Parallel Equivalent Circuit
The parallel equivalent circuit of the power cable is shown in the figure.
In the diagram, L and RX are the same as in the series equivalent circuit. Here, Rg represents the equivalent insulation resistance of the cable, which is typically very large under normal conditions. Cg represents the equivalent capacitance between a single phase of the cable and the metal shielding layer, and it does not differ significantly from C0. Generally, the parallel equivalent circuit is used when analyzing the DC circuit of the cable.
The relationship between series and parallel equivalent circuits:
Figure 2-1(b) and Figure 2-3(b) show the equivalent circuits and their corresponding phasor diagrams for resistance and capacitance, as illustrated in the figures.
Since the series and parallel circuits of the cables are completely equivalent, the power consumed by the two circuits and the angles φ and δ in the diagram are exactly the same. In R-C series and parallel circuits, only the resistor consumes energy, and its active power P is expressed by the following formulas:
Under normal conditions, the tanδ of the cable, which represents the dielectric loss tangent of the cable (see Section 2.9), is (1-10) × 10⁻³.
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