what's the fastest way for switches the high voltage?
Use a solid-state relay (SSR) DC type.

Figure 1. A DC SSR features optical isolation between the input and the output. Image source: Phidgets.com.
The control input is usually switched by 3 - 30 V DC and will require maybe 20 mA.
You need to select one that can handle the required output voltage and current. The external diode is only required on inductive loads.

By the way, 30 V isn't considered a high voltage in most applications.