Analysis on Thermal Behavior of Large Hydrogenerators Operating With Continuous Overloads

Abstract

Large capacity hydrogenerators are operated at overloads during the period of excess water flow in the river or frequency support to the grid at peak hours. The extensive conditions may extend to six weeks with 20% overload for a typical hydropower plant located in the northern region of India. High-power, low-speed, direct-driven hydroturbine synchronous generators (HTSGs) are having resistance in rising temperature and self-cooling techniques to withstand the multiple loading points. This article presents a 250-MW CB 870/300-28 HTSG machine modeling along with electromagnetic design and simulations through a three-dimensional finite-element analysis software. The temperature distribution of the machine, operates at 10% and 20% continuous overloads, are explored via a coupled thermal and fluid-dynamical analysis. The simulated thermal results at continuous overloads are presented and are validated with a case plant's test report. A parallel study when the load goes unbalanced at overloads is done through simulation and a prototype validation of a 2.2-kW machine is substantiated in addition. The strength and flexibility of the operation of this machine assist the generalized results to operate at 20% overload continuously with the utility of thermal distribution.