Power grid frequency data base  --- This dataset contains precisely time stamped (GPS referenced) frequency data from several power grids around the world in **one second resolution** and 1 hour excerpts of raw waveform data. This work is conducted by the [Institute for Automation and Applied Informatics][1] at [KIT][2]. A comprehensive list of locations and specific information for each campaign can be found under [Data Records][3]. In the initial commit, we present frequency measurements from **twelve** independent synchronous areas of different sizes as well as **synchronous records** (green markers on map). @[osf](483ua) For the **synchronous records** the points of measurement are located in Portugal, Germany, and Turkey, maximizing the geographical distance. @[osf](p86at) Data were collected using our self-developed device, the Electrical Data Recorder (EDR). It is a Phasor-Measurement-Unit(PMU)-like recording system that uses a GPS receiver for time stamping and as frequency reference. We connected the EDR mostly to conventional low voltage power outlets, in some cases to central connection point of a building. See [Data Records][3] for specifics on the locations and this [Data Descriptor on ArXiv][4] for details on the EDR and recording methodology. Citation --- When using this data, please cite this [repository](https://osf.io/by5hu/) via its DOI and the corresponding scientific articles, which provide additional information on the process of recording and data structure ([Data Descriptor on ArXiv][4]) and an initial data analysis ([Data Analysis at Nature Communications][5]). Acknowledgements ---- This work was supported by the Helmholtz Association under the program “Energy System Design”. We would also like to thank our colleagues and friends who have taken the EDR with them on business and private trips for data collection. [1]: https://www.iai.kit.edu/english/index.php [2]: https://www.kit.edu/ [3]: https://arxiv.org/abs/2006.01771 [4]: https://arxiv.org/abs/2006.01771 [5]: https://www.nature.com/articles/s41467-020-19732-7