You can provide frequency control in one part to keep another part stable. For example if you have a part of your grid with a high level of renewables (for exam

You can provide frequency control in one part to keep another part stable. For example if you have a part of your grid with a high level of renewables (for example, South Australia), system stability can be provided by large intertia generators in other parts of the grid (in our example, coal power stations in Victoria). Take away the interconnect, and the islanded part of the grid is no longer stable, requiring the renewables to be switched off and replaced with gas and diesel generators. This happened after a storm earlier this year: https://www.afr.com/companies/energy/sa-to-remain-cut-off-from-east-coast-power-grid-for-weeks-20200203-p53xb8 https://www.afr.com/companies/energy/sa-to-remain-cut-off-fr...