ah.. overhead wiring. yes , that is a direct strike .. hard to stop that one.
i'm talking underground trunks. lightning heats ground about 2 meters above where the cable sits. this still induces a massive jolt in the cable.
All i know is this stuff was tested according to CISPR and ITU. and it lives. We shot it many times with esd guns at 15 kilovolts. no problemo. ( i don't rememeber what the energy setting was though. 15 kilovolts doesn't say a lot. 15 kiovolts from 15 pf is different than 15 kilovolts from 1 uf .. ) By the way , this is not my design. i learned this from the telecom guru's at alcatel. they had a dedicated lab for this kind of stuff. They explained the moatign system , how to make sure there is enough crep , how to open up the soldermask for the esd guard ring ( drat , i forgot to do that in my quickly-slapped-together-layout : there should be NO soldermask around the testpins , nor underneath the first resistor. you need bare pcb. the reason is high-voltage creep.
long body resistor : 1206 is fine. that gives you enough creep.
Try to use thin film and not thick films. thin film is metal sputered and laser cut. thick film is printed ink and laser cut. thick film flashes over quicker than thin film.
there are 1206 resistors with high standoff voltages. they are typically blue in color ( as opposed ot a black strip , they have a blue strip on the alox base ) vishay and others make those. the blue material is an extra isolation layer to shield the resistive element. it is applied AFTER the laser trimming to seal the element from humidity.
you can omit the schmittrigger if you know the processor or whatever digital chip you use has these in the input stage. i just added those for completeness. if you omit the extra chip then the processor or chip is powere BEFORE the ferrite ( and not from between ferrite and resistor to the diode )
the ferrites are high-impedances for the pulses. there too you want long-bodies.
any connector shield needs to be plugged to the safety ground as well.
like a usb connector. it has 4 wings connected to the metal body and 4 pins : vbus d+ d- and gnd. the wings go to safety ground , the gnd pin goes to system ground ! try to route this connection (gnd pin) on in an inner layer. and create another bare copper ring around the pins.
the whole idea of creating bare copper is so the esd zap is attracted there and doesn't shoot into system ground
Once you are past the 10k moat there isn't much energy anymore. then you cross the 1k moat and the esd protection devices will eat the rest.
it is important the capacitors at the double diode can handle large voltages. you can get away with 10nf to 100nf but grab 250 volts . whatever spike goes rthrough the diode needs to be absorbed by these ( the zener will react , but the very narrow spikes will be shunted mainly by the capacitors. ) thos caps will probably be 1206 as well. in telecoms we used 2512 bodies ans some other weird number 32-something ( can't remeber , i have to look it up. we used wide electrode caps as well.
just like you have a 1206 capacitor ( 12 long 6 wide ) there is an 0612 cap ( 6 long , 12 wide , so the electrodes are wider but the distance between is shorter. this is for pulse currents.)
there is a lot to say about selecting the correct kind of parts .. most egnineers and hobbyists pick whatever they find in the drawer.. there is a reason for having all these different kinds of constructions , materials , body shapes , laser cutting differences ( l -cut , r-cut , modifed r-cut , meander-cut and plenty others )
someone ought to write a book about selecting passive components for function... you can easily fill a 500 page book on resistors and caps alone ..