The R&D Team of Passerro GmbH has developed the BDVB – Break Down Voltage - Basic Oil Stick. The BDVB Oil Stick, enables for the first-time online measurements of transformer oil dielectric breakdown strength. Using multi-frequency ultrasound spectroscopy, the Oil Stick determines simultaneously break down voltage (BDV), temperature (T) and oil humidity (Wc). Transformers are crucial infrastructure assets of Europe’s and the world’s power grids, which must be controlled and governed carefully. Today’s power supply with huge but fluctuant shares of renewable energy (solar, wind) seriously stresses transformers– leading to an increased degeneration of the transformer insulating oil and thus to a significant influence of performance and decrease of their life time. If the oil’s insulating capacity is down, transformers can’t resist higher voltages as well as the power load and often break down in fire after short circuit. A transformer loss results most often in tremendous damages: loss of production capacity, loss of power supply, loss of grid stability and supply security. The replacement time of power transformers lasts up to 80 weeks and is cost intensive. To date, no reliable online monitoring of the crucial oil parameters is available, and the transformers are operated merely in a manner of blind flying. Passerro developed the BDVB Oil Stick to TRL 6-7. Functionality has been successfully demonstrated, during long-time operation in transformers in Italy, Romania and Germany. The next step is the consequent commercialization and distribution of the device by efficient marketing and business development. The BDVB Oil Stick enables a groundbreaking transformer asset management system and allows the accurate utilization of the grid capacities. Moreover, it is a key enabling technology towards a smart grid.