-
Types
of fault
-
Shunt
faults
:
Three Phase fault, phase to ground fault, Magnitude of fault
currents for solidly grounded, high and low resistance
grounded
systems, fault detection in ungrounded system
-
Series
faults : one-phase open, two-phase open, effects on system
-
Equipment and typical protections :
-
Transformer
: Protections on HT side, LT side; Unit protections
(differential, REF) –
Applicable protections
based on ratings
-
Generator
: Plain over current and voltage restrained over current
protections, stator earth fault (95% & 100%)
protection,
Back up impedance protection, Unit protections (differential,
REF), Influence of neutral
grounding on protection
-
Feeder
protection –
Incomer to switchgear
-
Feeder
protection –
outgoing from switchgear
HT motor protection
– composite
protection, influence of source grounding LT
motor protection Tie
feeder protection –
Pilot wire protection Busbar protection
-
Typical
relays used for transformer, generator, feeder, motor, bus, pilot wire
protections in Numerical, mP
/ Static and Electro-mechanical ranges
-
Comparison
Chart: characteristics of relays of different vendors
-
Definition
– NI, VI, EI, LI characteristics – IEC curves – formula and
limitations
-
Application
of DMT and IDMT (NI, VI, EI, LI) in power network - Where to use and
where not to use
-
Numerical
relays – advantages, precautions in use / settings
-
Primary
and back up protection
-
Need
for coordination
-
3
S – Sensitivity, Selectivity and Speed
-
Discrimination
time – empirical formula: Fuse IDMT, Instantaneous to IDMT and IDMT
to IDMT for Electromechanical relays and numerical relays
-
Concept
of Plug setting multiplier and time multiplier setting
-
Criteria
for setting plug and time dial for IDMT / DMT relays
-
Phase
and Ground Instantaneous over current relays – application and
setting criteria, need for stabilizing resistor
-
Pilot
wire protection – How upstream operating time can be reduced
-
CT
brief primer : Protection class, accuracy and ALF, voltage developed
across CT secondary, CT for numerical relay applications
-
Class
room exercise : Step by step relay setting and co-ordination exercise for phase
fault and ground fault relays;
Application and selection checks with
conventional and numerical relays.
-
Case
studies : Selection
of relays for transformers of medium and large size, emergency
generators, motor feeders;
Selection of earth fault relays for solidly
grounded, medium resistance grounded and high resistance
grounded
systems.
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