OilQSens® - a new approach to transformer oil quality testing, online and continuous
Ölqualität, Condition Monitoring System, Oil Condition Monitoring, Oil Condition Monitor, Aging of Oil and Cellulose, Transformer Oil, Dissolved Gas Analysis (DGA), Monitor Water in Oil
Source: HSP Hochspannungsgeräte GmbH, Troisdorf
OilQSens® is an oil condition monitor ideally applied to oil quality testing in high voltage transformers, continuous and online, with data transmission via LAN/WLAN.
The transformers in power substations represent the largest part of the capital investment - protection of these assets is most important.
Fault states in power transformers are usually the result of oil degradation which can be due to a number of factors.
Early detection of changes in oil quality accurately predict the need for maintenance rather than relying on rigid inspection intervals or laboratory testing.
The patented measurement method (Patentnr.: EP 2 163 887 B1, Method and circuit assembly for measuring physical parameters in fluids and their application) combines a high sensitivity at a low noise with a broad measurement range.
OilQSens® represents a significant improvement on older technologies such as dissolved gas analysis (DGA).
Moisture (water) in transformer oils has a number of damaging effects. Electrical resistance is reduced which can faciltate partial discharge and decreases in breakdown voltage. The mechanical strength decreases due to the accelerated aging of cellulose caused by the water resulting in degradation of the paper. Also at high temperature, the glycosidic links of the cellulose break and thus reduce the degree of polymerization of the insulating papers, this is a measure of the life of the papers. Another damaging effect is the bubble effect, gas bubbles in the oil reduce the dielectric strength. Contaminants in transformer oil e.g. Impurities (in the assembly of the transformer) and aging products enhance the damaging effect in the transformer oil. The products of aging in transformer oil are carriers of positively and negatively charged ions. The aging rate and the formation of acids of the oil are proportional to the catalysts (metals such as copper, iron, lead), to the concentration of oxygen present and to the temperature of the oil. Metallic particles can arise from manufacture or from abrasion in the cooling system pumps into the oil. Cellulose fibres can be pulled from production and the progressive aging of solid insulating materials in the oil. The actual conductivity of pure oils is extremely low. However, the highly sensitive OilQSens® measures conductivity down to 0.1 picosiemens per metre and all values are accurately temperature compensated taking into account the unknown, changing quantity of unknown pollutants. Dielectric testing of transformer oil is an important parameter for efficiency of high voltage transformers. OilQSens® monitors permittivity and this has been shown to correlate accurately to the water in the oil. This measurement also uses the patented temperature compensation system. The web based, decentralised monitoring system is perfect for remote or inaccessible locations. Measurements are transmitted via LAN, WLAN or the serial interface.
The OilQSens® sensor system was developed in collaboration with the Competence Platform "center for strategic corrosion protection" Prof. Dr.-Ing. Kuipers of the University of Applied Sciences, South Westphalia.
Consultant for tribology, lubrication technology, etc., Prof. Dr. rer. nat. habil. Jürgen Gegner,
Institute of Materials Engineering, University of Siegen