Existing generator and grid operation... 1

[SyedUmairAli]

Hi All,

We have LV power plant our all generators running on sharing mode,now we have a project to import power from grid for this we installed 11/.04kv transformer.

We have to synch. our existing system with grid (forward synchronization) & also we need to synch. grid to our system means (reverse synchronization).

My question is when we synch. to grid so what is the mode of our generators, is they running on sharing mode or power mode (fixed load)????

If we purchase only one panel for both forward & reverse synchronization so what we have to instruct the panel maker for both functions???

Waiting for your valuable comments/suggestions, thanks.

 

[dpc]

When paralleled to the grid, the governors for the local generators will need to be in droop mode, not isochronous. Also, the voltage regulators will need to be switched to var or power factor control instead of voltage control mode. If provided breaker status inputs, the control systems can determine if you are tied to the grid and make the appropriate switch in control mode automatically.

But synchronizing will always involve adjusting the local generator speed (frequency), voltage and phase angle to match the system. You won't be able to adjust the grid.

 

[QBplanner]

VR is not necessary to switch to pf or Var control mode. Voltage control mode is also acceptable in some cases. Needs to work with utility side on the operating voltage range.

 

[dpc]

The voltage regulator mode depends on the relative size of the generators in comparison to the grid. A small generator will not operate successfully in voltage control mode when in parallel to the grid.

 

[waross]

I agree with dpc. The grid voltage would have to be rock solid to operate in voltage control mode. Any change in grid voltage would result in a change in the power factor. If there was a drop in the grid voltage, the dropping power factor may result in overheating the generator or a breaker trip, even though the Kilo-Watt load has not changed.
To sync, the generator(s) should be running slightly fast. The synchro-scope should be turning slowly clockwise. Once the breaker is closed, increase the governor speed setting until you have the load that you want. The governor should be in droop mode. Use a Watt-meter to monitor the load, not the ammeter.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[SyedUmairAli]

thanks for your reply,

but i want to know that it is compulsory to run all generators on baseload/fixedload or on load sharing mode??? i know droop mode is good for my situation.

what are the key points to synch. with the grid???what measures we have to take???

 

[waross]

You need someone familiar with your plant and familiar with the utility tariffs and with the contract under which you will be connecting to the grid. You will discuss critical loads and possible operating issues.
For instance, what will be the financial impact of the sudden loss of part or all of your generating capacity? Under some circumstances, it may be better to let the plant go down rather than to incur demand penalties that may persist for one or two years under some tariffs.
This is not a trivial question. The consideration may involve plant operators, senior management, the accounting department, someone familiar with ALL the financial gains and liabilities of co-generation, and someone familiar with the technical aspects of sync'ing and loading co-generators.
To sync, match the voltages and set the generator frequency slightly above the utility base frequency. Possibly +0.25 Hz fast. Close the breaker when the set is in synchronism with the utility and then adjust loading.

Bill
--------------------
"Why not the best?"
Jimmy Carter