Читать книгу Alternative Liquid Dielectrics for High Voltage Transformer Insulation Systems - Группа авторов - Страница 44

The complex permittivity of any dielectric medium can be represented as ε_c, is denoted in (2.1),

(2.1)

where σ is the conductivity and ω is the frequency of the source. The real part ε_r ′ is the measure of how much energy is stored by the material and the ε_r ″ represents how dissipative a material can be in reaction to an external electric field. On the application of an AC sinusoidal voltage source to the lossy dielectric in parallel combination with resistance R_p and capacitance C_p, the resultant current I is composed of two components: the conduction current I_c and the displacement current I_d, as seen in Figure 2.6a and b, which is related to the DDF as given in (2.2),

Figure 2.5 Comparison of ACBDV values of different oil samples.

Figure 2.6 (a) Parallel representation of the insulation. (b) Phasor diagram for parallel circuit. (c) Series representation of the insulation. (d) Phasor diagram for series circuit.

(2.2)

The power loss P can be represented in Eq. (2.3),

(2.3)