This deck talks about how NASA handles overall charge on the station:

https://ntrs.nasa.gov/api/citations/20110014828/downloads/20...

TL;DR they dissipate charge using three Plasma Contactor Units (PCUs) on the Z1 truss, and measure it using the Floating Potential Measurement Unit (FPMU) on the S1 truss. This clamps the ISS to within 20 volts of the local plasma.

https://en.wikipedia.org/wiki/Plasma_contactor

https://web.archive.org/web/20060929171819/http://space-powe...

https://www.nasa.gov/image-article/floating-potential-measur...