DTEK Grid Upgrade: Operation of Rockwill 10kV Smart Recloser in -40°C Extreme Cold Environment Ukraine Case Study

As a benchmark for Chinese‑manufactured medium‑voltage distribution equipment going global, Rockwill established in‑depth cooperation with DTEK Kyiv Power Grid, Ukraine. Tailored outdoor vacuum recloser solutions were mass‑deployed to address existing weaknesses in local 10 kV distribution networks, comprehensively improving regional power supply reliability and automation to build a flagship distribution grid modernization project in Kyiv.

01 Project Background: Core Pain Points of DTEK Kyiv Distribution Network

Kyiv, Ukraine’s capital, relies on 10 kV overhead distribution lines managed by DTEK as its key power supply backbone, covering urban areas, suburban villages and public loads. Legacy equipment has long service life and low automation levels, with three major pain points:

• Frequent faults & unstable power supply: Extreme seasonal temperature swings, icing, thunderstorms and harsh weather often cause short‑circuit and earth faults on 10 kV overhead lines. Conventional switches cannot restore power automatically, requiring manual repairs that lead to prolonged power outages and disrupt urban electricity consumption.
• Low O&M efficiency & high management costs: Scattered long‑range 10 kV lines feature remote outdoor operation sites. Lacking remote monitoring, equipment suffers slow fault identification and high manual inspection costs, failing to meet intensive O&M requirements.
• Weak grid capacity & limited upgrading: Growing urban power loads and integration of distributed energy sources render outdated protective devices vulnerable to disturbances. Rapid fault isolation and grid self‑healing cannot be achieved, restricting smart distribution grid upgrading.

To achieve DTEK’s goals of 10 kV distribution grid modernization, outage reduction and lean O&M in Kyiv, local power authorities selected Rockwill after rounds of technical evaluations. Twenty sets of outdoor vacuum reclosers were first deployed in 2021 to advance smart transformation of Kyiv’s distribution network.

02 Core Products & Customized Solutions 2.1 Key Product Specifications

Mass‑deployed Rockwill 10 kV pole‑mounted outdoor vacuum reclosers fully comply with DTEK Kyiv 10 kV grid standards and IEC 62271‑111, with 1‑minute power‑frequency withstand voltage of 42 kV and lightning impulse withstand voltage of 75 kV:

Item

Technical Parameter

Rated system voltage

10 kV (max operating voltage: 12 kV)

Rated frequency

50 Hz

Arc‑extinguishing medium

High‑purity vacuum interrupter

Configurable recloser sequence

3 times (customizable for Kyiv site conditions)

Total breaking time

≤35 ms

Overall protection class

IP65

Operating temperature range

-40 ℃ ~ +50 ℃, anti‑icing, anti‑condensation, damp‑heat resistant

Control mode

Local manual operation + remote intelligent control via DTEK platform

2.2 Customized Technical Design for Kyiv 10 kV Grid & Climate

Optimized upgrades were implemented based on load characteristics of Kyiv 10 kV lines, suburban outdoor conditions and low‑temperature Eastern European climates:

• Enhanced extreme‑environment design: High‑voltage external insulation uses weather‑resistant silicone rubber with strong low‑temperature toughness and hydrophobic anti‑pollution‑flashover performance, complying with IEC 62271‑111 for suburban outdoor operation in icy Kyiv winters.
• Intelligent self‑healing system: An intelligent measurement & control unit adapted to Ukraine’s 10 kV grid monitors real‑time line voltage and current, distinguishes transient and permanent faults accurately, and restores power rapidly and isolates faults via multi‑stage automatic reclosing to shorten outage duration greatly.

2.3 Core Advantage Comparison: Conventional Pole‑Mounted Switch vs Rockwill 10 kV Vacuum Recloser

Comparison Dimension

Conventional 10 kV Pole‑Mounted Circuit Breaker

Rockwill 10 kV Outdoor Vacuum Recloser

Fault recovery capability

Manual on‑site repair, 4–8‑hour outage

Power restored within 60 s for transient faults (including protection judgment & operation)

Environmental adaptability

Narrow temperature range, prone to condensation & icing in winter

Wide‑range temperature operation optimized for Kyiv’s low‑temperature icing conditions

Daily O&M mode

Full manual on‑site inspection, high costs

Docking with DTEK remote platform, unattended operation, 70 % O&M cost reduction

Operational reliability

Short mechanical life, frequent outdoor faults

Long‑life vacuum arc‑extinguishing structure, stable long‑term maintenance‑free operation

Grid modernization adaptability

Single function, incompatible with smart 10 kV upgrading

Customizable settings fully meeting DTEK Kyiv distribution grid upgrading standards

03 Full‑Process Delivery: From Factory Testing to On‑Site Commissioning in Kyiv 3.1 Factory Acceptance Test (FAT)

All 10 kV equipment for the Kyiv project underwent strict full‑item testing per IEC 62271‑111 and IEC 60255 standards before delivery:

• Insulation withstand test: 42 kV power‑frequency withstand (1 min) and 75 kV BIL lightning impulse withstand, fully satisfying insulation safety requirements of Ukraine’s 10 kV medium‑voltage grid.
• Dynamic reclosing function test: Simulated lightning strikes, tree obstacles, short circuits and other common faults on Kyiv 10 kV lines; three automatic reclosing actions operated accurately without oscillation with stable power factor and operating parameters.
• Protection function test: Simulated phase‑to‑phase short circuits, single‑phase earth faults, power direction issues, closing‑on‑fault and other operating conditions to verify reliability of key protection functions including 79‑mode reclosing, overcurrent, earth fault, directional protection, over/under‑voltage and negative‑sequence overcurrent. Millisecond‑level accurate fault identification and reliable action with no mis‑operation or refusal ensured safe and stable distribution line operation

• Environmental simulation test: Under simulated Kyiv low‑temperature and high‑humidity conditions (-40 ℃, 95 % humidity), equipment ran stably at full load for 72 consecutive hours with no abnormalities.

3.2 Packaging & Logistics

Core electrical components were vacuum‑sealed for moisture resistance against maritime humidity and extreme temperature fluctuations in Eastern European land transportation. Equipment was packed with thick fumigated solid wood cases and high‑strength shock‑absorbing materials to withstand ocean shipping and long‑haul land transport in Ukraine. Complete English technical manuals, IEC certifications, factory test reports and customs clearance documents were provided to comply with local import regulations for efficient delivery and customs clearance of the DTEK project.

3.3 Installation & Commissioning

Prior to commissioning, equipment passed type tests and certifications at Ukrainian national power laboratories (e.g., DTRC) to meet local grid standards.

• Rockwill dispatched bilingual professional technical teams to Kyiv for full‑process localized technical services for DTEK.
• Provided on‑site guidance for 10 kV pole‑mounted equipment foundation construction and earthing system layout to ensure long‑term outdoor operational safety.
• Completed high‑voltage cable termination fabrication, insulation testing and equipment hoisting & fixing in strict accordance with Ukrainian power construction codes.
• Configured localized protection settings and performed system linkage commissioning based on load fluctuation characteristics of DTEK Kyiv 10 kV grid.
• Conducted practical training and daily fault disposal instruction for DTEK local O&M personnel, delivering complete English technical documents for independent post‑project maintenance.

04 Project Outcomes: Data‑Driven Value & High Recognition 4.1 Key Operational Data

Field measured data from DTEK Kyiv Distribution Grid O&M Platform (2021):

• Significantly improved power supply reliability: Transient fault recovery time of renovated 10 kV lines in Kyiv was shortened from 4 hours to ≤60 s with rapid permanent fault isolation. Annual average outage duration for users in renovated sections decreased by 60 %–85 %.
• Optimized voltage quality and grid loss: Stabilized terminal voltage of 10 kV lines, restrained load fluctuations and reduced distribution line losses in suburban areas.
• Enhanced O&M efficiency: Monthly manual inspections of Kyiv suburban 10 kV lines dropped from 10 to 3 via remote O&M platforms, cutting comprehensive O&M expenditure by approximately 70 % compared with conventional circuit breakers and alleviating on‑site maintenance pressure greatly.
• Stable adaptability to extreme conditions: Equipment operated accurately and stably amid Kyiv’s harsh weather including severe winter cold, summer heat, thunderstorms and strong winds, verifying excellent outdoor weather resistance.

• In the 2021 DTEK Kyiv grid upgrading project, Rockwill products featured superior overall integration and faster remote response, compatible with DTEK‑specific protocols. 7×24‑hour non‑stop remote services reduced long‑term O&M costs substantially versus conventional alternatives, with higher overall cost‑effectiveness and stability.

Feedback from DTEK Kyiv Distribution O&M Department: Rockwill outdoor vacuum reclosers adapt well to local harsh operating conditions with fast fault response and stable performance. They effectively shorten outage time, lower O&M costs and deliver efficient full‑cycle services, strongly supporting safe and reliable operation of Kyiv’s distribution grid.

05 Project Value & Industrial Significance

This project greatly strengthened fault self‑healing capability of DTEK Kyiv 10 kV distribution network, secured power supply for the capital, and promoted transformation from traditional to smart self‑healing distribution grids, reducing line losses and improving grid operational efficiency. Serving as a replicable reference for urban distribution grid upgrading in Ukraine and Eastern Europe, it verified reliable performance of Rockwill 10 kV equipment under extreme Eastern European conditions, consolidated the brand’s global expansion advantages, deepened China‑foreign energy cooperation and boosted intelligent modernization of Eastern European power distribution infrastructure.

Adopting vacuum arc‑extinguishing technology instead of traditional SF₆ equipment, the 2021 DTEK Kyiv project generates zero direct greenhouse gas emissions (GWP = 0) during operation. Compared with conventional SF₆ circuit breakers, an estimated 12,000 kg CO₂e emissions are reduced over a 25‑year lifecycle (at an annual leakage rate of 0.5 %–1 %), making it an early benchmark for low‑carbon grid transition in Ukraine and complying with EU green grid guidelines for SF₆‑free equipment.

06 Full‑Lifecycle Operation & Management Services

Rockwill provides one‑stop localized full‑lifecycle O&M support in Eastern Europe for the DTEK Kyiv 10 kV grid modernization project.

Real‑time equipment data collection and early hazard identification are realized via 7×24‑hour remote online monitoring. Customized maintenance plans are formulated for local low‑temperature icing, high‑humidity and dusty environments.

A multi‑level service system combining regional spare‑parts warehouses in Eastern Europe and remote technical support from China headquarters ensures long‑term maintenance‑free stable operation of outdoor vacuum reclosers, safeguarding Kyiv’s power distribution network.

For project details or customized overseas distribution automation solutions, please contact Rockwill. We provide professional and efficient services to advance high‑quality global energy development.

Expert Q&A Summary

Q: What core technological breakthroughs did Rockwill’s 10 kV reclosers bring to DTEK Kyiv’s harsh‑environment grid upgrading in 2021?

A: Our 10 kV reclosers achieved stable operation at -40 ℃ ultra‑low temperatures in 2021, natively supporting the IEC 60870‑5‑104 protocol for direct SCADA integration. Long‑term O&M costs are 40 % lower than those of comparable international brands.

Q: What long‑term ESG value did the 2021 project deliver?

A: Each recloser uses no sulfur hexafluoride (SF₆), reducing 12,000 kg of CO₂‑equivalent emissions over 25 years and laying a foundation for Ukraine’s subsequent green energy transition.