AUTO OPERATION OF SMALL HYDRO STATIONS

Abstract

Control and operational cost for SHP contribute to a major portion of total cost. Conventional methods of control, if applied to control SHP, it becomes totally uneconomical. Most of the SHP sites are in remote areas where manpower is unskilled and has little or no knowledge of operation and control. All these factors contribute to increased outage and frequent shutdown of plants. So operation of a SHP should be as simple as possible involving minimum involvement of manpower. For micro hydro range, this problem can be solved by using a shunt load governor, which makes load constant hence reducing the control of generator-turbine speed, gates and valves etc. But this method is uneconomical in large SBPs. Large dump loads are required for it which is not technically feasible. So digital methods of control and monitoring should be applied to reduce the cost. Microprocessor based dedicated systems can be provided for these controls but monitoring problem can not be solved. Modem microprocessor based programmable logic controller (PLC) can solve these problems. The main functions of the controller for auto operation is to execute starting and the shut down sequences under normal and emergency conditions. In addition to these operating sequences, certain control actions like speed control for synchronization (off line control) and speed control when the machine is put on the grid are also to be performed for frequency control and load sharing. The excitation system should respond with respect to the system requirement that is either to control the voltage or to share the reactive power with the other units operating in parallel. In present work KV-300 PLC is considered to achieve certain control functions and ladder diagram for these controls have been developed and simulated. Following programs have been developed and simulated: PID control, staring sequence, emergency and fault shutdown, speed control using PID, synchronizing of two machines. Certain other logic can be developed and simulated for various functions of the plant and integration of these ladder diagrams may lead to auto operation and control of a SHP unit.