NZQA registered unit standard
28891 version 1
Page 1 of 4
Title
Demonstrate knowledge of instrument transformers used in
substations
Level
4
Credits
5
Purpose
People credited with this unit standard are able to demonstrate
knowledge of: current and voltage instrument transformers
used in substations; the principles of operation, and of the
construction of current and voltage transformers used on AC
and DC circuits; specifications, classes and terminal
identification of current and voltage instrument transformers;
safety requirements for maintenance of current and voltage
instrument transformers; and condition assessment for
instrument transformers.
Classification
Electricity Supply > Electricity Supply - Power System
Maintenance
Available grade
Achieved
Explanatory notes
1
This 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.
2
Performance 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 the latest version of Safety 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.
3
The phrase in accordance with industry requirements is implicit in all outcomes and
evidence requirements in this unit standard.
4
Definitions
Infrastructure ITO
SSB Code 101813
 New Zealand Qualifications Authority 2016
NZQA registered unit standard
28891 version 1
Page 2 of 4
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.
Industry requirements include 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.
Voltage instrument transformer (VT) and current instrument transformer (CT)
Outcomes and evidence requirements
Outcome 1
Demonstrate knowledge of VT and current CT transformers used in substations.
Evidence requirements
1.1
Types of CTs and VTs transformers used in substations are identified.
Range
1.2
instrument monitoring, control, metering, neutral
Location of CTs and VTs transformers are identified.
Range
includes but is not limited to: equipment bushings, outdoor free
standing, neutral transformers, switchgear.
Outcome 2
Demonstrate knowledge of the principles of operation, and of the construction of CT and
VT used on AC and DC circuits.
Evidence requirements
2.1
The operating principles of CTs and VTs are described.
Range
electromagnetic, electrostatic.
2.2
Construction of high voltage CTs and VTs is described.
2.3
Knee point operation of CTs and VTs is described.
Outcome 3
Demonstrate knowledge of specifications, classes and terminal identification of CTs and
VTs.
Evidence requirements
3.1
Nameplate information is analysed.
3.2
Accuracy classes are described.
Infrastructure ITO
SSB Code 101813
 New Zealand Qualifications Authority 2016
NZQA registered unit standard
28891 version 1
Page 3 of 4
3.3
Transformer ratios are described.
3.4
Terminal marking and polarity are described.
3.5
Rated output and burden is described.
Outcome 4
Demonstrate knowledge of safety requirements for maintenance of CTs and VTs.
Evidence requirements
4.1
Safety requirements for taking CTs and VTs out of service are described.
Outcome 5
Demonstrate knowledge of condition coding assessment for instrument transformers.
Evidence requirements
5.1
Maintenance requirements are described.
Range
5.2
may include but is not limited to: foundations, support
structures, oil leaks and/or spillage, low gas pressure, earth
connections, LV cabling, insulators, unusual noises, incorrect
output signals.
Condition coding assessment is described for CTs and VTs.
Planned review date
31 December 2020
Status information and last date for assessment for superseded versions
Process
Version Date
Last Date for Assessment
Registration
1
17 March 2016
N/A
Consent and Moderation Requirements (CMR) reference
0120
This CMR can be accessed at http://www.nzqa.govt.nz/framework/search/index.do.
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.
Infrastructure ITO
SSB Code 101813
 New Zealand Qualifications Authority 2016
NZQA registered unit standard
28891 version 1
Page 4 of 4
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
qualifications@infrastructureito.org.nz if you wish to suggest changes to the content of this
unit standard.
Infrastructure ITO
SSB Code 101813
 New Zealand Qualifications Authority 2016