It's worth it to tinker a bit with the playground before making sensors that shutdown the computer
Make sure in the playground settings page that Automatic maintenance mode is activated (should be, by default).
If you mess up a sensor and Aquasuite shutdowns the computer for no reason, it will only do so 3 times instead of locking you out of your PC.
Been there, done that! The Maintenance Mode was a great addition to get you out of an incorrectly configured shutdown command that triggers during normal operation.
OP - Welcome to the Forum and Aquasuite. There is another way to trigger a system shutdown but it is not supported on the Quadro. The Octo 8-channel fan controller has a Signal port that can be used with Alarm Cable
#53216 to force a hardware based shutdown. The Alarm cable piggybacks onto the header on your motherboard that the case power switch cable plugs into. The Alarm function outputs a momentary logic 0 on the Signal port which emulates pushing the case power button. Unfortunately, the Quadro lacks the Signal port so the Alarm cable cannot be used. The Octo costs a bit more than the Quadro but in addition to having twice as many PWM ports, it also has the Signal port and 2 RGBpx ports verses 1 on the Quadro.
As Remayz and Taubenhaucher explained, you can build a virtual sensor in the Playground and configure it to send a shutdown command to Windows if certain conditions occur. What triggers the shutdown command is up to you, so be careful using it or you could end up having the computer shut down every time Aquasuite starts. The Maintenance mode was added to get those who make this mistake out of this situation. I suggest buidling your virtual sensor but have it send a notification to Windows while you test. When you are sure that it's set up properly, then switch if from sending a notification to sending the shutdown command. Also, note that for this to work, Aquasuite and Windows have to be running. The advantage of the Alarm cable is that it is a hard-wired connection to the power switch header on the motherboard and it will still work if Windows is locked up or otherwise not running properly. If the data source that controls the Alarm is local to the Octo, it will work even if Aquasuite is not running. Note that the High Flow Next also has a Signal port that the Alarm cable will work with.