1st Step Load Shedding

February 13rd 2013 10:49, Java Bali grid total load demand was 19,442MW. Paiton #3 supplied 815MW and Tanjung Jati B #2 450MW. Somehow Paiton #3 trip and the frequency drop from 50Hz to 49Hz but it was not a topic that will be rise up on this post.

One-thing that more important is how the responsive of Tanjung Jati B#2 turbine control.




Paiton #3 is the biggest power plant in Java with total capacity 815MW and Tanjung Jati B #2 660MW also the biggest power plant was before Paiton #3 in commercial.



At the time just before Paiton #3 trip, Tanjung Jati B #2 already set to Governor mode. What is different between Governor (Gov) and Load Limit (LL) mode? You can read on http://anto-hendarto.blogspot.com/2012/07/free-gov-and-ll-mode.html but still can't make the reader satisfied or make confusing.

We are trying to add animation picture of turbine control while the frequency got disturbance for example one unit got trip and from that animation picture we can describe the summary as below.



I am sorry for not clear animation above, please click below this for clear animation picture.
http://i1180.photobucket.com/albums/x403/antohendarto7/Paiton3trip_zps1bfb3147.gif

1st even: Paiton #3 815 MW trip, the grid frequency drop below 50Hz.

2nd even: Frequency 50 to 49.7Hz, some power plant including Tanjung Jati B #2 turbine control still not response yet due to still inside Free Governor area (dead band set 49.7 Hz to 50.3Hz).

3rd even : Frequency 49.7 to 49.3 Hz, Flow Demand and CV Flow Demand fast increase from 71.7 to 81.8% (Flow Demand increase when frequency decrease). Governor set is a little bit decrease from 71.7% due to Load tend to increase causes by Turbine control valve react to open get signal from CV Flow Demand. Load limit set 81.7 (10% more that Governor set).

4th even : Frequency at 49.3Hz Flow Demand and CV Flow Demand separately (Flow Demand is higher that CV Flow Demand). Flow Demand is increase as frequency decrease. CV Flow Demand as line as Load Limit set. Governor set in rapid increase following Load Limit set 82.4% due to Turbine control force to manual control (Boiler Follow Mode).

5th even : Frequency at 49Hz is 1st Step Load Shedding 55MW. The Frequency start to increase and Flow Demand start to decrease as well. For detail information, please visit http://anto-hendarto.blogspot.com/2013/01/grid-disturbance.html. or http://anto-hendarto.blogspot.com/2011/12/load-shedding.html.

6th even : Flow Demand touch the Load Limit line (not describe on animation pic) after frequency back to dead-band (free governor area), Unit can be back from Boiler Follow to Coordinate Mode.


Governor Mode fact:
Load Limit set is priority The Load set.
Governor set is priority to maintain frequency steady about 50Hz and he react at outside Free Governor area.
Flow Demand is opposite from frequency.

CV Flow Demand is equal with Flow Demand when the value still below Load Limit set.
CV Flow Demand is equal with Load Limit set although Flow Demand is higher that Load Limit set.
Governor set is following the Load value (450MWnet or 500MWgross from 710MWgross is 500/710*100% = 70%).

Load Limit is always 10% above Governor set.
Turbine control force to manual if CV Flow Demand above Load Limit set.
CV Flow demand is fast increase while the value still below Load Limit set during frequency drop.
CV Flow demand is slowly increase if already as high as Load limit set.
Governor set always follow load demand but at outside free governor area and Turbine control force to manual, Governor set rapid follow CV Flow Demand and Load Limit Demand and after that acceleration as fast as Turbine Speed Droop.



The picture above clear explain that dead band 49.7 to 51.3 is for CV Flow demand equal to Flow Demand as blue line. CV Flow Demand equal to Governor set as green line acceleration as speed drop 5% is react when the frequency already 49.2Hz