Our modern society uses a lot of energy. With the rise of electric-powered devices in our everyday life, advanced communication technologies have been integrated into the existing power system to ensure that the power supply meets the demand. The Smart Grid improves efficiency and reliability of electricity supply, integrates more renewable energy into the power system, and much more. However, the integration of information and communication technologies into the power system exposes the grid to cyber threats. For example, major events such as the 2015 cyberattack on the power grid in Ukraine by Russian hackers, along with the widespread blackout in Mumbai after another attack in 2020, give just a hint of what kind of effect such vulnerabilities can have. This thesis aims to analyse the effect of cyber attacks on the smart grid. Employing a quantitative research approach, this study conducted a performance and power loss analysis of the smart grid through a simulation in MATLAB/Simulink using the IEEE 9-bus system. The study targeted two specific types of cyberattacks: the replay attack and the time delay attack. Both situations were examined with and without security measures in place. The research shows that the normal operation of the Smart Grid is severely affected by these cyber attacks. On average, the power loss due to these Attacks when a security mechanism is in place is approximately 3 MW, and 57 MW when no security mechanism is in place. This paper also advises mitigation strategies for this attack. A future work could be the implementation of a machine learning base detection system.