Hello,

I am an EE student who is designing a 10MW power plant. I am using a synchronous generator which means that I will have to use a synchronizer in order to phase match with the grid. I am just wondering where the synchronizer would be located? (right after the generator or right before the Grid?) Also, I will have several components coming between me and the grid such as a generator step up transformer, generator circuit breaker, surge arrester(s), instrument transformers, relays And I am not really sure which component comes first Could you help ?
Also, would you think that there are any major components that I happen to miss form list above?

Thank you,

 

Hi EE,

You should prepare a Single line diagram (http://en.wikipedia.org/wiki/One-line_diagram) for your project. Some related arrangements are available on the Web.

The synchroniser compares voltages and phase across the generator CB, and closes when both are matched within a tolerance window. The synchroniser automatically ramps up or down turbine speed to get a match. It takes into account CB closing delay and how fast the phase difference is shifting. The Gen CB is usually on the LV side of the step-up transformer.

 

"designing a 10MW power plant"

wow , ok that is a biggie , i hope you only meant "designing a single line diagram of a basic generator to grid scheme". even that is a tough assignment for a undergrad. i am uploading a small doc. this is the IEEE guide for generator protection. this will give you basically the CT, PT, breaker placement with respect to the generator and the generator transformer. there is a section which discusses in detail the protection (which includes the sync check relay relay scheme) for a unit transformer and unit generator scheme. you need to study this document and "visit a power plant" and try to understand and

visualize how things are done.

http://www.2shared.com/document/xS-SuQ3K/C37102-1995-_Generator_Protect.html

"synchroniser" - i hope you meant a sync check relay. there will be two separate PT's one in the generator line and another in the connecting bus. these two PT's are the input to the synccheck relay which checks for

a. phase angle match
b. frequency match
c. voltage match

between the incoming and the bus and gives a command to close(or permissive to close) to the generator breaker.

read the doc and you will get to know more.

 

The synchronizer uses voltages from Potential Transformers, sometimes called relay or metering transformers. One set will need to be connected to the generator output leads (busbars), and the other set will need to be connected to the "bus" or line leads (busbars).

The synchronizer can be located anywhere, because it's connected to the secondary output terminals of the two sets of Potential Transformers, which can be located just about anywhere because the primary input terminals can be connected to the busbars with wires (with suitably rated insulation).

The synchronizer will close a pair of contacts which will be placed in the generator breaker close circuit and which will provide the signal to close the generator breaker provided all the other permissives are met (there is usually quite a long string of contacts from various devices and protective relays that must all be closed to allow the generator breaker to close).

The synchronizer is typically mounted in the area where all the other generator protective relaying and metering is located, because the Potential Transformers providing the signals to the synchronizer will also be connected to many other devices (voltmeters; load transducer(s); protective relays; etc.). So it's convenient to locate all the devices using PT and CT (Current Transformer--something you didn't mention, as well, several of which measure the current flowing in the generator output busbars and the busbars on the bus side of the generator breaker) signals in the same location.

Some synchronizers are used just to provide "safety" for manual synchronization; while other also perform speed matching and voltage matching, two of the other very important aspects of synchronization. So, sometimes they also have outputs to raise lower prime mover speed (to raise and lower generator frequency), and outputs to raise and lower generator terminal voltage (typically through the AVR (Automatic Voltage Regulator)--the device that controls the excitation of the synchronous generator field).

Hope this helps a little more!