Details

The continuity of the electrical power supply is very important to consumers, especially in the industrial sector. Protection relays are used in power systems to maximise continuity of supply and are found in both small and large power systems from generation, through transmission, distribution, and utilisation of the power. A good understanding of their application, operation, and maintenance are critical for operating and maintenance personnel.

The strengths and weaknesses of the latest microprocessor (or numerical) relays as compared to the older electromechanical relays will be examined. You will also gain a solid appreciation of how the modern relay communicates not only to the central SCADA system but also between themselves, resulting in a truly multifunctional system that includes protection, control, and monitoring. Finally, you will gain a solid understanding of issues of reliability and security for the modern relay.

Programme Outline

Basics of Power System Protection

• Requirements of protection in an electrical system – Reliability, dependability, and security
• Types of faults

 Evaluation of short circuit currents

Fault calculations in simple circuits

• Earth faults and the role of system earthing
• Characteristics of protective relaying – Sensitivity, selectivity, stability, and speed

Protection using fuses

 Protective relay/release and circuit breaker combination

• Instrument transformers and their application in protection systems

Relays and their Development

• Types of protective relays (DMT and IDMT)
• Electromechanical and static relays
• Microprocessor and numerical relays
• IDMT characteristics are expressed as a mathematical function

Comparison of electromechanical/static and numerical relays – Key features: Flexibility/reliability/communications/SCADA interface – Cost – Integrated protection and control

Protection Coordination

 Time and current grading

Application of time and current grading

Grading using IDMTL characteristics

• Better grading through numerical relays

Typical Block Diagram of Numerical Protection Relay

 Typical block diagram

• Hardware and software architecture
• Sampling interval

 Extension of capabilities of relays in numerical design

• From individual protection relays to a complete protection management system
• Structure of the Intelligent Electronic Device (IED)

 Configuring substation automation using IEDs

Types of Numerical Protection Systems and Principles

 Functional protection relays

Equipment protection systems with multiple functions