Abstract: To detect the cables a HF test signal is used and the presence of cables detected from the energy radiated from the cable. Even a short wave radio tuned to an appropriate waveband can be used as a detector. If the section of cable is not live the signal propagates along the cable and bridges the isolating switch contacts to the live section. By the use of different test signals the presence of more than one cable can be detected.

Abstract: The measurement of partial discharge (PD) activity is used for monitoring the insulation condition. In particular, it is of importance to obtain an indication of the time to breakdown for high voltage distribution power cables, both for cable factories and for the utilities. In this paper the authors investigate the use of the Oscillating Waves method (OWTS) and of the Very Low Frequency (VLF) method to stress the insulation of service aged components and to detect partial discharge activity.

Abstract: Diagnostic testing of in-situ power cables is an emerging technology. Many diagnostic systems are being developed, both off-line and on-line that are providing much data. These data need interpretation and understanding as the technology emerges. This paper addresses some of the commercially available diagnostic methods and covers the field experiences with these diagnostics. Both PILC and polymeric insulated cables are included in the discussion.

Abstract: The paper reports on service field experiences with PD diagnostics on distribution cables using damped oscillating voltage waveforms: This test method was introduced some years ago in particular for on-site tests. Standard test procedures using continuous AC voltages are very cost intensive due to the high capacitive power demand of the cables and the resulting large sizes of the test sets, whereas other alternative methods do not reproduce similar PD than under service conditions. Experiences from the service field reveal that the oscillating voltage waveforms (OVW) method shows a very high sensitivity of PD detection and recognition of electrical treeing. Examples for critical assessment values have been determined for cross linked polyethylene (XLPE) cables as well as for oil-paper (PILC) cables allowing the network operator to decide which maintenance operation has to be performed on the distribution cable.

Abstract: The authors investigated a new life estimation method for service-aged, water tree deteriorated 22-77 kV XLPE cables by voltage withstand test. At first, they selected more suitable waveform for testing voltage from damped oscillating wave (OSW) and very low frequency wave (VLF) voltage as the instead of AC and DC. It was found that VLF voltage has high ability to detect of water tree, while was less harmful for water tree deteriorated cables. Breakdown tests under AC and VLF were carried out, using model cables and service aged XLPE cables. Based on the breakdown tests, they calculated optimal test voltage for remaining life estimation. Recently, they had onsite testing and confirmed the effectiveness of VLF testing.

Abstract: In this paper, a new cable voltage drop compensation scheme for ground power units is presented. The scheme is able to predict and compensate the voltage drop in an output cable by measuring the current quantities at the source. The prediction is based on an advanced cable model that includes self and mutual impedance parameters. The model predicts the voltage drop at both symmetrical and unbalanced loads. In order to determine the cable model parameters an automatic identification concept is derived. The concept is tested in full scale on a 90 kVA, 400 Hz Ground Power Unit with an output cable of 100 m. It is concluded that the performance is significant improved both with symmetrical and unsymmetrical cables and with balanced and unbalanced loads.

Abstract: We have developed the global assessment system for medium voltage power cable systems. Our purpose of diagnostic activity is the economic discrimination and maintenance of bad cables, which is likely to cause cable system failure. We have adopted the aging time constant method to construct the power cable assessment system for our diagnostic purpose. From the field application test results, we have concluded that our system is successful and convenient for the discrimination and maintenance of the bad cables economically.

Abstract: In many cases, in the diagnostics of (0.4-10)-kV power cable, guaranteed fault-free operation of the cable until the next checkup is required, without high-voltage testing. Nondestructive monitoring methods include: measurement of the insulation resistance and the absorption coefficient; recording of the time and voltage dependence of the leakage current; and archiving of cable echograms. The introduction of new test methods and equipment permits more effective cable diagnostics.

Abstract: Method for determination of voltage interference couplings in signal cables (2) in which the longitudinal voltage, i.e. the voltage between a signal cable and earth is determined from the product of the current flowing in a power cable (3), which is adjacent to the signal cable, and the frequency dependent impedance between power and signal cables.