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Controls: fundamentals of controls for utility and critical applications

What is a controller?

Controllers provide critical intelligence and automation to help keep the lights on for more people. They can quickly locate and identify fault conditions, improve system efficiency, or automatically manage line conditions or operations based on specific and customizable parameters.

Controllers empower smarter operating decisions and operate as the “brains” of connected distribution equipment providing:

  • Advanced intelligence that is highly customizable
  • Embedded cybersecurity with built-in encryption
  • Expandable and scalable design for a changing grid

The electric grid has served businesses and consumers for over a century. From generation to consumption, grid requirements are quickly evolving, and utilities must modernize to keep pace with change.

Standards for controllers are defined by ANSI/IEEE 3001.2-2017.

Quick links to controller fundamentals: Why use controllers | How controllers work | Types of controllers | Learn more

Why use controllers?

Power providers need advanced and adaptive automation solutions to improve power quality and delivery, line efficiency and reliability.  Controllers give utilities the flexibility to customize solutions for their unique conditions, which helps them to manage system activities and improve productivity.

Modular, flexible controllers are able to adapt to today’s challenges and support future needs of an increasingly changing grid:

  • Identifying and isolating faults, which reduces impact of outages to CAIDI and SAIFI
  • Improving monitoring and automation, even for systems with otherwise aging infrastructure
  • Handling of distributed generation and micro-grids to ensure optimum system performance
  • Reducing maintenance costs to service the grid
  • Advancing cybersecurity with integrated encryption and security tools that assist with NERC CIP compliance

With unvaried, precise operation that is based on real-time data and analytics, controllers provide a wide range of functionality that yields powerful benefits boosting power reliability, customer satisfaction and the bottom line.  


How do controllers work?

Put simply, controllers work with the protection and control system to automatically turn distribution equipment on and off as needed to maintain grid stability. They provide precise, unvaried operation based on real-time data and analytics and are customized to unique requirements.

Distribution automation systems are equipped with various controllers to automatically turn equipment on and off based multiple parameters, including var flow, watt flow, voltage level, current-flow, time-of-day or day-of-week.

Form 4D recloser control

Types of controllers

IdeaPLUS relay
  • Capacitor bank controls
  • Voltage regulator controls
  • Recloser controls
    • Microprocessor-based or electronic control
    • Hydraulic control
  • Switchgear control
    • Pad-mounted Source Transfer (PST) system control
    • Three-phase pad-mounted recloser control
    • Vacuum fault interrupter switchgear control

Voltage regulator control

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 on 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 single control. This new capability provides:

  • A single point of contact for communications
  • Supports multi-phase metering
  • Enables fewer controls to program and maintain

With integrated intelligence and communications, voltage regulators provide new functionality and intelligence that can be used in a variety of operational strategies using site metrics. Yet, they typically use the same function codes and interface of earlier controls. Field technicians familiar with earlier regulator control models should be able to use new technology with minimal training.

Designed with communications in mind, controls can support integrated communications, multiple protocol availability and digital metering for Class 1 accuracy. With Instantaneous metering, time- and date-stamped demand metering and profile records, controls provide voltage limiting capability, voltage reduction, reverse power flow operation and tap position tracking – all to improve power quality. 

Capacitor bank control

Capacitor bank controls are specifically designed to operate utility distribution line capacitors. A critical part of grid automation, capacitor controls are deployed to improve system efficiency and power quality.

Capacitor controllers can make control decisions based on advanced automation schemes utilizing local site voltage, var, time, temperature, and/or current measurements to manage system var flow while protecting site voltage. By adding communications, they can act as part of a broader automation solution with a SCADA or distribution management system to further enhance their effect on the distribution grid as a whole.

For greater accuracy when calculating site metrics, a capacitor bank controller allows users to monitor every aspect of a site with full three-phase voltage, current, power measurements and harmonic monitoring, as well as capacitor bank neutral current monitoring to react if bank maintenance issues occur.

VSA recloser
VWVE38X recloser

Recloser control

Controls provide the intelligence that enables a recloser to sense over-currents, select timing operation, time the tripping and reclosing functions, and finally lockout. 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 future upgradeability as application needs change for long-term benefit. These controls should also easily integrate with multiple vendor products and utilize a diverse range of communication protocols to facilitate integration into legacy and emerging networks.

Microprocessor-based or electronic recloser control

Microprocessor-based and/or electronic controls are housed in a cabinet separate from the recloser and permit changes to operational settings. A wide range of accessories is available to customize the basic operation, solving many application challenges.

Compared with the hydraulic control, they are more flexible, more easily customized and programmed, and have advanced protection, metering, and automation functionality.

Microprocessor controls typically utilize PC-based interface software to configure control settings, record metering information and establish communication parameters. It also provides analysis tools that include fault locating, event recording, and oscillography functions.

Electronic controls have been used in most three-phase reclosers (since mid-1980’s) and may still be in operation today.

Hydraulic recloser control

Hydraulic recloser control is used in most single-phase reclosers and in some three-phase reclosers. It is built as an integral part of the recloser. With this type of control, an overcurrent is sensed by a trip coil that is connected in series with the line.

When the overcurrent flows through the coil, a plunger is drawn into the coil to trip open the recloser contacts. Timing and sequencing are accomplished by pumping oil through separate hydraulic chambers or ducts.

For smaller reclosers, the reclosing energy is provided by springs that are charged by the series trip-coil plunger during overcurrent protection.

Larger reclosers are closed from a separate closing solenoid that is energized by line potential from the source side of the recloser.

Switchgear control for critical and utility applications

Switchgear controllers provide the intelligence for automation and remote operation that boosts system reliability. Monitoring data from sensors and connected equipment, the controller can turn off power or switch between sources to prevent power loss.

Vacuum fault interrupter switchgear control

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.

The controller for VFI switchgear can provide single-phase or three-phase protection, as well as resetting vacuum fault interrupters.  

Pad-mounted Source Transfer (PST) system control

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 alternate 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 customizable and able to meet specific and even changing requirements. Typically, the controls here provide source transfer and restoration configurations, 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 customized for specific automation applications. 

Three-phase pad-mounted recloser control

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, sectionalizing and transformer high-side protection.

The controller signals initiate tripping and closing. The signals produced by the control energize 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 program settings can be changed. The protective program can be further tailored to help maximize system operating flexibility. 

Smart VFI underground distribution switchgear solutions


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