A water feed deflector control of a hydro generator turbine has been replaced in the framework of Ostapievska hydroelectric power station reconstruction. A thyristor voltage control was used for synchronous generator excitation. Hydro generator operation is controlled by means of an M258 PLC (Schneider-Electric).
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-11, “PNS-11” – Microl, Ukraine) of direct currents and voltage into unified analogue signals. Magnetic ammeters and voltmeters are used to visually represent these values.
Temperatures of various zones of generator stators and slew drives are taken by means of Pt100 resistance thermometers and a converter to МВ-110 Modbus (Oven, Russia).
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 4.20 mA direct current, 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-12 (“PNS-12”, 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 protection
Parametric (based on elements parameters) generator-transformer line protection is provided by means of a peak current protection relay АЛ-5 (AL-5) and НЛ-6 (NL-6), НЛ-11 (NL-11), ЕЛ-11 (EL11) voltage relays.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.
Control of water feed to turbine blades
Control of water feed is realized by means of a deflector control based on a Slew Drive (IMO, Germany). The engine is set for direct current voltage and is powered by storage batteries; this solution allowed to operate the deflector machine even when the in-house voltage was out.
SCADA Supervisory Control And Data Acquisition system
SCADA (Supervisory Control And Data Acquisition) OpenSCADA system (Ukraine). 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.Station hydro generators can be operated in the following modes:
- Based on the water level (water level remains stable)
- Based on the active energy (a generator produces a set amount of active energy kW)
- Based on the reactive energy (a set amount of reactive energy kVAr can be generated or power factor can be used)
- Autonomous mode (operating without synchronization with the grid for the dynamic active load) (station in-house needs)
- The generator can work alone as well as with other generators.
- Manual local control (all operation modes can be regulated directly at the generator)
- Manual remote control (all operation modes can be regulated by a distribution board in the central control room)
- Automatic control ( with an HMI panel of generator operation board in the operation room and with the SCADA system by means of a computer from the operator’s room)
- Automatic remote control (by means of the WebServer through the Ethernet by means of WebBrowser)