RESULTS of All-Russian Conference "Technical-Economical Aspects of 20 kV Network Development"
(July 14, 2015, Moscow)
Moderator: S.A. Shumakher, leading expert of "ELECTRIC POWER. Transmission and Distribution" journal
Participants: 114 persons, including representatives of the Ministry of Energy of Russia, the headquarters, subsidiaries and affiliates of Rosseti, JSC UNECO, the Moscow Government, engineering companies, operation, design and research companies, equipment developers and suppliers (according to the list).
Issues for discussion:
- Is there any reasonable need of 20 kV voltage application in a distribution network of metropolitan cities and power grids of Russia instead of or in addition to the existing 10 kV and 35 kV voltage level? If yes, what are the cases and the criteria?
- What is the economics of construction and operation of 20 kV networks? How do these costs align with those of construction and operation of 10 and 35 kV networks? How will distribution network operation efficiency and electricity tariffs improve?
- What is peculiar about 20 kV network operation modes? What neutral operation modes are possible and preferable? What are the risks in solving technical and routine issues, including mandatory use of imported raw materials and process lines for 20 kV XLPE cable production?
- Do they use 20 kV networks in metropolitan cities only or is it possible to view this voltage level as basic in small towns and rural regions as well?
- Are there any technical solutions for integration of "20 kV islands" into a 10 kV network (taking into account different ways of neutral grounding) for provision of mutual redundancy, reliability and cost efficiency of consumer power supply?
- Is there a mechanism of existing 10 kV network transition to 20 kV voltage level? Is there any good example?
- What are (if any) technical peculiarities of 20 kV network application for design of power output diagrams of distributed generation facilities and isolation to the balanced load in conditions of power system failures?
- What is the market situation with regard to proposals of 20 kV equipment and availability (absence) of domestic raw materials for production of 20 kV XLPE cables? Is it important to keep the production lines of MV paper-oil insulation cables in Russia for mastering the production of domestic raw materials for 20 kV XLPE cable manufacture?
- Is it necessary to improve cooperation of domestic XLPE cable producers and JSC VNIIKP with State Institute of Flint-Organic Compounds (Russian defense contractor supplier) for creation of a new type of insulation for 20 kV cables with respect to import phase out objectives? What is the base cost of equipment for 20 kV networks and their automation means? How does it relate to the import phase out trend?
On completion of discussion the participants of the Conference have come to the following conclusions:
- Long-term practice of JSC UNECO and PJSC Rosseti Moscow Region in construction and operation of 20 kV cable networks in the Moscow city should be acknowledged positive.
- When solving tasks of advanced network development for consumer connection and reduce of energy losses in complicated conditions of laying utility systems, to recommend the stepwise substitution of 6-10 kV networks for 20 kV networks upon availability of comprehensive feasibility study.
- Main criteria of 20 kV voltage application in design of new construction and reconstruction of electrical networks should be as follows:
– Load density above 10 MW/km2;
– Need to transmit the power of 3-10 MW to the distance of 25-50 km.
- To approve the approach of PJSC Lenenergo and Yekaterinburg Electric Grid Company (EESK) to 20-35 kV voltage application in municipal power supply diagrams.
- To consider the need of carrying out special investigations to improve the procedure and calculation programs of XLPE cable heating in different conditions of laying, shield grounding, heat transfer and soil thermal resistance as an acute issue of design and operation of 20 kV cable networks in metropolitan cities of Russia.
- To consider the need of development and due approval of the procedure of core section and shield selection for 20 kV XLPE cables in the loading mode and the fault mode as an acute issue of design and operation of 20 kV cable networks in metropolitan cities of Russia.
- To consider the need of development and due approval of the procedure of potential offset prevention when using 20 kV XLPE cables as an acute issue of design and operation of 20 kV cable networks in metropolitan cities of Russia.
- To consider the need of development and due approval of the procedure of relay protection setting selection for 20 kV XLPE cables by condition of providing their operability on fault clearance as an acute issue of design and operation of 20 kV cable networks in metropolitan cities of Russia.
- In conditions of forced acceptance of margins in permissible cable load calculation formula and uncertainty of their parameters in design and operation that leads to the need of overestimating core sections, to deem the study of using modern technologies of 20 kV XLPE cable heating and operating condition monitoring, including fiber-optic technologies tested in a HV cable network, advisable.
- The need to accelerate the work on automation of 20 kV networks as a key factor of their reliable and cost-effective operation, including equipment monitoring, repair in compliance with the technical condition, reveal of reserves for power consumer and distributed generation facility process connection, fault location detection, remote control of power utilities in normal and emergency operating modes.
- The need to provide the resistive neutral grounding in design of a 20 kV cable network. To consider performance of investigations obligatory for justification of the choice of the optimal 20 kV network neutral resistance, its thermal resistance, relay protection types and settings.
- Feasibility of study the specific nature of overvoltage occurrence in a 20 kV network in conditions of its failure, use of vacuum circuit-breakers, disturbances in a HV system grid. To develop measures to restrict impermissible overvoltage levels.
- Feasibility of development by grid companies of their own company standards on design and operation of 20 kV networks with regard to their specific features and available relevant international and national regulatory framework.
- PJSC Rosseti should be involved into the process of 20 kV network design and operation standard development in its subordinate grid companies.
- Development of 35 kV networks should be deemed possible pursuant to relevant feasibility study in:
– municipal districts with established 35 kV network infrastructure;
– metropolitan cities – as the next step of 20 kV network development;
– rural areas - with the need for extended (up to 60 km) transmission of low power.
- To recommend all Conference participants to use "ELECTRIC POWER. Transmission and Distribution" journal as the main means (information resource) of forming the technical policy in the field of 20 kV network development.
- E.N. Guseva, chief editor of "ELECTRIC POWER. Transmission and Distribution" journal, should consider the following issues:
– Publication of the extended press release on conclusions of the Conference and participants' reports in the following issues of the journal and its website.
– Ongoing publication of research reports on design, construction and operation of 20 kV networks in the journal.
– To arrange similar offline events and vebinars on the regular base together with PJSC Rosseti Moscow Region, JSC UNECO, Yekaterinburg Electric Grid Company (EESK) and JSC Yugorsk Regional Electric Grid Company (YURESK) due to significance of the considered issues.