This paper illustrates IEC61850 based contingency managed load shedding application implemented at Gasco Ruwais.
The load shedding system is enabled with Primary load shedding for the loads under 132kV switchgear and Overload Shedding based on the 33kV transformer feeder availability. For the primary load shedding the system monitors five digital inputs from generation plant. When any of the five digital inputs received, based on the priorities assigned to each digital input the loads will be shed. Each DI is considered for 20MW load to be shed. When the LS application receives the first digital input, the amount of load to be shed will be 20 MW based on the shed priority assigned. The sheddable load data namely the active power consumption, breaker feeder position and the breaker truck position are communicated to the LS application through IEC61850 and as hardwired from the respective IED. The over load shedding come in to play when one out of the three transformers is running in substation-11A and the overload LS application triggers the fast load shedding action further.
Each sheddable load will collect the respective input data of Power consumption, Feeder position and Shed priority into an array software structure. This structure is called Load Priority Table. Each Load will communicate the Load Priority Table to the master load shed controller, which will summate an Accumulated Load Priority Table from all loads in the plant. The LS will use the Accumulated Load Priority Table as a basis to evaluate the amount of load assigned to each priority and decide the required magnitude of shedding.