Vlf sine 1 Hz – Universal voltage source for test- ing and diagnostics of medium-voltage cables
Consequences during practical use
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9 2020 gt thi nghiem dien 1 tc ktd19md38 7318
| 4. Consequences during practical use
For practical use, other aspects besides measurement accuracy and reliability must be taken into consideration. The following aspects are important during use in the field: • Easy transport and easy connection of measurement technology • Staff expenses, training • Time required for the connection • Time required for the measurement • Cost-benefit ratio • Relevance of measurement results for future maintenance Under these aspects, the VLF voltage sources can register low weight and its compactness as plus points compared to a 50 Hz voltage source. Furthermore, as the VLF sine source is considered for cable testing and diagnostic measurements (tan delta and PD), network engineers can per- form all relevant measurements on new and old cables only with one voltage source. Unlike the use of various voltage sources for different methods (e.g. Cos-Rect for withstand voltage test and OWTS for PD test), there are clear time benefits while using one voltage source, such as VLF sine: connection times are cut by half. While using one voltage source, it is also possible to apply test and measurement methods in parallel, e.g. during the Moni- tored Withstand Test: Monitored Withstand Test or Monitored Withstand Diagnostics (short MWT) means the partly simultaneous implementation of cable testing and cable diagnostics with the tan delta methods. As the test engineer must connect only one device for the MWT and then start a related workflow, he can perform the usual test after installing a new cable or repairing a cable route and simul- taneously determine the cable condition in a short time. A combination of testing and diagnostic measurement - the MWT - offers the following benefits: • Easy test setup, easy flow (no addition- al connections and no introduction to MWT needed) • Shorter test duration if the cable is in good condition • No cable overload • Result evaluation in real time • Interpretation of cable condition with Smiley sign on display • Precise results on cable condition Even the partial discharge measurement can be similarly integrated in a measure- ment and test cycle so that a PD test hardly requires any additional time. Information from the integral dissipation factor meas- urement and the local partial discharge measurement is complementary and gives network and maintenance engineers more criteria for evaluation. For the test engineer, using an easy and light voltage source for the cable testing and diagnostics means that he can meas- ure more cable routes in the same time than while using different voltage sources. In other words: the condition of almost twice the number of cable routes can be determined in the same time, which is of advantage for condition-based mainte- nance. |