I have a simple question for the software. temperature and potential energy are  very important parameters to judge whether simulation system is equilibrium. However, I construt a system of 300 water molecules, 300ps  MD simulation was performed, using NVT (T=277.15K)ensemble. In general, 300ps is enough for the system achieving equilibrium. But i find the temperature and energy does not obtain a stable value, they are fluctuating in the simulation process and  fluctuation range is big. The following figure and stable is temperature and energy change over time. I want to konw

whther the system is equilibrium, how to use temperature and energy to judge the water system is equilibrium.