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LV network monitoring in the Demo2
Type of solution
• Equipment / Hardware / Firmware • Information system
Manufacturer(s) implied (for equipment or hardware)
• ABB
• eMeter Siemens • Schneider Electric
Work Stream considered
LV Innovation
Location / Topology (with regards to distribution grid)
• MV/LV SS • Meter
• Other Centralized system (calculations, information system)
Thematic(s)
• Grid Monitoring / state estimation
Use Case(s)
Outage detection in the LV Network
Key figures
Demo2:
• ~10 600 Smart Meters connected to the demo site area • >100 secondary substations equipped with RTU supervision • Secondary Substation sizes range between
2 and 17 outgoing feeders • >600 outgoing LV feeders monitored
Table- 6 – Technical table of the LV network monitoring in the Demo2
Objective and technical requirements
The objective for the project is to demonstrate a solution for improved outage and power quality management of the Low Voltage network. The solution is based on the already existing Smart Meters, which Vattenfall deployed at all customers several years ago. The deployment of Smart Meters could be seen as the first step of a Smart Grid solution. Introducing RTUs to the solution will be the second step of a Smart Grid solution, which we believe will support further business development in order to reach for the smart energy enabler platform. This technology will support the development towards more micro-scale production, smart homes electric vehicles, reduced CO2 emissions etc.
Context & Objective
Demo2 is participating in GRID4EU with the main purpose to demonstrate a possible solution for LV network monitoring, by deploying intelligent equipment in secondary substations (RTUs) and use the Smart Meters at customer premises. Information from two different sources in the same LV network circuit, will be used and combined in an integrated back office system environment. The benefit of the solution is believed to support different user needs and operating functions such as network planning, optimization, power quality analysis, field service processes etc.
Figure 3 - Demo2 principal technical solution for LV network monitoring
The technical platform will have the possibility to provide better results compared to what data from a single component and system may provide. Both the RTUs and Smart Meters will add insight to the LV network current status and submit information in real time for operational management decisions in order to improve the quality of supply to the customers. The technical solution has the potential to be used in multiple ways and support different purposes. The monitoring platform will serve as a dynamic tool for fast and reliable power quality analysis as well as improved service to the customers.
Requirements
The orange areas on the map show where Vattenfall operate MV and LV network. About 83% of the secondary substations and approx. 57% of the customers are classified as part of the LV rural network. This is the reason why the number of customers on average per secondary substation for the Vattenfall LV rural network is relatively low, 14,4, compared to the average of 21,7 customers per secondary substation including both urban and semi-urban areas.
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These pre-requisites are important to understand when designing a cost efficient technical solution for LV network monitoring, with the purpose to improve outage and power quality management. The network topology has impact on the result for the chosen Demo2 technical solution for monitoring of the 400 V line in the secondary substations.
Typical Vattenfall rural network
In general, rural LV network is characterized by:
• Overhead lines common, with a mix of isolated and non-insulated wires. However in certain regions underground cables are becoming increasingly common as well
• 1-1,5 km between secondary substation and customer
• Mainly small pole mounted secondary substations, with smaller transformer ratings
• Majority of customers connected to the SS without fuses in cabinet to end user line, although this practice is no longer common for new connections
Figure 5 - Typical Vattenfall (Swedish) rural LV network
Given the situation for the LV network operations by Vattenfall, the Demo2 technical solution is designed primarily to identify LV group fuse faults in the secondary substation. This was a conscious choice, with respect to the network topology and the cost for the solution per secondary substation.
In general the solution is not designed to detect faults due to loss of load on one phase. Situations with instantly decreasing load on one phase should not be interpreted as an outage. It may happen that a customer behaves in such a way. Those kind of situations would require a specific power quality meter, in order to better judge the situation by the operators.
Identification of faults downstream street cabinets, e.g. broken fuse in cable cabinet, broken cables due to digging and trees on line3, faults only affecting single premises may be supported by the
Smart Meters event reporting, even though clear outages (power off) are not possible to detect in real time. As smart meters use PLC as the communication media with DC, it is not possible to use that media when there are power outage situations. However, the operator in the Control Center would be informed in near real-time that the communication was lost with smart meters (through Meter Down events). Then, if the operator started receiving Meter Down events for all the meters downstream a street cabinet, it would be very useful for identifying an LV fault in that street cabinet.
Development and implementation
The design of the RTU solution was made by ABB with input from Vattenfall on requirements and installation pre-requisites. All sites were visited and documented prior the deployment of the RTU cabinets.
3. Most 400 V lines are today changed from copper or iron core to Alu. The new lines are
The system environment, the location to host the system hardware, was selected based on primarily IT and Information security regulations. The hardware is located outside Vattenfall ordinary network, on a test net operated by Vattenfall R&D department. “Open” network connections between the Vattenfall corporate network and the Demo2 environment was not allowed to be established. Data was also needed to be anonymous.
Architecture and technical characteristics
The technical solution comprises of 3 parts:
• RTUs connected to each outgoing LV line, all three phases are measured. RTU’s are communicating with built in GPRS modem, using IEC 60870-5-104 protocol.
• Smart Meters at customer premises. Smart Meters are using PLC communication with the Data Concentrator in the secondary substation. DCs are communicating with built in GPRS modem, using OSGP protocol.
• Overlying system applications. ABB Micro SCADA Pro and DMS is collecting the RTU data and Schneider Electric AMI Platform Head End Titanium system is collecting the Smart Meter data. The AMI system is exporting the Smart Meter data, measurement values and events/alarms to eMeter/Siemens EnergyIP MDMS system.
Figure 6 - Demo2 metering equipment in the LV network
Lab tests
ABB functionalities
The use of a RTU solution in secondary substations allows the detection of outages and LV faults.
• The RTU detects an outage or a LV fault, e.g. a drop in current on one or more phase, and reports a warning to the SCADA system. This improves the fault awareness time.
• The SCADA generates an alarm, which is instantly processed by the DMS to red mark the line in questions to indicate the loss of power. This improves the fault location time.
• The isolation work is done manually by the operator who uses information mainly from the RTU to work more efficiently. This information will help to reduce the isolation time in field. DMS
Within the Distribution management system (DMS600) ABB has implemented two functionalities. Both target operator awareness and in aim to shorten lead time in fault location and fault resolution times (SAIDI);
• AMR Meter Event visualization
- A functionality which processes selected high priority events from the meters at customer premises and maps them to the right meter in the DMS. The DMS has a complete representation of all customer meters on the feeders monitored within the demo. This
Ca 1000-1500 meters
Street Cabinet Supply line fuse to all customer premises In normal case (>95%) = 35A
L1 L2 L3 L4
LV fuse, normally 63A-125A Transformer 50-200kVA HV fuse (400 V) (Overhead line) Pole mounted (Overhead line) (Ea rth ca ble) Line fuse ∼35A to 63A Group fuse
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functionality allows an operator to quickly spot where a specific customer event is located. In figure 7 below, each Number is a meter and the 7276967 meter has been marked red due to a “Device tampering” event. The substation that the meter is connected to (XSS000109) is also marked red for ease of tracking.
Figure 7 - ABB DMS Visualization of events from customer meters
• Current or voltage drop visualization
- As a way to signal a drop in current on a feeder or voltage drop in the busbar in the LV network. ABB has implemented a functionality that mimics the behaviour of the DMS in case of a breaker opening. When the SCADA gets a signal that a line drops to near zero current, the fictive breaker is set as open and the line in question is marked red to indicate the loss of power.
The combination of these two functions gives an operator swift indication when a fault occurs. This enables quick action to be taken, either to monitor that power is restored or to initiate an investigation.
SYS600 Historian
The SYS600 Historian is a historical database. It is dynamically updated and presents live data along with historical data to give graphs of measured values. The operators choose content. Through discussions with Vattenfall operations staff ABB has created graphs that helps operator monitor, live or historically, the consumption, power quality and technical losses.
• Technical losses
- The historian has access to data on energy supplied on each outgoing feeder in any substation. At the same time the system receives meter data on consumed energy from the individual meters connected to the feeders. Historian then produces a graph where supplied energy, consumed energy and the diff on a selected feeder or substation is shown. By setting this up per station, it is easy to identify troublesome stations and on those set up monitoring for the individual feeders to further pinpoint the source of the technical loss.
Figure 8 - Graph of energy and losses. Red is the difference between energy supplied (orange)
and energy billed (green)
- In the report pictured below three lines are shown. Green shows consumption data based on aggregated data from customer meters. Orange shows supplied energy as measured in the secondary substation. Red shows the difference, which is unbilled energy. This report can help detect power theft.
(Please note that the feeder producing data for the graph has been chosen for its irregular consumption pattern, to illustrate the functionality of the report).
• Graphs for power quality monitoring and analysis
- The multimeters in the field provides a range of data for each phase per outgoing line. The values cover active power, reactive power, power factor, frequency, accumulated energy and harmonics. Out of these values the operators choose which data to view and to what granularity.
- Historian supports resolution down to millisecond level and allows for combination of values within the same graph. To visualize this, the picture in figure 9 shows the total harmonic distortion as a percentage deviation from pure 50Hz.
Figure 9 - THD as percentage deviation from pure 50 Hz
All values stored in Historians database can be exported to spreadsheet format. The selection of data can be done from the graphical interface where the operator marks the timespan to be exported. This means that the historical database can be used both for at a glance monitoring and for analysis to provide input for proactive maintenance.
eMeter Functionalities
EnergyIP MDMS platform provides a tool for in-depth analysis of customer and network behaviour. The high level functional configurations and integrations relevant to EnergyIP MDMS testing in order to run MDMS properly are:
• VPN environment
The demonstration application is installed as a “stand alone” solution, separated from the operating Vattenfall system environment.
• Asset Synchronization
Network assets and relationships was made in a one-time synch with Vattenfall Master systems and EnergyIP. The same with ABB DMS/RTU system data.
• Meter Read and Event processing
Interfacing with the AMI system (measurement values and events/alarms) is done via VIP (Vattenfall Integration Platform). Data from the DMS_RTU is processed using a file format point
to point connection.
The reporting framework Analytics Foundation is designed to pull data out of EnergyIP’s MDMS and create a purpose built database. From the wide range of reports, only Load Analysis and Device Event reports were used for Demo2 analysis.
• Data from MDMS dB to Analytics Foundation dB using ETL – (Export/Transform/Load)
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Field implementation
ABB and Vattenfall field implementation
ABB has created a series of metering cabinets for the GRID4EU. Uniformity and common components has been the key focus in the design process. All cabinets use the same RTU, multimeters, antennas and power supply. To cover all 100+ installations only four different cabinet sizes have been used. The adaptation of the cabinets is done by varying the number of multimeters, one per each outgoing group.
Figure 10 - Snippet from a layout showing two of the larger cabinets and their suggested number
of multimeters
This approach allows for fast and efficient design and construction. That is a central factor in cost efficiency in the perspective of a bigger roll-out where the number of stations is significantly higher. It does however require the DSO to have good knowledge of the stations where the cabinets are to be installed.
In many cases an inventory of the stations is needed in order to assert that the right number of multimeters are installed and that there is room to mount the equipment.
The largest cabinet (LARGE) in the Demo2 is 600x800x200 mm (BxHxW) and houses up to 16 multimeters. The smallest cabinet (MICRO) is 300x600x200 and houses 1-3 multimeters. All cabinets contain power supply, heating and communication equipment (GPRS modem in the RTU).
Figure 11 - The smallest cabinet in the Demo2 family, model designation ‘MICRO’
They are prepared to be mounted on poles or walls. All cables run through the back plate in order to minimize exposed parts. All equipment is DIN-rail mounted on a separate back plate. This allows installation to be done without the cabinet at indoor stations where the available space is an issue.
Figure 12 - In bigger stations the solution can be taken out of the housings and be mounted
on any available space in that substation
System implementation
System implementation was made in the Vattenfall R&D location Älvkarleby and is connected to a test net, entirely separated from the ordinary Vattenfall corporate network.
In order for the Demo2 environment to operate as intended it is depending on information from outside connections. There are three different kind of connections between TestNet and external sources; client VPN, system VPN and SFTP.
• Client VPN (orange lines) is used primarily to administrate the systems by the Demo2 partners.
• System VPN (green lines) is used by the communication service provider Sierra Wireless for RTU data collection.
• SFTP (blue lines) is used for transferring Smart Meter data from Vattenfall to Demo2 system environment.
Figure 13 - Demo2 system set-up as a stand-alone solution
Technical results
ABB Technical results
The results are divided between the performance of field equipment and the technical innovation of the DMS600 and Historian functionalities developed.
RTU performance
When RTU’s are used for network monitoring, like they are in Demo2, the reliability of their communication becomes a key factor. One of the central KPI’s of the projects measures the population of RTU’s on just this. Out of 108 RTU the following performance results have been determined.
Average RTU availability after field visits, fine tuning of RTU configuration and upgrade of firmware was recorded to approximately 95%. An increase in the availability from peak low 50% on average before improvement actions were undertaken.
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The communication process has tested both GPRS/2G and 3G technology. Comparing the GPRS/2G with the 3G technology result in an advantage for the 3G technology when being used in a Smart Grid context. The 3G technology especially supports the RTU <-> SCADA process in the need for maintenance work, real-time monitoring and higher data traffic volumes.
In order to reduce the data traffic volume between the RTU and the SCADA system, the RTUs are activated with deadband. The RTU is collecting and storing data, individual values, up to the defined limit for the deadband threshold, which is a change in the RMS value for more than 50 percent compared to the previous value. The RMS value can be changed by more than 50 percent immediately from one value to another and in this case the RTU will send the data to the SCADA system. Alternatively, the RTU will collect and store the change in RMS values until the accumulated sum of those changes is greater than 50 percent from the previous value. This will then trigger a sending of data to the SCADA. The longest interval between two data packages sent from the RTU to the SCADA system should not be more than 60 seconds. This configuration of the RTU will not impact the functionality of the solution. Large deviations in the values will be immediately reported as “warnings” and normal operation will be reported with less frequency Typical data usage per RTU depends on the size of the secondary substation and the power quality on the LV network. For the project period the volume range between approximately 1000-4500 kB per day.
AMR events
The AMR events function uses a Graphical User Interface (GUI) within the DMS600. It sorts incoming events by type and reporting substation. Each event contains information on which meter has sent it, time stamp when it was sent from the MDMS system, type of event and which secondary substation that signaling meter is connected to. The info about the substation is given as extra information to help reduce the time needed for fault restoration. The operator chooses to locate or reset the alarm using buttons in the GUI. If the locate function is enabled, the map system of the DMS zooms to the LV network where the meter is located and high lights the specific meter. This function makes it possible for an operator to easily monitor large LV grids for specific event types or trends. The system uses the IEC61968-9 interface to send real time events and alarms to the DMS.
Figure 14 - The AMR event GUI. Active alarms are sorted based on event/alarm type and each even contains all
information needed for operator analysis.
Statistical data and PQ monitoring
Within the results for PQ monitoring ABB’s Historian suite provides a range of graphs based on any combination of the provided data. Consumption data from meters and secondary substations combined provides technical losses data or graphs
on feeder, station or LV grid level. For an example of graph, see figure 15 above.
Figure 15 - Available data from RTUs
The main part of the data available comes from the RTU’s and is listed in figure 15. It should also be noted that the database provides functionality to import data from other devices in the Demo2 system such as meter data using CSV files.
eMeter Technical results
Especially Load Analysis and Device Event reports will be studied for the Demo2 demonstration.
Load Analysis
Load analysis reports show load usage data, load curves, and load duration curves. These reports provide a way to drill into load usage, from a high-level overview showing load usage and load duration.
The Load Curve for a Substation, illustrated below, is an example of the comparison of substation load compared to the nameplate and derived rating of the low voltage substation transformer. This can be useful to study season, or daily peaks or the impact of load switching. The loading below shows a trending loading decrease from the beginning of April.
Figure 16 - Demo2 Load curve for a substation presented in EnergyIP
Comparing the Load Curve to the DMS_RTU data can provide additional insights to the analysis. The individual meters may be graphed to illustrate the customer that has the highest contribution to the aggregate load of a substation or feeder. In the sample below “Feeder- Multiple AMI Meters” meter A contributes close to the entire feeder loading.
Figure 17 - Demo2 Meter contribution to the entire feeder loading presented in EnergyIP
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Device Events
Device Event reports can be used to track outage issues, trends, and impacts. These reports provide a way to drill down into events from a high level substation view to individual customers or single delivery points (SDP).
For the demo period events were received from March through August into the Analytics Database for study, refer to “Device Events Summary” below. Events are sorted into predetermined buckets for easier analysis and focusing on outages June 6 is a spike for the time period. The Device Event Summary Table shows that 192 SDPs experienced an outage at that time.
Figure 18 - Demo2 Device event summary table presented in EnergyIP
Elements of Cost & Benefits Analysis
Even though the RTUs are installed on the outgoing LV lines, the RTUs can also support operation on the Medium Voltage side of the secondary substation. A broken fuse on the MV side (10 kV) can be detected by the RTU due to the fact that the load on the LV side then will become asymmetrical. Therefore the benefit analysis includes also MV side.
The JRC (Joint Research Centre) report, “Guidelines for conducting a cost benefit analysis of Smart Grid projects”, has served GRID4EU with guidelines for calculating Smart Grid Cost Benefit Analysis (CBA). The JRC report is grouping these benefits into four categories Economic, Reliability, Environment and Security. These four JRC categories includes 23 possible benefits for Smart Grid projects. This analysis has focused only on reduced sustained outages defined as: “Reduced outage time through early awareness of failure event by DSO. Potential outage time reduction due to shorter restoration time thanks to information that help in localization of outage and better management of maintenance
personnel”.
The benefit was analysed in terms of reduction of SAIDI in minutes by using the deployed RTU solution in rural secondary substations. The work covered to analyse the outage management process with and without the support of RTUs and identified the type of faults as well as the number of registered MV and LV faults in 2014 that would have been possible for this solution to detect. An average on the number of affected customers per MV high voltage and LV low voltage fuse faults was also defined.
The final calculation of the impact on SAIDI that this RTU solution may have on reduced sustained outages faults, according to JRC terminology, is estimated to be in the range of 5-12 percent, or approx..6-15 minutes reduction of SAIDI for both MV and LV network.
The analysis showed a result which was not anticipated from the beginning. Initially the scope for the BC was only to analyse what impact measurement in secondary substations could have on reduced sustained outages in the LV network. The results showed that the benefit would be greatest for the MV case that is where the RTU is anticipated to contribute with most value.
This analysis has only focused on one of the 23 benefits in the JRC model. If other of those benefits were to be included as well, e.g. reduced sustained outages and others, it is most likely that the overall benefits would be higher. It is further anticipated that other network company processes may benefit from the introduction of LV network monitoring, such as for instance Power Quality issues and network planning procedures, that additionally may even further increase the overall benefit.
Another perspective would be to also include how the Smart Meters together with the RTUs could contribute to the benefit, as described in chapter 3.2.1.2 under technical losses. Such an analysis would perhaps identify a larger volume of faults that could be qualified to be included in the analysis, as well as support activities in the general process in a positive way.
Furthermore investments in and deployment of Smart Grid technology are not solely made out of direct benefits to the network operation but to a large extent also for improving the network services to the customer and the society as a whole. Such benefits are often regarded as quite substantial and, in the case of customer benefits, it is of uttermost importance to a network company to keep their customers satisfied. If this can be achieved by reducing outage time, etc, Smart Grid investments may be regarded as immensely beneficial to the image of the network company and consequently quite valuable.
Replication, next steps and up scaling
Replication and up scaling (exploitation) of the solution for Vattenfall is dependent on a) choice of strategy for LV monitoring, b) funding for the investment, c) LV SCADA/DMS system implementation in production system environment and d) process re-engineering and organisational change of work in the control center.
Exploitation in line with the Demo2 technical solution will require full deployment of IEDs in secondary substations combined with new system interfaces between the Enterprise system EnergyIP MDMS and the IEDs, e.g. by integrating the MDMS with a LV SCADA and DMS system. This type of system functionality may also be supported by other system applications used in network operations. The choice of solution depends on the cost for development, implementation, license fees and access to the application by the different user groups within the DSO.
Intellectual property (IP)
Any IP rights are not identified for the DSOs, such rights are more of interest for system vendors and manufacturers of equipment. IP rights will be applicable for system application functionality as well as equipment design and functionality. In the Demo2 case this will be applicable for the ABB SCADA and DMS solution and the design of the secondary substation measurement solution. It will also be applicable for the eMeter solution and configuration of the EnergyIP MDMS functionality, including the Analytics Foundation.
Regulatory challenges
The roll out of Smart Meters in Sweden was driven by new regulations in 2009.
Conclusion and key messages
The project operation has demonstrated a successful design of the technical solution in the secondary substations, where defined fault cases are successfully identified by the RTUs. Warning messages from both RTUs and Smart meters are sent to the overlying SCADA system. These messages are processed by the SCADA system and announced in the SCADA alarm lists and displayed in the DMS.
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From the alarm lists in SCADA, the system functionality takes the user directly to the alarmed LV line in DMS, which is clearly marked in the user interface of the network topology. The DMS system can visualize the LV network at different zoom levels, where the most detailed level is at a single measuring point (residential meters). In EnergyIP MDMS in-depth analysis can be made using data from both RTUs and Smart meters.
A general comment to the Demo2 results is that a Smart Grid concept for the LV monitoring may be shaped and created differently depending on the actual network situation. It is assumed that the RTU solution has greatest benefit in rural network areas. The simplified Business Case analyses, performed by Demo2, showed a potential benefit of 5-12 percent reduction of SAIDI for both MV and LV rural networks. A more advanced solution, i.e. increased investment per LV line, may improve SAIDI even more, but the improvement of SAIDI may not be correlated with the investment cost.
The average number of faults per MV or LV feeder per year are not that many and the “basic” average Smart Grid investment cost
per secondary substation today is substantial. The evaluation has shown that it is reasonable to assume that a large scale roll-out of the solution would first carefully analyse the quality of supply in the MV and LV networks in order to find those network areas where the benefit would be greatest. Also the most suitable level of technical solution needed will most probably be evaluated, e.g. for very small pole mounted secondary substations only monitor voltage and current on the LV side of the transformer and not on the individual LV line(s) or just use the AMR infrastructure.
As a first step, the chosen level of Smart Grid solution is assumed to differ between rural and urban areas, types of secondary substations (pole mounted, larger ground stations, smaller kiosks etc) and retrofit installations versus deployment of new secondary substations etc. The future LV monitoring solution will contain a combination of different technical solutions, from only using the Smart meters to use advanced equipment in secondary substations and perhaps also downstream individual LV lines.
Demo2 Challenges Conclusion Key Messages
Data collection using
RTUs. Solution is tested and verified. The LV failures, (phase faults) are detected and reported within seconds to the overlying SCADA system.
LV monitoring also support MV monitoring. The solution has no battery back-up power, (no last gasp functionality). This is a limitation in the way that it could be difficult for an operator to determine if a warning is an outage or if it is only loss of communication.
Data collection using RTUs / Communication technology
2G and 3G communication technology both support a Smart Grid solution for LV network monitoring.
For uses such as maintenance and service of the RTUs it is far more efficient to use a faster 3G connection. This is also a good preparation for later stages where DSO’s might want to pick up larger files from the IEC 61850 network in the secondary substation.
ABB MicroSCADA Pro, Historian and LV DMS
Demonstrated applications for display of data, visualization of LV network monitoring as well as creation of reports and graphs for in-depth analysis.
There is a potentially enormous amount of data provided by the components.
By integrating Smart Meter measurement values and events, the system platform provides a powerful tool for LV network monitoring both at each outgoing LV line from the secondary substations as well as in the end of the line, on individual meter level.
Carefully select the only needed data for analysis and visualization in order not to overload the operator with unwanted information, which in the worst case may obscure the potential problems from the Dispatch Center.
eMeter EnergyIP MDMS Processing and display of data from both Smart meters and RTUs to support dynamic in-depth LV network Smart Grid analysis.
The EnergyIP MDMS is a powerful tool for network optimization and maintenance analysis, supporting with dynamic findings by combining the data received from both RTUs, (secondary substations), and individual meters.
Demos Business Case analysis
The Demo2 BC analysis for JRC reduced sustainable outage benefit showed an overall potential reduction of SAIDI with 5-12% improvement for both MV and LV network outage management.
This analysis only focused on one of the JRC defined benefits. A broadened scope would perhaps increase the benefit potential for LV network monitoring. Such an analysis should include other company processes and customer/ societal factors.
