Assessment & Testing of Alternative Cut-outs

Objective

The objectives of the project can be summarised as follows:

• Identify alternative cut out equipment used outside of GB and prove that they are suitable for replacing in service cut-outs.
• Identify novel arrangements and practices from DNOs outside of GB and assess whether or not they can negate some of the known problems that existing cut-outs in GB have.
• Generate and disseminate enough learning to drive more informed inspection, maintenance and replacement cut-out regimes within each GB DNO.
• Generate and disseminate enough learning to influence the BS 7657 and the ENA engineering recommendation for inspecting cut-outs.

Problem(s)

Each Low Voltage (LV) customer is connected to the distribution network by fused cut-out equipment normally (but not always) located within the customer’s property or in a meter box. This cut-out equipment belongs to the Distribution Network Operator (DNO) and provides the interface between the DNO and the Meter Operator (MOP). The fuse fitted in the cut-out equipment provides a means of disconnecting the customer’s wiring in the event of a fault occurring on the wiring within the property.

Both the DNO and MOP have the authority to connect/disconnect wiring to the cut-out equipment and seal this equipment to prevent unauthorised interference. Only the DNO has authority to replace a blown fuse.

Historically DNOs have not separately inspected cut-out equipment for defects themselves, but do currently have a number of different measures in place to effectively manage these assets, such as visits from meter operators to periodically replace meters.

Cut-out equipment in customers’ premises can become damaged which could result in live conductors becoming exposed or cause current to leak to earth. These conditions are potential hazards to the occupants of the premises if left unresolved. It is also possible for cut-out equipment to overheat under certain conditions and this has been identified as a possible cause of fires in customers’ premises. Similar reliability issues of cut-out equipment have been reported by DNOs in the past.

The UK Government is currently supporting the mass roll out of Smart Meters. These Smart Meters will have Automatic Meter Reading (AMR) functionality, which will enable the remote communication of meter readings to the supplier, negating the need for them to visit individual premises to obtain meter readings. This means the regular inspections by MOPs will no longer take place increasing the risk of a potential cut-out failure being detected.
 

Method(s)

This project will look at alternative cut-out equipment used by network operators outside the UK and assess the suitability of these as a potential replacement for existing equipment. This aims to negate the issues that have been highlighted by various DNOs and a number of external stakeholders. It will attempt to achieve this by comparing the new technologies against existing equipment used by GB DNOs under normal operating conditions, but also under any known failure modes.

The project will also consider potential novel arrangements of the currently used cut-out assemblies, as well as practices followed by utilities outside the UK with the aim of finding possible solutions to identified problems.

• Scope

  The scope of the project is to identify alternative, more reliable cut out equipment used by non-GB DNOs (or novel arrangements and practices) and prove they are suitable for replacing the ones currently used by GB DNOs.

  The main benefits expected from the project can be summarised below:
  
  Safety benefits: 
  
  The project is looking to identify, test and approve a more reliable and robust cut-out assembly, compared to the ones currently used by GB DNOs. Learning from the project will also be used to inform standards and recommendations around the inspection requirements for cut-outs. Both aim to decrease the risk of disruptive cut-out failures and consequently any related safety risks.
  
  Financial benefits:
   

  • Following the point above, there will be a reduced risk to damaging third party assets and property. Therefore, we expect that following the project fewer insurance claims will be made against GB DNOs.
  • Avoiding disruptive cut out failure will also help reduce the amount spent on investigation fees following cut-out faults.
  • By targeting the replacement of cut-outs (starting with the highest risk types), a decrease in the number of reactive cut-out replacement following the report of a defect or failure is anticipated. There will also be a financial benefit from having planned rather than unplanned replacements.

  Network reliability:
  
  More robust and reliable cut-out assemblies on the network and more informed cut-out inspection regimes will mean less disruptive cut out failures. This will increase GB network’s reliability and help avoid power cuts.

• Success criteria

  The project will be successful if it manages to satisfy the following criteria:

  • Identify alternative cut-outs (to the currently in-service cut-outs in the UK) to trial in the testing cells (following the desktop review and assessment)
  • Prove whether the alternative cut outs identified are suitable for replacing current cut outs used by DNOs in GB
  • If they are suitable:
    • Provide evidence to enable BS 7657 and the ENA engineering recommendation for inspecting cut-outs to be revised based on final recommendations.
    • Facilitate more informed decisions on inspection, maintenance and replacement of cut-outs and influence relevant regimes within each DNO.
• Potential for new learning

  The following learning is expected to be generated through the project:

  • Assess whether there are either alternative cut-outs or novel arrangements and practices currently used by non-GB DNOs that negate the reliability problems GB DNOs are facing with in service cut-outs.
  • Assess if these can be used on GB’s distribution network.
  • Understand the probability of failure for both in service cut-outs and the identified alternative ones. This should influence inspection, maintenance and replacement regimes within each GB DNO.

  All learning will be shared with all GB DNOs (4 other DNO groups are partners in the project) in the form of reports and recommendations. The aim is to influence inspection related engineering recommendations and standards (such as the BS 7657), so learning will be shared with the industry from the revised standards.