What is substation and distribution automation?
Substation and distribution automation helps utilities remotely monitor, control and regulate assets and networks in real time. This helps ensure two things:
- A fast and appropriate response to events, such as a power outage.
- Uninterrupted power services for consumers.
Substation automation (SA) refers to the use of data from intelligent electronic devices (more information on IEDs further down) within a substation, which helps utilities comply with grid standards.
Distribution automation (DA) systems are a set of intelligent sensors, processors and communication technologies downstream from a substation that enables an electric power utility to remotely monitor and coordinate its distribution assets, and operate these assets in an optimal manner with or without manual intervention.
In other words, DA allows individual devices to sense the operating conditions of the grid around them and adjust to improve the overall power flow and optimize performance. The sensors and communications associated with DA can provide early detection of devices that might not be working properly, allowing a utility to replace those devices before a failure occurs.
In terms of service restoration, intelligent electrical devices with DA capabilities will not only immediately identify an outage has occurred, but will also pinpoint the specific devices that are experiencing the fault. Grid operators can then route around the problem and restore power.
Let’s break down the core components of substation and distribution automation.
Intelligent electronic devices and controls
Since utilities are becoming more data driven, decisions can’t be made unless accurate data is available. That’s why intelligent electronic devices (IED) are important. IEDs are microprocessor-based controllers of power system equipment such as reclosers, voltage regulators and capacitors, racks/banks with intelligent controls, and circuit breakers with relays.
Cyber-secure communications for critical infrastructure
When critical infrastructure communications are cyber-secure, it means all messages to and from the substation are genuine, sent from authorized sources and do not carry malware.
When it comes to protecting the entire power grid, it’s important to guard high-voltage IEDs from unauthorized access. Maintaining secure communications is also an important part of remaining NERC CIP compliant.
Remote terminal units
A remote terminal unit (RTU) is a microprocessor-controlled electronic device that interfaces objects in the physical world, such and controls and IEDs, to a distributed control system or SCADA (supervisory control and data acquisition) system. This is done by transmitting telemetry data to a master system and by using messages from the master supervisory system to control the connected objects.
Modern substation automation devices offer a seamless and scalable solution for automating and providing visibility to power system networks, replacing traditional single protocol RTUs with a complete substation gateway controller.
Supervisory control and data acquisition
Supervisory control and data acquisition (SCADA) transmits and receives logic or data from IEDs and sensors on electrical equipment and instrumentation devices in utility, telecommunication or industrial applications.
Power system elements ranging from pole-mounted switches to entire power plants can be controlled remotely over long-distance communication links. Remote switching, telemetering of grids (showing voltage, current, power, direction, consumption in kWh, etc.), and automatic synchronization are used in some power systems.
Smart sensors are analog or digital transducers or actuators combined with a processing unit and communication interface.
This technology helps utilities improve the efficiency of distribution system operations, which is done by improving outage management and capacitor bank maintenance while providing critical system information not previously available on transformers and isolated sections of the power grid.
Outage management system
An outage management system (OMS) is an electric distribution system operators use to manage power restoration efforts. Utilities set situational intelligence to determine the best course of action, improving crew assignments, reliability and service levels.
Fault location, isolation and service restoration
Fault location, isolation and service restoration (FLISR) involves the following technologies, which work in tandem to automate power restoration, reducing both the impact and length of power interruptions:
- Automated feeder switches and reclosers
- Line monitors
- Communication networks
- Outage management systems
- SCADA systems
- Grid analytics
- Data processing tools
- Distribution management systems (DMS)
Distribution management system
A distribution management system (DMS) is a collection of applications designed to monitor and control the entire distribution network efficiently and reliably, improving service quality in terms of reducing outages, minimizing outage time, and maintaining acceptable frequency and voltage levels.
Integrated Volt-VAR compensation
Volt-VAR management refers to the process of managing voltage levels and reactive power (VAR) throughout power distribution systems. These two quantities are related because as reactive power flows over an inductive line, that line sees a voltage drop.
VVC encompasses devices that purposely inject reactive power into the grid to alter the size of that voltage drop in addition to equipment that more directly controls voltage. Integrated Volt-VAR compensation (IVVC) is an advanced function that determines the best set of control actions for all voltage-regulating devices and VAR control devices to achieve one or more specified operating objectives without violating any of the fundamental operating constraints (high/low voltage limits, load limits, etc.).
Automatic source transfer
Automatic source transfer (AST) is an electrical mechanism that switches a load between a primary and back-up source. Some transfer switches are manual, in that an operator makes the transfer by throwing a switch, while others are automatic and switch when they sense one of the sources has lost or gained power.
An automatic transfer switch (ATS) is often installed where a backup generator is located so the generator may provide temporary electrical power if the utility source fails. The utility may also pick up temporary power from a designated feeder from a different substation or utility.