SOPD SCADA Systems 5 — Questions and Answers
Question 1: What is the function of the SCADA front-end processor (FEP) or communication processor?
- Render graphical one-line diagrams for operator workstations
- Handle all communications with RTUs, concentrating field data before passing it to the SCADA server (Correct answer)
- Perform power flow calculations for the transmission network
- Archive alarm and event data to the historian database
Correct answer: Handle all communications with RTUs, concentrating field data before passing it to the SCADA server
The front-end processor manages all RTU communication protocols, handles polling or unsolicited message reception, and passes processed data to the main SCADA server.
Question 2: Under NERC FAC-002, what information from SCADA is critical during a facilities study or interconnection review?
- The age and model numbers of all RTUs in the system
- Real-time and historical measurements that define current facility ratings and loading (Correct answer)
- The number of operator workstations available at the control center
- Communication latency statistics for each RTU communication channel
Correct answer: Real-time and historical measurements that define current facility ratings and loading
NERC FAC-002 requires accurate facility ratings information; SCADA measurements provide the evidence of actual loading conditions against established thermal and stability ratings.
Question 3: What is meant by 'SCADA data quality' in the context of power system state estimation?
- The visual clarity of SCADA display screens in the control room
- The accuracy, completeness, and timeliness of measurements used to build the system model (Correct answer)
- The number of data points per substation compared to industry benchmarks
- The percentage of RTUs using encrypted communication protocols
Correct answer: The accuracy, completeness, and timeliness of measurements used to build the system model
Data quality in state estimation refers to whether measurements are accurate, current, and sufficient in redundancy to allow the estimator to produce a reliable converged solution.
Question 4: Which type of SCADA control is used to automatically maintain a substation bus voltage within defined limits by adjusting a tap changer?
- Supervisory control (manual operator command)
- Automatic voltage regulation (AVR) via closed-loop control (Correct answer)
- Sequence of events recording trigger
- Load shedding interlock
Correct answer: Automatic voltage regulation (AVR) via closed-loop control
Automatic voltage regulation uses closed-loop logic within the SCADA or substation controller to continuously adjust transformer tap positions and keep voltage within acceptable limits.
Question 5: What does the term 'ICCP' (Inter-Control Center Communications Protocol) enable in SCADA operations?
- Direct communication between RTUs and operator workstations bypassing the SCADA server
- Real-time data exchange between different utilities' or reliability coordinators' control centers (Correct answer)
- Encrypted storage of SCADA configuration files on backup servers
- Automatic failover between primary and secondary communication channels
Correct answer: Real-time data exchange between different utilities' or reliability coordinators' control centers
ICCP (IEC 60870-6/TASE.2) is the standard protocol enabling real-time data sharing of system conditions, schedules, and control between interconnected utility and reliability coordinator control centers.
Question 6: When evaluating a SCADA alarm flood situation during a system disturbance, what is the recommended operator strategy?
- Acknowledge and silence all alarms immediately to restore screen clarity
- Focus on the first alarms that appeared to identify the initiating event, then work subsequent alarms (Correct answer)
- Disable all non-critical alarm thresholds until the disturbance is resolved
- Log out and let the backup operator handle the disturbance without alarm distractions
Correct answer: Focus on the first alarms that appeared to identify the initiating event, then work subsequent alarms
During an alarm flood, operators should prioritize the earliest alarms to identify the root cause, as subsequent alarms are often consequential effects of the initiating event.
Question 7: What is the primary purpose of sequence-of-events (SOE) recording in SCADA systems during a grid disturbance?
- Automatically restore tripped equipment to service in the correct sequence
- Capture millisecond-resolution timestamps of status changes to reconstruct the event timeline (Correct answer)
- Generate real-time notifications to the reliability coordinator during the event
- Log which operator acknowledged each alarm during the disturbance
Correct answer: Capture millisecond-resolution timestamps of status changes to reconstruct the event timeline
SOE recorders capture device state changes with high-resolution timestamps (1–2 ms accuracy), enabling post-event analysis to determine the exact sequence and timing of operations during a disturbance.
SOPD SCADA Systems 5
What is the function of the SCADA front-end processor (FEP) or communication processor?