Transmission Control Center Desks
The transmission control centre is the real heart of every utility’s power system operations. Typical transmission control centres have three main desks – the generation, transmission and scheduling desk.
The transmission desk is basically responsible for overall security of the bulk power system. The transmission desk runs different kinds of analysis on the transmission system, constantly looking for weak spots and constantly asking “how can I get out of this?”
The system operator has several tools at his or her disposal to perform these analyses:
- State Estimator
- Power Flow
- Contingency Analysis Application
- Optimal Power Flow
- Security Enhancement
This is the main application that is the eyes, ears, and arms for the operator. Through this application, sensors in the field send in data into the control center. Alarms get issued when data exceeds one or more limits that are set for them. SCADA also allows the operator to control devices in the field, such as open/close circuit breakers, change transformer taps, and so on.
It could even be something like the status of a substation door (open/close).
The incoming data from SCADA has all kinds of variables—generator output MW, MWh, MVAR, and MVARH, power flow values through lines measured either in MW and MVAR or current values in amperes. Much of this data is sensed in the field, collected by devices called RTUs or IEDs, which then send the data to the control center through a dedicated set of communication lines.
SCADA has one main problem. It does not know if the data is accurate or not. It cannot also confirm whether the circuit breaker status is open or not, even if the data that comes in says so. These errors could happen due to the meter either reading wrong or just malfunctioning.
It could also happen if the meter parameters are adjusted in error, leading to inaccurate conversion from raw to engineering units. When this happens, the information is still reported as is, and this is where the state estimator comes in.