Distribution automation: fundamentals of distribution automation

Certain electrical system events are temporary. Distribution automation is used to react to these events without requiring a utility action. Such automation includes reclosers, regulators and capacitor banks. A tree branch can be blown by wind into contact with a conductor. That contact creates an overcurrent that is cleared by a recloser and its overcurrent protection settings. A few seconds later, the wind abates and the tree branch is no longer in contact with the conductor. The automation in a recloser supports automatic reclosing for just such an event. The recloser recloses and remains closed because the fault no longer exists. Without the recloser, a utility employee would have to troubleshoot the fault in order to restore electrical service. That troubleshooting effort could either take a few minutes or up to several hours. There is significant benefit to electric utility customers if automation can be configured to react to system events.

Some electrical system events can be mitigated by a single automation device. Other electrical system events require wide-area analysis and multiple automation devices. The robustness and bandwidth of communication networks have increased dramatically over the last 20 years such that two-way communication now enables this type of wide-area analysis. There is further benefit to electric utility customers if additional operational events can be responded to with automation.

Eaton’s Yukon Feeder Automation software makes use of real-time data for improved reliability, faster restoration and minimised customer impact. Yukon Feeder Automation (YFA) software integrates real-time data to detect distribution system disturbances and automatically reconfigure the system, significantly improving reliability while reducing the number of customers affected. This advanced, dynamic, self-healing software solution empowers utility engineers to easily change automation settings and perform service restorations in approximately 30 seconds to 2 minutes, significantly decreasing outage time, System Average Interruption Duration Index (SAIDI) and System Average Interruption Frequency Index (SAIFI).

• Fault management, voltage loss management and load management
• Simple configuration
• Self-healing system
• Server-based application with centralised communication architecture

Eaton’s Volt/VAR management software applications monitor real-time voltages, watts and VARs from load tap changers (LTCs), regulators, capacitors, medium-voltage sensors and additional monitoring points such as customer meters. These software applications help electric utility companies implement smart grid strategies while enhancing system optimisation. Because these software applications support power factor and voltage management, the delivery of electricity is more efficient, of a higher quality and less costly – enabling electric utilities to benefit from a greater percentage of energy being delivered to paying customers, deferred installation costs for new generation plants and a greener energy footprint.

• Voltage and power factor control
• Conservation voltage reduction support
• Easy implementation, management, monitoring, maintenance and data importation with real-time visual displays, graphs, alerts and historical data
• Voltage management during forward and reverse power flow conditions due to the integration of renewables
• Optimised performance through the collection and analysis of real-time feeder voltages, watts and VAR flow from regulators, capacitors and other monitoring points

Eaton’s GridAdvisor Series II smart sensors achieve reliable outage detection and operational efficiency. GridAdvisor Series II smart sensors with integrated communication are designed to save utilities both operation and maintenance costs by reducing drive time and keeping capacitors operating at peak efficiency. Hot-stick installable, these sensors are the easiest way to gain SCADA visibility across the electric power distribution network. Accommodating all voltages, currents, overhead, padmount and vault applications in a single unit, the GridAdvisor Series II smart sensor meets or exceeds IEEE Std 495 2007 standards, making it suitable for both overhead and underground applications. 

• Self-contained and conductor-mounted, with patented energy-harvesting technology
• Hot-stick-installable on conductor sizes 6mm to 51mm (0.25” to 2”) in diameter
• Real-time line monitoring at nearly any location via DNP3 protocol, with detection of directional fault targeting and capacitor bank fuse failure
• Communications flexibility with integrated HSPA+/CDMA cellular modem and Bluetooth radio
• SCADA visibility
• Native DNP3 protocol support

Eaton’s GridServer smart sensor software simplifies smart sensor integration and reduces complexity with powerful, secure tools. Using Eaton’s GridServer software, utilities can dramatically simplify the integration of their entire fleet of smart sensors, significantly reducing the number of operational hours required to set up, commission and integrate sensor data into various enterprise applications. Concentrating thousands of sensor connections into a manageable data set over a service-oriented architecture, GridServer software provides a secure data path into an electric utility company’s operations centre. At the same time, the software reduces complexity by acting as a single point of integration to enterprise applications, managing data acquisition and brokering the appropriate points of interest to multiple back office systems. The GridServer Manager client application provides an intuitive, powerful interface to help administrators quickly and easily manage their sensor assets, publication of data and user access to the system.

• Template-based configuration of sensor data points
• Intuitive drag-and-drop configuration interface
• Flexible data concentration of thousands of smart sensors
• Manageable data connection for SCADA or OMS using DNP3 or ICCP
• Uses existing IT infrastructure with Active Directory integration

Eaton’s Automatic Source Transfer (AST) system enhances system reliability for critical loads with high-speed communications and reliable switching between two sources. The automatic source transfer (AST) system is ideally designed to protect critical loads that cannot tolerate a sustained loss-of-voltage event. The customised Form 6 recloser controls communicate via PeerComm, a high-speed peer-to-peer protocol, enabling transfers to an alternative source in as few as five cycles. Multiple long-range communication options are available, supporting not only premium electric utility loads but also vital feeders with multiple high-profile valued customers.

Flexible, user-selectable restoration options quickly return the electric utility system to normal:

• Local restoration – each control is manually operated
• Automatic restoration/manual initiation – restoration to the preferred source is manually initiated from either control
• Automatic restoration/automatic initiation – occurs once the preferred feeder voltage returns

Eaton’s CBC-8000 capacitor bank control is designed to operate utility distribution feeder capacitors. Offering increased security, simplified installation, reduced training and lower cost of ownership, the highly flexible control can be readily deployed in advanced automation schemes such as Eaton’s Yukon Integrated Volt/VAR control, SCADA and distribution management systems.

• Modular, economical controllers support stand-alone functionality and a variety of communication configurations
• Three-phase power quality measurements
• Voltage control algorithm to address feeder voltage violations
• kVAR algorithm to optimise power factor to user-selectable target

Controls provide the intelligence that enables a recloser to sense overcurrents, select the timing operation, time the tripping and reclosing functions and finally, lock out. There are two basic types of control schemes used; an integral hydraulic control or a control located in a separate cabinet.

These types of controls are the simple solution for new reclosers and a replacement for legacy controls on currently installed reclosers. They are critical for important service restoration operations, with instant access to operating functions to quickly determine the status of a device, locate faulted phases, check counters and find other critical information.

With comprehensive metering, recloser controls can help reduce operating costs:

• Providing accurate load current measurements to balance feeders
• Improving system planning with real-time data reports
• Increasing efficiency through quick fault location and identification

Plug-and-play parts incorporated into the control facilitate easy installation, service and replacement. These design elements are specifically incorporated to ensure the ability to upgrade in the future as application needs change for long-term benefit. These controls should also easily integrate with multiple vendor products and use a diverse range of communication protocols to facilitate integration into both legacy and emerging networks.

New generation voltage regulator controls provide enhanced power quality. While designed for today’s applications, they provide forward compatibility and the ability to be applied to nearly any voltage regulator in service today.  

The latest generation control technology can provide multi-phase voltage regulation, so that two or three regulators can be operated with the use of a single control. This new capability features:

• A single point of contact for communications
• Support for multi-phase metering
• Fewer controls to programme and maintain

Vacuum fault-interrupter switchgear provides medium-voltage switching and protection in critical applications. The controller provides the intelligence to automate the operation of the switchgear and boost reliability. The controller carries loads with feed redundancy and provides remote monitoring and operation as well as advanced protection through integrated metering and SCADA functionality. Controllers can support feeder protection, reverse power, overcurrent, under/overvoltage and frequency applications.

In critical applications that require always-on power, pad-mounted source transfer systems are used to increase reliability for critical loads. PST switchgear provides automatic transfer between preferred and alternative sources. The controller helps reduce outages during the time it would otherwise take to return to normal power. The controls for the switchgear should be customisable and able to meet specific and even changing requirements. Typically, the controls here provide source transfer and restoration configuration, overcurrent protection, metering and SCADA. Ultimately, the controller enables faster service restoration through real-time data and integration with SCADA systems and feeder automation software. Manufacturer-provided tools can enable customers to create custom-engineered logic for hardware control, status, communications, operations and indication. The data collected can be customised for specific automation applications.

Automatic circuit reclosers are used for reliable and economical overcurrent protection in underground distribution systems. The controllers for the pad-mounted reclosers coordinate and enable feeder protection, sectionalising and transformer high-side protection. The controller signals initiate tripping and closing. The signals produced by the control energise the operating circuits in the recloser and release the stored-energy trip mechanism when an overcurrent occurs. Recloser operations are programmed on the controller, which is designed to provide unvaried and precise operation. It is the controller that provides close coordination with other protective devices on the system. When the system requirements need to change, the controller’s programme settings can be changed. The protective programme can be further tailored to help maximise system operating flexibility.