Apparatus 2 Flashcards
are used in AC system for measurement of
electrical quantities i.e., voltage, current, power, energy, power factor,
frequency
Instrument Transformers
is to step down the AC
System voltage and current
Basic function of Instrument transformers
is
used to step down the
current of power system
to a lower level to make it
feasible to be measured by
small rating Ammeter (i.e.,
5A ammeter)
CURRENT TRANSFORMER (C.T.)
is used
to step down the voltage of
power system to a lower level
to make is feasible to be
measured by small rating
voltmeter i.e., 110 – 120 V
voltmeter
POTENTIAL TRANSFORMER (P.T.)
is an absolutely essential device in the modern
world, and one of the most important safety mechanisms in your
home
The circuit breaker
These breakers are rated for use at low voltages up to 2 kV and are
mainly used in small-scale industries.
Low voltage circuit breakers
These breakers are rated for use at voltages greater than 2 kV. High
voltage circuit breakers are further subdivided into transmission class
breakers.
o Those which are rated 123 kV and above
o Medium voltage class (lesser than 72 kV) circuit breaker
High voltage circuit breakers
These are designed to use inside the buildings or in weather-resistant
enclosures. They are typically operated at a medium voltage with a
metal clad switchgear enclosure.
Indoor circuit breakers
You can use these breakers outdoors without any roof due to their
design. Their external enclosure arrangement is strong compared to the
indoor breakers and can withstand wear and tear.
Outdoor Circuit breakers
The breakers whose enclosed tank is at ground potential are known as
dead tank circuit breakers. Their tank encloses all the insulating and
interrupting medium. In other words, the tank is shorted to ground, or
it is at dead potential.
Dead tank circuit breakers
These breakers have a tank housing interrupter that is at a potential
above the ground. It is above the ground with some insulation medium
in between
Live tank circuit breakers
This breaker uses air as an insulating and interrupting medium. The
breaker is sub-classified into two types:
oLow voltage circuit breaker whose value lies below 1000 V.
oHigh voltage circuit breaker whose value is 1000 V and above.
Air circuit breaker
It uses oil as an interrupting and insulating medium. These breakers are
divided into two types based on the pressure and amount of oil used
Oil circuit breaker
These breakers use vacuum as the interrupting medium due to its high
dielectric and diffusive properties
Vacuum circuit breakers
The current ratings for this breaker are less than 100A and has only one
over-current protection built within it. The trip settings are not
adjustable in this circuit.
MCB (Miniature Circuit Breaker)
Current ratings for these breakers are higher than 1000A. They have
earth fault protection along with current protection. The trip settings of
the Molded Case Circuit Breaker can be adjusted easily.
MCCB (Molded Case Circuit Breakers)
This breaker has one hot wire and one neutral wire that operate at 120
V. When there is a fault, it will interrupt just the hot wire.
Single pole circuit breaker
This is used for 220 V. There are two hot wires, and both the poles need
to be interrupted.
Double pole circuit breaker
These are safety switches that trip on ground fault current. The GFCI
breaker interrupts the electrical circuit when it detects the slightest
variance between phase and neutral wires.
GFI or GFCI circuit breaker (Ground fault circuit interrupter)
The AFCI breaker interrupts the circuit during excessive arc conditions
and prevents fire. Under the normal arcing condition, this breaker will
be idle and won’t interrupt the circuit
Arc Fault circuit interrupter (AFCI)
is an electrical safety device built around a conductive strip
that is designed to melt and separate in the event of excessive
current.
fuses
The device which is used for the protection of the equipment at the
substations against travelling waves.
LIGHTNING ARRESTERS
is automatic device which senses an abnormal condition of
electrical circuit and closes its contacts.
PROTECTION RELAYS
are used as a
protective device, as they are
sensitive to the effects of dielectric
failure that can occur inside the
equipment they protect.
Buchholz relays
