Introduction
Introduction
to Protective Relays, Importance of Selection of Relays, Correct Relay
Settings and Co-ordination.
Types of Relays
Non-directional
and directional over current relays, voltage relays, frequency relays,
power relays, impedance
relays, instantaneous over current relays.
Application
of Various types of IDMT Relays
Types
of IDMT over current relays - Normal Inverse, Extremely Inverse, Very
Inverse, Long Time Inverse.
NEMA
device numbers
NEMA
device numbers for various function protection and control relays.
Stages
in Fault Clearance
Devices
for protection system. Requirement for successful fault clearance.
Primary
and Backup Protection
Definition
of primary protection and backup protection. Examples, Zones of
protections.
Need
for Co-ordination of over current relays
Why
co-ordination is required. Discrimination by current, discrimination by
time and discrimination by both time
and current. Examples of each type.
Protection
of Transformer
Recommended
protection for delta-star transformer of various ratings. Recommended
protection for star-star
transformer.
Transformer
differential protection, transformer restricted earth fault protection.
Protection
of Rectiformers
Typical
protection schemes for rectiformers
Protection
of motors
LT
motor protection : Fuse and relay co-ordination, selection of correct type
of relay.
HT
motor protection : Thermal protection, stalling protection, unbalance
protection, short circuit phase and
ground protection.
Protection
of feeders
Pilot
wire protection, Requirements of pilot wire protection.
AC
connection diagram of over current relays
Schemes
for three over current and one earth fault, two over current and earth
fault. Residual / CBCT connection
of earth fault relays.
Typical
DC connection diagram
How
to read schematic diagrams, cross references on drawings.
Understanding
typical protection schemes
Power
circuit, control circuit, reading of drawings.
Importance
of maintenance of DC system
DC
control supply and its importance.
Auxilliary
Power Supply
Universal
voltage relays, relays with external droppers resistor.
Introduction
and Application of current transformer for protection relay
Metering
class CT, general purpose protection class CT, special purpose protection
class CT. Instruments safety
factor, knee point voltage, excitation current, accuracy limit
factor, burden of CTs.
CT
Performance and its influence of Relay Operation
Selection
of CT specification.
|
