Unit Description and General Aims

The objective of this unit is to provide students with a detailed knowledge of the building blocks of a power system in terms of transformers and switchgear. Information covered in this unit will include: the theory of transformers and switchgear; their design and construction features; and, their operation, maintenance, testing, online monitoring and health index assessment. On completion of this unit, students will be able to: specify the appropriate equipment to use for a given application; plan an installation; explain the commissioning and maintenance requirements of the equipment; and, troubleshoot any problems that may occur. Students will also undertake a project involving transformers and switchgear specification, selection, and operation, contextualised to their country/state.

Learning Outcomes

On successful completion of this Unit, students are expected to be able to:

1. Explain the fundamentals of transformers and their modelling.
   Bloom's Level 2
2. Compare different transformer types and their applications in the industry.
   Bloom's Level 4
3. Apply the basic principles for transformer testing, monitoring, and maintenance.
   Bloom's Level 3
4. Select circuit breakers by assessing applications at different voltage levels.
   Bloom's Level 5
5. Select the appropriate type of switchgear for an industrial power facility and determine the specifications for the selected switchgear.
   Bloom's Level 6
6. Plan the facilities required for a substation installation (including one or more transformers and MV switchgear), whilst keeping environment and sustainability aspects in mind.
   Bloom's Level 6

Student assessment

Overall Requirements: Students must achieve a result of 50% or above in the exam itself to pass the exam and must pass the exam to be able to pass the unit. An overall final unit score of 50% or above must be achieved to pass the unit once all assessment, including the exam, has been completed.

Prescribed and Recommended Readings

Required textbook(s)

• IDC Technologies reference books on Transformers, Circuit breakers (Course code TF and CB)
• [1]-ABB - Transformer Handbook , Business Unit Transformers, Copyright © 2004 ABB 
• [2]- ABB Switchgear Manual, 10th revised Rdition 

Reference materials

• Transformers: Basics, Maintenance, and Diagnostics, U.S. Department of the Interior Bureau of Reclamation, April 2005, 'https://www.usbr.gov/tsc/techreferences/mands/mands-pdfs/Trnsfrmr.pdf'

Number of peer-reviewed journals and websites (advised during lectures)

Unit Content

Topic 1

Transformer Fundamentals

1. Electromagnetic induction
2. Transformer equations
3. Basics of single phase and three-phase transformers (star and delta connections)
4. Equivalent circuits of a transformer: design, exact and approximate circuits
5. Approximate Voltage Drop in a Transformer

Topic 2

Transformer Construction

1. Phasor diagram and voltage regulation of a transformer
2. Transformer ratings and efficiency
3. Basic components
4. Insulation and cooling
5. Mounted accessories, tap changers (off-load and on-load)
6. Introduction to eco-efficient transformers

Topic 3

Transformer Operation

1. Installation requirements of transformers, fire prevention, and control
2. Parallel operation
3. Special types: Dry Type Transformers, Furnace Transformer, Rectifier Transformer/K-Rating
4. Power and distribution transformers
5. Practical Transformers on No Load and Load

Topic 4

Transformer Maintenance and Testing -1

1. Transformer inspection and maintenance
2. Testing of transformer oil, and drying of transformers
3. Transformer tests during commissioning and maintenance

Topic 5

Transformer Maintenance and Testing -2

1. Predictive testing (DGA, Frequency response, PD measurements, DP/Furan analysis etc.)
2. DGA and Electrical tests results interpretation

Topic 6

Online Transformer Monitoring & Protection

1. Transformer online monitoring system
2. Transformer health index assessment
3. Transformer protection
4. Different Transformer oils (FR3-mineral oil, Ester oil and MIDEL)

Topic 7

Basic Principles of Current Interruption – Disconnectors and Circuit Breakers

1. Offload, load break, and fault interrupting devices
2. Circuit interruption, basic principles of arc behavior
3. Transient recovery voltage, current chopping/pre-strike in circuit breakers
4. General requirements of circuit breakers (Main and arcing contacts, arc quenching devices)
5. Switching transients due to inductor/capacitor switching and transformer switching and methods used (Resistor break, point-on-wave switching)
6. Circuit breaker ratings and applicable standards; special applications
7. Duty cycle and other test requirements

Topic 8

LV and MV Circuit Breakers

1. LV circuit breakers types with air as quenching medium (ACB, MCCB, MCB, ELCB)
2. Historical background – bulk oil and minimum oil circuit breakers
3. Vacuum CB, SF6 CB and Auto-Reclosers for MV applications

Topic 9

HV Circuit Breakers & Online Monitoring System

1. Air-blast CB and SF6 CB for HV applications
2. Operating mechanism of LV/MV CB (direct actuation/mechanical stored energy type) and HV (pneumatic and hydraulic)
3. Control circuit of CB and interlocks
4. Circuit breaker online monitoring
5. Circuit breaker condition assessment

Topic 10

LV, MV Switchgear

1. Switchgear definition and types
2. LV and MV switchgear construction
3. Switchgear components and applications
4. Standards (IEEE, IEC, ANSI) applied for switchgears (HV/MV/LV)

Topic 11

HV Switchgear

1. LV and MV switchgear ratings and standards
2. HV outdoor switchyards and bus configurations
3. Gas-insulated switchgear
4. Alternatives for SF6 in GIS switchgear

Topic 12

Unit Review

In the final week students will have an opportunity to review the contents covered so far. Opportunity will be provided for a review of student work and to clarify any outstanding issues. Instructors/facilitators may choose to cover a specialized topic if applicable to that cohort.

Software/Hardware Used

Software

• Software: EasyPower
• Version: 9.6 or 9.7
• Instructions: Use remote Lab to access this software OR download demo version.
• Additional resources or files:
  • Demo: http://www.easypower.com/products/EasyPower/EasyPower_demo.php
  • Full Version: To access the software, log into our Remote Lab 10 (Lab 10) Remote Lab ProfiBus, or Remote Lab 12
• Software: PSCAD
• Version: 5
• Demo: https://www.pscad.com/knowledge-base
• Remote lab: 13

Hardware

• Hardware: N/A

Unit Changes Based on Student Feedback