Upload
atulsontakke11
View
234
Download
0
Embed Size (px)
Citation preview
7/30/2019 substation protection.
1/25
SUBSTATION PROTECTION
Atul sontakke.
7/30/2019 substation protection.
2/25
OUTLINE
2
Introduction
Nature and Causes of faults
Components of Protection
Fuse and its types
Relay and its types Circuit breaker
Earthing
Isolator
7/30/2019 substation protection.
3/25
Introduction
3
A Substation covers various equipment such as Circuit Breakers,
Isolators, Earth Switches, Lightning Arresters, Grounding System and
etc. Protection scheme is designed to limit the effects
of disturbances in the power system which is allowed to persist, may
damage plant and interrupt the supply of electric energy. The
greatest threat to the security of a power supply station is short
circuit which imposes sudden and violent change in he power
system. Rapid isolation of the fault by nearest switchgear will
minimize the damage. It covers various types of protection used inswitchyard such as relays, circuit breakers and etc.
7/30/2019 substation protection.
4/25
NATURE AND CAUSES OF FAULTS
4
Insulation failure.
Conducting path failure.
Overvoltage's due to lightening or switching surges.
Puncturing or breaking of insulators.
Failure of conducting path due to broken conductors.
Faults due to poor quality of system components or because of faulty
system design. System design.
7/30/2019 substation protection.
5/25
COMPONENTS OF PROTECTION
5
FUSES
MCB/MCCB
RELAYS
CIRCUIT BREAKERS
EARTHING
ISOLATOR
7/30/2019 substation protection.
6/25
FUSES
6
Fuse-Fuse is a piece of wire of a material with avery low melting point. When a high current flows
through the circuit due to overloading or a short
circuit wires gets heated and melts. As a result, the
circuit is broken and current stops flowing.
Types of fuses. Low voltage fuse.
KIT-KAT fuse.
HRC (High rupturing fuse).
Semiconductor fuse.
High voltage fuse.
Drop out fuse.
7/30/2019 substation protection.
7/25
MCB (Miniature Circuit Breaker)
Type Tripping Current perating Time
Type B 3 To 5 time full load current 0.04 To13 Sec
Type C 5 To 10 times full load current 0.04 To 5 Sec
Type D 10 To 20 times full load current 0.04 To 3 Sec
7/30/2019 substation protection.
8/25
Application of MCB
8
B Curve MCB-This type MCB is used for resistive load.
e.g. Heater, Oven.
C curve MCB- This type MCB is used for inductive load.
e.g. Fan, Washing M/C, Fridge, motor, AC, Transformer,
D Curve MCB- This type MCB is used where High inrush current is
available.
e.g. Induction motor, Transformer.
7/30/2019 substation protection.
9/25
MCCB (Moulded Case Circuit Breaker)
MCCB is used for protecting of low-voltage electrical wires and
connected equipment, against overloads and short-circuits.
Rated current up to 1000 A.
Trip current is adjustable. The advantage of MCCBs for very large ratings is their compact size.
An ACB is physically larger, but more cost-effective for higher ratings.
7/30/2019 substation protection.
10/25
RCCB(Residual Current Circuit Breaker)
Phase (line) and Neutral both wires connected through RCCB.
RCCB trips the circuit when there is earth fault current.
The amount of current flows through the phase (line) should return
through neutral.
Any mismatch between two currents flowing through phase andneutral detect by -RCCB and trip the circuit within 30Miliseconed
7/30/2019 substation protection.
11/25
ELCB (Earth Leakage Circuit Breaker) An ELCB had a current sensing coil in series with the ground cable, so
the supply would be tripped if current occurred in the ground lead.
This was often combined with a voltage sensing coil on the frame
also, which used a separated ground some distance away.
The original use was for larger motors and generators/transformers,
where the insulation can fail, and the voltage on the frame of the
machine can rise dangerously above ground due to the ground
resistance and fault current.
7/30/2019 substation protection.
12/25
Relays
Relays are electrical switches.
7/30/2019 substation protection.
13/25
Types of Relay. Over current relay.
Under voltage relay.
Earth fault relay.
Phase sequence relay.
Time delay relay.
Buchholz Relay.
Frequency Relay.
7/30/2019 substation protection.
14/25
Buchholz Relay.
7/30/2019 substation protection.
15/25
High voltage circuit breakers
open or close a circuit under all conditions. Viz. no load full load and
fault condition.
it can be operate manually and automatically under fault conditions.
Under normal operating condition, the contact remains close and thecircuit breakers carries the full load-current continuously.
7/30/2019 substation protection.
16/25
Classification of circuit breaker.
Oil circuit breaker- Which employ some insulating oil for arc extinction.
Air-blast circuit breaker- in which high pressure airblast is used arc extinction.
SF6-Sulferhexafluoride gas is used for arc extinction.
Vacuum CB- Vacuum is used for arc extinction. 33kV.
7/30/2019 substation protection.
17/25
Oil circuit breaker.
Advantages of Oil Circuit Breaker (OCB)As an Arc extinguishing medium oil has the following
advantages:
1. Oil produces hydrogen during arching. The hydrogen helps
extinguish the arc.
2. Oil provides insulation between the contacts after the arc
has been extinguished
Disadvantages of Oil Circuit Breaker (OCB)
1. Oil is inflammable and may cause fire hazards. When a
defective circuit breaker fails under pressure, it may cause an
explosion
2. The hydrogen generated during arcing, when combined with
air, may form an explosive mixture
3. During arcing, oil decomposes and becomes polluted by
carbon particles, which reduces its dielectric strength. Hence,
it requires periodic maintenance and replacement.
7/30/2019 substation protection.
18/25
Vacuum Circuit Breakers
Advantages
Very long lifetime of the contacts (This
provides longer breaker life.)
Less maintenance required
Less moving parts in mechanism
Less force needed to separate thecontacts (since the distance between them
is shorter.)
Environment friendly. Since interruption
takes place in vacuum medium, VCBs do
not require
gas or liquid addition. This reduces thepossibility of leakage of gas (or any
material) that can
be harmful for environment.
7/30/2019 substation protection.
19/25
Air blast Circuit breaker.
7/30/2019 substation protection.
20/25
SF6 circuit breaker.
Advantages
Simple construction, less cost.
SF6 gas is non flammable, non toxic
Maintenance free
Ability to interrupt low and high fault
Excellent Arc extinction.
7/30/2019 substation protection.
21/25
EARTHING
21
Types of Earthing -
Plate Earthing Pipe Earthing
7/30/2019 substation protection.
22/25
Measurement of Earth Resistance
22
http://electricalnotes.files.wordpress.com/2011/11/11.png7/30/2019 substation protection.
23/25
ISOLATOR
23
Circuit--Isolator Isolators are available in
ratings from 11 kV to 132kv.
in 1200 A, 1600 A, and 2000 A versions.
Style like Side--break, vertical- break,
centre break styles. can be furnished, to
suit almost any substation layout.
7/30/2019 substation protection.
24/25
ELECTRICAL SLD
24
7/30/2019 substation protection.
25/25
Thank you