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.