Connecting a new power plant both thermal conventional and VRE to either distribution system or transmission system will have impacts on the existing system, whether it is positive or negative. To be able to connect to a 20 kV distribution system, it must comply to Perdir 0064/2019. While connecting to transmission system (150 kV or above), it must comply with the Grid Code. Therefore, an in-depth study is required to analyse the impacts and to find the suitable mitigation if there is any negative impact when connecting a new power plant to a system.