An RCD, or Residual Current Device, essentially shuts off the electricity much quicker than a standard circuit when it detects a fault. The speed at which it does this can be the difference between a person surviving an electric shock or not. An RCD is also known as a Safety Switch.
Do we need an RCD on the farm?
I consider a farm workplace a potential 'hostile environment', so YES, you should have an RCD installed on your main power board to cover your whole workplace including workshops, sheds and houses.
For further clarification refer to:
South Australia Work Health and Safety Regulations 2012 - under the Work Health and Safety Act 2012 - Version: 1.9.2024
(1) This regulation applies in the following circumstances:
(a) electrical equipment is used in an environment in which the normal use of electrical equipment exposes the equipment to operating conditions that are likely to result in damage to the equipment or a reduction in its expected life span, including conditions that involve exposure to moisture, heat, vibration, mechanical damage, corrosive chemicals or dust;
(b) electrical equipment is moved between different locations in circumstances where damage to the equipment or to a flexible electricity supply cord is reasonably likely;
(c) electrical equipment is frequently moved during its normal use;
(d) electrical equipment forms part of, or is used in connection with, an amusement device.
(2) In a circumstance set out in subregulation (1), a person conducting a business or undertaking at a workplace must ensure, so far as is reasonably practicable, that any electrical risk associated with the supply of electricity to the electrical equipment through a socket outlet is minimised by the use of an appropriate residual current device.
or Safework SA