--- title: "SCADA in a power system" subject: "Power Plant Equipment" chapter: 4 key: "semester_7/power_plant_equipment:scada-power-system" source: https://www.bctengineer.com/q/semester_7/power_plant_equipment/scada-power-system site: BCT Engineering --- # SCADA in a power system Power Plant Equipment · Chapter 4: Substation Equipments - Asked in: 2070 Asar, 8 marks; 2081 Bhadra, 6 marks; 2080 Baisakh, 4 marks; 2074 Chaitra, 4 marks (asked 4 times) - Video: [What is SCADA In Power System ? Explained | TheElectricalGuy](https://www.youtube.com/watch?v=M2TUCd_hyHQ) — Gaurav J - TheElectricalGuy - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/power_plant_equipment/scada-power-system - Whole chapter: https://www.bctengineer.com/md/semester_7/power_plant_equipment/chapter-4 ## Question Describe how a SCADA system can be implemented in a power system. ## Short answer An RTU at each substation acquires data from CTs, PTs and IEDs, transmitting it over fibre/PLCC using IEC 60870-5-101 to a master station with HMI. Steps: survey points, install RTUs and communication, set up redundant servers and databases, test. Functions include data acquisition, supervisory control, alarm recording, and EMS applications like AGC. ## Answer **SCADA (Supervisory Control And Data Acquisition)** is a computer-based system that collects real-time data from power stations and substations, shows it to operators at a control centre, and lets them control equipment remotely. #### Architecture ```text +-------------------------------+ | Master station (control ctr) | | SCADA/EMS servers, HMI, data | | historian, alarm printer | +---------------+---------------+ | communication (fibre, PLCC, microwave, radio, GSM) +------------+------------+ | | | +---+---+ +---+---+ +---+---+ | RTU 1 | | RTU 2 | | RTU 3 | +---+---+ +---+---+ +---+---+ | | | CT, PT, relays, CB aux contacts, OLTC, transducers in plant / substations ``` #### Components 1. **Field devices:** CTs, PTs, transducers, breaker status contacts, tap-position indicators, intelligent electronic devices (IEDs, numerical relays). 2. **Remote Terminal Unit (RTU):** installed at each substation/plant; acquires analog values (V, I, MW, MVAr, f) and digital status (CB open/closed, alarms), converts them to digital data and executes control commands from the master. 3. **Communication system:** carries data between RTUs and master using protocols such as IEC 60870-5-101/104, DNP3, Modbus, IEC 61850. Media: optical fibre (OPGW), PLCC, microwave, radio. 4. **Master station:** servers and software that poll RTUs, process data, raise alarms, store history and run applications. 5. **HMI:** operator consoles with single-line diagrams, trends and alarm lists. #### Implementation steps 1. Survey the plants/substations and list the points (analog, digital, control) to be monitored. 2. Install transducers/IEDs and RTUs in each station and wire them to CTs, PTs, CBs and isolators. 3. Build the communication network (e.g. OPGW fibre with PLCC as back-up) and choose the protocol. 4. Set up the master station with redundant servers, database of all points and HMI displays. 5. Test point-to-point, then commission and train operators. #### Functions in a power system - **Data acquisition:** voltage, current, power, frequency, energy. - **Supervisory control:** open/close CBs, change transformer taps, start/stop units. - **Alarm and event recording** with time stamps (sequence of events). - **Trend and historical data** for analysis. - **EMS applications:** automatic generation control (load–frequency), economic dispatch, state estimation, load shedding. - **Distribution automation:** fault location, isolation and restoration. #### Advantages - Fast, accurate information and quick fault response. - Fewer staff at unmanned substations. - Better reliability, economy and security of supply. In Nepal, the NEA Load Dispatch Centre at Siuchatar uses SCADA to monitor and control the integrated grid. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What does a Remote Terminal Unit (RTU) do? A. Acquires analog and digital data at the station, converts it to digital data and executes control commands from the master B. Stores all historical data for the whole network C. Carries data between stations as the communication medium D. Displays single-line diagrams to the operator Answer: A. RTUs are the field-side interface; the master station and HMI do storage and display. (Key point: RTU function) 2. What is the master station's job? A. Measure current using CTs at each substation B. Poll RTUs, process data, raise alarms, store history and run applications C. Modulate speech on a high-frequency carrier D. Switch generators on its own without operator input Answer: B. The master servers collect and process data from all RTUs; HMI consoles present it to operators. (Key point: Master station) 3. Which sequence best matches the SCADA implementation steps? A. Set up master station, list points, test, then install RTUs B. Build the HMI, commission, then survey the plants C. List points, install transducers/RTUs, build communication network, set up master station, test and commission D. Install RTUs, commission, then choose the protocol Answer: C. You must first know the points to monitor, then equip stations, link them, build the master and finally test. (Key point: Implementation order) 4. Which of these is a supervisory control function of SCADA? A. Replacing the CT in a substation B. Choosing the conductor size of a line C. Winding the transformer coils D. Opening and closing circuit breakers and changing transformer taps remotely Answer: D. Supervisory control means remote operation of CBs, tap changers and units from the control centre. 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