The paper, prepared by CIGRE WG D1.03 (TF 09), presents the guidelines for risk assessment procedure on defects in GIS based on PD diagnostics. The procedure, described in detail in CIGRE Technical Brochure 525, starts with sensitive PD measurement to detect the critical defects and follows with identification of the type of the defect and its location inside the GIS. This information taken together with other essential data from laboratory measurements, manufacturer's experience, design aspects and trend analysis of the PD activity, are the base for the estimation of the criticality of the defects. Finally, the risk assessment is performed based on the estimated dielectric failure probability and failure consequences that can be different in case of on-site testing or in service activity.

Due to increasing decentralized energy production and rising energy consumption, DC transmission at the MV level is becoming ever more important. The two main advantages are the operational advantages of MVDC transmission and the higher transmission capacity. To qualify MVAC cables for DC operation, it is important to determine the electrical parameters of the insulation. One key parameter of the DC insulation is the conductivity, which is obtained from LC measurements. Additionally, space charge accumulations can be detected. In this contribution results from leakage current measurements with varying thermal and electrical stress are presented. Additionally, LC measurements during polarity reversal cycles were carried out.

Insulator diagnostics is still a topical issue. No one has yet found out how to accurately determine the condition of all insulators and decide when replacement or maintenance is required. Insulators are one of the main components of a transmission and distribution system and must withstand high voltages in all weather conditions. Moisture and dirt are the main factors influencing the insulating properties of insulators. This article deals with the effect of pollution on a porcelain insulator. An Omicron MI 600 measuring system monitors the changes in the dielectric loss factor and leakage current in a wide frequency range (10 Hz to 1 kHz) to evaluate the contamination level. We applied three high voltage levels (5 kV, 7.5 kV, and 10 kV) to the porcelain insulator to monitor changes in the mentioned quantities with various frequencies. The measurement results confirmed the usability of the dielectric loss factor and leakage current for the diagnosis of insulator pollution. The dielectric loss factor showed more promising results than the leakage current.

With the events related to the energy transition, a shift from a traditional towards a decentralised power generate-on can be observed. The growing use of volatile, renewable energy sources culminates in the need for storage as well as transportation capabilities in the grids of tomorrow. Transmission and distribution grids worldwide are based on alternating current (AC), a well-established technology. This concept works reliable and stable but comes along with some restrictions. The transmittable power is limited by factors like the need for reactive power, which affects the maximum transmission length. Furthermore, dielectric losses as well as the skin effect limit the efficiency of AC power transmission. Due to these restrictions, the use of Direct Current (DC) can be beneficial. The Medium Voltage Direct Current (MVDC) power transmission is a promising approach to enhance the transport capacity of transmission links, such as cables or overhead lines. As several publications point out, the possibility of converting existing Medium Voltage Alternating Current (MVAC) overhead lines (OHL) to DC operation, the aspect of using overhead lines in such systems has to be investigated. Therefore, locally used MVAC insulators (Austria, Indonesia) as well as conductors are tested in terms of flashover strength and audible noise behaviour under DC-voltages. Environmental parameters like moisture, temperature and surface pollution are to be considered.