Hi friends,

I'm facing problem in display value of Grid power. Grid power display value in genset controller is different from protection relay value.

for lower values 200 kw or 400 kw these values are same, but at higher values 1200 kw or 1300 kw there is 250 kw to 300 kw difference. So please help me to solve this problem.

Regards
devendra

 

devendra,

You really haven't provided very much information to be of much use in providing a meaningful response. Which value is higher?

However, most of the time these problems happen because the two meters use two different sets of CTs/PTs for their sensing, and some "auxiliary" power losses are reflected in the difference.

So, you will need to look at where the two meters derive their signals to understand the difference--which will most likely be "auxiliaries" (lights; fans; pumps; etc.).

In other words, a generator produces "x" KW. And a plant requires "y" KW. That means the amount of power available to export to the grid or the load is "x-y"--hence the difference between the meters.

Some plants even have automatic transfer switches to change from grid supply to local (in-house) supply for auxiliaries when the load gets above a certain level.

Without being able to see the schematic drawings for the generator-set and the protective relays at your site, it's very difficult to say with any certainty what the difference reflects--but it's not unusual for there to be a difference at many sites.

Hope this helps!

 

Another thing to look at is the accuracy of all the equipment used to obtain the reading. In particular, CT's used for protection are not as accurate as those used for metering. Metering CT's are specially designed to provide high accuracy and linear response at normal power levels. Protection CT's sacrifice accuracy at normal power levels to provide accurate (much less then metering though) readings at high fault level currents.