This unit of competency has been developed for Engineering Tradesperson – industrial electrician apprenticeship training and the recognition of trade-level skills in fault finding and rectifying single and three-phase transformers.

It includes the operating principles of transformers, their construction and open circuit and full load characteristics; types of transformers used in transmission and distribution systems, appliances and welding machines; hazards associated with step and touch voltages, induced voltages and stored energy particularly with high voltages; earthing requirements to limit the rise of touch voltage; safe working procedures for connecting and testing and fault finding transformers.

This unit covers the skills and knowledge required to meet the Electrical Regulatory Authorities Council (ERAC).

Essential Performance Capabilities (EPCs):

EPC 18 – Describe the basic construction, principles of operation, and typical applications of the main types of transformers.

And

Essential Performance Capabilities (EPCs) classified as ‘critical’:

EPC 19 – List the key safety issues of various types of transformers, including AS/NZS 3000 requirements.

EPC 48 – Demonstrate knowledge and understanding of the significant dangers of High Voltage equipment and distribution systems.

Some jurisdictions require the holder of this unit to be licensed or certified and users should check with the relevant authorities.

Band: A

Unit Weight: 4

Evidence required to demonstrate competence in this unit must be relevant to and satisfy the requirements of the elements and performance criteria on at least two (2) occasions and include:

following work instructions, standard operating procedures (SOPs) and safe work practices

identifying and interpreting circuits, drawings and specifications relevant to the work to be undertaken

determining the electrical and non-electrical isolation requirements to prevent the creation of hazards linked from the loss of machine/system/process control according to established procedures

using lock out tag procedures with appropriate tags/signs

proving electrical isolation and following established safety rules prior to working on electrical equipment or wiring

ensuring all electrical equipment and tools are tested and tagged and up to date

observing work health and safety (WHS) precautions and considerations when dealing with instrument transformers especially current transformers and high voltage equipment

applying fault finding and diagnostic techniques on at least two (2) or more of the following single and three-phase transformers and their associated control circuits:

instrument

current

voltage

oil filled transformers

high voltage power transformers

low voltage power transformers

neutral

distribution:

step up

step down

complying with the Australian/New Zealand Wiring Rules for the installation and safety requirements of transformers, including limiting the rise of touch voltages

performing the following tests in accordance with specifications and regulatory requirements:

basic insulation resistance, continuity and winding identification tests

open and short circuit tests

carrying out routine maintenance on transformers

documenting all necessary repairs in accordance with SOPs.

Evidence required to demonstrate the required knowledge for this unit must be relevant to and satisfy the requirements of the elements and performance criteria and include knowledge of:

safe work practices and procedures and use of personal protective equipment (PPE)

operating principles of transformers, including:

principles of mutual induction and how it relates to a transformer

phasor diagram for a transformer on no-load and the voltage and current components

factors that determine the value of induced voltage in a transformer winding

transformers ratios both voltage and current

calculate the value of output voltage given the input voltage and turns ratio of a transformer

transformer losses, including:

eddy current losses and the use of laminations to reduce this effect

hysteresis losses and core materials to reduce this effect

copper losses also referred to as primary/secondary losses or I2R losses

transformer efficiency and the effect flux leakage has on it and its related formula, i.e. transformer efficiency =

voltage regulation as applicable to a transformer and its related formula, i.e. voltage regulation =

power in a transformer, i.e. power in = power out

impedance ratio and reflected impedance

percentage impedance as applied to transformers and how its value affects the value of the available short-circuit current

calculating the percentage impedance of a transformer and determine the percentage impedance of a transformer from test results

transformer construction, including:

single and three-phase transformer cores and winding arrangements

transformer ratings, i.e. in kVA

relationship between transformer cooling and rating

methods used for natural and forced cooling of transformers

properties and tests that are conducted on transformer oil

winding polarities and polarity identification of single and three-phase transformers

four common methods of connecting the primary and secondary windings of a three-phase transformer, i.e. star-star, delta-delta, delta-star and star-delta

three-phase tertiary windings and the purpose they perform

changing transformer ratios, i.e. off-load and on-load changing

transformer auxiliary equipment and their function (bushings, surge-diverters, tap-changers, hot oil and winding indicators, breather, Buchholz relay and conservator)

application of transformers, including welders

paralleling of single-phase transformers, including:

ensuring their voltages are equal

instantaneous polarities are identical

consequences of incorrectly phased transformers

paralleling of three-phase transformers, including:

the need for paralleling

ensuring they are of equal voltages, same phase sequence and phase voltages are in step and the consequences if they are not

testing of transformers, including:

performing basic insulation resistance, continuity and winding identification tests

testing of final connections, i.e. in star, delta and open-delta configurations and transformer ratio

safe working procedures when connecting and testing transformers

open and short circuit tests

dielectric tests

special transformers, including:

potential and current transformers and the reason why they are used

construction and application of potential and current transformers

work health and safety (WHS) hazards associated with instrument transformers especially current transformers where the secondary must never be open-circuited under any circumstances as it will cause a potentially dangerous voltage to be present at the secondary terminals

instrument transformer load or burden ratings

safe working procedures of potential and current transformers

commissioning and testing instrument transformers

transformers with multiple secondaries and tapped windings

advantages and disadvantages of auto-transformers

calculate the voltage and current in the windings of an auto-transformer

high-reactance or leakage transformers

applications of auto-transformers and instrument transformers

Australian/New Zealand Wiring Rules installation and safety requirements for transformers

dangers of high voltage equipment and distribution systems, including:

step and induced voltages

sources of induced voltage and stored energy

creepage and clearance requirements

application of safe working procedures in the vicinity of high voltage equipment.

Assessors must:

have vocational competency in fault finding, testing and rectifying single and three-phase transformers at least to the level being assessed with relevant industry knowledge and experience

satisfy the assessor requirements in the Standards for Registered Training Organisations 2015 and comply with the National Vocational Education and Training Regulator Act 2011 or equivalent legislation covering VET regulation in a non-referring State as the case requires.

Where possible assessment must occur in operational workplace situations. Where this is not possible or where personal safety or environmental damage are limiting factors, assessment must occur in a sufficiently rigorous simulated environment that reflects realistic operational workplace conditions. This must cover all aspects of workplace performance, including environment, task skills, task management skills, contingency management skills and job role environment skills.

Conditions for assessment must include access to all tools, equipment, materials and documentation required, including relevant workplace procedures, product and manufacturing specifications.

Assessment processes and techniques must be appropriate to the language, literacy and numeracy requirements of the work being performed and the needs of the candidate.

This section describes those required skills (reading, writing, oral communication and numeracy) that are essential to workplace performance in this unit of competency.

Foundation skills essential to performance are explicit in the performance criteria of this unit of competency.

Maintenance and diagnostics