Power Factor in a Steam Power Plant

Google = Power factor

Regards JD.

What is the range, how can it useful for good operation of plant.

First of all the power factor is a product of the system, reactive and capacitive loading, REACTIVE is caused by such things as electric motor windings, CAPACITIVE is largely caused by the transmission lines, and this effects the voltage, REACTIVE pulls the voltage down, CAPACITIVE pushes the voltage up, This is monitored by system control, which advises the power plant to adjust the alternator voltage by increasing or decreasing excitation, excitation varies the power factor, its range for good plant operation is a maximum or leading of plus Cos 0.8, the power factor running in a minus direction is not good, as this leads to under excitation, resulting in pole slip, which can be dangerous, so its range is lagging as little as possible, and leading to a maximum of 0.8, and is useful for good operation when close to zero, the company does not get payed for the extra current when leading and produces less heat in the system, resulting in better efficiency.

Hope this explains it a bit better regard JD.

Interesting concept steam power factor correction.

Install a receiver as a capacitor?

In the electrical realm, "power factor" depends on the characteristics of the loads (inductive, resistive, capacitive). The electrical supplier may need to be aware of these, but I am not sure that much can be controlled from the supplier's end. (Nor from the generators in a local or non-grid context).

"Power factor" may have some other meaning as regards steam power plants. Some clarification might help.

Well, you are really talking about the power factor in the generator of the steam power plant, and that is primarily dependent on the power factors of the connected load.

If you supply power to a high power factor load, most all of the generator's output is kws which can be billed for.

If you suppy power to a lower power factor load, some of the generator's output is kvars which are not (usually) directly billed for.

Those kvars use up generator capacity and transmission / distribution line capacity.

I am by no means a generator expert, so I may be off in some points, particularly the next:

I don't know of a way to control the power factor of the generator, you have to "control" the power factor of the loads connected to the generator. That "control" can only be by means of persuasion. (A billing penalty for low power factor is one of those means of persuasion.)

By the way, the kvars relate to the need to build up an electric field in each connected rotating device before the electric power is used for actual mechanical rotation. That magnetizing power is returned to the system (the grid) on each reversal of the supply voltage (each reversal of the sine wave), so it is not totally wasted, but the capacity in the transmission lines and generator is wasted.

Actually you control the Reactive Power, and hence the Power Factor, through the field/excitation current of the generator..

Thanks--I didn't know that!

Re: By the way, the kvars relate to the need to build up an electric field in each connected rotating device before the electric power is used for actual mechanical rotation. That magnetizing power is returned to the system (the grid) on each reversal of the supply voltage (each reversal of the sine wave), so it is not totally wasted, but the capacity in the transmission lines and generator is wasted.

I could / should have gone on to say that capacitors work to increase the power factor by storing that magnetizing power temporarily during the reversals of the sine waves.

If there are power factor correction capacitors in the feed to the inductive load, when the power (i.e., charge) used to magnetize the coils is moving out of the coils during a reversal of the supply current, that charge is moved into storage in the capacitor (in its electric field). As the reversal continues, the charge stored in the electric field of the capacitor is moved back to the magnetic field in the inductive load.

This repeats with each reversal of the supply current.

Thus, with a power factor correction capacitor, that charge has to be transmitted only between the capacitor and the inductive load, not all the way back to the source. Thus the load on the transmission lines and source generator is less.

The generator can generate, and the transmission lines carry more kws because they don't carry the kvars associated with that magnetizing current for the inductive loads.

here is a list of "Power Plant Performance Factors" relating to steam power plants, "Power Factor" is not one of them.

http://www.engineeringtoolbox.com/power-plant-efficiency-d_960.html

Hi Bilal

Power factor is the difference between real power and apparent power, i don't know how you can control this from the steam generation end, apart from installing some power factor correction.

Power factor correction, is used to reduce the line current on inductive loads, if you have motors that have a low power factor connected to the generator system your line current will be higher, than if you had high power factor motors connected.

The way we over come this problem is to introduce capacitor banks to improve the power factor, these capacitor's have a KVAR ratting usually calculated in a binary order for the particular application. To control how many capacitor's are connected to the system at any time, you would have to install a power factor energy management controller.

To install this type of energy management, you would have to have your installation surveyed, by an energy management consultant, this could save you a lot energy.

But, then again if you loads are continuous and you don't have many motors, may be easier to install capacitors on each individual motor.

I don't know enough about your application, to tell you which way to go, But in high power usage applications, the pay back by installing Power factor can be as little as 2 years.

Also by improving the power factor, you get the added bonus of having more power available to run other equipment.

Cheers

Joe

Is it "Plant Load Factor" what he is asking for?

In the UK in 1952 a tannery C W Pittard & Co (trading since 1760 from memory) in Yeovil, Somerset in the south of England use an Allen (an Oxford manufacturer) steam engine coupled with a 150kva AC Alternator to generate as standby capacity for the tannery plant. I must contact my original employer still uses such an item, it became a method of Power Factor correction for the factory. The electrical load on the plant had it's own 750 KVA transformer with an 11kv supply, 415 secondary.

During 1965 when the steam engine was rebuilt for the first time in 18 years the alternator was rebuilt as well. Hand painting lacquer on the windings was nothing new even today, I remember providing the Megger test, hand wind up generated test in those days, forget press button testing. I was the apprentice who undercut all the mica on the commutator probably a two or three day operation, all completed by hand. No Dremels in those days. Connected to a new panel, new everything in controls at the new plant.

On line the power generation was to generate in parallel with the National Grid and the complete NO, NO, there was a reverse current relay to prevent any power being supplied to the Grid. If it had reverse operated the breaker would have thrown out of the Alternator breaker immediately within one cycle I guess.

The power factor on the meter was always .89, very steady, and Unity was mentioned as the ideal. The process to synchronise with the Grid was manual, to adjust the excitation and then at synchronism was to hit the breaker handle or it would throw out the breaker. My incredible boss decided to try after a few days operation with a modern Brush distribution panel, his instruction, "over-excite the exciter and see what happens??? I did and we both were amazed, (although I believe Denis's opinion was it would happen) I observed what I believed was the impossible, a totally incredible result! At the copper busbars we were able to generate at .98, we could produce a leading power factor but that isn't allowed or advisable. I was on day release courses with local Tech Colleges, Yeovil and Bridgwater and lecturer's visited the firm to witness such an operation. They were all disbelieving of such an event. Does anyone else know if it is common practice. The firm got an additional 15Kw every hour for 144hrs per week, unless my calculation is wrong

1948 when the plant was new it was manually changed over to operate zones on the factory production, as electrical load was available. It took a lot of monitoring to check against overload as failure of the electricity supply could be a very expensive error. Leather is a valuable product and critical to be processed on a continuous basis, often for 24hrs. or the leather becomes so much scrap.

Pittard's was the first privately owned business to be allowed to generate in parallel with the National Grid in the South possibly the UK. At that time the Electricity supplier was the Southern Electricity Board many years before privatisation n the UK, privatisation occurred in the mid eighties.

If the OP was referring to electrical generation from a steam power plant, the power factor can be controlled in several ways: 1) by varying the excitation of the exciter field, 2) by having someone in distribution system controlroom switch on or off capacitor banks, and 3) vary the loading on very large inductive motors with built in power factor adjustment controls. The latter is rarely used anymore but used to be the norm in the industry forty years ago or longer. The first choice is by varying the excitation voltage of the exciter, and when the season gets hotter (summer use) the capacitive banks are switched in. This process is generally used to increase line voltages to the proper levels. Large generators can do a great deal to control line voltages with "fine tuning" capabilities. Capacitor banks are generally used when generators in the system are being var loaded at or near capacity. When large changes are required and by being switched in, capacitor banks bring loading closer to normal to allow the generator to run at a normal range. Excitation changes made on the exciter field at this time are made to adjust for final var loading at the generator end.

If the OP is referring to plant loading factor (for the steam generator as opposed to the electrical generator which is being driven by the steam from the steam generator via steam turbine), he needs to specify plant loading factor.