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Title / Demonstrate knowledge of introductory concepts in power system protection
Level / 4 / Credits / 10
Purpose / People credited with this unit standard are able to: demonstrate a basic knowledge and understanding of the power system in operation within New Zealand; demonstrate knowledge and understanding of basic protection concepts; demonstrate knowledge and understanding of the fault types identifiable in power system protection systems; draw a single line diagram showing circuit characteristics; demonstrate knowledge and understanding of basic low voltage (LV) protective devices; demonstrate knowledge and understanding of the types, ratios, and classes for CTs, capacitive voltage transformers (CVTs) and VTs, and the calculation of secondary currents from theoretical full load currents for CTs and their ratios; demonstrate knowledge of the danger of open circuit operation of a CT and precautions and safe working practices; and demonstrate knowledge of safety and safe working practices when operating in a HV environment.
Classification / Electricity Supply > Electricity Supply - Power System Maintenance
Available grade / Achieved
Entry information
Critical health and safety prerequisites / Unit 14287, Use and maintain test instruments used within the high voltage electrical industry, or demonstrate equivalent knowledge and skills.
Explanatory notes
1 This unit standard is intended for off-job assessment. The range statements across the unit standard can be applied according to industry-specific equipment, procedures, and processes.
2 Protection systems may include those associated with prime movers, generators, transformers, bus work and distribution networks including: fault detection systems, shutdown and alarm initiation systems, electrical protective relays, voltage and current transformers, field devices, transducers, programmable logic controllers, computers, and alarm annunciation systems.
3 Sources of information include but are not limited to the International Electrotechnical Commission (IEC), the Institution of Engineering and Technology (IET), the American National Standards Institute (ANSI), and the Deutsches Institut für Normung e. V. (DIN).
4 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 regulations and codes of practice recognised under that statute; the Health and Safety in Employment Act 1992; and the Resource Management Act 1991. Electricity supply industry codes of practice and documented industry procedures include the Safety Manual – Electricity Industry (SM-EI) (Wellington: Electricity Engineers’ Association, 2010). A full list of current legislation and industry codes of practice is available from the Infrastructure ITO, PO Box 2759, Wellington 6140.
5 The outcomes of this unit standard are equivalent to the learning outcomes of the New Zealand Board of Engineering Diplomas (NZBED) course component DE5413 Power Protection Systems 1 Level 5. If a candidate has completed the NZBED course component related to this standard then they can apply to the ITO for Recognised Prior Learning (RPL). Further information about this process may be obtained from the Infrastructure ITO, PO Box 2759, Wellington 6140.
Outcomes and evidence requirements
Outcome 1
Demonstrate a basic knowledge and understanding of the power system in operation within New Zealand.
Evidence requirements
1.1 The importance of the power system to New Zealand is described.
Range current loads, projected demand.
1.2 The structure of the National Grid and the distribution networks through to consumer is described.
Range generation, High Voltage Direct Current (HVDC) link, transmission voltages, major exit points.
1.3 The types of generation, load patterns, and basic operational constraints are described.
Range introduction to HV transmission, HV substations, distribution substations.
1.4 The role of components in the power system is described.
Range circuit breakers, switch gear, transformers, voltage transformers (VT), current transformers (CT), protection equipment.
1.5 The ability to read and understand single line diagrams is demonstrated.
Outcome 2
Demonstrate knowledge and understanding of basic protection concepts.
Evidence requirements
2.1 The physiological effects of electric shock on humans are described.
2.2 The need for protection equipment is explained.
Range time/current characteristics, short circuit and overload, prospective short circuit currents (PSCC).
2.3 Basic circuit break fundamentals are identified.
Range bulk oil, air blast, vacuum, sulphar hexafluoride (SF6), kilovolt amps (kV) ratings, current interruptions, containment and levels of faults, different types of faults, arc quenching mechanisms.
2.4 Point-on-Wave circuit breakers are described.
Outcome 3
Demonstrate knowledge and understanding of the fault types identifiable in power system protection systems.
Range includes but is not limited to – transient faults, high resistance faults, incidence of faults on power system equipment.
Evidence requirements
3.1 The origins of faults are identified and named.
3.2 The types of earthing systems are identified and the phase to earth fault is described.
3.3 Proposals are provided for the protection against earth faults.
3.4 Detection and clearance of faults are described.
3.5 The effects of these types of faults on the system, system stability, overloads and the effects of loss of supply are described.
3.6 The short circuit current of a power transformer from its capacity and impedance is calculated.
Outcome 4
Draw a single line diagram showing circuit characteristics.
Evidence requirements
4.1 A simple power system single line diagram is developed.
4.2 A short circuit megavolt amperes (MVA) is calculated on the diagram.
4.3 Fault currents are calculated.
4.4 Equipment MVA fault ratings are identified.
Outcome 5
Demonstrate knowledge and understanding of basic low voltage (LV) protective devices.
Range up to 11kV.
Evidence requirements
5.1 Fuse characteristics, ratings, and selection for overload and prospective fault situations are described.
5.2 Circuit breaker ratings are identified.
5.3 Residual current device (RCD) operations, ratings, and testings are described.
5.4 Ring main unit (RMU) circuits are described.
Outcome 6
Demonstrate knowledge and understanding of the types, ratios, and classes for CTs, capacitive voltage transformers (CVTs) and VTs, and the calculation of secondary currents from theoretical full load currents for CTs and their ratios.
Evidence requirements
6.1 The different ratios and classes of CTs and VTs are described in detail.
6.2 Three examples are identified of how CT specifications, primary currents, and circuit burden are used to calculate the secondary currents for a CT and to determine if the results are permissible values.
Range includes but is not limited to – magnetisation curves, knee point saturation, protection versus metering types, ratios.
6.3 The examples given describe discrimination in detail and explain how it was achieved in each case.
Range includes but is not limited to – supply networks, motors, transformers, generators.
6.4 The role and function of instrument transformers are described.
Range different classes, accuracy classifications, acceptance testing, earthing of secondaries.
6.5 Connection diagrams are drawn.
Range CT, VT, CVT.
Outcome 7
Demonstrate knowledge of the danger of open circuit operation of a CT and precautions and safe working practices.
Evidence requirements
7.1 Theoretical explanations for not operating a CT in an open circuit condition are stated.
7.2 Safety issues about operating open circuit CTs are described.
7.3 Precautions and safe working practices when engaged in testing power system protection schemes are identified and described.
Range includes but is not limited to – step and touch voltages, safe working distances, current loops, instrument maintenance, applicable legislation, industry codes of practice.
Outcome 8
Demonstrate knowledge of safety and safe working practices when operating in a HV environment.
Range up to 400kV.
Evidence requirements
8.1 Precautions and safe working practices when engaged in electrical testing of equipment and protection schemes are identified and described.
Range the effect on humans of electric shock and the dangers of electrical power arcs (relevant recent electrical industry accidents with analysis of their cause may be included), maintenance and repair work procedures, troubleshooting, testing on energised electrical circuits, components, or systems.
8.2 Managing potential hazards in the workplace is discussed.
Range use of appropriate personal protective equipment (PPE) for the work environment, maintaining PPE in a safe and reliable condition, inspection of PPE prior to use, procedures for inspection following any incident, basic instrument and hand tool maintenance and care.
8.3 Work authorisations are described.
Range levels of authorisations, how to request work authorisations, responsibilities, examples of documents in current use, typical commissioning programs.
8.4 Electrical work hazards in the workplace are identified.
Range defined work areas, lock and tag procedures, structure diagrams (up to 400kV) including but not limited to proximity to higher voltages (400kV), exposure to higher fault levels, step and touch voltages, electrostatic charges, emergency response systems and procedures to follow to ensure safety in the event of an incident.
This unit standard is expiring. Assessment against the standard must take place by the last date for assessment set out below.
Status information and last date for assessment for superseded versions
Process / Version / Date / Last Date for Assessment /Registration / 1 / 20 November 2009 / 1 December 2012
Revision / 2 / 22 October 2010 / 31 December 2019
Revision / 3 / 21 July 2011 / 31 December 2019
Review / 4 / 20 July 2017 / 31 December 2019
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.
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.
Infrastructure ITOSSB Code 101813 / Ó New Zealand Qualifications Authority 2017 / / New Zealand Qualifications Aut