AboutDave Nyce Expertise I have been an electronics engineer for 25 years. I can answer questions on analog and digital circuits and my specialty is sensors.
Experience I am the inventor on 23 US patents, and also some foreign ones. Developed sensors for over 25 years. Licensed private pilot (airplane and rotorcraft), have HAM radio license. I'm not an expert in computer networking.
Expert: Dave Nyce Date: 12/24/2006 Subject: Gas Turbine Generator
Question 1.In the protection system of generator, there is under/over frequency relay. How does this relay detects the under/over frequency? Does it has anything to do with the load demand?
2.For generator, the speed is constant. Let say 15000rpm. this is the speed of the turbine that drive the generator. When there is a demand for more power, how can the generator do it. What are the factors that can increase the generation since the speed is fix, the frequency is fix. Or how can the generator increase the power generated? If we increase the fuel, the speed that rotates the turbine hence the generator is still constant. So how can generator do it?
3.Which one comes first. We increase the generation to cater to the load demand. For example,early generation is 4MW, then suddenly the operation guy said want to start 3 big motors with total 2.5MW. So we need to adjust the generator to increase another 2.5MW which at the end the total generation will be 6.5MW. So we are providing the power first prior to motor starting. If we do not increase it at first, and then the motor starts, the power might not be sufficient ie 4.5MW only.And can cause tripping
Or generation will automatically increase when the 3 big motors been started? So at the end the total will be 6.5MW. The load is increasing simultaneously with the starting.Actually I do not know how to ask this question.
Answer 1. There are several ways. One way is to use a counter that counts the frequency signal for a fixed time period, the number of clocks counted in that time period is proportional to the signal frequency. Another way is to use a schmitt trigger to activate a fixed time period one shot. Then filter the one shot output to get a DC voltage that represents the frequency.
2. When power demand is low, it is like driving your car on a flat highway at 60 MPH. When demand is high, it's like going up a hill at 60 MPH: it means that you have to give it more gas even though you are still going 60 MPH. i.e. when more power is needed, the generator requires more torque to turn it at the same speed.
3. First the motor turns the generator to get 60 HZ. Then, if the power demand increases, the frequency will start to drop. To compensate, the motor fuel feed is increased.
All motors will turn at the speed needed to maintain 60 Hz. As power demand increases, as needed, the motors will get more fuel to maintain the frequency and depending on the power demand.
