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IEC 61850-3 a Must-have for Substation Designers
The Smart Grid revolution is transforming the energy industry by using digital technology to deliver electricity from suppliers to consumers in a more intelligent, efficient, and transparent way. Embedded control and communication devices are central to this transformation by adding intelligent automation to "dumb" electrical networks. In addition to the IEC 61850 communication standard, IEC 61850-3 sets ruggedized and environmental standards for networked systems used in power substations.
IEC 61850 defines an Ethernet-based protocol
used in substations for data communication.
Substations implement a number of controllers
for a variety of purposes, including protection,
measurement, detection, alarms, and monitoring.
System integrators are often slowed down by
the fact that the controllers produced by different
manufacturers are incompatible, since they do
not support the same communication protocols.
The problems associated with this incompatibility
can be quite serious, and result in increased
costs for protocol integration and system maintenance.
The IEC 61850 standard defines a new protocol
that allows equipment and devices in a substation
to communicate with each other. Many well-known
manufacturers, such as ABB and Siemens, are
dedicated to using IEC 61850-based devices that
can be used as part of an open and versatile
communications network for substation automation.
A number of new substations in Europe and North
America, for example, now require that all equipment
and devices used in the substation are IEC
61850 certified.
Power Substation Basics
Power substations play a critical role in transporting
electricity from power plants to homes, businesses,
and factories. However, a typical power grid
can be comprised of hundreds of substations
that need to be monitored and controlled. Thanks
to the rapid growth of computer and communication
technology, power substations are becoming more
automated and reliant upon intelligent devices
to monitor and control unmanned facilities.
Fast and reliable networking solutions such as embedded computers are a key factor to establishing successful substation automation systems. Embedded computers provide a reliable and economical solution for automating power substation networks.
Substation automation systems are made up of three physical layers:
• The bay layer
• The communication layer
• The substation layer
The bay layer
consists of protection units and control units,
and is based on the RS-485 bus.
The communication layer
serves as the core of the entire remote monitoring
system. It not only collects data from the protection
units and sends the data to the back-end control
center, but also transmits commands from the
control center to the control units, such as
switching on and off the various system devices,
capacitors, and converter transformer taps.
The substation layer
provides 100 Mbps Ethernet support for back-end
servers, security workstations, as well as prevention
mechanisms to protect against electrical isolation
interference and circuit breakers that are not
set properly.
Generally speaking, devices
in the bay layer collect data in real time and
then transmit the data to the communication
layer, which sends it to the substation layer.
The communication layer essentially functions
as a transitional center that receives data
from both the bay and substation layers, and
consequently its performance and reliability
ensure stable operation for the entire system.
Traditional IPC versus Newer Embedded Technology
Compared with the more traditional IPC (industrial PC), the newer embedded computer technology is exerting considerable influence on the structure of control systems. By replacing the IPC's hard drive with flash or DOM (disk on module) memory, the RISC-based architecture of embedded computers provides users with fan-less operation and low power consumption. Embedded technology eliminates the aspects of traditional IPCs that reduce the lifetime of the computer, such as the need for add-on boards or cards for system expansion, which seldom meet the strict anti-shock and anti-vibration demands of harsh industrial conditions.
To solve this problem, embedded systems use a highly integrated design that incorporates several interfaces, including serial, Ethernet, and digital I/O. This type of design significantly enhances system reliability and operational stability. Moreover, embedded computers that come with the operating system pre-installed (typically either Linux or Windows) provide a ready-to-run platform that satisfies real-time industrial application demands, and also ensures that system maintenance costs and effort are kept to a minimum.
In response to the trend of deploying embedded
systems in substation automation, more and more
companies (including traditional IPC manufacturers)
are producing embedded computers to tap into
this growing market. However, many IPC manufacturers
have done their tapping by simply downsizing
the dimensions of their computers without making
significant design changes to the hardware and
software. This strategy fails to satisfy system
integrators' repeated demands for embedded systems
that offer built-in serial-to-Ethernet communication
in addition to programmability.
IEC 61850-3 is Tailored for Substations
When used as a unified communication protocol
in substations, the IEC 61850 standard provides
benefits that help substation designers construct
a complete, Ethernet-based communication system.
These benefits include:
Integrated Protocol: The costs associated with setting up a monitoring system in a substation that uses different communication protocols (e.g., DNP3.0, UCA, and IEC 870-5) can be prohibitive. The IEC 61850 protocol is preferred since programmers only need to use one protocol to develop the required monitoring applications.
Maintenance and Implementation: System designers find it easier to select components and controllers that have been designed specifically to meet the standard requirements of the IEC 61850 protocol, saving on both implementation and system maintenance.
Time-to-Market: The fact that leading manufacturers such as ABB, Siemens, and Areva are producing integrated ICE 61850-based products saves time, since system integrators can design systems with products right off the shelf.
The Challenging Requirements of IEC 61850-3 Certification
The IEC 61850-3 standard specifies the hardware
design requirements for IEC 61850 devices used
in substations. IEC 61850-3 devices must meet
three major requirements. The three requirements
focus on EMI, wide temperature, and shock and
vibration resistance.
Strong EMC design to protect against EMI: EMC (electromagnetic compatibility) is important since unprotected devices are easily damaged or destroyed when exposed to high levels of EMI (electromagnetic interference). Providing the necessary protection presents hardware engineers with a serious challenge, since it often requires using expensive components designed to handle electromagnetic interference. In addition to choosing the right components, engineers must also spend a good deal of time testing their design.
-40 to 75°C operating temperature range: The wide temperature requirement is important since substation environments can experience temperatures as high as 75°C and as low as -40°C. The wide temperature requirement can be satisfied with an efficient heat dissipation design for extremely hot surroundings, and an intelligent self-warming system that kicks in when the temperature drops to extremely cold temperatures.
Anti-shock and anti-vibration: IEC 61850 devices must meet a 50G anti-shock and 5-500 Mhz anti-vibration requirement to ensure continued operation after being dropped from a rackmount in a device cabinet. The key to satisfying this requirement is to use protective components that work like a cushion to protect the device when it falls.
How Moxa's DA Series Computer Conquered These Challenges to Become the World's First IEC 61850-3 Certified Embedded Computer
The engineers for Moxa's DA-681-I-DPP-T embedded computer faced a number of challenges in the design and development stage, and their dedication and hard work paid off when Moxa's DA-681-I-DPP-T became the first embedded computer in the world to receive IEC-61850-3 certification.
EMC: The biggest challenge when designing products with EMI immunity is determining the most optimal combination of voltage step-down regulators and current limiting resistors. After a good deal of trial and error, Moxa's engineers settled on a combination of two voltage step-down regulators and one current limiting resistor.
A voltage spike is met first by a voltage step-down regulator that clamps the voltage to 75 V. Next, a current limiting resistor isolates both high voltage and current, followed by the second voltage step-down regulator that clamps the voltage to 12 V. This strong EMC design protects the computer and components from being damaged by voltage and current electromagnetic interference.
Wide temperature: Moxa's IEC 61850-3 embedded computers employ a heat sink plus intelligent heater combination to battle hot and cold temperatures. Moxa introduced an "L-type" heat sink (Patent Pending) that is used to keep the computer's internal temperature cool enough to ensure reliable operation in temperatures as high as 75°C.
The "L-type" heat sink includes a metal plate that resides inside the embedded computer's housing, and abuts the computer's main heat sources. The "L-type" heat sink is particularly efficient since the heat produced internally is absorbed by the plate before being dissipated from the sink. In addition, the embedded computer uses an intelligent heater mechanism that automatically raises the internal temperature when the computer is used in an extremely cold environment.
L-type heat sink
Anti-shock and anti-vibration: Moxa's IEC 61850 embedded computers have been certified to withstand 50 Gs and vibrations of between 5 and 500 MHz. The computers have also been subjected to a 6-sided 25 cm drop test under normal working conditions, ensuring that the computer is well protected when used on moving objects or when an earthquake occurs.
Moxa's DA-681 embedded computer is specifically
developed to meet IEC standards, and to provide
system integrators with multiple Ethernet ports
for substation automation. The DA 681 can perform
numerous industrial automation tasks, including
data control, data acquisition, and numerical
computing thanks to various embedded application
programs.
Visit the following site
to learn more about the DA-681 with IEC 61850-3
certification:
www.moxa.com/Event/Sys/2009/IEC_61850-3/index.htm
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