The incorporation of blockchain technology in smart grids has proven the utmost promise in improving the security, transparency and efficiency of energy distribution systems. At the very same time, as smart grids become fundamental parts of modern energy infrastructure, their vulnerability to cyber-attacks and advanced threats poses dire security and reliability issues. This paper examines the potential of smart grid protection using post-quantum blockchain technologies as a paradigm shifting approach. The integration of post-quantum cryptographic algorithms to blockchain infrastructures guarantees the construction of a new security framework which can withstand subsequent quantum attacks. The paper starts with shedding light on smart grid structure and its corresponding salient security features and identifying the gaps and challenges of contemporary security frameworks. It then provides an overview of fundamentals of post-quantum cryptography and the advantages of blockchain technology for smart grid systems. An implementation is provided to prove the concept of post-quantum blockchain deployment and demonstrates the practical benefits and associated issues, which include secure energy trading and data assurance. The results of the implementation highlight the dire need for a decisive approach in providing security to smart grids, advocating for the life-long mitigative effort under the vision of developing smart grids protected with post-quantum blockchains.