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Title / Demonstrate knowledge of power transformers used in substations
Level / 4 / Credits / 3
Purpose / People credited with this unit standard are able to demonstrateknowledge of:the types of power transformers and regulators; power transformer principles; power transformer components and construction; power transformer alarms and protection systems;power transformer maintenance; and condition assessment of power transformers.
Classification / Electricity Supply > Electricity Supply -Power System Maintenance
Available grade / Achieved
Explanatory notes
1This unit standard is intended for assessment off-job. The range statements and evidence requirements across the unit standard can be applied according to industry specific equipment, procedures, and processes as applied in the electricity supply industry.
2Performance and work practices in relation to the outcomes and evidence requirements must comply with all current legislation, especially the Electricity Act 1992 and any subsequent amendments, any regulations, codes of practice recognised under that statute; Health and Safety in Employment Act 1992 and any subsequent amendments;, Resource Management Act 1991 and any subsequent amendments; electricity supply industry codes of practice; and documented enterprise procedures. These include the latest version ofSafety Manual – Electricity Industry (SM-EI)Wellington: Electricity Engineers’ Association.
A full list of current legislation and industry codes is available from:
Infrastructure Industry Training Organisation
PO Box 1245
Hamilton 3240.
3The phrase in accordance with industry requirements is implicit in all outcomes and evidence requirements in this unit standard.
4Definitions
Asset owner refers to the owner of an electricity supply network that takes its point of supply from Transpower NZ, and delivers electricity to industrial, commercial and residential customers.
Industryrequirementsinclude all asset owner requirements; manufacturers’ specifications; and enterprise requirements which cover the documented workplace policies, procedures, specifications, business, and quality management requirements relevant to the workplace in which assessment is carried out.
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of types of power transformers and regulators in a substation.
Evidence requirements
1.1Commonly used types of power transformers and regulators are identified.
RangeSingle and 3 phase power transformers, autotransformer, regulator, local service transformer.
1.2The function of transformers and regulators are described.
Outcome 2
Demonstrate knowledge of power transformer principles.
Evidence requirements
2.1 The theory of the operation of a transformer is explained.
2.2 Characteristics of power transformers are explained.
Rangeconnections, phasing, vector groups, losses, transformer
percentage impedances, voltage regulation, tertiary windings,paralleled transformers
2.3 The function and operation of tapchangers is explained.
Rangeon-load, off-load
Outcome 3
Demonstrate knowledge of power transformerscomponents and construction.
Evidence requirements
3.1 Components and construction of transformers are identified and explained.
Rangemay include but is not limited to: cores, windings, insulation, cooling systems, tanks, tapchangers, input/output connections, earthing arrangements.
Outcome 4
Demonstrate knowledge of power transformer protection systems.
Evidence requirements
4.1 Reasons for transformer protection areidentified and explained.
Range may include but not limited to: input supply, output loading, fault loading, temperature, gas evolution, oil level changes, voltage impulses
4.2 Protection systems are explained and demonstrated.
Rangemay include but is not limited to: electrical, gas and oil, temperature, impulse, tap changing.
Outcome 5
Demonstrate knowledge of power transformer maintenance.
Evidence requirements
5.1 Inspection and service requirements for power transformersare identified and explained.
Rangeincludes but is not limited to: protective coating, seismic, oil leaks, cooling equipment, tap changers, cabling, wiring, terminations, protective relays.
Outcome 6
Demonstrate knowledge of condition code assessment of power transformers.
Evidence requirements
6.1 Condition coding process is described for power transformers.
Planned review date / 31 December 2020Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for AssessmentRegistration / 1 / 17 March 2016 / N/A
Consent and Moderation Requirements (CMR) reference / 0120
This CMR can be accessed at
Please note
Providers must be granted consent to assess against standards (accredited) by NZQA, before they can report credits from assessment against unit standards or deliver courses of study leading to that assessment.
Industry Training Organisations must be granted consent to assess against standards by NZQA before they can register credits from assessment against unit standards.
Providers and Industry Training Organisations, which have been granted consent and which are assessing against unit standards must engage with the moderation system that applies to those standards.
Requirements for consent to assess and an outline of the moderation system that applies to this standard are outlined in the Consent and Moderation Requirements (CMR). The CMR also includes useful information about special requirements for organisations wishing to develop education and training programmes, such as minimum qualifications for tutors and assessors, and special resource requirements.
Comments on this unit standard
Please contact the Infrastructure Industry Training Organisation at if you wish to suggest changes to the content of this unit standard.
Infrastructure ITOSSB Code 101813 / New Zealand Qualifications Authority 2018