HV Pinpoint
| Funding mechanism | Network Innovation Allowance (NIA) |
|---|---|
| Duration | Mar 2024 - Oct 2024 |
| Estimated expenditure | £719K |
| Research area | Optimised assets and practices, Net zero and the energy transition |
Objective(s)
The project aims to:
- Develop 3-phase online HV cable sensors capable of detecting phase-to-phase and phase-to-earth pecking events, which don’t require CTs
- Develop a Pulse Injection Generator (PIG) which can be used to validate event location
- Develop sensor mat which can pinpoint events from street level
- Test the developed devices in lab, trial network and live network environments
- Combine the developed devices into an integrated system which can be used for end-to-end pre-fault management
- Develop a system which works on three ended circuits
- Develop system in a way which can be installed and operated non-invasively, without needing to break apart switchgear end-boxes, which can be used with a range of cable/switchgear types
- Develop a portable system not reliant on test van techniques
- Improve understanding of the cost of the devices and operational cost of the method, and how this could be scaled to rollout across NGED/other DNOs
Problem(s)
HV faults on the underground network account for a large proportion of unplanned outages, where customers may remain off-supply until the fault is found and repaired. Given the role of electricity in supporting the decarbonisation of transport, heat and industry, it is becoming increasingly important to find ways to proactively avoid these faults. Current fault finding methods are limited, as although a broadly correct defect location can be found through sectionalising, labour intensive test-van based methods are required for precise location of the fault before a repair can be planned.
NGED’s Pre-Fix project started to address this problem by developing a pre-fault capability to proactively detect, locate and repair anomalies before they deteriorate into faults. The developed system also offers improvements to NGED’s post-fault response by reducing the time and resources required for locating faults. However, the Pre-Fix method is limited as although it can provide a pre-/post-fault location up to the correct circuit section, it cannot provide accuracy that is suitable to instruct excavation, and is currently untested at scale on NGED’s network.
A precise defect location can be found using Partial Discharge (PD) mapping techniques, but we would like to find a more flexible method to pinpoint the anomalies. PD mapping faces certain limitations such as requiring on-site, offline testing using a specialised test van and not being applicable on multi-ended circuits. The suitability of this method to validate pecking events identified by Pre-Fix is also under question as it tests phase-earth defects whereas Pre-Fix has identified that most pre-fault activity is phase-phase. The results from PD mapping rely on experienced personnel to interpret them, are heavily weather dependent and cannot be used in a post-fault scenario. The operational capability of PD mapping is also a constraint due to the current limited number of test vans with the required equipment for PD mapping and availability of trained staff to carry out the testing.
Further problems related to Pre-Fix that this project aims to address is that the monitoring devices used within Pre-Fix rely on substation CTs, which are not installed in all substations, and alternative devices for detecting phase-to-phase activity require access to individual phases within switchgear end-boxes, which is invasive and time consuming.
This project will also address a problem from an asset management perspective. An analysis of the age profile of NGED’s 11 kV cable population compared to the NGED DSO’s Best View forecast for peak primary demand out to 2050 has revealed that a large spike in cables reaching their mean life expectancy coincides with a large increase in demand, related to the uptake of Low Carbon Technologies (LCTs) essential to the energy transition such as heat pumps and EVs. In order to make the best use of resources to address the spike in work required as the network ages, ultimately coming from customers’ bills, whilst ensuring that the network can supply the demand required for net zero, being better at pinpointing the minimum amount of work to do on the old cables with enough capacity is essential to enable us to focus on reinforcing the old cables without enough capacity. The analysis shows this becoming increasingly important within three price control period.
Method(s)
This project aims to develop a system and methodology for detection and precise location of pecking events in the HV underground network. This solution may be utilised by NGED in conjunction with the Pre-Fix method to provide a more precise location for detected anomalies, or as an alternative pre-fault method.
The work packages will focus on the research and development of several enabling technologies, consisting of existing low-TRL technologies and two completely novel street-level devices. These will be brought together into an integrated system that realises an end-to-end pre-fault management process which follows the steps of Detect, Locate, Validate and Pinpoint (described in the work packages below) to find a precise, validated defect location. The aim of this method is to reduce the amount of excavation required for repair (and therefore cost) through providing a pinpointed location and to improve confidence in this location through validation using a combination of independent technologies/methods.
This project will address certain barriers to scale of a HV pre-fault response capability by working towards the specific requirements below:
- Using sensing that doesn’t require HV Line Circuit CTs
- Wraparound sensors capable of detecting both phase-phase and phase-earth pecking events which can be installed around cables leaving switchgear end-boxes
- Non-invasive live installation and operation
- Compatibility with a range of cable types, including three phase and triplex style cables
- Portable system not reliant on van-based techniques, which might be inappropriate given the intermittent nature of pecks, variance in predicted locations and resource limitations
Work Package 1: Detect
This work package will develop the capability to detect fractional cycle pecking events using wraparound 3-phase online HV sensors and Precision Event Timing Units (PETUs) at cable ends which upload data to a webserver. Outputs will include lab, training network and live network tests, upgrades to the existing PETUs and development of the webserver.
Work Package 2: Locate
This work package will develop the event location calculation using cable end PETUs and Time of Flight (ToF) methods. The location will be cross referenced with cable joint records, recent street works and Pre-Fix plotting of anomalies from iHost, before being plotted on a route mapping diagram. Outputs will include lab, training network and live network tests, development of the webserver and upgrading the mapping location system.
Work Package 3: Validate
This work package is focused on validating the mapped event position with its real-world position. A novel Pulse Injection Generator (PIG) will be developed which will be used to inject a sequence of pulses at the mapped location. This will be converted into a positional location which will be compared to the mapped location. The PIG will be moved and the process repeated until the distances converge, giving a validated real-world event position. Outputs from this work package will be an optimised design, device prototype and lab and live network tests.
Work Package 4: Pinpoint
This work package looks at finding a precise event location. A novel pinpoint board will be developed which can accurately detect the location of pecks within underground cables beneath it using electro-magnetic effects. The board will be placed over the validated location found in WP3. When the next event occurs, the mat will provide in-place fault location. This will be verified with the PETUs at all circuit ends and a repair job can be planned. Outputs from this work package will include a prototype pinpoint board, and lab and live network tests, initially targeting cables laid at a depth of 600mm.
Work Package 5: Integrated System
This work package is responsible for integrating the technologies developed in the other work packages into a working system. Outputs will include reviewing operational lessons, updating user and design requirements, optimising element designs, implementing and testing elements, lab testing the integrated prototype system, live network tests on known and unknown events, lessons and designs for live network trial systems and stage reports.
Work Package 6: Reporting
This work package will produce inception and final reports.
Measurement Quality Statement
Measurement quality will form a key part of the analysis at the three testing locations set out for this project. We will analyse and validate the measurement quality of all sensors forming part of the system, and this will be used in deciding whether to proceed at the two stage gates set out in the project.
Data Quality Statement
Data will be captured at the lab, Sundridge and Coventry testing phases of this project. This will be processed and stored using the webserver that forms part of the HV Pinpoint system, with cyber security assurance being carried out prior to the commencement of this data capture.