It all comes down to the production of a potential or voltage gradient along the ground surface and it's best to stay well away.
What's a gradient?
If you put a poker into a fire, the point of the poker can be red hot and at a temperature of maybe 500 degrees C. However the handle is only at the temperature of your hand. If you move your hand along the poker towards the tip, the temperature rises along its length. That's a thermal gradient. Similarly, atmospheric pressure decreases with increase in altitude and water pressure increases the further you descend downwards below sea level. Those are examples of pressure gradients.
Voltage Gradients Along the Ground Surface
The voltage of medium, high or extra high voltage power lines can be anything up to 400,000 volts or 400 kV (e.g. the lines carried by the tall pylons at the dump on the Naas road in Kilcullen, that transmission line extending all the way down to Moneypoint Power Station on the Shannon Estuary). Most lines however are at a lower voltage of 10 kV (classified as medium voltage). Those are the ones you'll see supported on single poles, locally supplying transformers that drop voltage to 230 V (classed as low voltage) to provide power to homes and small business premises. When one of these lines touches the ground, that point of contact is at 10 kV, but far away from the line, the voltage will drop off to zero. So this results in a voltage gradient along the ground surface. The voltage between any two points on the ground can be dangerously high because of the gradient, especially if a higher voltage line has fallen, such as the 38 kV lines that often supply smaller substations like the one in Kilcullen. The voltage gradient would be steeper, closer to the point of contact with a line on the ground. This is the reason why cattle can be electrocuted if there's a lightning strike. The voltage difference between their front and hind legs can be thousands of volts. So current flows up their front legs and down their hind legs and can cause electrocution. For a two legged human, the situation isn't as bad. However if they fall on the ground, they can potentially be electrocuted if their hands touch the ground. In this scenario, their whole body acts as a circuit, electricity flowing through their hands, heart and feet, possibly causing heart fibrillation and failure.
There are two 38 kV lines supplying Kilcullen's substation, those lines coming from both Newbridge and Stratford. (the substation is near the turn for the Glen of Imaal on the N81) . The reason for the two feeds is because of the redundancy built into Ireland's electricity grid. If one line breaks, the other line can provide a feed. Also more than one generating station can provide power using either feed. Similar to the Internet, the grid is like a fishing net, so power can find its way around the system, even if there's a "hole" in the net.