Learnings

Outcomes

Stage 1

The project has assessed and reported the current working practices, equipment and standards used by the UK network operators as well as global practices and standards. This has been completed for both WS1 and WS2.

During the research element of the project the initial phase was to request the network operators to produce a series of documents that were commonly used throughout their business and in accordance with the UK standards. Documents were requested from each DNO as follows:-

• Applicable Code Of Practice for the temporary earthing of OHL circuits.
• Work Instructions/Procedures for the temporary earthing of OHL circuits.
• Approved/Type registration of equipment used for temporary earthing including OHL and Mobile Generation
• Work Instructions/Procedures for the temporary earthing of mobile generation.
• Applicable Code Of Practice for the temporary earthing of mobile generators
• Safety Bulletins/Alerts related to temporary earthing issues

A questionnaire, consisting of 20 questions, was also sent out to a number of staff within the participating DNOs to gain further insight into current working practices and equipment used, which included earth leads, line end clamps, earth end clamps and operating poles. The feedback and answers received was utilised to determine the areas most in need of improved operating/working practices. The answers from this questionnaire and the information collated from internal documents and procedures, fed into the work completed during stage 2 of the project.

Particular observations to note from the questionnaire were:-

• Consider alternative earth end clamps that are currently available in the market, that are easier to apply/remove when being operated from an extended insulated rod
• Ensure that all operational equipment utilised across the business units are compliant with the current UK standards
• Encourage where possible improved methods of earthing that reduce the exposure time of personnel working at height
• Identify simple methods of applying a recordable tag that identifies the location of each locally applied earth to assist in the deployment and recovery immediately prior to re-energisation
• Review methods for obtaining soil resistivity levels adjacent to temporary generator locations to enable the correct levels of earthing to be applied
• Consider alternative methods of reference earthing such as plate electrode technology to manage the use of generation in areas where driven rods are problematic

Stage 2

The project identified a number of products that either new to the market or not yet widely used within the UK DNOs. There were various aspects of OHL temporary earthing work (WS1) that the project assessed for new equipment to improve the current working practices. These aspects included:

• Conductor end clamps (all types) – UK and overseas suppliers
• Telescopic earthing poles - UK and overseas suppliers
• Systems enabling safe earthing from ground level - UK and overseas suppliers
• Robustness of terminations between earth lead and end clamps – compare methods of attachment across the ESI.
• Simple methods of marking and accurately recording position of applied drain earths on the job-site.

The following is a list of equipment assessed and demonstrated during the project.

Telescopic Poles

•  Pentapole
•  PEC3560R

Conductor End Clamps & Deployment Methods

•  Autoclam
•  Nevers
•  CHC31
•  CE88 Prototype Horizontal Clamp
•  CE72 Prototype Clamp

From the feedback received from attendees of the demonstration day, the project recommends that there is further investigation into the Autoclam, CE88 and CE72 products. An in-person demonstration as well as risk assessment by individual networks is recommended to determine whether these products can be integrated in BaU. The other products trialed showed some benefits and could be investigated further, however the potential efficiency savings were not obvious from the virtual demonstration.

Information for these products can be found on the manufacturer’s websites or available on request from the project.

In addition to this equipment, a product using Near Field Communication (NFC) tags has been identified during the project to assist users with recording exact location of asset placement to provide guidance in the recovery of the assets at the end of the temporary works. The asset will require the addition of the NFC tag which can be attached in many ways in a secure spot that is readily accessible to the user to read the tag. The tag has the capability to receive up to 90 text characters which can describe the item, record the purchase date, inspection date or any relevant information.

WS2 saw the project investigate different methods of obtaining reference earth using plate electrodes for earthing of temporary generators.

As part of the study plate electrodes were trialled on tarmac and concrete surfaces. Different numbers of plate electrodes were studied as well as the use of different interface mediums to potentially enhance the earth values obtained. The results of these studies are shown in the table in the Supporting Documents.

With the earth resistance value required to be between 20 Ω and 200 Ω, from the table of results, this can only be achieved using plate electrodes in parallel and a saltwater rag or similar as an interface medium. The desired values can only be achieved on concrete only. For the saltwater rag system on concrete, a constant feed of saltwater would be needed as the earth resistance value would increase as the saltwater rag dried out.

It is recommended that further trials/studies could develop systems that obtain the desired values, however given the results it is unlikely that suitable earthing values can be obtained using plate electrodes as an alternative to the current driven rod systems that are in use.

Lessons Learnt

The demonstration day provided useful learning for the project partners in being able to observe the new equipment, identified as part of WS1, in operation. Due to the need to complete this demonstration day remotely, it is recommended that any DNO seeking to investigate implementing the equipment into BaU, that an in person demonstration is arranged. The lesson learnt in this instance, that for new equipment trials only in person trails will result in definitive outcomes.

As part of WS2, the use of plate electrodes for earthing of temporary generators was examined. The results of these studies showed that the minimum earthing values could not be reached in all scenarios but there was some initial promise shown in using this approach for concrete.