For the first time in Russia, IDGC of Volga, JSC used the LPD-Monitor partial discharge on-line monitoring system by SebaKMT for diagnostics of 35 kV cable at working voltage. Subject to testing was the power cable at the 110/35/6 kV “Agregatnaya” substation providing for power supply of industrial enterprises and residential users within the central regions of Saratov. Application of such diagnostic equipment has multiple advantages. The works do not require de-energization, and the cable continuously remains on-load during measurements. Therefore, mains switching is unnecessary. With its sixteen channels available and small weight, LPD-Monitor is ideally suitable for mobile and simple check of cables for frequency discharge critical values. Even a brief testing taking no more than twenty minutes provides a sufficient amount of data. The data analysis by the integrated software allows decision making concerning maintenance or an in-depth diagnostics with the help of the OWTS system. Remote access via a GSM-modem permits control of relevant measurement results and frequency discharge activity at any time. Interest of IDGC of Volga, JSC for such equipment is attributed to increased significance attached to reliable power supply of medium and high voltage cable lines. These tools frequently appear to be the only solution enabling to tackle the problem of growing electric energy consumption in large cities. Currently the company is engaged in a number of projects involving operation and construction of such facilities in Saratov, Samara, and Orenburg. Evidently, adequate technical aids are required for their fail-safe service. At the moment, the company actively uses the OWTS HV 150 mobile diagnostics system for these purposes. The device implementation is expected to provide for establishing a multi-tier cable lines monitoring system, enhancing cable lines efficiency, and reducing operational costs.