Bodnarivka hydroelectric power station has two 300 kW synchronous generators, the established capacity is 600 kW. Generation voltage is 0.4 kV. An automatic operation system has been installed. The main device for station control is a Programmable Logic Controller (PLC). Nowadays PLCs are applied to quickly establish control systems.
TWIDO controller from Schneider-Electric (France) that is designed for small and medium automation is used, which fits the requirements of the given system.
to its discrete inputs: information from monitor control machines (system start and pause, etc), from additional contacts of commutation devices and from the automatic synchroniser on the possibility of connecting generators to the network and other discrete sensors;
to its analogue inputs: information on the voltage values and generator excitation currents, temperature of generator stators and water level values;
to its rapid action discrete inputs: information on the frequency of generator rotor rotation;
through the communication channels: information from the digital multimeters (network parameters analyzers) on the values of the electric parameters of the generators.
A PLC processes the information obtained, defines the status of the system, establishes accident conditions and based on this processed information for both normal and emergency conditions provides:
discrete signals to control switches and other commutation devices (relays etc)
analogue signals to control generator exciters and water drive feeds giving water to the generator turbine blades.
Measurement devices and converters
Electronic parameters of the generators are measured with DIRIS A40 (Socomec, France) digital multimeters with communication modules that transfer the obtained data to the PLC. These multimeters also show the information measured on digital displays.
Since people have better reaction to needle instruments rather than digital ones, needle analogue ammeters and alternating current voltmeters were used for visual presentation of the currents and voltages of the generators.
Controllers measure excitation currents and voltage of the generators by mean of measuring converters (ПНС-1, “PNS-1” – Microl, Ukraine) of direct currents and voltage into unified analogue signals. Magnetic ammeters and voltmeters are used to visually represent these values.
Measurements of temperatures of various zones of generator stators are provided by means of a special PLC module: a module of RTD analogue inputs and PT1000 platinum resistance thermometers (Termoprylad, Ukraine).
Controlled thyristor rectifiers are used as generator exciters (they are using step-down transformers from 0.4 kV busbars) that are known for their rapid reaction and are controlled by unified signals of 0..10 V direct voltage, enabling direct (with no additional conversion) control of the rectifiers from the controller analogue outputs.
Connecting generatrors to the network.
CircutorSynchroMAX (Circutor, Spain) automatic synchroniser was chosen for automatic synchronisation of generators with the network. It receives instant measurements of the voltage of the generator and the network, calculates effective voltages, frequency values and phase difference between the generator and the network voltages and gives signals to lower or raise generator frequency and to connect the generator to the network while taking into consideration the time of turning the switch on.
Automatic synchroniser is turned on by the controller, which also connects measured signals of networks and generators values and is operating simultaneously with the automatic synchroniser. The signals to lower or raise the frequency and the signal to connect a generator to the network are transmitted from the generator to the controller which controls the voltage and frequency of an applicable generator and the operation of an applicable switch.
Two ПНС-2 (“PNS-2”, Mikrol, Ukraine) converters were used to adjust the effective generator voltage accurately to the effective network voltage. They convert alternating current into a unified analogue signal (one is used for the network voltage and establishes the primary value and the other one is used for the generator voltage and establishes the adjusted value).
Commutation devices connecting generators to the network are using automatic switches (Moeller, Austria) with motor drives that are highly reliable and also protect generators from current overload and short circuits.
Power ring protectionTo provide generator-transformer line protection based on the element parameters, the abovementioned automatic switches have been used along with backup protection means such as fuses. The generating system is additionally protected by the PLC which receives measurement data and establishes emergency conditions. In the event of such conditions the PLC produces signals to switch off generators, close the generator turbine deflectors and block thyristors.
Water supply to turbine bladesWater supply control is provided by motor drives that are controlled by Altivar 312 frequency drives. Uninterruptible power supply is provided by means of gel batteries and a Xantrex inverter.
SCADA Supervisory Control And Data Acquisition system
SCADA (Supervisory Control And Data Acquisition) system WinCC (SIEMENS, Gernamy) is used to visualise manufacturing processes, acquire and register measured data and information about the conditions of the devices, mechanisms and the systems in general.
SCADA application enables better adjustment, more accurate measured information, logs of statistical data on the normal routine operation parameters and emergency events. Analyzing this data helps predict the future system operation, understand the causes of emergency situations and prevent them from happening in the future.