HV Motors and Transformers: Design, Operations and Trouble-Shooting

Introduction

​In 1882 Sir Thomas Edison built the world’s first electricity generating station in New York. The supply of Electricity spread rapidly across the globe in the ensuing years. Today, over a century later, the use of electrical energy has become commonplace. The transfer of electricity from generating sources is carried out using many components and sub-systems. When the components are connected together to supply various types and levels of electrical load, the result is usually referred to as a NETWORK. This course addresses the behavior of High Voltage (HV) Networks and the testing and maintenance of one of the principal components in Electrical Networks i.e. Power Transformers. Voltage levels up to 400kV are addressed.

Electricity is high-grade energy. In industry one of its principal uses is the supply of motive power using motors. The course also addresses large induction and synchronous motors, supplied at voltages from 3.3 kV upwards

Objectives

• Develop  existing knowledge of HV Systems and their components including Power Transformers and Motors
• Understand and apply Regulations for Safe Working on HV Apparatus and Systems
• Study the requirements for Operation and Maintenance of  HV Systems and Components 
• Latest Developments in HV Technology. 

Training Methodology

This is an interactive course. There will be open question and answer sessions, regular group exercises and activities, videos, case studies, and presentations on best practice. Participants will have the opportunity to share with the facilitator and other participants on what works well and not so well for them, as well as work on issues from their own organizations. The online course is conducted online using MS-Teams/ClickMeeting.

Who Should Attend?

The course is designed for Engineers and Technicians who are responsible for the:- Design, Operation, and Maintenance of HV Networks including Power Transformers and Motors who may require to refresh their knowledge and acquaint themselves with the latest developments in the technology.

Course Outline

Day 1:

• Revision of Electrical Fundamentals
• Exercises
• Revision of Power Transformer Fundamentals 
• Revision of Motor Fundamentals
• The Institute of Electrical Engineers (IEE) and introduction to publications and electrical supply information
• HV Regulations and the working environment
• Case Studies and Exercises
• Review of Health and Safety
• Regulations for HV Equipment and Systems
• Basic Insulation Principles and Problems

Day 2:

• Review of HV and EHV Power system Components and Selection
• Overhead Lines
• Underground Cables
• Circuit Breakers
• Disconnectors
• Ring Main Units
• Power Transformers
• Metering Transformers
• Exercises
• Principles of Grounding and Induced Voltages
• Case Studies and Exercises
• Insulation in HV and Extra High Voltage (EHV) Systems
• Causes of Fault Conditions on Apparatus and Systems
• External Causes
• Internal Causes

Day 3:

• Types of Power Transformers
• Core Types
• Single-phase
• Three-phase
• Phase Relationships – Phasor Circuits
  • Delta/Star and Star/Delta
  • Star/Star
  • Interconnected-Star Connection
  • The Autotransformer
  • Volts per Turn and Flux Density
  • Tappings
  • Impedance
  • Multi-Winding Transformers including Tertiary Windings
• Dielectrics
• Core Steel
• Winding Conductors
• Insulation
•  Transformer Oil and other dielectric liquids
• Exercises and Case Studies
• Large HV Induction Motors (3.3kV to 11 kV)
• Construction
• Vertical High Thrust and Submersible
• Ratings
  • Rated Voltage
  • Rated Starting Current
  • Effective Reactance, Xm
  • Continuous Current, Measurements and Calculations
  • Horsepower
  • Rated Frequency and “slip” (AC     only)
  • Rotational Speed (RPM)
• Transformer and Other types of  Starters
• Variable Speed Drives
• Testing and Diagnostic Software
• Fault Finding
• Maintenance
• Mechanical Considerations and Balancing Large Synchronous Motors
• The reasons for employment.
• Utilization
• Construction – an Overview
• Field Control Systems – AVR’s
• Testing and Diagnostic Software
• Special maintenance requirements
• Case Studies and Exercises

Day 4:

• Transformer Testing
• Transformer Outages for Testing and Maintenance
• Network Security Considerations
• Safety Considerations
• Isolation Principles
• Switching Co-ordination
• Planned and Unplanned Switching
• The Permit to Work System – Why is it necessary? – How to work safely
• Work Before the Outage
• Work During the Outage
• Case Studies and Exercises
• Protection and Alarm Supervision
• Motors
• Transformers
• In-Service Transformer Testing and Maintenance
• Core Insulation Resistance and Inadvertent Core Ground Test
• Winding Resistances
• Resistance
• Across Windings
• Turns Ratio/Polarity
• Phase
• Excitation Current at All
• Tap Positions
• Short Circuit Impedance
• Insulation Resistance to
• Ground
• Capacitance
• Power Factor/Dissipation
• Factor
• Induced Voltage/Partial
• Discharge
• Bushings
• Capacitance
• Dielectric Loss
• Power Factor/Dissipation Factor
• Partial Discharge
• Temperature (Infrared)
• Oil Level (Sight Glass)
• Visual Inspection (Cracks and Cleanliness)
• Case Studies and Exercises
• Transformer Testing Continued
• Insulating Oil
• Dissolved Gas
• Analysis
• Dielectric Strength & Interfacial
• Tension
• Acid Number
• Visual Inspection
• Color & Water Content
• Oxygen Inhibitor
• On-Load Tap-Changers
• Contact Pressure and Continuity
• Temperature (Infrared)
• Turns Ratio at All Positions
• Timing
• Motor Load Current
• Limit Switch Operation and Continuity
• Tap Changers - No Load
• Contact Pressure and Continuity Centering
• Turns Ratio at All Positions
• Visual Inspection
• Tanks and Associated Devices
• Case Studies and Exercises

Day 5:

• Motor Testing Requirements
• Torque
• Speed
• Power, Mechanical and Electrical
• Dynamometer
  • Eddy Current
  • Hysteresis
• Dynamometer Controller
• Power Analyser
• Software
• Transformer Diagnostic Software
• External Sources of Transformer and Motor Failure – Power Supply Electrical Disturbances
• Internal Transformer and Motor Failures
• Case Studies and Exercises
• Management Issues - Treating Equipment Outages as a Project
• Information versus Data
• Balancing Costs and Benefits
• Planning with Activity Models
• The Planning Sequence
• Network diagrams – dealing with complexity
• Critical Path Analysis and Resource Allocation
• Case Studies and Exercises
• Review and Course Evaluation