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Title / Demonstrate knowledge of power transformer theory for electricity supply
Level / 3 / Credits / 3
Purpose / This unit standard covers knowledge to single- phase and three-phase power transformer theory as used in the electricity supply industry.
People credited with this unit standard are able to demonstrate knowledge of: the principles of transformers; and transformer connections and configuration.
Classification / Electricity Supply > Electricity Supply - Core Skills
Available grade / Achieved
Explanatory notes
1This unit standard is intended for assessment off-job. The range statements across the unit standard can be applied according to industry specific equipment, procedures, and processes.
2Safety of personnel and plant must be a priority throughout the assessment. If the safety requirements are not met the assessment must stop and the candidate will be assessed as not yet competent.
3Performance 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, and any regulations, codes of practice recognised under that statute, Health and Safety in Employment Act 1992, the Resource Management Act 1991, and their subsequent amendments, electricity supply industry codes of practice and documented enterprise procedures. These include, Safety Manual – Electricity Industry (SM-EI) (2004) Wellington: Electricity Engineers’ Association.
A full list of current legislation and industry codes is available from:
Infrastructure Industry Training Organisation
PO Box 1245
HAMILTON.
4The phrase in accordance with industry requirements is implicit in all outcomes and evidence requirements in this unit standard.
5Definitions
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.
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.
Asset owner standards are the approved documented work site methods for carrying out work on an electrical supply network to the standard required by the asset owner.
6This unit standard is intended for use in the assessment of Line Mechanics, Cable Jointers and all terminology should be related to that sector of the industry.
7Simulated electrical workplace installation is recommended, but not limited to, in order to meet the demonstration outcome of this unit standard.
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of the principles of transformers.
Rangesingle-phase, three-phase.
Evidence requirements
1.1Construction of a transformer is drawn, the parts are identified and their function is described.
Rangeiron core, primary and secondary windings, tapping and tapping switches, oil filled, tanks, bushings, mountings.
1.2Principle of operation is explained through use of diagrams.
Rangemagnetic fields, mutual induction.
1.3Transformation ratios are described and expressed as a formula in simple calculations.
Outcome 2
Demonstrate knowledge of transformer connections and configuration.
Rangesingle- and three-phase transformers;
star connections, delta connections, combination delta-star configurations, paralleling and single wire earth return (SWER).
Evidence requirements
2.1Connections and configurations are drawn and fully labelled.
Rangevoltages, phase to phase, phase to neutral, and phase to earth are shown.
2.2The purpose of earthing connections is described in accordance with current performance and work practices.
Outcome 3
Demonstrate knowledge of carrying out phasing tests on electricity power transformers.
Rangelow voltage (LV), High voltage (HV) transformers.
Evidence requirements
3.1Phasing terms are described.
Rangeincludes but is not limited to – vector groupings for transformers, phase markings and identification of conductors (R, W, B, A, B, C);
evidence of two is required.
3.2Purpose of phasing checks is described.
3.3Methods for testing of phasing of transformers in HV systems are demonstrated.
Rangemay include but is not limited to – use of phasing phones, use of HV phasing and voltage detection equipment;
evidence of two is required.
Planned review date / 31 December 2018Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for AssessmentRegistration / 1 / 25 October 2007 / 31 December 2016
Review / 2 / 20 March 2014 / 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 you wish to suggest changes to the content of this unit standard.
Infrastructure Industry Training OrganisationSSB Code 101813 / New Zealand Qualifications Authority 2019