DEVELOPMENT OF PLC BASED CONTROLS FOR A HYDROELECTRIC POWER PLANT

Abstract

A hydro power station needs simultaneous measurement and control of a number of variables located in different places in the station using suitable instruments placed close to the respective variables. The measurement data from these instruments can be acquired and control implemented simultaneously, centrally and reliably by networking them with a computer using RS-485 for communications [1]. The thesis work is carried out taking a hydro-turbine generator test rig in the laboratory of Alternate Hydro Energy Centre as the test system of 1.5 kW capacity. The measurement data is acquired from the remote data acquisition modules namely analog input module and frequency/counter module. Speed and load control are implemented using digital output module whereas the excitation control is implemented using analog output module. All these modules are connected to the PC by means of RS-485 network. The RS-232 port of the PC is converted to RS-485 port using a RS-232 to RS-485 converter module. Data acquisition and control logic is implemented in Labview by calling the appropriate SubVI's corresponding to the remote data acquisition modules. This enables online monitoring of five parameters speed, inlet head, outlet head, valve position, differential pressure at Venturi and consequent control of three parameters namely speed, load and excitation.