ECT has been made analogous to starting a car. The operator inserts a key and turns to the “ON” position. The control system conducts a system safety check, and only when no malfunctions are found a start is permitted. If a fault condition is found, it is displayed in the programmed language. If the system is OK, the operator will then turn the key to the spring-loaded “START” position momentarily and release it, as in starting a car. The PLC will then automatically conduct the start sequence, including pre-warming the turbine, slow acceleration to synchronous speed, synchronize and command the breakers closed. The PLC then automatically shifts to back-pressure control (for back-pressure induction generator applications) or to speed-governing (for synchronous generator applications). The control software checks critical system parameters 5 times per second, and will initiate alarms and shut-downs as required to protect the turbine. The PLC based controls can be integrated with plant-wide DCS Scada systems, and even be remotely monitored using the Internet. In general, no dedicated turbine operator is required.
ECT panels are provided with the various fault Monitoring and Protection systems
• Over speed / Over frequency
• Under speed / Under frequency
• Earth leakage trip
• High Temperature trip of bearings and Lube oil
• High Temperature of Generator Winding
• Low Lube Oil Pressure
• Low air pressure to the control valve
• Reverse Power relay with time delay
• Emergency Trip
In case of any fault the turbine is tripped immediately and audio visual indications are turned on for operators attention HMI also indicates the type of the fault occurred
The ECT control panels have the following:
1. POWER PANEL:
It has circuit breaker (MCCB or ACB) Current Transformers, Bus bars, Various metering instruments such as Ammeter , Voltmeter, Power factor Meter, kW meter, Energy meter and indicating lamps, fuses etc
2. INSTRUMENTATION PANEL
It contains PLC, DAC (Digital to Analog Converter), ADC (Analog to Digital Converter) Trip Indicators, HMI, and Emergency push button, key to turn on turbine etc. The main function of PLC is to monitor the system all the time and to control the backpressure accurately. Back Pressure is controlled by PID action, which is an inbuilt function of the PLC. PLC compares the backpressure set point and actual pressure .If two are not equal then it opens or closes the pressure set point and actual pressure. If two are not equal then it opens or closes the pressure control valve through DAC to match them closely
3. Best-of-breed maintainability
The ECT is constructed from only 160 individual components, including fasteners and other small parts. It takes about 4 hours to assemble from single components, using a set of simple wrenches, without any special tools or fixtures. Most parts can be handled easily by one person or two at the most, making cranes and other material handling equipment unnecessary for maintenance.
Al major repair/maintenance actions can be accomplished within a short time, even replacement of a turbine wheel or gearbox internals, only done by one mechanic. This makes the ECT the most “maintainable” one of all steam turbines.