| 摘要 |
Cable diagnostic test methods, systems and apparatus are disclosed that utilize "standing wave" principles to facilitate identification and location of insulation defect(s) along a power cable. The methods/systems measure dissipation factors and dielectric constants associated with the power cable insulation and the impedance of the power cable conductor at any number of points or sections along the axial length of the cable. In an exemplary embodiment, the disclosed method involves (i) connecting an alternating voltage source to a cable at a "sending end" thereof; (ii) applying a voltage to the cable at a first frequency to set up a traveling wave along the cable that is reflected at the "receiving end" thereof; (iii) permitting a standing wave pattern to be established along the cable by the traveling wave and the reflection thereof; (iv) measuring the total complex power loss (S<SUB>in</SUB>) at the sending end of the cable; (v) calculating the standing wave voltage at any point/section of the cable based on the load impedance (Z<SUB>L</SUB>) connected at the receiving end of the cable, and the characteristic impedance (Z<SUB>O</SUB>) of the cable, or the measured/calculated cable parameters for the first frequency of the voltage source, (vi) repeating the foregoing steps while one of: (1) varying at least one of: the load impedance (Z<SUB>L</SUB>) connected at the receiving end of the cable, the first frequency of the voltage source; the output impedance of the voltage source, a combination of the load impedance (Z<SUB>L</SUB>), the output impedance of the voltage source and the first frequency of the voltage source, and combinations thereof; (2) interchanging sending and receiving cable ends; and (3) a combination thereof, and (vii) determining a dissipation factor (tan delta) and a dielectric constant (∈'), for the insulation, and an impedance, for the conductor at predetermined points/sections along the axis of the cable.
|
