Stockholm’s municipal power utility, Stockholms Elnät, has successfully completed the deployment of ABB REM543 control devices across 120 medium-voltage distribution substations as part of its city-wide smart grid modernization initiative. The upgrade, finalized in Q4 2025, aimed to address critical challenges posed by aging control systems, including prolonged outage durations, inefficient fault localization, and limited compatibility with renewable energy integration.
The Challenge: Aging Infrastructure Struggles with Modern Power Demands
Prior to the upgrade, Stockholms Elnät’s substations relied on control systems installed in the early 2000s. These legacy systems presented significant operational hurdles: average outage durations exceeded 90 minutes per incident, primarily due to manual fault detection and isolation processes. Additionally, the outdated controls lacked the precision to manage the variable power output from 400+ rooftop solar installations and 15 small-scale wind farms connected to the distribution grid, leading to frequent voltage fluctuations and 12-15 grid stability incidents annually. The utility also faced rising maintenance costs, with annual expenditures reaching €1.2 million due to frequent component failures and the need for specialized technicians.
“As Stockholm transitions to a carbon-neutral city by 2030, our power grid must be agile enough to handle growing renewable energy penetration while ensuring uninterrupted service for 1.2 million residents and 120,000 businesses,” said Mats Andersson, Grid Modernization Director at Stockholms Elnät. “Our legacy control systems were a bottleneck—too slow, too unreliable, and unable to keep pace with the demands of a smart grid. We needed a control device that could deliver real-time data, automate fault response, and integrate seamlessly with our existing SCADA system.”
The Solution: ABB REM543’s Advanced Control Capabilities
After a rigorous evaluation of competing solutions, Stockholms Elnät selected the ABB REM543 for its advanced feature set tailored to smart grid applications. Key capabilities of the REM543 that addressed the utility’s challenges include:
- Real-Time Fault Detection & Isolation: The REM543’s built-in IEC 61850 communication protocol enables sub-second data transmission, allowing the utility’s control center to detect and isolate faults within 5 minutes—down from 45 minutes with legacy systems. Its advanced algorithm analyzes voltage, current, and frequency data to pinpoint fault locations with 99.2% accuracy.
- Seamless Renewable Integration: The device’s flexible control logic supports smooth integration of variable renewable energy sources, automatically adjusting voltage and reactive power to maintain grid stability. It also provides real-time monitoring of renewable energy output, enabling better load forecasting.
- Remote Monitoring & Maintenance: The REM543’s web-based interface allows technicians to monitor substation performance and perform software updates remotely, eliminating the need for 70% of on-site maintenance visits. Its robust design, rated for operating temperatures from -40°C to +85°C, ensures reliable operation in Stockholm’s harsh winter conditions.
- Scalable Integration: The device integrates seamlessly with Stockholms Elnät’s existing ABB SCADA system and future smart grid technologies, including demand response programs and electric vehicle (EV) charging infrastructure management.
The Results: Significant Outage Reduction & Cost Savings
Six months after full deployment, the ABB REM543 has delivered transformative results for Stockholms Elnät:
| Metric |
Before REM543 Deployment |
After REM543 Deployment |
Improvement |
| Average Outage Duration |
92 minutes |
59 minutes |
35% Reduction |
| Annual Grid Stability Incidents |
12-15 |
2-3 |
83% Reduction |
| Annual Maintenance Costs |
€1.2 Million |
€648,000 |
46% Reduction |
| Fault Localization Time |
45 minutes |
5 minutes |
89% Reduction |
“The ABB REM543 has been a game-changer for our smart grid transformation,” Andersson noted. “The reduction in outage time has significantly improved customer satisfaction, while the cost savings have allowed us to invest in additional renewable energy integration projects. We plan to deploy the REM543 across 80 more substations by 2028, covering the entire Stockholm metropolitan area.”
Johan Carlsson, ABB’s Global Product Manager for Distribution Grid Solutions, commented: “The REM543 is engineered to address the unique challenges of modern distribution grids—resilience, renewable integration, and operational efficiency. Stockholms Elnät’s success demonstrates how the device can help utilities accelerate their energy transition goals while delivering tangible operational and financial benefits.”
