b) Insofar as the tax is imposed upon persons distributing, supplying, furnishing or selling electricity for use or consumption and not for resale, the following general principles will apply in determining whether or not transactions are in interstate commerce:

1. 1) Where a taxpayer delivers electricity through continuous lines from a point in Illinois to a point outside of Illinois, such transactions are in interstate commerce, and the taxpayer is not liable for tax with respect to gross receipts therefrom.
2. 2) Where a taxpayer not engaged in business in this State delivers electricity through continuous lines from a point outside of Illinois to a point within Illinois, the transaction is in interstate commerce, and the taxpayer is not liable for tax with respect to his receipts therefrom. However, if such company is engaged in the business in Illinois of distributing, supplying, furnishing or selling electricity brought within this State for use or consumption and not for resale, such transactions do not constitute interstate commerce, and the tax will apply.
3. 3) Where a taxpayer delivers electricity through continuous lines from one point in Illinois to a second point within Illinois, the transaction is not in interstate commerce, and the taxpayer will be liable for tax with respect to his receipts therefrom. This rule applies irrespective of the fact that a portion of the continuous lines of the taxpayer through which electricity passes are situated outside Illinois.