Underground power cable diagnostics

: transmission line parameter extraction and online defect positioning

Samenvatting

Underground power cable is employed to transfer MV (medium-voltage) and LV (low-voltage) electricity within the Netherlands. Consequently, power cable diagnostic becomes a popular subject which involves the transmission line parameters of the power cable and the impedance variation at the defect position. In the first part of the paper, a technique is introduced for extraction of the transmission line parameters of power cable from scattering (S)-parameter measurement. The process is realized by compensating the influence of the connector between the measurement port and the power cable. It is shown that the connector should be treated as part of the transmission line instead of a simple characteristic impedance change. Furthermore, research has been conducted to quantify how the transmission line parameters depend on temperature. This phenomenon is verified by the extraction technique both for Cross-Linked Polyethylene (XLPE) cable and Paper-Insulated Lead Covered (PILC) cable. In the second part of the paper, an online defect positioning technique is proposed, based on the fact that cable defects normally cause impedance variation at the defect position. To this end, the cable impedance is monitored at a Ring Main Unit (RMU) with the help of online impedance measurement technique. The measurement utilizes a Bulk Current Injection Probe (BCIP) clamped around a conductor inside the RMU. The frequency domain impedance is transferred into the time domain impulse response by applying the Inverse Discrete Fourier transform (IDFT). Thus, the frequency domain impedance variation can be observed in time domain which includes the defect position information.

Datum prijs	31 okt. 2014
Originele taal	Engels
Begeleider	E.F. Steennis (Afstudeerdocent 1), Y. Li (Afstudeerdocent 2) & Peter A.A.F. Wouters (Afstudeerdocent 2)