Multi-cycle cooling system adopting seawater for cooling

The invention relates to a multi-cycle cooling system adopting seawater for cooling, which fully utilizes the advantage that a mature deionized water technology is used as a cooling medium and the convenience of seawater resources, solves the problems of high seawater corrosivity, marine biological pollution, difficulty in water taking and the like, improves the reliability and stability of an offshore platform system. For cooling of core equipment of the offshore platform such as a converter valve, a transformer and a heating and ventilation system, the aging problem of a heat exchanger with long working time is considered, the performance of the core equipment is evaluated, control parameters of the whole circulation system are adjusted, the cooling effect is ensured on the basis of ensuring energy conservation, the stability of the whole circulation system is improved, particularly, an intermediate isolation loop is additionally arranged between cold source seawater and deionized water circulation, oil pat