DEAR friends I am new to this forum.

We, are operating a big fertilizer complex comprising Ammonia plant Urea and Di ammonium Phosphate. Our Ammonia is an old plant, design for 60hz power, purchased and relocated from USA. We have no other option to operate our plant on 60hz. Any effort to convert it on 50hz needed major design modifications. We have our own generation, powered by two GE frame 5 gas turbines approximately 23MW each, 13.8kv, 60hz ( American system). Complex total load is around 22 TO 23 MW. BOTH TURBINES RUNS IN PARALLEL AND SHARE 50 -50 LOAD. Two Gas Turbines (GT) are operated in Combine Cycle mode with HRSG. With One GT in "Droop" mode one in " Isochroous" mode controlled by GE Mark 5.

We are planning to sell our surplus 45% power (60hz) to utility grid at 50hz. For connecting 50 c/s utility grid we have to sought a solution which is most reliable and least disturbing to our system and productivity. As the grid to which we are planning to connect is far much bigger then our system approximately 2000MW or even bigger.

Power we trying to put on 50hz grid is approximately 15 to 20 MW. With the following details; GENERATION VOLTS: 13.8KV. 60HZ, 3 phase GRID SIDE CONNECTIVITY OPTIONS: 132KV OR 11KV AT 50HZ. We need your help to sought most feasible and economical solution in this regards.

Please clarify the following:

1) What could be the possible ways or technical means to synchronized two different systems.

2) What type of Frequency Converter you can offer and would be most suitable choice in our case.

3) Static or Rotary ? which design could be most suitable choice.

4) What type of stability issue may encounter if two system are connected through Frequency converter (static or rotary).

5) Or any other convenient reliable solution for this scenario Hoping the early response from your side.

Best regards,
Waqas

[email protected]

 

You will have to install a "Motor Generator Set" which will run on 60 Hz and will generate 50Hz.

 

I find this a very interesting question, and not just because it's been asked twice.

With the frequency problems of the so-called 50 Hz grid in your part of the world, why in heaven would you want to subject your plant to this kind of torture?

You should be asking this question of the major electrical equipment manufacturers, and see if they have some kind static converter which would "de-couple" the two systems. An AC to DC to AC system.

If you use a rotating exciter, you will likely not be able to maintain a stable 60 Hz in your plant.

 

Wagas, operating a 60 Hz machine at 50 Hz is do-able, at least theoretically! That said, then, what are the concerns?

1) I suggest you review jojo's comments in Control.com's thread # 1026249406, responding to a similar question posted in July '08.

2) Adding to his comments, problems can arise if the generated wave is substantially distorted when compared to a sine-wave.

3) Also any device designed for 60 Hz, such as PTs, CTs, circuit breakers, control devices, protective relays, etc, may exhibit substantial performance inadequacies when operated at 50 Hz.

4) Other concerns are the effects lower frequency will have on the generator's parameters. One example is that all impedances will be 16.7% lower, thereby increasing its short-circuit duty.

5) If the 60 Hz machine has a shaft-mounted exciter, it may not be abe to handle the field requirement at 50 Hz.

In closing, I believe any course-of-action you take should involve seeking advice of the original machine's manufacturer!

Regards, Phil Corso ([email protected])

 

Wagas, here is an idea based on a study provided for a Pakistan Ammonium Plant in the early '70s. The idea was to simultaneously vary the speed of all process drives, by varying the generator's speed! Following is my suggestion:

1) Provide two 13.8kV busses; one 50 Hz, the other 60 Hz.

2) Connect the older (I have an aversion to the word "old") to the 13.8kV, 60 Hz bus.

3) Install VFDs on your large commpressor drives (induction or synchronous) connectable to both the 50 or 60 Hz busses via interlocked feeder breakers.

4) Use the 13.8kV, 50 Hz, machines to feed grid.

Just food for thought!

Regards, Phil Corso ([email protected])

 

The folks who do HVDC transmission might have a solution. 60Hz at the
generator -> rectification to HVDC -> Inversion to 50Hz at 132 KV or
whatever required voltage.

Regards,
Tomy Zacharia

 

Wargas, what did you decide to do?
Phil Corso

 

The only practical solution for this situation is the use of HVDC system. Try to google on the words as there are plenty of installation worldwide. The ones that I could think of would be the HVDC in Japan and Malaysia-Thailand HVDC link. However usually this kind of installation would be carried out between countries due to the heavy cost involved. For your case, I think it would not be cost effective. But its worth while to give a try and come up with some costing