Generators wired up in parallel

[fulham sparks]

Can someone explain how it's done please and why? Cheers!

 

[Technician]

One generator on site may not on its

own provide all the power and its

protective devices may cause it to

cut out on overload.

Paralleling generators is the method

of providing the power from more than

one unit, however, if the generators

are AC then they have to be synchronised

and prior to connection the phase rotation

sense has to be checked.

Essentially, all of the primary generators

on the grid are rotating at the same speed

and any part of one rotor is at all times

in the same position with respect to any

other rotor part in each of the turbine halls.

 

[Andy™]

same way power stations are. all sync'd together, and all needed because 1 isnt enough

 

[fulham sparks]

Cheers for that! How are they physically wired in parallel though? How are they connected?

 

[roys]

Look up "droop control" on google, there is a lot better descriptions than I could attemp to write on here. For a generator to be synched the speed has to be adjustable done by varying the fuel governor this alters the frequency and the voltage has to be adjustable this is done by altering the AVR. So basically a cheap chinese genny won't do it.

 

[Technician]

On the grid, the generators (alternators) are connected to the

power station switchgear with massive circuit breakers. I have

no idea about what these look like but they essentially connect

the alternators to the step-up transformers that put the power

out to the grid (National and Super grids).

How much current they carry, have no idea. Check out the Drax

website.

"Synching 0n" is a procedure where the incoming machine is checked

against the grid frequency and the its speed is raised till it matches

the grid frequency. This process may take a day. Following closure of

the breaker the incoming machine is loaded up by gradually increasing

the governor setting till it is just a fraction faster than the other

grid machines.

The rotating machines are three stage steam turbines in HP, IP, and LP

expansion stages (High, Intermediate and Low Pressure) and the Drax turbine

sets have three LP stages. Blade length in these machines is in excess

of three feet and they usually are twin flow turbines.

The turbines all rotate upon one axis and the set heats up as load is increased.

With expansion of the stators, the expansion of the rotors, both the actual and

relative expansions of the sets and the relative movement of the rotors within

the stators have to be monitored and the turbines are loaded up over a period that

could be extensive to ensure that stator and rotor expand at notionally the same

rate. In some power stations the total expansion of the set could be as much as

1.9" measured at the governor end. One turbine foot in the set has to expand so

that the other end can be fixed and this is usually the end where the condensers

are mounted upon the LP sections. Consequently the expansion has to be allowed

and the governor end where the steam from the boiler is admitted is usually the

place where this takes place.

I could go on at length but I think that is about it.

 

[SteveT]

out of my league!!!!!!!!!!!!!!!!!!!!

 

[Technician]

Speed droop; the most important characteristic

of a speed governor. The total drop in speed

with increase from no-load to full load expressed

as a percentage of no-load speed. IIRC.

 

[Sharpend]

Look up "droop control" on google, there is a lot better descriptions than I could attemp to write on here. For a generator to be synched the speed has to be adjustable done by varying the fuel governor this alters the frequency and the voltage has to be adjustable this is done by altering the AVR. So basically a cheap chinese genny won't do it.

I bet they've tried!