Learnings

Outcomes

Technical Papers

 V. Peesapati, R. Gardner, J. King, S. Jupe, J. Berry: “Understanding the harmonic performance of voltage transformers for distribution system power quality monitoring”, 25th International Conference and Exhibition on Electricity Distribution (CIRED), Madrid, June 2019

 P. Davis, P. Wright, J. King, S. Jupe, S. Pinkerton-Clark: “Voltage Transformer Harmonic Characteristics for Distribution Power Quality Monitoring”, 26th International Conference and Exhibition on Electricity Distribution (CIRED), 2021 (accepted for presentation)

 J. King, A. Forster, S. Jupe, S. Pinkerton-Clark: “A View of 2020 Power Quality within GB Distribution Networks”, 26th International Conference and Exhibition on Electricity Distribution (CIRED), 2021 (accepted for presentation)

 J. King, D. Wiley, S. Hoda, S. Jupe, S. Pinkerton-Clark: “An Integrated Platform for Power Quality Monitoring”, 26th International Conference and Exhibition on Electricity Distribution (CIRED), 2021 (accepted for publication)

Reports

PQM Market Research Report:
This report summarises the findings from a market research exercise on power quality monitors (PQMs) that was undertaken to inform the selection of PQMs for the PNPQA project. The research exercise comprised of identifying vendors of PQMs and examining their products to determine the key features of different PQM devices.

Power Quality Monitor Remote Communications Initial Feasibility Assessment:
A report of early work done in the project; this consisted of assessing the feasibility of interfacing with several PQMs that were in use by WPD or that had been identified for potential future use by WPD, so that PQ data can be communicated remotely.

Envoy/PQube3 Interface Factory Acceptance Tests:
This report is both a test specification and a test record for the Factory Acceptance Test of the Envoy firmware modifications to interface with PSL PQube3 PQ monitor.
Envoy/a-eberle PQI-DA smart Interface Factory Acceptance Tests:
This report is both a test specification and a test record for the Factory Acceptance Test of the Envoy firmware modifications to interface with a-eberle PQI-DA smart PQ monitor.

Envoy/Siemens SICAM Q200 Interface Factory Acceptance Tests:
This report is both a test specification and a test record for the Factory Acceptance Test of the Envoy firmware modifications to interface with Siemens SICAM Q200 PQ monitor.

Power Quality Monitor Pilot Trial Analysis:
Prior to the wide scale trial of communicating PQ monitors, a pilot trial with a single monitor took place to help guide the preparations and reduce uncertainties. The monitor and a communication hub were installed at Meaford C Bulk Supply Point (BSP) in June 2018 and data from the 6 weeks after installation was analysed and the findings presented in this report.

Trial Area and Site Selection:
This report describes the development and application of a methodology for the selection of trial areas and sites for the wide scale power quality monitoring trial within the project.

Proposal for Additional 11 kV Sites:
This report described and applied a methodology for identifying and selecting additional 11 kV sites to be monitored as part of the PNPQA project, which was developed as the project budget allowed for additional monitoring to be installed.

PQ Trial Data Analysis Scope:
This report outlined the scope for PQ trials data analysis. As the project would generate around 1.5 billion measurements, having a clearly defined scope for the analysis of that amount of data was vital.

PQ Trial Data Analysis Report:
This report contains the analysis and key findings from the remote PQ monitoring trial.

Power System Analysis Tools Review:
This report is a review of several power system analysis tools in order to recommend which tool would be used for the future-looking power quality studies as part of the PNPQA project. Requirements for the tool were developed and used to compare 20 different tools that were available at the time, including those is use in WPD.

PQ Study Objectives & Methods:
This report outlined objectives and methods for the future-looking power systems studies as part of project.

PQ Study Results:
This report presents the implementation, results, and key findings from the future-looking power system studies of the potential impacts of increased penetrations of LCTs.
Six monthly project progress reports:
These are standard project progress reports that are produced every 6 months.

Project close down report:
The project close down report as required under the NIA process.
Energy Networks Innovation Process Project Closedown Report Document
8 Energy Networks Association

Documents
 Standard Technique Relating to the Installation, Configuration, and Commissioning of Power Quality Monitoring Using the PSL PQube3
 Standard Technique Relating to the Retrieval, Monitoring, and Analysis of Power Quality Data using iHost
Systems
 Automated software for vendor-agnostic retrieval and analysis of PQ data from remote monitors, integrated in to Nortech’s iHost platform
Processes
 Process for installing and commissioning PQ monitors as defined by the Standard Technique.
 Process for analysing PQ monitors data as defined by the Standard Technique.
Presentations & Dissemination Events
 CIGRE UK webinar on project findings
 Presentation at ENA Power Quality & EMC Working Group

Lessons Learnt

·        Primary Network PQ 

The standard way of assessing PQ is to use the 95th percentile aggregates of data taken over a week-long measurement period. However, the year or more of monitoring data gathered by the project has revealed that the 95th percentile aggregates can vary significantly from week to week, so basing PQ assessments on a single week of measurements may over- or under- represent existing PQ issues. 

·        Primary Network PQ 

Monitoring every site within a 33 kV network has revealed that PQ can vary significantly across the sites, meaning that PQ data gathered at a single site may not be representative of the conditions at other sites. Therefore, monitoring should ideally be located at the network infeed and the remote ends as a minimum to achieve broader PQ visibility and capture more representative data. 

·        LCT PQ impacts 

Comparing PQ during LCT operation and during outages is a very straightforward way to understand the PQ impact of a specific LCT, but realistically this can only be achieved through constant monitoring. 

·        LCT PQ impacts 

The influence of LV-connected LCTs, such as heat pumps and electrics vehicles, on higher voltage networks (e.g. Primary Networks at 33 kV) is still uncertain, and could be a major source of PQ issues as the uptake of LV-connected LCTs accelerates. 

·        PQ monitor features 

Market research revealed at least 20 manufacturers of PQ monitors that met the basic requirements expected for the project. However, none had identical interfaces meaning bespoke work was needed for each to enable remote communications with the monitors. 

·        PQ monitor features 

Whilst the 3 different PQ monitor models trialled during the project allowed the same aggregated continuous PQ monitoring data to be obtained (typically aggregated every 10 minutes), they varied significantly in their event triggering and recording capabilities. The ability to record high-resolution waveform data and RMS data – typically at half-cycle resolution, ideally for 10s or more – were both found to be useful. Triggers for rapid voltage change (RVC) were useful at capturing data during network faults, even at sites that did not see the fault current. Triggers for rate of change of frequency (RoCoF) were only available for one of the monitors but are useful for capturing RoCoF events that can lead to distribution generation tripping such as the low frequency event of 9th August 2019. 

·        PQ data transfer 

Communications surveys during the pre-installation site surveys revealed that no single mobile network provider could provide coverage at all sites, particularly for 4G. Therefore, roaming SIM cards were used so the communications hub could use whatever providers are available at each site. 

·        PQ data transfer 

Two different monitors were interfaced with using IEC 61850. Testing of these monitors revealed differences in their implementation of IEC 61850, in particular the file transfer mechanism, which prevented a single “standard” interface from being used for both monitors. 

·        PQ data transfer 

One of the monitors interfaced using IEC 61850 required constant polling in order to obtain the most recent measurements. This approach occasionally led to small amounts of data being lost as the monitor was sometime unable to reply to all requests. Furthermore, if communication between the monitor and communication hub was lost for a period, almost all monitoring data for the period cannot be subsequently retrieved using the IEC 61850 protocol as implemented on the monitor. As the PQ monitoring data does not need to be transmitted continuously, transfer of the data via file transfer is preferred as it can be carried out asynchronously, is more robust to temporary communications loss, and is less resource intensive. 

·        PQ data transfer 

Generally, file-based transfer of monitoring data from the remote sites into the central data analysis server was found to be very robust, even when faced with very poor signal strength and communication outages of a week or more. Generally, the data for a single day of monitoring could be compressed into a few MB, so many months – or even years – of data could be stored locally prior to upload. 

·        Remote reconfiguration 

PQ monitors that use files for configuration and firmware updates allowed remote reconfiguration and updates to be achieved, which was used effectively in the project to avoid site visits to achieve the same outcome. This was not possible for the monitors that needed a direct connection to the vendor’s software for updates due to: 1) IT rules preventing the software being installed and used on the central monitoring server, 2) network routing preventing direct traffic between the central monitoring server to the PQ monitors, and 3) the potential for poor signal strength to slow or stop communications between the central software and remote PQ monitors. Furthermore, file based transfers could be automated, removing the need for manual intervention to reconfigure or update PQ monitors in the field.

·       Time synchronisation

Time synchronisation using NTP over the 2G/4G network was observed to deliver adequate performance for general PQ monitoring, with generally <1 s difference in clocks between sites. Adding GPS-based high resolution time synchronisation would have added some cost of the PQ monitoring equipment and complicated the installation process as an external antenna must be fitted to access the GPS signals. 

·        PQ monitor installations 

Occasional instability of one PQ monitor was observed, so a method of remotely triggering a power cycle was developed using a non-latching relay to interrupt the power supply, driven by the communications hub. This was used a few times and avoided needing to visit site to reset the units. 

·        PQ monitor installations 

The project trialled semi-permanent “plug & play” PQ monitor installations, which used PQ monitors in small enclosures that could be placed inside existing cabinets – or on the top or side using magnetic mounting feet – with voltage test lead and current (clamp CT) inputs. The “plug & play” monitors could be installed with 1-2 hours with 1-2 personnel, including sourcing power and post-install checks, and did not require any outages. There was no significant time saving if current monitoring is skipped. 

·        PQ monitor installations 

The “plug & play” PQ monitor installations were sped up by pre-configuring and pre-commissioning the monitors (using secondary injection) and communications hubs prior to going to site. This reduced the complexity of install checks on site to a simple single A4-sized checklist. 

·        PQ monitor installations 

One downside of the “plug & play” installations was that the power supplies used were not backed up, so if a network fault occurred the power supply to the PQ monitors could be lost along with the monitoring data up to the point of the outage. This could be solved by attaching the monitors to the substation batteries (if spare capacity is available) or by integrating a small uninterruptable power supply (with battery) alongside the PQ monitors. 

·        PQ data analysis 

Most PQ monitoring is based on average measurements taken every 10 minutes. However, having some metrics (e.g. voltages and currents) also available at higher sampling intervals and with minimum and maximum aggregates was found to be useful in understanding device behaviour (e.g. short term variations in solar PV power output) and for observing network faults (e.g. by looking for short-term spikes in current and dips in voltage). 

·        PQ data analysis 

For offline analysis of large PQ datasets, using the hierarchical data format (HDF) rather than CSV or spreadsheets allowed for much more efficient storage and retrieval of data, and easy integration in to automated analysis scripts. 

·        VTs for harmonic monitoring 

33 kV and 11 kV VTs pass through signals at the harmonic frequencies typically measured (up to the 50th harmonic) but introduce attenuation in the output magnitude at higher frequencies. 

·        VTs for harmonic monitoring 

Close attention must be paid to the frequency response of the measurement system in addition to the VT under test, as this can influence the results. Calibration of the equipment at harmonic frequencies is vital in addition to calibration at the fundamental frequency. 

·        VTs for harmonic monitoring 

The ability of 3-phase VTs to transfer triplens harmonics – which typically are in phase – varies significantly depending on the construction of the VTs.