Remote Control Equipment Overview

Power system operators need data that quickly alerts them to problems and allows for timely corrective action. This data must be in real-time.

Data for SCADA systems needs to be organized for effective analysis and should be available with a fixed memory capacity. Hard copies should be accessible in chronological order.

Displays can be visual (VDUs, mimic diagrams), recorded (loggers), or audible (bells/hooters).

Post-mortem data analysis needs can impose time constraints on data collection and reporting.

Training of operators and maintenance personnel is essential, along with provisions for system modification by designers.

Integrating a new SCADA system with an older one may require careful consideration of power supply, cabling, and parallel operation.

A balanced approach is necessary when designing a SCADA system to maximize data usefulness, considering financial constraints and diverse user needs.

Large-scale computerized systems for supervising and controlling power systems, collecting data (data acquisition) and controlling actions.

The unit at the power station/substation that communicates with the main SCADA system, collecting data and receiving control commands.

The physical and electrical conditions at power stations and substations, impacting equipment like RTUs and transducers.

A critical factor in SCADA equipment, as temperature changes can affect the accuracy and reliability of measuring components like A/D converters and transducers.

Unwanted electrical signals generated by power equipment and controls affecting SCADA systems.

Techniques used to block or reduce the impact of unwanted electrical signals, like noise, enhancing SCADA equipment reliability.

Methods to protect SCADA equipment from sudden voltage spikes called surges, improving system reliability.

Components designed to prevent the intrusion of dust, moisture, or other harmful elements. Important for outdoor use.

Measures taken to prevent rust or damage from the harsh environment to SCADA equipment.

The SCADA system uses Digital Address Time Division Multiplexing (DATDM) for communication between the Master Station and Remote Terminal Units (RTUs).

Each data exchange between the Master Station and RTUs follows a specific protocol, ensuring accurate and reliable information transfer.

The SCADA system stores important data for analysis, including alarms, events, feeder current and voltage, and relay operations.

A dual UPS system provides uninterrupted power to the SCADA system at the Master Station, ensuring continuous operation even during power outages.

The RTU is the heart of the SCADA system at the power station, collecting data and receiving control commands.

The process of continuously checking the state of critical components in a power station, such as circuit breakers, reclosers, and isolators. This includes recording status changes and providing real-time information.

A device that acts as an intermediary between the monitored equipment and the RTU, providing isolation for safety and ensuring compatibility.

The indications for status monitoring are obtained from contacts mechanically actuated by the monitored device. These contacts are then processed by the RTU.

Interposing relays are used because there may not be enough spare switch contacts on the equipment, the distance between the RTU and the equipment may be significant, and for protection against harsh environments.

The supervisory control aspect of SCADA systems allows operators to remotely control equipment, such as circuit breakers, reclosers, interruptors, and isolators.

Control functions are executed through interposing devices that connect to the station control circuits, relaying commands from the RTU to the equipment. These interposing devices ensure safety and compatibility.

A communication system where multiple RTUs share a single communication channel, requiring each RTU to have a unique address for identification.

Factors that influence communication system configuration include the number of RTUs, the number of data points and their update rates, the locations of the RTUs, and the available communication infrastructure and technologies.

Railway SCADA systems often use a party line one-on-a-few configuration, where the master station communicates with multiple RTUs through a shared channel.

Each RTU connected to a party line communication channel must have a unique address to differentiate it from other RTUs. This address is used by the master station to identify and communicate with each individual RTU.

A physical board at the control center showing the status of the traction power supply system. It displays the energized/de-energized state of sub-sectors, interrupters, and circuit breakers.

The MDB's main purpose is to provide an overall view of the traction power supply system to the operator. It's a visual aid for quick system understanding.

The MDB is smaller than conventional mimic boards due to the availability of detailed information on VDUs (Visual Display Units).

Visual Display Units (VDUs) in SCADA systems allow operators to see and interact with system data. They can view diagrams for telecontrol, alarms, trends, and other information.

LEDs on the MDB and/or VDUs that indicate system status, faults, and warnings.

The software that controls the SCADA system, allowing for multi-user, multi-tasking, network communication, and real-time applications.

The VDU displays in a SCADA system are versatile, semi-graphic, and colored. They allow for telecommands, blocking/deblocking control points, viewing alarms, and performing other operations.

VDU displays can be accessed by simple keyboard operations. Predefined options allow for efficient navigation between displays.

The SCADA system continuously scans RTUs (Remote Terminal Units) in a predefined sequence to gather equipment status, alarms, events, and measurements.

SCADA systems, like the one described, are used to supervise and control large-scale power systems by collecting data, issuing control commands, and providing information to operators.

Remote control capabilities of SCADA systems, allowing operators to change the state of equipment like circuit breakers and isolators.

A communication system where multiple RTUs share a single channel, each requiring a unique address for identification.

Communication configuration is influenced by the number of RTUs, the required data points and update rates, RTU locations, and the available communication infrastructure and technologies.

Each RTU connected to a shared communication channel must have a unique address for identification. This helps the master station differentiate and communicate with them individually.

A technique that uses a single communication channel to transmit multiple pieces of information simultaneously.

A technique that divides the available communication channel into separate frequency bands, each of which carries a different piece of information.

A technique that divides the communication channel into time slots, each of which carries a different piece of information.

A unit of measurement for the number of signal changes (or symbols) transmitted per second.

A unit of measurement for the amount of data transmitted per second.

A modem that uses separate timing sources at both ends of the data link to synchronize data transmission. It divides the message into short blocks to resynchronize frequently.

A modem that transmits a synchronizing clock signal along with the data, ensuring precise synchronization between transmitter and receiver.

Efficient for short messages with quick synchronization, ideal for short bursts of data.

Supports very long messages and high data rates, ideal for continuous data transmission.

Asynchronous modems are generally cheaper and slower, while synchronous modems are more expensive but handle higher data speeds.

Using light signals through thin glass fibers for data transmission. This is favored in many power systems due to its immunity to electrical interference, high bandwidth, and flexibility.

Key advantages of optical fiber communication in power systems include high bandwidth, resistance to electromagnetic interference, physical flexibility, and safety in hazardous environments.

Optical fiber communication, while advantageous, can be costly to implement, requiring specialized connectors and training. Short runs may not be cost-effective due to the cost of necessary electronics.

A communication method where information is encoded by changing the amplitude (strength) of a carrier signal.

A communication method where information is encoded by changing the frequency (pitch) of a carrier signal.

Information sent in only one direction from a transmitter to a receiver. Think of a radio broadcast where only the station sends signals.

Information sent in both directions, but only one direction at a time. Think of a walkie-talkie where both people can speak, but not simultaneously.

Information sent simultaneously in both directions. Think of a phone conversation where both parties can speak at the same time.

Communication methods can be categorized as simplex, where information only flows in one direction, half-duplex, where information flows bi-directionally but not at the same time, and full-duplex, where information flows simultaneously in both directions.

A good format is efficient (high information-to-bit ratio), secure (detects errors), flexible (handles various data types), and easy to implement in hardware and software.

A message typically has three parts: message establishment (receiver identification), information (data to be transmitted), and message termination (error checking and end marker).

Message security checks involve performing logical operations on the data to create check bits. These bits are transmitted with the message. The receiver performs the same operations and compares the results with the received check bits. If they match, the message is accepted. Otherwise, a retransmission is requested.

This field helps the receiver identify the correct message among many possibilities and filter out noise.

This field carries the actual data to be sent, encoded for the receiver to decode and use.

This field provides security checks to ensure the message's integrity and also signals the end of the message.

It includes a start marker (S), an address (M), a data or code field (M), a security code (Sec Code), a message end marker (Add.RTU Mess End), and possibly other fields depending on the application.

Synchronization ensures that the receiver and sender are aligned in time, allowing the receiver to properly interpret the incoming data stream.

A unique address allows the master station to differentiate between multiple RTUs sharing the same communication channel.

The Synchronisation field, consisting of two bits (space followed by a mark), helps the receiver identify the start of a new message. It enables the receiver to correctly align itself with the incoming data stream.

The RTU address is a unique identifier for each remote terminal unit (RTU) on a shared communication network (party line). This allows the receiver to select the message intended for it, even when multiple devices share the same communication channel.

The BCH security code is a 5-bit check code included in the message termination field. It allows the receiving logic to detect most message errors and request retransmission if necessary, ensuring data accuracy.

The Select Before Operate sequence is a safety mechanism that ensures accurate control of devices by requiring a specific sequence of messages. This safeguards against unintended actions caused by faulty or rogue messages.