Perpustakaan Digital ITB

Cables are an essential component in the power distribution system; if the failure occurs in the cable system, it becomes a serious inconvenience to our society. Therefore, diagnostics to determine the health of cable are critical. Knowing the initial condition of the cable when it will install or knowing periodically the condition of the cable that has operated from the threat of external interference is essential because, in this phase, failure usually occurs. Various electrical test methods have developed to diagnose cable conditions that can divide into two essential categories, namely in the ability to identify defects such as globally or in bulk and spatially or locally. Locating and detecting degraded portions of defect becomes very important because it is related to the next preventive step that must take considering that replacing cables throughout the section is an incorrect choice both in terms of cost and time. The problem that often occurs in the field is the occurrence of soft defects that often occur when installing cables due to various factors such as being pinched, punctured, or peeled. Over last year, many methods based on non-destructive tests such as Line Resonance Analysis (LIRA), Broadband Impedance Spectroscopy (BIS). Time Domain Reflectometry, Joint time-frequency domain Reflectometry is carried out. Apart from the non-destructive method, it also does not require a source or higher test voltage approaching Uo but only a low voltage ± 5 Vpp, so it is very flexible to do in the field. The BIS method is still being developed and researched because there are still many challenges in processing and the ability to interpret test result data. The approach used is to conduct experimental laboratory experiments and simulations with ANSYS Electronic Desktop software. An RG 58 CU cable of 33.5 meters used in the experiment, divided into four sections, 3 meters of which were probes to DUT, 15 meters of the whole section, 0.5 meters of degraded portion, and 15 meters at the end was regular cable. Each section is connected using an individual BNC connector for RG 58 CU cables. The degraded portion is done by using several types. The first is to use mechanical damage by bending beyond the cable's tolerance limit until there is a change in the geometry of the cable. The second is by connecting the resistance (100 Ohm) or capacitance (10 nF) value using the T joint connector, adding capacitance or resistance values will change the impedance value at that point so that the change in impedance value interpreted as a degraded portion. The simulation was done by using three models, namely normal conditions with a length of 33.5 meters, a model with a mechanical damage section, and a model with a peeled off 90-degree damage section. The next approach is to compare test results with simulations designed with the same parameters as the experimental setup. From the test results compared with the simulation results, it found that the type of defect caused by the mechanical press and the peeled parts have different characteristics where the mechanical press will have a smaller impedance value with increasing frequency. In contrast, the peeled part has the opposite characteristic. Besides, the IT transform method and IFFT method both of them can detect precisely the degraded portion at 18.5 meters from 33.5 meters total length of the cable under test. IT transform is easier to use but has to have a frequency range that matches the velocity factor of the cable being tested besides the initial or healthy conditions of the cable must be known as a comparison factor. If using the IFFT method, the constraints found are noise interference so that the correct windowing and signal processing is needed and also to get a smaller resolution, a higher frequency range is needed.