Any experts here  can    advise . 
This is in relation to  RCCB  tripping  when there is lightning  far away  .
how do you measure  the leakage current  in your    house  .  ( on a normal sunny day .

And
what is the  best way  to protect  your  pc  and  unifi  equipment  from  lightning  surge or strikes .

Then we put numbers to it.  A lightning strike nearby to a long wire antenna (designed to be most sensitive to E-M fields) can result in thousands of volts on that antenna wire.  Then connect a one milliamp Neon glow lamp (ie NE-2) to that antenna lead.  Voltage then drops to maybe 60 volts.  Because the induce surge has high voltage if current does not flow.  And has near zero voltage if even less than one milliamp flows.

Induced surges are made irrelevant by what is already inside every electrical device.

Lightning struck a lightning rod.  That means maybe 20,000 amps was flowing down the lightning rod's hardwire to earth.  Just 1.3 meters away, inside, was an IBM PC.  It did not even blink.  And either did any other office electronics.  That was a major E-M field confronting electronics - that did not even cause a software program to flicker.  Because the destructive power of nearby E-M fields is overhyped by speculation.  And does not exist once we include relevant numbers.

A tree was struck by lightning.  Some ten meters distant, a cow died.  Wild speculation assumes the cow was killed by an induced surge.  Of course not.  Lightning is a connection from a cloud (maybe 3 km up) to earthborne charges (maybe 4 km distant).  That path also went up the cows hind legs and down its fore legs.  What only observation speculated was an induced surge, in reality, was a direct strike.  Conclusions only from observation create junk science.  Once the many facts (with numbers) are learned, then that observation results in a completely different conclusion.

Nearby lightning strikes are either direct strikes or do not do damage.  Nearby strikes that would trip an ELCD/RCD must somehow create what trips it.  Not a voltage.  A current that exceeds 100 ma.  Induced surges just do not have that current.  But many assume it was a induced surge rather than discover it was actually a direct strike.

Furthermore an ELCD/RCD requires that current to flow for tens of milliseconds or longer.  Lightning is a microseconds event.  too short to trip it.  Something completely different (ie a follow-through current) may be relevant.  But that is not a nuisance trip.  That is a problem that must be protected from.  And that is something that should not happen if other solutions are properly implemented.

And that current is microamps or less.  Much of electricity flows outside the wire - the skin effect.  Like the nearby lighting strike, it can create high voltages only when no current is flowing.  ELCD/RCD is not about voltage.  It is about current.  That leakage may be in the microamp or nanoamp region.  Well below what is normal leakage in electronics (powered off or on).

Skin effect is why AC power wires cannot carry any more current if thicker.  And why voltage on one wire can create a voltage (with almost no current) on another.  Skin effect applies to all frequencies down to but not including zero hertz. The point - skin effect explains why one wire can induce a voltage on another.  And create maybe nanoamps of current - virtually a zero current.

So what is relevant?  Leakage from wires is totally irrelevant - once we put numbers to that speculation.  Most leakages are from appliances.  Which is why some RCDs do not trip for a massive (less than) 5 milliamps.  And why an RCD of 100 milliamps is massively above that normal leakage currents.

Described were some reasons for 'nuisance tripping'.  In each case, due to some actual defect.  For 'in the wall' wires to create nuisance tripping, insulation of two wires must be so massively compromised that wire separation is well less than 1 mm.

There are simple techniques for finding that defect.  But the usual suspects are being ignored.  ELCB/RCDs are almost last on a list of possible suspects.  Tripping is reporting a defect.

The point of skin effect is overlooked.  You said wires leak current.  That that leakage can even be measured by 20 volts on a meter.  That 20 volts is not leakage currents.  It is an induced voltage created because current flows outside of a wire - skin effect.  Current associated with that 'skin effect' created voltage is probably nanoamperes.  Completely irrelevant to any ELCB/RCD operation.

Wires are not the typical source of microamp leakage currents.  Appliances are.  Even that resulting current is so low that a 5 ma RCDs should not trip. So a 100 ma RCD is well above what would cause an ELCB/RCD trip.

A 100 ma trip is saying that some defect existed.  One example of why is 'follow through' current. Correct the reason for that current rather than blame induced currents by adjacent L-N wires.  Replacing a 100 ma RCD with a 300 ma one is only to cure symptoms.  Instead, address the actual problem.