GENERATOR SYNCHRONIZATION

[arnsam]

Hi to all engineers.

May I know if it is possible to synchronize two gensets of different kVA operating at the same frequecief and voltages.

If possible where can I get (purchase)the synchronize unit for two generators of 300 and 500kVA?

 

[davidbeach]

Yes, it is possible. Generator pitch is of much more concern than the ratings. The generators will need controllers capable of operation in parallel with other sources rather than just stand-alone operation. While there are many possible companies to supply the necessary components, I will mention just the one that pays my salary;

http://www.basler.com.

I'm sure that other here will mention other companies that could also be considered.

 

[ScottyUK]

Siemens, GE, ABB, Brush, all make synchronising relays. There are several North American manufacturers who also make them, but I only know them by name rather than having worked on their equipment. No doubt one of the US readers will add their favourites to the list.

You must check that your generators are capable of operating in parallel - there will be a specific mode which enables 'droop' in the governor. Droop is a method of allowing two generators to operate in parallel and share load. At least one generator will also require the ability to accept commands from the synchronising relay to raise & lower speed and voltage. On small sets such as these, the generator manufacturer may the best people to talk to: the Siemens synchroniser was listed at ~£15k last time we priced one. Most small generator OEMs have a range of controllers, from the most basic type through to more sophisticated ones which incorporate the features you need and more. Certainly Cummins-Onan and Caterpillar offer such options.



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[cuky2000]

There are many manufacturers of synchronizer products. Check if the enclose information could help.

http://www.woodward.com/pdf/ic/82383.pdf

 

[rbulsara]

Whether or not the same rating, please make sure that 'pitch' of the windings of the two generators is the same or very close to same, otherwise you will have obectionable (high) circulationg currents

 

[Jari]

Hello Everybody!
This question can be simple but also ….
There were very little information and details about the generators and control system, if these generators are from same manufacture and have same kind of control system then you normally don’t have problems. You must check that these generator control systems have option for running parallel.
They have always designed these control systems that you can add more units. One important thing is also what kind of setting values you have in AVR:s and engine controllers. The droop values must be same in AVR:s and controllers. Responding dynamic also so that they respond with same percentage to any change of active power and reactive power. Somebody mentioned circulation currents, if this problem occur you can put breaker to smaller generator neutral. Always when parallel then other neutral is open.
There are also other synchronizers available, we are using Deif what is very simple.
Some words about control modes for AVR:s an controllers. You can run both with droop and voltage droop. Other possibility is run when you are parallel smaller with kW control and PF control. In that case you must have CT for AVR and power transducer for controller. All the AVR:s and controllers don’t have these options. We are using ABB Unitroll 1000 AVR:s and Woodward controllers (723). The bigger generator can then speed droop and voltage droop. Idea for this is that smaller generator is running base load and the bigger is responding for load. Can be also other way but this give bigger scale for load change.
I don’t know if these smaller generators have isochronous option for engine controller and VDC or Cross current function for AVR for sharing the reactive power and active power. It is also possible run but that needs little bit puzzle the other unit.
It is hard to say what is best solution for you and how important use this (ready to invest some money also)?
With the generators there is not common solution for functions. You must choose from normal modes solution for you what fit your need.
Merry Christmas and happy new Year.
Jari/Finland

 

[jtkirb]

many factors here. You need to be able to match all phases, control speed, control voltage, and control load (unless you desire a manual control)

We use Woodward products for speed and load control.
Basler makes some simple sync check relays

JTK

 

[waross]

I advise a utility that used to use 5 diesel gensets. There were three 350 KW sets and two 600KW sets. They were paralleled as needed acording to the load. Sometimes a 600, sometimes a 600 + a 350, sometimes 2 600"s etc. The cat diesels had hydraulic governors. As long as the droop is correctly set on the governors, the sets will share the load in proportion to their capacity.
Manual synchonization requires a synchroscope. You can use one for each generator, or as we did, one for the plant and a multy pole swiotch to connect it to the generator being put on line. Each generator requires an extra ct, and a Automatic Voltage regulator with a paralleling connection. Also a $3. switch to switch from single operation to parallel operation.
All the paralleling connection is in the AVR is is a resistor that biases the voltage sensing to balance the power factor of the two sets.

 

[waross]

If you're on a really tight budget, get an old text book and look up synchronising lamps.

 

[jtkirb]

text book? hook two 15W, 120 volt CLEAR lamps in series- one end to gen phase A and the other to bus phase A. NOT SUGGESTED wihout a scope, but that is what we do to back up the sync scope. Why? We had a scope go bad and was out of whack by 90deg. I ALWAYS use scope lights to back up a scope.

JTK

 

[ScottyUK]

The lamp connection I recall uses three lamps: connected a-C; b-B; c-A. When lamp B is fully dark and the other two are of equal brightness, you have synchronism or something very close to it. I've also seen it wired for all dark to indicate sync, but I prefer the first connection - I find it gives better 'feel' for judging synchronism on a live system. If you replace one lamp, replace all three together with the same brand and type.


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[waross]

When I started working with a small utility, the instruments always gave a jump when syncronising. That is the volt meters, ameters and watt meters and the syncroscope. The synchroscope would then come to rest at about 15 Deg off center.
I found that when the station was built, someone had taken the voltage refrence for the main buss incorrectly. I can't remember the details, but at the time I calculated that the error was 15 Deg, and that is how much the 'scope would deflect after closing the breaker. Since day one, they had been closing the breaker when they were 15 Deg. off sync. The backup lights used the same connection, and would glow dim after closing.
The bad connection was on the bus, and the generators synced to the bus so it didn't matter which set was coming on-line. The same error affected them all.
I calculated that there was about a 200 volt difference when they closed the breaker. This was a 480 volt station.
Cat diesels, 3 V-8's at 350 KW, and 2 V_12's at 600 KW.

 

[itsmoked]

waross where are most of these small utilities running diesels?? Only one I ever saw was in Dawson, Yukon Territory.

 

[waross]

Small world. Years ago I spent some time in Carmacks, Yukon Territory.
About 200 miles south of Dawson.
I'm a lot further south now. The utility serves an island off Honduras in Central America.
The island is Guanaja. It is the island where hurricane Mitch stalled for four days. The hurricane tore the roof off the plant and rained salt water on the generators for the best part of four days. When we took the cover off the junction box on the first generator, salt water poured out. The cables exited the top of the junction boxes, and were not sealed very well. The water ran down the cables and into the junction boxes. There was a white high water mark at the level of the opening into the windings. It took several days, but we were able to put the generator back in service.

 

[waross]

itsmoked
About 20 years ago, I worked on two small generators (15 KVA, & 40KVA) near Lac La Barge.