Distribution System Training

The objective of this module is to examine the features of overcurrent protection, including different types of overcurrent relay and typical applications.

After completion of this module, the participant should be able to understand the following concepts, and apply them in day-to-day work practice.

• Increase in current magnitude due to the occurrence of a fault
• Fuse operation due to overcurrent
• Thermal relay operation
• Detection of fault by overcurrent relay and subsequent trip of the circuit breaker to disconnect the faulty circuit
• Instantaneous overcurrent relays
• Limitations of the instantaneous overcurrent relay
• Construction of the electromechanical type time overcurrent relay
• Function of the time overcurrent relay
• The inverse time characteristic
• Application of overcurrent relays to protect radial distribution lines
• Three phase and ground fault protection by overcurrent relays
• Setting the overcurrent relay
• Downstream protection devices, including fuses and reclosers
• Coordination of overcurrent relays and downstream protection devices
• Voltage restraint overcurrent relays
• Directional overcurrent relays
• Polarizing the directional relay
• Features of static electronic relays
• Fundamentals of microprocessor relays
• The microprocessor type overcurrent relay
• Microprocessor relay adjustments
• Microprocessor relay multiple functions
• Self monitoring functions
• Microprocessor relay communication to substation control systems