The engine must obviously be equipped for automatic start & run.
Usually, the start will be initiated by the loss of supply voltage from the normal source. Run-up of the genset will be automatic, at which point it can be connected to the load after the normal source is isolated, usually by operation of a circuit breaker.
Automatic transfer back to the normal supply also needs to be considered.
If the station is unmanned, there will probably be some provision for remote monitoring &/or alarm when the geneset is running.
I suggest that you get professional engineering help in setting up a system such as this, as there are a lot of factors involved.
A VARIETY OF ATS (AUTO TRANSFER SWITCH) ARE AVAILABLE IN THE MARKET WHICH BASICALLY IS A CHANGEOVER PANEL WITH SWITCHGEAR AND CONTROLGEAR. THE CONTROLGEAR MAINLY COSISTS OF WATCHDOGS LIKE UV/OV RELAYS, FREQUENCY RELAYS ETC. CONTINOUSLY MONITORING SUPPLY CONDITIONS AND TIMERS WHICH CONTROL THE INSTANT OF CHANGEOVER ( SMALL DURATION SAGS AND SURGES CAN BE BYPASSED).SINCE YOURS IS A UNMANNED STATION YOU NEED REMOTE MONITORING PANEL FOR SENSING D/G POWER, CRANKING BATTERY CONDITION,FUEL TANK LEVEL,ETC.
An Automatic Transfer Switch is the least expensive way to go. I assume this is one (1) Standby Generator application. You would need to add acessories such as battery charger and jacket water heaters to ensure 10 second starting. I design these systems for a power systems company and if you need direct help contact me at joneil@darrequipment.com