Generator
Speed measurement / alarm
A coal power plant generator is necessary to produce electricity in a coal-fired power plant.
A turbine-driven electrical generator contains a stationary stator and spinning rotor. In operation, it generates up to 21,000 amperes at 24,000 volts of three-phase alternating current (approx. 500 MW). This is a critical part of how coal generates electricity in the power plant.
The rotor spins in a sealed chamber cooled with hydrogen gas. The system requires special handling during startup, with air in the chamber first displaced by carbon dioxide before filling with hydrogen. This ensures that a highly explosive hydrogen-oxygen environment is not created.
In this application, monitoring the speed of the rotor using a two-wire NAMUR sensor is very important to avoid over-speed, a critical factor in ensuring that the coal power plant generator operates efficiently. A solution for rotor over-speed protection is to use the PR 5725D programmable frequency indicator adding local readout and 2 relays for over-speed alarms and sensor error detection. The 4...20 mA output signal from the PR 5725 is connected directly to the control PLC.
What are frequency to current converters and what are they used for?
Application:
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What instrumentation challenges exist in coal-fired power plant generator monitoring?
Generators in coal-fired power plants produce high electrical and magnetic fields that create severe electromagnetic interference for nearby instrumentation. Temperature measurement of stator windings, cooling gas, and bearing oil requires signal conditioning that rejects this interference while maintaining measurement accuracy. PR Electronics devices with greater than 60 dB signal-to-noise ratio and 2.3-2.6 kVAC galvanic isolation prevent generator electrical noise from reaching the control system. The PR 4179 AC/DC Transmitter monitors generator output current and voltage for load management and protection.
How does PR Electronics support generator protection and monitoring in power stations?
Generator protection requires monitoring of multiple parameters: stator winding temperature (via embedded RTDs), bearing temperature, hydrogen or air cooling system temperatures, exciter current, and output power. PR Electronics provides the PR 5437A for head-mounted RTD conversion at the generator, the PR 4116 for DIN-rail multi-input signal conditioning with alarm relays, and the PR 4179 for AC current and voltage monitoring. For safety-critical generator trip functions, the PR 9116A Universal Converter provides SIL 2 certified signal conditioning.
What role does the PR 4179 play in monitoring coal electricity generator output?
The PR 4179 AC/DC Transmitter converts generator current transformer (CT) and voltage transformer (VT) secondary outputs into isolated 4-20 mA signals for the DCS or SCADA system. It accepts AC inputs from 0-1 A and 0-5 A CTs and AC voltage inputs for generator output monitoring. This enables real-time monitoring of generator load, power factor, and phase balance from the control room. The 2.3 kVAC galvanic isolation protects the DCS from high-energy transients that can originate from generator switchgear operations and fault events.
