Power Generation: Site Design, Installation, and Connection

[balag5]

  We are using Woodward’s Load share module 9907-175 in the1.8MW CAT Diesel generator (emergency) . The DG works fine in the island mode, but when DG is paralleled with the normal power supply, every time, within seconds of paralleling, DG incomer and normal power incomer trips on reverse power and over-current respectively.  The droop mode has been selected in the load share module during both island and parallel operations. Could this event be because of existing droop setting of load share module or load gain setting? Pls advice the remedial measures to be taken to enable the DG run in parallel mode sharing the load. Appreciate your help.

Thanks,

Gobinath

[mikel]

The load share module is intended to allow the CAT engine to share load with another load share lines type device, such as another LSM or a 2301A Load Share governor. For paralleling to the grid you would need an additional device, like a Generator Loading Control, look up Woodward publincation 82434 for an explanation of how it works.

Mike L.

[sdc-DEIF]

Hi mike

You have an interesting combination of errors.

Reverse power and overcurrent at the same time.

I think that the answer to your problem can be found from the overcurrent alarm. Normally when you run in island you are running with fixed frequency and fixed voltage.

When you run parallel to grid you need to control the power and the power factor. From your description you have with the droop only changed the fixed frequency control to a power control when parallel. Your AVR is still trying to maintain a fixed voltage and as you are connected to the grid then it is the grid voltage it is trying to control. (your generator is large but not large enough for that J)

So when you are running parallel with the grid you need to change the AVR so it controls the Power Factor instead. Then it will automatically accept the grid voltage as its own and this will limit the current. ( simplified explanation). You are not saying what AVR you have but if you have the CDVR this can be programmed using a binary input when parallel.

This might also solve your problem with the reverse power as the droop on the engine is based on the current. As the current is raising as a function of your current voltage control, the your speed setting is lowered driving the engine into reverse power. In principle it might be the delta between the generator voltage and the grid voltage who determines if it is a reverse power or an overcurrent you trip on. Small difference will be reverse power and a larger difference will be overcurrent.

Best regards

Søren Dahl Christensen

DEIF A/S

Technical presales Manager

Plant Management Solutions,

Power Technology Diesel

[see-deif]

Both suggestions above are good things to check.

Has it ever worked or is this a new installation?

I would add IF you have the right load share module(s) on the genset and the mains connection, do you have it connected correctly? A simple pair of swapped wires on the load share lines could do this. You should have 3 wires: KW, Comm, KVAR.

You could use only droop mode if it was enough -- I would start at 5% if you are not using the load share lines -- on both KW droop on the speed control and KVAR droop on the voltage control. You don't HAVE to have KVAR/PF control, but if you don't you will need to adjust the voltage almost constantly

Last suggestion: paralleling is tricky business. Consequences are huge!  Yes, your genset, too, could end up on it's side or it's back!! Broken couplings, sheared shafts, damaged generators...anything is possible.

Do you have a power system study done to determine the correct protective settings, like overcurrent and reverse power?  

Get some help from someone with paralleling experience...you will be happy you did!

Best regards

Steve

[MarianT]

Hi,        

   From my experience with CAT gen-sets on Eneria PS  the Woodward LSM is build to work on load sharing lines, working with anther genset(s).

             When you work on parallel to mains you must have installed one synchronizer (preferred with load control).

             If you have problem with reverse power usually on Woodward LSM it comes from one of CT (is not correct connected and the LSM (or incorrect grounded) and is measuring incorrectly the genset power driving the engine throttle down instead of up when droop mode is active CB on).

My advice to you is when you try to test to keep up all protections down to minimum possible step.

Use procedure from below link: page 16 to 19 (Woodward Manual 02036 (Revision F))

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&frm=1&source=web&cd=1&ved=0CFIQFjAA&url=http%3A%2F%2F...

Best of … parallel time

[KSP_rao]

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balag5 wrote:

  We are using Woodward’s Load share module 9907-175 in the1.8MW CAT Diesel generator (emergency) . The DG works fine in the island mode, but when DG is paralleled with the normal power supply, every time, within seconds of paralleling, DG incomer and normal power incomer trips on reverse power and over-current respectively.  The droop mode has been selected in the load share module during both island and parallel operations. Could this event be because of existing droop setting of load share module or load gain setting? Pls advice the remedial measures to be taken to enable the DG run in parallel mode sharing the load. Appreciate your help.

Thanks,

Gobinath

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Hi,

The  Caterpillar  LSM  doesn't have  a  provision  directly synch  to  Grid   and  Load  share - This  alone  works  as  a  PWM  Sensor  when  grid  synch  is  required - Load  sharing  is  require  another  controller  SPM  Synchronizer  or  to  bias  signal   for  the  speed  input  to  be  connected   to  24, 25 Terminals   with  this  LSM

I  suggest   Woodward   Easygen   controller   enables  this  speed  bias  with  LSM  to  adjust  the  speed  to  take  care  of   KW  Load  sharing  when  it  is  connected  to  grid.   

It  also  require  to  integrate  Voltage  Bias  from  Easygen  to  CDVR  terminals   to  take  care  of  Volge control

Then  Esay gen  to  set  as  base  load  controller  input   from  Synch  breaker  to  Easygen  to  activate  base  load.

Also  proper  tuning/settings  to  achieve  the  above  will  give  healthy  synchronizing.

I suggest  to  take  a  Woodward  engineers  support  to  achieve  these  things.