Transmission and distribution equipment

In 2020 and 2021, our CIGRE work was done mainly by virtual meetings, with couple of hybrid meetings occurring in 2021. The reduced personal contact created a challenge to keep the Working Groups going, organize online conferences and symposiums, review papers, etc…. The overall effort from all the participants was extraordinary. Many thanks to the editors, special reporters, Working Group leaders and members, Strategic Group members, and all other participants for their commitment to CIGRE. This effort kept us alive!

On the contrary, 2022 was much more enjoyable CIGRE year. In the second half of the year, many face-to-face meetings again took place. Our biannual CIGRE Session in Paris took place in person, which was certainly the highlight. With more than 3700 registered delegates, it has been the second-best attended conference in the history.

The technological field of activity of SC A3 remains identical to the past two years and reflects the strategic 3D objectives of CIGRE – Decentralization, Decarburization and Digitalization - objectives as follows:

1. Innovative design and technologies (e.g. DC circuit breakers, SF6 free technologies)
2. Requirements for equipment in changing network conditions and environmental conditions (e.g. offshore applications, adverse weather conditions)
3. Incorporation of intelligence into T&D equipment (e.g. controlled switching, low power instrument transformers, digital twin technology, edge computing)
4. Monitoring and diagnostics of T&D equipment (e.g. transition to non-intrusive technologies)
5. New and improving testing techniques (e.g. superimposed test technics for HVDC equipment)
6. Reliability assessment and lifetime management of ageing equipment
7. New designs and additional requirements in T&D equipment (e.g. generator circuit breakers, fault current limiters, fast acting switchgear)

The structure (refer to picture 1) of the study committee remains also unchanged. By the structure, SC A3 shall be able to identify and react quickly to trends and problems and to set up quickly Working Groups. The SC A3 has currently 24 regular members, 6 additional regular members for especially distribution topics and 16 observer members. For many members the position as a CIGRE representative starts in 2022. Nearly two third of the study committee was renewed after the last meeting in person in 2018.

SC A3 Recent Activities

The highlight was of course the CIGRE Session 2022 in Paris, which took place in person. For SC A3 the CIGRE Session started with one of the most participated events during the Session, the workshop on SF₆ gas alternatives. In continuation of the workshop series, which was already conducted in 2021, SC A3 in conjunction with SC B3 and SC D1 led the workshop. Over 250 participants were present showing that the environmental impact of the insulating and interrupting media of T&D equipment is a hot topic, if not the hottest topic now. The second highlight was a tutorial on field experience and handling on vacuum switching devices. The convenors and members of WG A3.40 and B4/A3.80 did the tutorial. More than 100 participants listened to the state of the art and experience of vacuum switching devices. As final event of the SC A3 organised events the group discussion took place. The 2022 group discussion meeting of SC A3 was held on Friday, 02nd of September 2022 in the well-known procedure in a morning and afternoon session. 51 prepared contributions were shown. Several spontaneous contribution were given during the group discussion meeting. A discussion, which could be livelier, followed most of the contributions. The Sparkup tool for interactive participation of the auditorium was an enrichment. Spontaneous contributions and suggestions provided many interesting ideas. The Session was of interest to all participants from a technical viewpoint. The number of participants was over 266 in total.

The SC meeting was also held in conjunction with the Paris Session. During these first face-to-face meeting after nearly 2 years a lively discussion about the status of the work, future projects, topics of Working Groups and the next events took place.

The utility advisory board (UAB), which was formed during the pandemic in 2020, proceeded its work in 2022. Robert Le Roux lead the group and as Secretary Man-Im (May) Anongpun from Thailand was appointed. The feedback on questions and the activities are less for the moment but face-to-face meetings are planned in the next future to boost the work.

Completed Working Groups and Corresponding TBs

Two A3 associated Working Groups A3.41 “Interrupting and switching performance with SF6 free switching equipment” and JWG B4/A3.80 “HVDC Circuit Breakers - Technical Requirements, Stresses and Testing Methods to investigate the interaction with the system” completed their work and the Technical Brochures (TB 871 and TB 873) have been published and are available at eCIGRE respectively.

The TB 871 deals with the technology, availability and application of SF6-free transmission and distribution switchgear. It focuses on the mainstream of upcoming SF₆-free current interruption technologies, on the one hand based on interruption in natural-origin gases and their mixtures with fluoronitrile (C4-FN), fluoroketone (C5-FK), and on the other hand based on technical air-insulated vacuum circuit breakers. Despite of the different physical characteristics of the SF6-free alternatives, minor modifications enable similar performance, application range and size as their SF6 equivalents, at present up to 170 kV. Products and (pilot) projects with SF₆-free switchgear are reported.

The TB 873 shows different HVDC converter technologies and system configurations including the basic monopole and bipole VSC-HVDC circuits as well as the series-and parallel-connected LCC, VSC hybrid HVDC configurations. It gives an understanding of the different types of HVDC CB technologies and aspects of key component design, condition monitoring, fault sensing and identification. A fist overview on the relevant national and international standards and technical specifications regarding HVDC CB requirements and their applications in actual projects is given.

New Working Groups

In 2022, a new Working Group A3.48 was established. The title of WG A3.48 is “4^th CIGRE Reliability Survey on Transmission and Distribution Equipment”.

WG A3.48 was established to update the reliability performance on substation equipment. The fourth reliability survey collected the data on equipment serviced in 2014-2017 with an expanded scope to cover generator circuit breakers, vacuum circuit breakers, and surge arresters, in addition to SF₆ circuit breakers, disconnecting switches, earthing switches, instrument transformers and GIS with the focus on major failures. The collected data includes service experience of ageing equipment serviced over 40 years.

Reliability of substation equipment in power systems is of major concern especially for transmission and distribution system operators and asset owners. A major failure of substation equipment may result in significant system outages with the associated power restoration efforts. For these reasons, CIGRE periodically conducts an international reliability survey on substation equipment in power systems that can provide good feedback on the validity of international standards.

WG will publish a series of TBs and technical reports to update the reliability performance on equipment in 2023.

Active Working Groups

In 2022 all active Working Group (WG) / Joint Working Group (JWG) activities related to SC A3 are listed in the table below.

The progresses of active WG’s managed by SC A3 are summarized as follows:

WG A3.39 is collecting field experience with Metal Oxide Surge Arresters (MOSA), focusing on the reliability issues on the system and equipment since they have a function to protect other equipment in the substation. The WG clarifies the consistency of design and testing requirements for MOSA’s based on field experience. A reliability survey was carried out to understand how actual field stresses can be covered by the requirements on MOSA’s, including the consequences of short-circuits. The WG cover also the reliability of MOSA in HVDC applications. A detailed reliability survey on MOSA and other equipment was done. Results that were sent as feedback on the survey were compiled and evaluated. The TB is expected to be delivered in 2023.

WG A3.40 was established in 2018 and is investigating the technical requirements and testing consideration that will help to develop efficient and reliable MVDC switches and circuit breakers. The first results were shown in a tutorial during the Paris session 2021.

WG A3.42 was the third Working Group established in 2018. The content of the WG is to study the frequency and detailed phenomena of the major incidents of conventional instrument transformers, and provide the possible causes analysis, countermeasures, adequate diagnostic techniques and recommendations for improvement. The WG may also suggest additional type testing and routine testing requirements of instrument transformers for reducing the possibility of incidents. In 2021, Zoltan Roman (US) has taken over the lead of the group.

WG A3.43 started to work end of 2018. This WG focuses on what to do with the data collected from the diagnostic activity and monitoring systems to assess the switchgear condition and estimate its end of life. The WG will collect and analyse the voluntary information provided by utilities and manufacturers about how the end-of-life of T&D switchgear is estimated. The WG has close cooperation with B3.48 dealing with health index for substations to be in line with their concept. The final target is having a toolbox to enhance the use of monitoring and diagnostic data in a shared and more comprehensive way to reach a quantitative description of the current state of the switchgear condition.

JWG A3/A2/A1/B1.44 was established in 2019 and will investigate the consequence for the electrical equipment of situations in the transmission and distributions systems in which the operating voltage can temporarily exceed the highest voltage for the equipment (Um).

WG A3.45, also founded in 2019, will investigate methods for the identification of frequency response characteristic of voltage measurement systems. Due to the change in the production of energy the influence on the power quality of the electrical energy is given. Continuous voltage signals beginning from DC as an offset up to several 10 kHz can appear. For transient voltage signals, the resulting frequency may be in the range from 0.5 MHz up to 10 MHz. The relevant instrument voltage transformers based on the conventional technology and the non-conventional low power technologies (both analogue and digital) will be analysed and categorized. Studies on physical dependencies, interferencies and impact on the accuracy will be made.

WG A3.46 is the third WG that started in 2019, and is the first Working Group that deals with the topic generator circuit breaker in general. Therefore, the topic of the WG is quite broad and covers the history, the current state of the art and possible future applications. The aim is to provide users with a “cookbook” when dealing with subjects, such as among others typical network layouts of different power plant types, case studies for short-circuit calculation or voltage transients, protection systems, heat dissipation with busbar dimensioning isolated phase busbars, requirements for fabrication and site acceptance tests, condition monitoring and life cycle analysis. Additional experiences on requirements and their background of generator circuit breakers with its combined equipment of earthing-, starting- and breaking switch, as well as their technologies and testing possibilities shall be given.

WG A3.47 is the youngest Working Group in A3 and was founded at the end of 2021. The call for experts has been made and the first meetings are planned for mid-2022. The Working Group will deliver a technical brochure on lifetime management of indoor medium voltage switchgear. The WG will focus on the environmental, safety, equipment reliability, equipment changes of use and logistical factors and recommend options for increasing the in-service life of the switchgear. Options will include various factors such as retrofitting of components, replacement, and other measures such as work practices.

In addition to the work of the Working Groups, SC A3 members have lively discussions not only between and in preparation of the events.

Upcoming A3 events

Finally, here is an outlook on 2023 SC A3 events:

• 6^th - 8^th March 2023 CIGRE International Symposium in Muscat, Oman:
  Transition to Innovative, Sustainable and Resilient Power systems
  More information here

• 9^th - 12^th May A3 & B3 Colloquium in Birmingham, UK:
  The role and impact for T&D Substations and Equipment in delivering
  More information here

• 4^th – 7^th September: CIGRE International Symposium in Cairns, Australia:
  The End to End electricity System: transition, development, operation and integration
  More information here

For more detailed information about upcoming and past events and activities are published on the webpage or the current events and highlights can be followed on LinkedIn.

Contact

• Contact of the Chair and/or the Secretary of the Study Committee