Page 388 - Handbook of Electrical Engineering

376 HANDBOOK OF ELECTRICAL ENGINEERING

Figure 13.14 Interference and screening circuit of cables that are run in parallel with each other.

L s is the self-inductance of the cable core.
M sc is the mutual inductance between the screen and the core.

For the couplings between the cables

M 3s is the mutual inductance between the interference cable and the screen of the
signal cable.
M 3c is the mutual inductance between the interference cable and the core of the
signal cable.

For the components connected to the cables

R in is the internal resistance of the signal source.
R o is the output or load resistance on the signal source.
R e is the resistance of the common earth path of the signal cable.

Consider two cases, firstly a cable without a screen and secondly one with a screen. The two
cases will then be compared.

Case A. Signal cable without a screen.
The summation of voltages and emfs in the signal cable is:-

V in = (R in + R c + jωL c )I c + jωM 3c I 3 + (R o + R e )I c