ROCOF setting for industrial plant

[JakeLong]

Hello,

I'm working on a project regarding relay settings for an industrial plant, <10 MW. They are able to supply the plant fully through their syn. generator or through their connection to the grid, or a combination of both. It's been decided that they want ROCOF protection on their incomer relay, to trip the grid in the event of fast frequency changes.

I'm having trouble finding concrete information on calculating the settings of this relay, and was hoping some of you might be able to help me.

 

[crshears]

First things first . . .

At what voltage level is this facility connected to the grid? And how was it determined there could be enough grid ROCOF to warrant the expense of this protection?

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[JakeLong]

Of course, the facility is connected at 10 kV. The ROCOF function should only be turned on the incoming relay which already has this function available. I think it's a way of future proofing the plant. But it might be that the over/under frequency stage is enough in it self.

 

[bacon4life]

What are you hoping to accomplish by tripping the connection to the utility grid? I suspect you cannot find info on appropriate settings because it tripping the plant connection to the grid during a frequency drop will make the whole grid less stable. The trend in the USA has been to add requirements for generators to stay connected for minimum durations during frequency disturbances.

 

[davidbeach]

The setting requirements, if they exist, should be spelled out in the interconnection agreement. But as mentioned, the requirements are generally to stay connected to help the system ride out the event. The exception is that separation is allowed when the connection to the transmission system is lost.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[waross]

I understand that the plant may or may not be co-generating.
Will ROCOF be active at all times or active only while co-generating?
Have you evaluated the effect of block loading on the plant generation if ROCOF disconnects while the plant is drawing a substantial amount of power from the grid?

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[redlinej]

ROCOF on the main is used for anti-islanding protection to separate the plant from the main in the event the mains fail to prevent the generator from feeding out to the grid and creating its own island. Also, the relay signals the genset to switch modes from fixed kW mode to isochronous or droop mode.
Research G99 relay protection to see how to set the ROCOF protection.

 

[waross]

Thanks redlinej.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!