In recent years, Renewable Energy Power Plant (REPP) such as Solar Power Plant (SPP) and Wind Power Plant (WPP) are the most popular types of REPP and have been developed and operated widely in the world because of their advantages as clean energy, cheap fuel cost, and the investment costs are decreasing significantly. Recent years in Indonesia, SPP and WPP have started to be developed in several regions. Based on the Long Term Planning of Indonesia Government, in 2025 it is targeted that around 23% of the total energy mix in Indonesia will come from REPP. But on the other hand, the two types of power plants have intermittent/ variable characteristics that vary rapidly according to weather and solar intensity conditions even naturally uncontrollable by the system operators. It is categorized as Variable Renewable Energy (VRE). This Intermittent nature has the potential to endanger the stability and reliability of the network. Statistically, there have been several power outages in Europe, Australia and the United States triggered by the mass operation of VRE power plants. One of the root causes is lack of Grid Code that clearly regulates the operational of VRE. It raises a lot of researches to discover appropriate and specific adaptations of the existing Grid Code that unique for each network based on its characteristics, government policies, and the availability of local natural resources. This paper presents a comprehensive literature review on Grid Code that has been implemented not only in Indonesia but also abroad. This paper also reviews characteristic of VRE from various textbook references, government regulations, and scientific journals. Furthermore, this paper explains the results of literature review on the adaptation of existing Grid Code toward VRE penetration in each network based on government regulations and scientific journals not only in Indonesia but also abroad.