b3 Special Report 2012

7/28/2019 b3 Special Report 2012

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SPECIAL REPORT FOR SC B3(Substations)

Wolfgang DEGEN*/Peter GLAUBITZ*

Special Reporter

A combination of ageing infrastructure, the rising use of renewable energy sources requiringintegration into existing grids, rising demand for electricity, a need to improve transmission efficiencyand energy security, are translating into growth in the electric power transmission and distributionmarket. To tap the full potential of renewables, a transmission grid overhaul is often necessary tooffset intermittency issues and accelerate deployment of distributed renewable generation. This andthe use of UHV transmission levels will also reduce losses leading to increased industrialcompetiveness.

Over the forecast period many regions and countries will experience strong growth in the electricpower market as a number of governments and utility companies rush to upgrade and expand thetransmission and distribution infrastructure.

Emerging national electric power transmission & distribution equipment markets such as China, India,and Brazil will drive growth in the market while the US and major European countries will remaincentral to transmission and distribution market sales, as these economies have to invest heavily in theirelectricity generation, transmission and distribution networks in order to adapt them to the changinggrid conditions. Growth in other national and regional markets is expected to increase sharply, asnational, regional and continental electricity grids are interconnected.

The four main strategic directions for CIGRE technical activities and as well for SC B3 Substations

are:

• The Electrical Power System of the Future: super grids, smart grids...• Making best use of the existing power system• Focus on environment and sustainability• Communication on power system issues to the audience

Substations are the backbone of the power supply worldwide regardless of the country or region,where they are located. All these substations however are built to different standards: Developedcountries with lower growth rates often have high quality demands, while in less developed countries,large energy demand growth rates are the predominant driver of needs.

*[email protected] ; [email protected]

CIGRE 2012

B3 - 00



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What is common for all new development is that these varied drivers have a significant impact on thedesign, size, location, service behaviour, efficiency and availability of the substation, whether existing,being changed or replaced or newly planned. Criteria to satisfy the basic design needs are reliability,affordability, sustainability and acceptability from technical, economic and environmentalperspectives.

Another driver for building of new substations is the increasing age of existing equipment withinherent increase in the cost of maintaining and reduced reliability of equipment. For HV equipment,some of which has been in service for 40 years, residual life is becoming a more and more importantissue. Some of the key drivers that may influence the residual life of a substation can be summarisedas follows:

Equipment factors such as equipment condition / reliability but also maintenance or repaircosts, knowledge about the switchgear, availability of consumable spares for repair/extension

Changing system requirements including the availability and cost of outages, requirements forhigher level of technical performance (e.g. rated current / short circuit current) or for extension

or reconfiguration And last, but not least, external factors such as changes of the asset management strategy of the user, changing legal requirements, changing environmental/ecological demands orchanging health and safety regulations.

Consequently the Preferential Subjects for the Session 2012 followed these different needs anddevelopments and were chosen under three main topics as follows:

• PS1: Substation Solutions enabling the Smart Grido Role of the HV substation in realizing the Smart Grido Substation management enabling smart grid implementationo Substation automation and communication systems

• PS2: Substation Developmentso UHV substationso Offshore substationso AC/DC-substationso Environmental impact of substations

A total of 26 papers addressing these 2 Preferential Subjects of 2012 have been selected for thesession. These interesting papers and contributions on quite different aspects to the CIGRE Session2012 make a valuable contribution to the active work of Study Committee B3. The significant effortsexpended by the authors in producing these papers are truly appreciated.

The papers quite often address more than one preferential subject, so that it is quite difficult toorganise the questions according to the different subtitles. On the other side, some papers address thesame topic, so that they are considered together and covered just by one question. The followingquestions have been derived accordingly:

• PS1: Substation Solutions enabling the Smart Grid:

Although the global recession caused reduced electricity demand in nations all over the world,recovering economies and powerful growth from emerging markets are creating an atmosphere forstrong growth in electricity generation. Future demand and load balance scenarios, including the

impacts of climate change and greater renewable energy penetration need to be considered. The needto consider the effectiveness of wide area transmission lines and dynamic line ratings on congestedgrids will lead to smart grids with multidirectional power flow on transmission and distribution levels.



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Smart grids require data to flow seamlessly from all installed devices as switchgear, control andprotection devices, meters and sensors to the control centres. This leads to various challenges not onlyin terms of collecting the data but in operating the grids. However the power systems remain the same,and the substations and its smarter use in the line of interaction between generation to customers willhelp to effect improved utilization of energy.

In the first paper the performance of real-time monitoring of transients using optical devices as sensorsin place of instrument transformers is described. Optical sensors handle a wide spectrum of signalswith rise times in the range from nanoseconds in events such as Very-Fast-Transient (VFT) signals tomillisecond rise time switching events in transmission systems. A test set-up for measuring transientsin high-voltage systems is described.

Question 1.1: How important are these transient measurements for smart grid operations? Arethere other field experiences with measurement of transients using opticalsensors? What can be said about the long term behaviour of such measuringdevices?

Mixed Technology Switchgear (MTS) has been on the market for several years. Its compactness offersa range of different, mainly space saving solutions. Paper B3-102 describes the design features andadvantages of mobile substations, using such a design approach. The advantages described are fullfunctionality of a substation, but having a compact and movable standardized installation with reduceddelivery time. Different application examples were presented.

Question 1.2: What are the drivers for the implementation of fast deployment installations?How necessary or effective is the standardization of the equipment design? Whatabout the installation period for such temporary use? Are there otherexperiences in mobile substation application?

Energy transmission is an important link between generation and the consumer. To operate such

systems effectively, a lot of data has to be transported. Utilities need to develop networks withflexibility, compactness, with capability for on-line monitoring and digital communication. IEC 61850is an advanced technological solution to the handling of such data and has been in use for severalyears. It offers a solution balancing the demanding criteria of safety and high service continuity.

The IEC 61850 suite of power systems communications protocols provides capabilities that cansignificantly reduce the cost of designing, commissioning, maintaining, and upgrading transmissionand distribution substation automation systems. This international standard has been deployed atthousands of sites in Europe and the rest of the world and has been identified also as part of theupcoming North American smart grid standards framework. It specifies how the next generation of electrical automation equipment will communicate.

Papers B3-103, B3-105 and B3-111 together report on different service experiences and suggest a roadmap for adoption of IEC61850 in high-voltage substations. Paper B3-105 discusses considerations forutilities in understanding present protocol and application software maturity.

Question 1.3: Is IEC 61850 the right tool for smart grid implementation? Is there alreadyenough service experience to evaluate IEC 61850 for complex systems? What arethe consequences for substation operations? Which testing methods are suggestedto be applied, in particular for the use in systems like smart grids?

Paper B3-103 and paper B3-108 describe a strategy for optimizing the use of IEC 61850, while paperB3-111 presents a special multivendor project for optical current sensors and protection relays.Considerations suggest the installation of non-conventional instrument transformers (NCIT) resultingin more simplified and compact primary layouts as well as improved safety, reliability and reduced



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physical footprint, all together with reduced cost. Tests of the process bus using GIS equipped withnon-conventional transformers are required to prove feasibility.

Question 1.4: What are the considerations of manufacturers in regard to this approach? Whatare the expected consequences of such an approach? Are there utilities withexperiences of these issues?

The integration of offshore wind power into the transmission grid is essential for developmentof smart grids. Paper B3-104 presents results of investigations on the specific electrical andoperational environment of wind turbines. It is found, that there seems to be a lack of application standards for such equipment types. Regarding the wind turbine environment, newspecific service classes in the relevant IEC 60721 standards are suggested, covering thedifferent operating conditions.

However wind turbines are just a part of the necessary offshore installation. Other electricalcomponents are involved in this kind of generation include substations, transformers, control

and protection equipment, cable connections etc.Question 1.5: What are the considerations for all components, used under offshore conditions?

Which are the expected consequences on products used in off-shore conditionsand how is life cycle behavior assessed? What are the specific issues to beconsidered for AC substations applied to off-shore wind farms? Are therealready service experiences of utilities on these issues?

Besides building new substations, the upgrading of existing substations has importantconsiderations. Decisions between replacement or refurbishment are not the only options, alsousing existing substation footprints for new, more compact equipment is another approach.There has been increasing importance placed on reducing environmental impact of substations in recent years. Options include new aesthetic solutions, better integration into theenvironment or placing entire substations underground.

While paper B3-106 reports on experiences with such space saving solutions, becoming morea common practice of utilities, paper B3-110 presents a number of interesting examples of integration of substations and lines into its geographic service area. Such projects followtypically the evaluation of life-cycle cost, performance, behaviour and environmental impacts.Last but not least a sensitivity analysis is required to address the different aspects of theindividual parameters of each utility and application.

A number of such projects are already known.Question 1.6: However are there examples of projects, where such a solution does not work?

What about the cost-effectiveness of integration of substations and lines into thegeographic service area? Are these applications with reduced footprint also of interest, even if there is enough space available?

Paper B3-107 pointed out, that it is often required to extend or replace installed substations withintheir existing location or footprint by hybrid substations, mixing air insulated and gas insulatedtechnology. For air insulated busbars with busbar disconnecting switches in combination with mixedtechnology switchgear (MTS) the capability of the switches and their behavior during busbar transferoperations must be considered. The given rated transfer current values may not be sufficient if an

existing AIS substation using air insulated busbars operates in combination with GIS bays.



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Question 1.7: Are there already experiences with such mixed solution installations in thisregard? What have manufacturers done or plan to solve these problems? Arethere other problems to be expected, if AIS equipment and MTS equipment aremixed within a common substation?

Substations are quite often at remote places and not protected adequately against intruders. Also theequipment fault detection might become a problem. For such cases paper B3-112 suggests the use of asubstation robot using lights and infrared cameras to inspect a substation installation. In a virtualsubstation, a computer controlled, self-learning robot was “trained on the job”.

Question 1.8.: Are there other examples known of robot activities for the inspection of substations? What are the typical activities for the necessary inspection of remote substations? Isn’t remote data acquisition and control sufficient?

Together with the growth of the power systems in some countries such as India, the voltage levelshave been increased to 765 kV and even to 1200 kV for long distance, high power transfer in thenational grids leading to design challenges. Paper B3-113 describes the various problems to find an

appropriate technical, economic and ecologically compatible solution for a 750 kV substation.

Planning and construction of more than 30 AIS substations is underway following the commissioningof the first such substation more than four years ago. Service experience of the different substationcomponents due to the specific stresses at these high voltage levels was reported.

Question 1.9.: What are the general experiences with 750 kV substations and higher? Are therespecific design and operation issues to be considered in comparison tosubstations at 550 kV or below? Can other utilities, confirm in particular coronaproblems that might occur?

• PS2: Substation Developments

As previously mentioned, the electric power industry is fundamentally driven by the increased demandfor electricity. While the global growth in the use of electrical appliances in industrialized countrieswill lead to the need for higher voltage levels and breaking capacities, connecting the 1.44 billionpeople currently without access to electricity will be pivotal to its general future growth. Theincreasing movement towards more sustainable and lower carbon technologies will also play a criticalrole in new substation installations.

Conversely, high capital costs in a time of financial stringency, unclear legislation on greenhouse gasemissions and the renewed controversy surrounding nuclear power will, to a certain extent, restrain theprocesses.

However substations will always be needed in the future. The only question might be which type of substation will see the greatest growth: UHV substations, offshore substations or AC/DC-substations?One important question is how to operate the substation in the changing environment and in a moreand more complex grid – the smart grid. Furthermore what will be the environmental impact of substations in the future?

Several papers try to answer these questions. Papers B3-201, B3-202 and B3-208 suggest theconsequent implementation of on-line monitoring systems as a solution. These intelligent monitoringsystems can be used stand-alone or within an integrated system for electric power stations andsubstations as part of a smart grid. The good knowledge of the equipment status due to monitoringenables the exchange of collected data in a structured IEC 61850-compliant manner. A new

“Substation Watch” architecture, which integrates the communication protocols, is suggested.



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Using data for on-line monitoring applications offers information on the status of the equipment andcan provide the opportunity to implement condition-based maintenance. Further complexity of smartgrids might require such approaches, however how reliable will such systems be? The knowledge of failure rates of primary products is quite well developed.

Question 2.1: What are the failure rates of monitoring devices? Are there already experienceswith the operation of such systems under different failure modes? Are thereother possibilities to respond to these problems?

If restrictions prevent the construction of a new substation, uprating and/or upgrading of the oldsubstation will remain a solution. Paper B3-203 describes such a solution in a downtown area of alarge city for a substation more than 50 years old. The refurbishment of MV and HV systems andcomponents includes the switchgear, now using gas insulated technology, transformers, the controland protection systems and the cable connections at the same space.

Question 2.2: Are there other examples for this type of refurbishing activity? What are thespecific problems of such an approach? What are the technical, ecological and

economic benefits of such solutions? Do manufactures offer enough flexibility forthese very specific installations?

Paper B3-204 describes an investigation in reducing the effects of short circuit forces by specificmeasures applied to low voltage switchyard equipment. It is presented that it is possible to optimizesubstation layout and to mitigate the forces when applying the IEC 60865 standard. The analysisdemonstrates that this approach allows more flexibility in design practice when considering pinchforces.

Question 2.3: Do other utilities also have experiences in this regard? Are there specificgeometries or other design solutions which could be recommended for bundledconductors and spacer distribution?

The condition assessment of existing substation equipment is important. For instrument transformersas well as for power transformers, with oil-paper insulation, the harming effects of water are wellknown. However measurement techniques, which can be applied to power transformer, are presumedto not be usable for instrument transformers. Paper B3-205 provides information on a technique usingdielectric response analysis in a wide frequency range. A successful case study is presented.

Question 2.4: What are the practices of other utilities to check the dielectric condition of instrument transformers? What are the failure rates and failure modesassociated with dielectric failures of ITs?

The use of hybrid switchgear has been previously extensively reported. Hybrid switchgear (alsoknown as MTS), together with an optimized bus scheme can offer the right solution from thereliability and economic perspective. However Life Cycle Cost (LCC) calculations for the individualdecision of a utility must accompany these processes. Paper B3-206 gives an example.

Question 2.5: Can this approach be considered as a standard solution for such cases already?Which are the main drivers for such solution?

Paper B3-207 reports on possible risks to effective grounding in a substation during reconstruction. If neighbouring ground grids will be disconnected due to this reason, unsafe conditions such as un-acceptably levels of ground potential rise and touch and step voltages might violate the safety criteria.

Due to the different kinds of arrangements of substations and the complexity associated withneighbouring substations, an overall ground philosophy must be considered on a “case by case” basis.Typically manufacturers offer a solution just for their product.



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Question 2.6: Are there known grounding problems of this type in substations? Is the supportof manufactures sufficient for the utilities? Who is doing the job?

In recent years, numerous additional characteristics, e.g. partial discharge activities, have been addedto the list which should be monitored for the condition assessment of GIS substations and GIL drivenby utility needs. Due to the implementation of digital devices a so called “GIS Watch” architecture, aspresented from paper B3-208 and using IEC 61850 structures, enables utilities to have an full timeoverview of the operating condition of the equipment.

It has already been mentioned in the two last session periods, that there remains a discrepancy betweenthe reliability of the primary equipment and its lifetime and those of the attached digital devices.

Question 2.7: Are there new experiences in relation to the reliability of these monitoringdevices? How large is the impact of false failure indication on the primaryequipment? How effective is remote monitoring? How are utilities handling theseissues?

During the service period of substations there are a range of technical, economic and ecologicalreasons to modify existing substations. Changing customer demands such as minimization of life cyclecosts, high availability, high flexibility and compact solutions for existing areas are some drivers, butalso the need to consider changing technical parameters such as short circuit uprating is required.

Paper B3-209 presents “Guide lines for Uprating and Upgrading of substations” on behalf of workinggroup B3.23. The paper presents the different options, discusses the consequences on components andoffers a checklist of the possible issues.

Another approach to upgrading is presented by paper B3-211. It describes a new way to upgradeexisting substations through increasing the operational voltage but keeping the existing BIL level. Thisassists in maximising the utilization of existing infrastructure.

Question 2.8: What do manufacturers and utilities think of such approaches? How can reliabletest results be achieved for the up-rated equipment? Are there cost benefits for areplacement by new equipment with full guarantee?

A substation refurbishment and extension project is presented by paper B3-210. Beside the descriptionof the procedure of this turnkey project in the paper it is predicted, that due to “the limited GIScapability, compatibility problem of spare parts and long maintenance time AIS will still be the maintype of substation design”!

Some B3 papers to this session present solutions using mixed technologies switchgear (MTS) toextend e.g. air insulated switchgear. Most manufacturers now typically offer a range of equipmenttypes for all applications: air or gas insulated, indoor or outdoor, single units or compact design.

Question 2.9: How do utilities judge the application of AIS, MTS and GIS equipment? Canthey agree? What are the decision factors and in which way can a decision isprepared and decided? Is a life cycle consideration generally used for thedecision?

The paper B3-212 describes the consequences for the substation technology due to technical andenvironmental changes of the grid and the society. In particular substations in service since the 1960’sand 1970’s show a degradation of reliability and maintenance problems. This paper reported that agedGIS and air insulated switchgear have recently been replaced by new GIS.



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Question 2.10: What kind of new technologies are applied for up-rating /up-grading existingsubstations? Are there any successful experiences to minimize the planed outagetime in order to keep proper service during the modification work?

A worldwide trend in the implementation of renewable energy generation to the load centres inexisting networks is pushing the utilities to higher transmission levels. UHV transmission lines whichhave lower relative energy losses over large distances are used for these connections. However untilnow the experience with UHV-specific problems of 765 up to 1200 kV is limited. Working groupB3.29 conducted an investigation of on-site acceptance test, commissioning test and maintenance.Paper B3-213 describes on-site tests at a 765 kV UHV substation following the B3.29 suggestions.

The impact of effective on-site testing is becoming more and more important.

Question 2.11: What is the optimized on-site test procedure to ensure the proper functionality of the equipment? What are the test experiences of UHV substations so far? Canimprovements be suggested already?

Apart from transformers, the main focus of a substation is normally considered to be the switchingelements. The interconnection of the different components comprising the switchyard equipmentneeds to be considered with the same approach to quality normally applied for primary equipment.Paper B3-214 discusses quality problems with connectors due to material and manufacturing failures.The required quality level and performance tests are specified. As conclusion field tests wererecommended to not to be sufficient enough for the assessment of used connectors.

It is quite obvious that the effective transfer of power through a substation is as strong as its weakestelement in the transportation chain.

Question 2.14: What are the experiences of other utilities with the quality of connectors? Canmanufacturers give information about how to define quality? Are there other

elements in the power line through a substation which need more attention?

b3 Special Report 2012

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