What method can be used for outdoors circuit protection when transmitting DC or analog signals?
All protection circuits need a voltage-divider action, thus both a series impedance and a shunt impedance. The TVS diodes are the shunt. 

Often the only series impedance is the WIRE INDUCTANCE. 

You can improve the protection by adding series impedance: resistors and/or inductance.

Here is how I've suppressed serious trash: 2 series inductors and 1 parallel capacitor, used 3 times







simulate this circuit &ndash; Schematic created using CircuitLab