It does not have a sign on it and has 2 wires so I presume it is 275kv.
As I said, that is a rule of thumb. The size of the insulators and height of the tower is the real give-away, at least of the voltage the line is designed for (sometimes they are operated at a lower voltage for a while), but this is harder for the untutored eye to gauge. There should be danger signs on the tower at low level and the voltage will be written on this.
I am now in a panic as the house is only 70 meters from the line and our main electric cable is 5 meters off the ground running parallel to the high voltage line with approx 200 meters to the transformer.We do suffer from power surges could this explain it.
As I said earlier, this is something to be aware of and manage, not to to panic about. Assuming my guess about the induced voltages is correct, that they are tens of volts, then I doubt it. Overhead lines from isolated transformers in what I assume is a rural area are noted for power surges of various sorts, whether there is a transmission line nearby or not. Finding out whether the transmission line is the cause or not would involve using expensive monitoring equipment. I would consider poor voltage regulation due to long lines and dodgy tap changers to be a more likely cause.
