Smart Grid and Transformers 1

[prc]

We are hearing a lot about Smart Grid and IEC61850 communication protocol nowadays. How these will affect transformer technology? What changes will be necessary in transformers to meet these developments in T &D of electrical power?

 

[DTR2011]

I would say that the technology can affect transformers in several ways. The first would be more sensors, such as temperature, liquid level, on line oil (DGA & Moisture), etc. The signals from these can be easily brought back to the control room, via fiber optics, where the data can be combined into useful information. Next would be better voltage / var control using on load tap changer control. Finally, the use of merging units (CT/VT), which again convert the analog signals to digital at the source, such as the transformer control box and then the signal is brought back to the control / relay room via fiber optic cables. GE has something called a "Brick" that accomplishes this, although they did not fully follow the IEC 61850-9-2 LE standard.

Some of this is not any smart grid or 61850 "magic", it is simply replacing copper with fiber. Tap changer controls currently (generally) run on some kind of protocol and the speed between DNP and 61850 is not really an issue for raising / lowering taps, considering the time it takes for the mechanical end of things.

I had to maintain 70 very high end transformer monitoring systems some years back. This system had tap changer monitoring, DGA, Oil moisture and a few other components. Each had its own proprietary protocol which was fed into its own RTU at the transformer, which in turn fed the data upstream. Dealing with 4 different protocols, when making changes and then making everything work to the RTU and then up to SCADA was quite a chore. This was especially true when problems were not intuitively obvious and were not at the device level, but in the protocol conversion. I imagine having a uniform platform for all of the devices would have made things much easier to deal with.

In the USA, 61850 is still slowly being adapted, even though all of the major USA manufacturers have adapted it. I think all of the utilities are waiting for someone else to try it. I personally see a lot of promise in the merging units and how these can substantially reduce the wiring and installation costs for protection applications.

I would be curious to see how others across the world are using 61850 on transformers as well.

 

[prc]

Let us define the smartgrid and IEC 61850.

1) A smart grid is an evolved grid system that manages electricity demand in a sustainable, reliable and economic manner, built on advanced infrastructure and tuned to facilitate the integration of all involved.

Smart grid is a combo of power distribution system,telecommunication devices and electrical gadgets which can predict and respond to energy usage patterns of both suppliers and consumers

Smart electricity - efficient power for a sustainable world :

Smart grids will provide more electricity to meet rising demand, increase reliability and quality of power supplies, increase energy efficiency, be able to integrate low carbon energy sources into power networks.

Smart grids possess demand response capacity to help balance electrical consumption with supply, as well as the potential to integrate new technologies to enable energy storage devices and the large-scale use of electric vehicles.

Smart grid is a electricity network that can cost efficiently integrate the behaviour and actions of all users connected to it –generators, consumers and that do both –in order to ensure economically efficient, sustainable power system with low losses and high levels of quality and security of supply and safety. It is further understood that although elements of smartness already exist in many parts of todays grid, the difference is mainly in the capability to handle more complexity in an effective way. Accordingly, a Smart Grid must employ innovative products and services together with intelligent monitoring, control, communication and self-healing technologies.
Smart Grid Projects in Europe : Lessons Learned and Current Developments by EU Joint Research Centre (ISBN 978-92-79-20487-6,2011)

A smart grid delivers electricity from suppliers to consumers using digital technology to save energy, reduce cost and increase reliability. Such a modernized electricity network is being promoted by many governments as a way of addressing energy independence or global warming issues. Many smart grid features readily apparent to consumers such as smart meters serve the energy efficiency goal. The approach is to make it possible for energy suppliers to charge variable electric rates so that charges would reflect the large differences in cost of generating electricity during peak or off peak periods. Such capabilities allow load control switches to control large energy consuming devices such as hot water heaters so that they consume electricity when it is cheaper to produce. To reduce demand during the high cost peak usage periods, communications and metering technologies inform smart devices in the home and business when energy demand is high and track how much electricity is used and when it is used. Prices of electricity are increased during high demand periods, and decreased during low demand periods. It is thought that consumers and businesses will tend to consume less during high demand periods if it is possible for consumers and consumer devices to be aware of the high price premium for using electricity at peak periods. When businesses and consumers see a direct economic benefit to become more energy efficient, the theory is that they will include energy cost of operation into their consumer device and building construction decisions.
Smart Grid_ An Introduction_ US Dept of Energy _2012


2) Smart grid is the future for electrical systems, as it is designed to meet the four major electricity requirements of our global society: capacity, reliability, efficiency and sustainability.Smart grid solutions to meet the huge demand for electricty-1GW per week for next 20 years.High quality electricity whenever needed without interruptions_HV DC back to back &FACTS extensively.Energy to be saved at all areas -generation, transmission and distribution.Low carbon energy sources will be integrated in to system in a big way.

Smart metering
Energy Efficiency
Intelligent on line monitoring and control
Transmission Automation
System Integration
High Reliability
Environment friendly materials, accessories and manufacturing processes.
Increased flexibility with system stability and quality of supply

Use of Smart equipmentnt, having dynamic loading capability,automatic decision support instructions to system users,Safe failure, self healing technology features, integrated expert systems

HV DC back to back system to isolate synchronous AC systems
FACTs solutions for optimising the utilisation of existing infrastructure and power flow management
Energy storage devices
Smooth integration of energy from wind mills and solar power sources
Operational technology(OT) and information technology(IT) under the same roof

3)IEC 61850: The International Electrotechnical Commission ( IEC ) standard for substation automation replaces a great many communication protocols that require the use of use protocol converters, which are basically “transla¬tors” that help electronic devices using different machine languages transmit information to each other. The prob¬lem is that protocol converters can cause messaging errors and delays. A single communication standard for substation automation removes the need for “translators,” helps customers lower maintenance and operating costs, and makes installations easier to expand or modify

 

[waross]

Possibly the most basic for distribution transformers may be temperature monitoring and logging to detect overloading transformers and identify transformers that may have suffered some inferred loss of life due to repeated overheating/overloading. The economy version would be powered from the monitored transformer so that a loss of signal may set an alarm, inferring a power outage.

Bill
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"Why not the best?"
Jimmy Carter

 

[DTR2011]

If the transformer has CT's already, adding some kind of through fault monitor / alarm as a tool for condition assessment wouldn't hurt. I know SEL offers this in their 387/487 relays, but have never seen the function utilized.

 

[prc]

Smart grid is a journey,not an end state that can be defined.It is not a revolution,but a gradual transformation of the systems that have served us for many years in to a more intelligent,more effective and environmentally sensitive network to meet turbulent, changing needs of tomorrow.

Human ingenuity and innovative spirit can achieve results that cannot be imagined today.Example see the latest generation smart cell phones where Apple made the breakthrough.In electric grid we cannot claim such disruptive technologies in recent times.During the first half of last century,T&D engineers had unique problems every week, to solve.Tesla during his evening years was thinking of transmitting electric energy with out wires.He believed that man can just plug in unlimited amount of energy from universe.Camille ( Italian who worked at GE's Pittsfield Transformer factory and co-author -with L F Blume- popular book Transformer Engineering )who took maximum patents on transformer technology, predicted in early 50's that US will drop man on moon in 1967 (not far off from actual year).He even designed a transformer for using in moon !

There is a popular comparison that underscores the pace of change -or lack there of it-in electric T &D.If Graham Bell were somehow brought to 21st century, he would not be able to recognise the components of modern telephone -smart cell phones,texting,cell towers, PDAs etc while Thomas Edison, one of the early architects of electrical grid, though would be bit surprised with the large increase in size and ratings, would be totally at home in a modern substation.

 

[prc]

Transformers are getting adapted for Smartgrid in a number of ways:

1) Green Transformers are being offered by a number of manufacturers.These are transformers with high efficiency and with bio-degradable insulating fluid instead of mineral oil.ABB offers this range with BIOTEMP insulating oil( natural esters made from sunflower oil.Japanese use palm oil).High efficiency is achieved at no-load by using amorphous cores or superior grade silicone steels,working at low flux density.Low current density with unique measures for stray loss reduction, results in low load losses.Utilities insist for star rated distribution transformers with low levels of losses.

2)Transformers are made with less noise,major pollutant not tolerated in cities.Even 100 MVA units with 50 dB noise levels are possible.

3)Environment friendly materials are only used- Mercury contacts from instruments are changed to magnetic contacts.Silicagel with cobalt chloride( standard blue indication- cobalt salts are suspected to be carcinogenic)are replaced with gel with organic indicators.Asbestos paper is totally prohibited.

4)Water based paints are replacing solvent paints.

5)Fail safe transformers. Transformer fires usually start with failure of oil filled paper insulated HV condenser bushings.Dry type bushings( RIP- Resin Impregnated Condenser Bushings) are used in critical or vulnerable units( eg Generator step up)to prevent such devastation.

6)Maintenance free Transformers- maintenance free silicagel breathers where silicagel is reactivated automatically.Better oil preservation systems.Hot dip galvanised radiators.Distribution transformers with stainless steel tanks or superior surface treatment systems.

7)Short circuit proof transformers proved by short circuit withstand test as a design verification test.

8)On-line monitors- Already on-line hydrogen and moisture monitors are widely used in large transformers.More sophisticated on-line monitors (monitoring more parameters) are available for critical transformers.
9) On-line filters for tap changer arcing chambers.This improves reliability of line end tap changers in large EHV auto-transformers.