Unequal Load Sharing Between Generators

Paata,

Welcome to the forum.

We wish you will contribute and learn from this forum.

Your first post was indeed very well written, and lot of details have been included.

The problem you are facing can be because of many reasons.

a) Is your LSM 201 have load sharing lines ? If yes, are they connected?

b) Check the AVR droop setting. Keep it same for both generators.(typically 2%)

c) Also check for proper screening of signal cables.( ground the screen at one end preferably at LSM end).

d) Check the CTs of both gens are they corectly connected.

e) If all these have done, change LSM and check.

The generator which produces more voltage will hog away the reactive load ( kvar), and the generator which is running at more speed will hog away the active load.(kw).

Please keep us posted on the status of your problem.

Good luck

Thank you very much for prompt response, comments and recommendations.

I have been out of plant for several days and supposedly will be there in few days. So I can not provide you with information regarding equipment's on site installation details so far. Once I am on site I'll carry out all checks as per your suggestion. For time being I can only provide you with general info regarding generation system: it was commissioned almost four years ago. The problem I discussed, developed just several months ago, actually we never faced this problem before and in my opinion all installation works must have been done properly. However, once I am on site I'll carry out all checks anyway.

Thanks again,

Paata

1) Please confirm whether these machines are already running and problems developed recently ?

or The machines are under commissioning stage.

The problems are purely on adjustments of LSM.

For proper Reactive power sharing the voltage control is necessary.

Ramesh,

Thanks for prompt reply and recommendations.

Our plant generation has already been commissioned and generators have been running for almost three years. The problem I discussed was developed recently - for about several months. So as per your suggestion I will try to make some adjustment on LSM and AVR and see what happens.

Thanks and Regards,

Paata

No.

If the sets are already in operation for three years and the problem cropped up recently,Possibilities are

1) some one would have altered the settings.

2) one of the controllers become faulty.

3) Some bias /control cables Loose connection.faulty.

There must have been some incidence took place in around generators.Please examine.

The problem may be minor.

Thanks, I agree with you.

On site installation must have been done properly by vendor's representative, otherwise sets wouldn't work properly from the beginning. I am pretty sure, that no alterations have been done to control system settings. Consequently, checks must be carried out according to items 2) and 3).

Question: what will be the worst condition or what operating mode can generation develop in case problem not solved ?

Hello Paata,

Thanks for the feedback.

As the reactive load is showing disparity when load changes, it points to AVR not responding. The one which not sharing/picking the reactive load is the one which is sluggish.

It will be process of elimination for ( LSM/AVr) before you can come to the solution.

Answer:

It can create lot of problems like reverse power, trips,and alternator overheating etc.

The sooner it is sorted out the better.

Good luck.

Thanks for prompt feedback and advise,

If I correctly understood, reverse power trip will occur if generator G1 starts motoring, i.e. starts consuming both active and reactive power followed by alternator (rotor) overheating. As for G2, it should be overheated as well even before G1 starts motoring, since G2 should be taking the whole reactive load thus significantly increasing total current value in stator windings. Am I correct ?

Hello,

The problems regarding unequal load sharing and load hunting have been sucssesfully solved. Your suggestions really helped. Adjustments were done as per instruction manuals of LSM and AVR. Actions and results are given below:

1). Adjustment of "SENSITIVITY" setpoints on LSMs - equal active load shearing achieved;

2). Adjustment of Gain regulators on engine controls - hunting eliminated;

3). Adjustment of "VOLT ADJ." setpoints an AVRs - voltages values brought to normal;

4). Adjustment of "DROOP ADJ." setpoints on AVRs - equal reactive load shearing achieved;

The thing is, that for unknown reasons potentiometers on AVRs and Gain regulators were adjusted at different setpoints. In addition, devices probably developed some problems in time which could be the reason of some deviations in setpoints.

For time being system is working steadily.

Many thanks for support and cooperation.

Regards,

Paata

Good.We are satisfied at least we helped someone thro this forum to solve the issues.

In this state of affairs you can not run the sets in parallel, this will lead to reversepower and one set tripping and consequently tripping the second set on over load.

One of the AVRs may not be functioning effectively.

You can check this by running the sets individually and loading each set from 0% to 100%.Observe the voltage variation ,this should be same for both the sets.Please check.

Thanks Ramesh,

Everything is clear. All I need to do is to carry out several checks on site. I will keep you informed.

Dear forum group,

I found the interesting thread discussion and I wonder if anyone here may suggest how to estimate the additional power consumption by having a malfunctioning AVR.

Thank you.

Dear Mr.Paata,

1. Few weeks back a similar topic appeared and several members have given valuable points. Few conditions are to be satisfied for Parallel Operation, as all of us know.

2. The Important Character for Load Sharing is PRIME MOVER (TURBINE OR DIESEL ENGINE) GOVERNOR DROOP CHARACTER, and ALTERNATOR VOLTAGE DROOP CHARACTER, and WILL DECIDE LOAD SHARING PATTERN. The LEAST DROOP CHARACTER WILL SHARE MORE OR HIGHEST LOAD.

3. In your 2nd Point you have stated that the G2 takes MORE LOAD - which CLEARLY INDICATES IT HAS A SHALLOW DROOP CHARACTER ( LESS SLOPE or GRADIENT OF DROOP Vs. LOAD) than G1.

4. In your 3rd Point You have mentioned G2 takes more Re-Active Load. This is understandable since for the higher kW, kVA has to be high and hence kVAR will ALSO have to be HIGH and we know kVAR^2 = kVA^2 - kW^2.

5. YOU have not given the 2nd Generator Capacity. Is it possible to get the DROOP Character for Governor and ALTERNATOR and post.?

THANKS,

DHAYANANDHAN.S