Sorry you are getting confused about what it is the Regulations apply to.
To put it in simple terms, the ground does not have to comply with HASAWA.
If a worker then digs a hole in the ground, that task must comply with HASAWA.
Electricity does not have to comply with the EAWR.
How you use electricity when conducting a task for work must comply with the EAWR.
An installation in a building which is not used for work purposes does not have to comply with the EAWR.
How you use the electricity provided by that installation when conducting a task for work must comply with the EAWR.
An installation in a building that is a place of work, must comply with the EAWR.
How you use the electricity (irrespective of whether it is for a task of work) provided by the installation, must also comply with the EAWR.
Compliance with the EAWR can in many respects be achieved by compliance with BS7671.