Single-phase cable

As explained in Chapter 1, the evaluation of wave propagation related parameters necessitates eigenvalue/eigenvector calculations. Because of 

In a high-frequency region, the following relation is satisfied in (3.1)  

The modal propagation constant y is given in the following equation from the actual propagation constant matrix [T] as explained in Chapter 1  

The actual characteristic impedance [Zq] is obtained from the aforesaid equations in the following form  

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It should be noted that the impedance and admittance in this equation become a matrix when a conductor system is composed of multiconductors. Remember that a single-phase cable is, in general, a multiconductor system because the cable consists of a core and a metallic sheath or a screen. In an overhead conductor, no conductor internal admittance y exists, except a... 

The impedance and admittance of a single-phase cable are presented in matrix form because the cable contains two conductors ... 

Section 3.2.1 addressed the impedance and admittance of a single-phase cable. This section addresses the impedance and admittance of a cross-bonded three-phase cable and how 6x6 impedance and admittance matrices can be reduced to 4 x 4 matrices. 

Assume that the sample cable in Section 3.2.4 is buried as a single-phase cable. Find the impedance and admittance matrices for the single-phase example cable using EMTP. Use the Bergeron model and calculate the impedance and admittance matrices at 1 kHz. From the impedance and admittance matrices found in (1), find the phase constants for the earth-return mode and the coaxial mode using the voltage transformation matrix... 

A cable fault, immobilizing one of the phases. Effects of single phasing... 

A key factor in the design and choice of earth continuity conductors, e.g. cable armouring, bonding straps, and fault current protective devices is the earth loop impedance . This is especially the case for solidly earthed low voltage systems, whether they be three-phase, single-phase or even direct current systems. 

Conductor cross-sectional area (mm ) 1 Two-core cable, d.c. (mV/A/m) 2 Two-core cable, single-phase a.c. (mV/A/m) 3 Three- or four-core cable, three-phase (mV/A/m) 4... 

V single-phase for supplies to items of equipment which are robustly installed such as floodlighting towers, small hoists and site offices. These supplies must be wired in armoured cable unless run inside the site offices. 

All local distribution in the United Kingdom is by underground cables from sub-stations placed close to the load centre and supplied at llkV. Transformers in these local sub-stations reduce the voltage to 400 V, three-phase and neutral distributor cables connect this supply to consumers. Connecting to one-phase and neutral of a three-phase 400 V supply gives a 230 V single-phase supply suitable for domestic consumers. 

In Great Britain, electricity is generally supplied from the National Grid to most factories where it is transformed to a 440 V, 3-phase a.c. supply at 50 hertz (Hz) with single-phase supply at 240 V. The voltage drops along mains cables may be considerable, particularly... 

For jobbing work, small, single-phase, portable TAs are available up to 2 kVA capacity. A length of flexible cable is provided, usually terminating in a BS 1363 fused plug for insertion into 230 V domestic socket outlets. The... 

Gas-insulated bus and cable A cable and a gas-insulated bus are represented either as three single-phase distributed lines with their coaxial mode surge impedance and propagation velocity or as a three phase distributed line system. As a gas-insulated substation involves a significant number of gas-insulated buses/lines, the pipes are, in most cases, eliminated by assuming zero voltage. 

Figure 3.12 illustrates a circuit diagram of a single-phase coaxial cable. In the figure, the characteristic impedance of each section is defined as follows ... 

Circuit diagram of a single-phase coaxial cable. 

We will now discuss the wave propagation characteristics of a three-phase single-core cable. Figure 3.13 and Table 3.2 show a cross section and the parameters of a tunnelinstalled cable. 

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