanced section.
In an identical manner, symmetrical and asymmetrical π section (i.e., the section whose structure looks like a π) can be configured (Figure 3). In asymmetrical π section, the shunt arm impedances are not identical while for the symmetrical π section, the shunt arm impedances must be identical.
Here, the net series arm impedances being Z1 in each case, the shunt arm impedance is the parallel combination of the individual shunt arms.
Figure 4 represents the unbalanced and balanced π section in exactly similar way to that in T-section.
An asymmetrical π section can also be represented in the form of balanced and unbalanced modes and the equivalence between modes exists till the mode of connection is same. A balanced form of π network is known as a “O” section also.
When the network section looks like “L”, the configuration is termed as L section (figure 5). It may be observed that L-section is merely a specific case of the asymmetrical T-section with one series arm equal to zero value or of the asymmetrical π section with one shunt arm equal to infinity.
It is obvious that both the symmetrical T or π section can be split into two halves. Each half is then known as half-section (Figure 6).
Configuration wise, a half section looks like L-section.
Figure 7 represents a lattice section where the series arms are given by the impedances between (a and c) and (b and d). The diagonal arms are frequently termed as cross arms. Figure 7(a) represents are asymmetrical lattice section while figure 7(b) represents symmetrical lattice section. The lattice section is usually a balanced structure.
When the series arms of a T-section are bridged by an impedance, the section is termed as bridges T-section Figure 8 represent asymmetrical and symmetrical bridge T-section.
Figure 9 represents a balanced and unbalanced from of a bridged T-section.