Table of Contents
Digital Substation: Measurement and Transparency
The digital substation is evolving from a conventional grid node into a central measurement, information and control point in the distribution grid. For grid operators, it becomes particularly relevant when distributed generation, e-mobility, heat pumps, battery storage systems and dynamic load flows place new demands on medium- and low-voltage networks.
At its technical core, the digital substation provides continuous transparency across several grid levels: earth fault and short-circuit location, power quality measurement, feeder current measurement with I-Sense, IT security and centralised data analysis. It therefore supplies real measurement data for grid operation, planning, disturbance analysis and grid status assessment.
Instead of deriving grid situations solely from models, forecasts or selective measurements, grid operators can use measured values directly from the substation. This improves the basis for switching operations, maintenance decisions, grid expansion planning and the integration of decentralised generation as well as flexible consumers.
Key Takeaways
- Grid transparency - The digital substation makes relevant grid quantities visible at medium- and low-voltage level.
- Fault location - Systems such as EOR-1DS and EOR-3DS support earth fault and short-circuit location.
- Low-voltage feeders - With I-Sense, feeder currents in the substation can be recorded easily, economically and scalably.
- Centralised analysis - WebPQ® supports visualisation, reporting, alarming and secure data provision.
From Grid Node to Measurement and Information Point
For a long time, secondary substations were primarily technical transfer points between medium voltage and low voltage. The energy transition is changing this role. This is exactly where load flows are bundled, reverse power flows become visible and disturbances can be detected close to the grid node.
The digital substation uses this locational advantage. It records measured values where they are particularly meaningful for distribution grid operation. This creates a central data point for grid transparency, condition assessment and future automation functions.
The combination of several tasks is particularly valuable: earth fault and short-circuit location on the medium-voltage side, power quality assessment, feeder current measurement on the low-voltage side and secure communication with the control centre or central data platforms.
Three Levels of the Digital Substation
A digital substation creates transparency by combining measurement data from medium voltage, low voltage and central data processing. Only through this connection does a complete picture emerge of disturbances, load flows, power quality and the current condition of the local grid node.
1. Monitor Medium Voltage
On the medium-voltage side, fault detection and power quality are the main focus. Earth fault and short-circuit events can be localised faster, while power quality data provides information about voltage events, harmonics or flicker.
- Earth fault and short-circuit location
- Switching states and substation information
- Assessment of voltage quality
- Data for control centres and grid operation
2. Make Low Voltage Visible
On the low-voltage side, the individual feeders of the substation become transparent. This enables grid operators to identify which feeders are heavily loaded, where reverse power flows occur and how flexible consumers such as charging infrastructure, heat pumps or storage systems affect grid behaviour.
- Utilisation of individual feeders
- Load flows and reverse power flows
- Unbalances and dynamic load changes
- Measurement data for grid status assessment, planning and operation
3. Analyse Measurement Data Centrally
The data level makes the recorded measured values usable for operation, analysis and integration. Measurement data is visualised, assessed, documented and securely transferred to higher-level systems such as control centres, SCADA systems or grid status platforms.
- Centralised analysis and visualisation
- Reporting and alarming
- Secure interfaces
- IT security, role-based permissions and audit logs
Medium Voltage: Locate Faults and Assess Power Quality
Continuous transparency at medium-voltage level forms the basis for efficient grid monitoring and fast fault location. In the digital substation, the focus is particularly on earth fault location, short-circuit location, switching states and the analysis of power quality.
Fault passage indicators such as EOR-1DS and EOR-3DS enable reliable detection and location of earth fault and short-circuit events in medium-voltage networks. In combination with suitable sensor technology, currents, voltages, power values and fault events can be recorded.
Additional information, such as the position of the switch disconnector or the feeder earthing switch, can also be provided. This data can be forwarded to control centres or higher-level systems so that faults can be narrowed down more quickly and switching operations can be prepared more precisely.
Fault Location in Medium Voltage: EOR-1DS and EOR-3DS
EOR-1DS
The EOR-1DS is suitable for compact substations when combined short-circuit and earth fault indication with cost-effective fault location is required.
EOR-3DS
The EOR-3DS is designed for digital substations and modern low-power sensor technology. It combines fault location with measurement value provision and digital system integration.
Power Quality as an Additional Transparency Component
In parallel with fault location, continuous monitoring of voltage quality is becoming increasingly important. Power quality measurement systems provide information about voltage quality, harmonics, flicker, THD and short-term voltage events. Especially with growing feed-in from photovoltaic and wind power systems, this transparency is crucial for identifying grid problems at an early stage.
For a reliable assessment, measured values must be evaluated in a standards-oriented manner. Limit value assessment according to EN 50160 supports grid operators in documenting voltage quality parameters in a comprehensible way and classifying technical deviations.
Video: EORSys for Future-Proof Secondary Substations
Fault location, monitoring and integration for modern digital grids
Low Voltage: Measure Feeders and Create Grid Transparency
In addition to medium voltage, the low-voltage level is also being systematically integrated into measurement and monitoring concepts. New requirements are emerging in distribution grids due to photovoltaic systems, charging infrastructure, heat pumps, battery storage systems and increasingly dynamic load flows.
For grid operators, this creates the need to record the currents in the individual feeders of a substation more transparently. Only with a sufficient data basis can utilisation, reverse power flows, unbalances and long-term load developments be assessed reliably.
Measurement Concept for Low Voltage
A suitable technical solution consists of permanently installed measurement technology and scalable feeder current measurement. The PQI-LV can record and process measurement data at low-voltage level. With I-Sense, additional current measurements can be implemented in individual feeders, for example to assess utilisation, load trends and reverse power flows.
I-Sense should be understood as feeder current measurement for substations. The solution supports grid transparency and operational decisions, but does not replace a complete normative assessment of voltage quality. A standards-oriented power quality assessment is carried out via the respective measurement system and the appropriate analysis software.
- Current measurement of individual low-voltage feeders
- Load flows and reverse power flows from photovoltaic systems
- Load trends caused by charging infrastructure, heat pumps and storage systems
- Measurement data for grid status assessment, planning and operation
New Installations
In newly built digital substations, the measurement solution can be integrated directly into the substation planning. Feeders, sensor technology, communication and data provision are considered together from the outset.
Existing Installations
In existing substations, a retrofit concept with I-Sense enables additional feeder current measurement without having to rebuild the substation completely.
Rollout
A uniform measurement concept for new and existing installations simplifies rollout, operation, data integration and subsequent analysis across many substations.
Data, IT Security and Centralised Analysis
Measured values become usable information for operation, planning and analysis
As grid infrastructure becomes increasingly digitalised, IT security, data integrity and controlled system integration are becoming more important. Measurement and communication systems must provide precise data while transmitting, managing and making it available securely to different user groups.
WebPQ® is used as a central platform for analysing and visualising measurement data from permanently installed power quality monitoring devices and fault recorders. The software supports structured analysis, reporting, trend analysis, alarming, dashboards and the provision of measurement data for higher-level systems.
Secure Access
- Central user management, user rights management, role-based access control and audit logs ensure that access, roles and changes in the system can be managed transparently.
Secure Communication
- Encrypted communication via HTTPS, dedicated certificate management and security by design support the protected transmission and processing of sensitive measurement data.
System Integration
- LDAP integration, an open REST API and interfaces to control centre, SCADA, monitoring and grid status systems enable controlled integration into existing IT and grid operation structures.
These functions are particularly important when measurement data from many digital substations is integrated into control centre, SCADA, monitoring or grid status systems. The more strongly a substation is integrated into operational processes, the more important traceable access, clear role models and secure interfaces become.
Technical Building Blocks of the Digital Substation
A digital substation is not a single solution, but a coordinated system consisting of sensor technology, measuring devices, fault location, communication, data storage and analysis. The following overview shows typical building blocks and their technical benefit.
| Grid level | Task | Relevant solution | Technical benefit |
|---|---|---|---|
| Medium voltage | Earth fault and short-circuit location | EOR-1DS, EOR-3DS | Locate faults faster, document events and increase grid transparency |
| Medium voltage | Power quality monitoring | Power quality measurement systems from A. Eberle | Assess voltage quality, harmonics, flicker, THD and short-term events |
| Low voltage | Feeder current measurement and grid transparency | PQI-LV with I-Sense | Record feeder currents, load trends, reverse power flows and utilisation of individual feeders |
| Across substations | Centralised analysis and reporting | WebPQ® | Visualise measurement data, create reports, analyse trends and provide data securely |
| IT and control technology | Secure integration | WebPQ®, open interfaces, role and rights concepts | Integrate data in a controlled manner into existing IT, SCADA and monitoring structures |
Suitable System Components from A. Eberle
PQI-LV
Class A power quality analyser and fault recorder for low voltage. Suitable for continuous monitoring, power quality, event recording and the integration of additional feeder current measurements in substations.
I-Sense
Feeder current measurement for low-voltage feeders in substations. Particularly relevant for retrofit concepts, load trend analysis and additional transparency in modern distribution grids.
WebPQ®
Central analysis software for power quality measurement data, reports, dashboards, trend analyses, alarms and the transfer of data to higher-level systems.
I-Sense
Feeder current measurement for digital substations
I-Sense enables simple, cost-effective and scalable current measurement for individual feeders in the substation. The measurement data helps grid operators make load trends, reverse power flows and utilisation in the low-voltage grid visible.
WebPQ®
Centralised analysis and provision of measurement data
WebPQ® is the central analysis software for measurement data from digital substations. The platform supports visualisation, reporting, trend analysis, alarming and the controlled transfer of data to higher-level systems.
Conclusion and Next Steps
The digital substation is an important building block for intelligent distribution grids. By combining earth fault and short-circuit location, power quality measurement, feeder current measurement and centralised data analysis, it creates continuous transparency across several grid levels.
For grid operators, this means that disturbances can be analysed faster, load flows can be assessed more effectively and the impact of photovoltaics, e-mobility, heat pumps and storage systems can be managed on the basis of measured values. In combination with secure communication structures and central analysis platforms, the digital substation becomes a central data point in grid operation.
As a next step, check which substations in your grid should be prioritised for medium-voltage monitoring, feeder current measurement with I-Sense or centralised power quality analysis. A. Eberle supports grid operators in selecting suitable measurement, sensor and analysis systems.
FAQ - Frequently Asked Questions
What is a digital substation?
A digital substation is a substation that integrates measurement, communication and analysis technology. It records relevant grid quantities at medium- and low-voltage level and provides them for grid monitoring, fault analysis, grid status assessment and automation.
Why is the digital substation important for modern distribution grids?
The energy transition is leading to more dynamic load flows due to photovoltaics, e-mobility, heat pumps and battery storage systems. A digital substation makes these changes measurable and helps grid operators assess grid situations realistically and derive technically sound measures.
What role does I-Sense play in feeder current measurement?
I-Sense enables current measurement of individual feeders in the substation. The solution helps grid operators make load trends, reverse power flows and utilisation in the low-voltage grid visible. A complete normative power quality assessment is carried out via the respective measurement system.
Which products are technically suitable for a digital substation?
Can an existing substation be retrofitted?
Yes, an existing substation can be extended with additional measurement technology as part of a retrofit concept. I-Sense can be used for low-voltage feeders to record additional current measurements in individual feeders and make them available for monitoring, operation and analysis.
What is the importance of IT security in a digital substation?
IT security is crucial because measurement data and status information are increasingly transferred to control centre, SCADA and IT systems. Role-based permissions, encrypted communication, audit logs, certificate management and controlled interfaces help support system integrity and secure operation of digital substations.
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