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Title / Carry out routine inspection and service on high voltage indoor metal clad circuit breakers and bus
Level / 4 / Credits / 4
Purpose / People credited with this unit standard are able to: prepare for inspection, testing and servicing on high voltage indoor metal clad circuit breakers; make the circuit breakers and bus safe for work; carry out routine inspections and diagnostic tests; carry out servicing; perform function tests and pre-service checks; and complete documentation.
Classification / Electricity SupplyElectricity Supply - Power System Maintenance
Available grade / Achieved
Prerequisites / Unit 14287,Use and maintain test instruments used in the high voltage electrical industry; Unit 14294,Carry out insulating oil sampling and voltage breakdown tests; Unit 14700,Apply and remove safety measures in an electricity supply environment; Unit 14701,Manage electricity supply work control system; Unit 12296 Apply earths to and remove earths from electrical conductors, plant, and equipment; or demonstrate equivalent knowledge and skills.
Core electrical theory is essential knowledge underpinning the performances required by this unit standard.
Guidance Information
1This unit standard can be assessed against in a workplace environment, or in a training or educational environment if simulated equipment response and examples are able to be provided, or in a combination of both environments.
2Performance and work practices in relation to the outcomes and performance criteria must comply with all current legislation, especially the Electricity Act 1992, and any regulations and codes of practice recognised under that statute; the Health and Safety at Work Act 2015; and the Resource Management Act 1991. Electricity supply industry codes of practice and documented industry procedures include the Safety Manual – Electricity Industry (SM-EI) Wellington: Electricity Engineers’ Association. A full list of current legislation and industry codes is available from Connexis Infrastructure ITO
3The phrase in accordance with industry requirements is implicit in all outcomes and performance criteria in this unit standard.
4‘Industry requirements’include all industry and workplace documented policies, procedures, specifications, business and quality management relevant to the workplace where assessment is carried out.
5All work practices shall meet documented enterprise maintenance standards, including the quality management requirements, and the documentation of activities, events, and decisions.
6The range of this unit standard is limited to carrying out diagnostic testing and applying preventative maintenance and replacement repairs, where necessary, on high voltage metal clad circuit breakers with integrated switchgear bus, and is normally done at electricity supply substations. Note: gas insulated switchgear is not included in the scope of this unit standard.
7The following terms and abbreviations relate to this unit standard:
GIS=Gas insulated switchgear
CB=Circuit breaker
SF6=Sulphur hexafloride gas.
Outcomes and performance criteria
Outcome 1
Prepare for inspection, testing and servicing on high voltage indoor metal clad circuit breakers.
Performance criteria
1.1The scope of work and equipment to be serviced is identified from client requirements.
Rangemay include but is not limited to associated ‘check and/or inspection lists’, procedures and client required diagnostic tests and servicing for – metal clad switchgear with circuit breakers types such as oil, SF6, vacuum; with integrated bus bar systems insulated with air, or compound, and which may have pneumatic, solenoid or motor-spring mechanisms.
1.2Personnel and equipment are resourced for the required work.
Rangemay include but is not limited to – tools, spares, materials, ‘inspection sheets’, procedure sheets.
1.3The inspection, diagnostic testing and servicing requirements are interpreted and analysed for determining the performance and quality standards required.
Rangemay include but is not limited to – manufacturer’s guidelines, client maintenance standards or enterprise guidelines.
Outcome 2
Make the circuit breakers and bus safe for work.
Performance criteria
2.1The required access permit, or recognised equivalent, is received, checked, and signed.
Rangeincludes a careful check of the isolations to ensure the access permit or recognised equivalent provides a safe work environment.
2.2Additional isolation from other energy sources on the circuit breaker is applied.
Rangemay include but is not limited to – releasing or spragging spring closing energy systems, isolating actuating trip coils and motor drive systems, release or isolation of hydraulic or pneumatic pressure systems, switching of internal cabinet heaters, if possible CB racking out or down from cabinet.
2.3The work party is fully briefed on the equipment to be worked on, work to be done, safe working zone and safety features in place, and has signed the access permit or its approved equivalent. All communication with the work party is clear and unambiguous.
Rangemay include but is not limited to the ability to resolve any concerns the work party may have over the isolations and the delineation of the safe work area.
2.4Safety measures are available and prepared to protect the environment and personnel.
Rangemay include but is not limited to – oil spill clean up and bunding facilities, protective clothing, storage for oil, breathing filters, the safe work area has been identified and marked.
Outcome 3
Carry out routine inspections and diagnostic tests.
Performance criteria
3.1The CB defect history and operational records are scrutinised, and incidents indicating service needs noted for attention during the routine servicing.
Rangemay include but is not limited to – serious fault interruptions, malfunctions, reported problems, thermovision test results.
3.2The inspections carried out identify any damage or defects.
Rangemay include but is not limited to – oil leaks, signs of overheating, contact damage, abnormal wear of operating mechanism, any visual evidence of damage to bushings and spouts.
3.3The diagnostic tests are carried out and the results analysed for interpreting the servicing required.
Rangemay include but is not limited to – insulation resistance tests, time travel, contact resistance, minimum operating voltage, alarm and pressure settings, gas leaks detection, bus section resistance, cable box compound level.
3.4The results of the diagnostic tests are recorded to meet the client requirements.
Rangemay include but is not limited to – completing enterprise check lists, electronic data records, client reports.
Outcome 4
Carry out servicing.
Performance criteria
4.1Oil recovery and treatment is completed consistent with enterprise or client requirements.
Rangemay include but is not limited to – storage treatment and re-testing before re-filling the circuit breakers.
4.2The major or minor invasive servicing is carried out following enterprise or client procedures.
Rangemay include but is not limited to – repair or replacement of worn parts, mechanism adjustments, cleaning circuit breaker, mechanism lubrication, bushing spouts checked, SF6 bottle replacement, SF6 filtering, bushings and spouts cleaned, earthing system, auxiliary contacts, fires suppression system.
4.3The re-assembly of the circuit breaker is carried out in the approved manner provided by the maker.
Rangemay include but is not limited to – all components being assembled in the correct order, with proper fit and secured in the specified way, oil replaced into circuit breaker to correct level.
Outcome 5
Perform function tests and pre-service checks.
Performance criteria
5.1Work party is advised of a trial operation about to start.
5.2All services and necessary control features are reinstated and approval obtained for function tests.
Rangemay include but is not limited to – control circuits, mechanism, power and indication.
5.3All the function tests required are completed without malfunction and to standard.
Rangemay include but is not limited to – insulation resistance tests, time travel, contact resistance, minimum operating voltage, alarm and pressure settings, gas leaks detection, bus section resistance, cable box compound level.
5.4All the maintenance tools and facilities are removed and the circuit breaker left in the ‘ready-for-service’ condition.
Rangemay include but is not limited to – checking all tools removed, all connections tight, all panels returned, all valves set to ‘in-service’ position, service or maintenance disable switch in correct position, CB returned to service.
5.5All equipment worked on is inspected and set for return to service.
Rangemay include but is not limited to – confirming all equipment and the work party are clear, all operational equipment which has been worked on is now set ready for service.
5.6Return of access permit, or its equivalent, is confirmed.
Rangemay include but is not limited to – confirming all members of the work party have signed off, the equipment is returned to service without incident.
Outcome 6
Complete documentation.
Performance criteria
6.1The ‘as found’ and ‘as left’ conditions are recorded in the plant history.
Rangemay include but is not limited to – analysis and reporting of any defects, correct completion of the plant and defect history, including replacement spare fitted.
6.2The equipment condition status is recorded.
Rangemay include but is not limited to – operation counter noted, number of trial operations noted, pressures and auxiliary service quantified.
6.3The routine and inspection service records are completed to meet the client requirements.
Rangemay include but is not limited to – written records or electronic data reporting.
This unit standard is expiring. Assessment against the standard must take place by the last date for assessment set out below.
Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for AssessmentRegistration / 1 / 27 April 1998 / 31 December 2020
Revision / 2 / 11 February 2004 / 31 December 2020
Rollover and Revision / 3 / 20 June 2008 / 31 December 2020
Review / 4 / 24 January 2019 / 31 December 2020
Consent and Moderation Requirements (CMR) reference / 0120
This CMR can be accessed athttp://www.nzqa.govt.nz/framework/search/index.do.
Infrastructure ITOSSB Code 101813 / New Zealand Qualifications Authority 2019