PowerPoint - Introduction to Protection Relay_RevB
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Transcript of PowerPoint - Introduction to Protection Relay_RevB
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Introduction to Protection Relay
Presented by: Ir.S.Gopinath
Date: 07/11/2012
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Contents (cont.)
2.3 Principle of Relay
( Case study: CX-M Relay operation for
11kV VCB)3. Current Transformer ( CT) & Voltage
Transformer (VT)
4. Relation between Relay and CT/VT
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Contents (cont.)
5. I.D.M.T setting of Phase Overcurrent Protection
relay
( Case study: Calculation on Electromechanicalrelay ( Overcurrent ) for Radial distribution
system)
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1. Renewable Energy: Concentrated Solar
Power (CSP) CSP systems use mirrors or lenses to concentrate
a large area of sunlight, or solar thermal energy,
onto a small area.
Concentrated light is converted to heat, which
drives a heat engine(usually a steam turbine)
connected to an electrical power generator.
Example: 11MW PS10 & PS20 Solar Power Plant
http://en.wikipedia.org/wiki/Solar_thermal_energyhttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Steam_turbinehttp://en.wikipedia.org/wiki/Heat_enginehttp://en.wikipedia.org/wiki/Solar_thermal_energy -
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2. Introduction to Protection Relay
IEEE defines a relay as an electric device that is
designed to input conditions in a prescribed
manner and after specified conditions are met, to
cause contact operation
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2.1 Electrical system Protection
isolation of a problem area in the system quickly
so that the rest of the system as much as possible
is left continue service.
The five(5) basic features are:
- Reliability
- Selectivity
- Speed of Operation
- Simplicity
- Economics
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Some related device numbers are: ( stated in
IEEE C37.2-2008)- undervoltage relay (27)
- field circuit breaker (41)
- thermal relay (49)- instantaneous overcurrent relay (50)
- lockout relay (86)
- differential protective relay (87)
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2.2 Causes & Types of Fault
faults can interrupt the healty operation of the
power system.
The type and nature of faults in a three-phase
system are normally classified as:
- Phase & ground
- Permanent
- Transient
- Semitransient
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Phase & Ground fault
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Permenant Faults
- created by punturing or breaking insulators,breaking conductors and objects falling on the
ground conductor
Trasient Faults
- created by transient overvoltages such as
lightning.
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2.3 Principle of Relay
Relay has two mechanical parts:.
- Firstly, the contact(s) of the relay
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- Secondly, the device that forces the terminal tomove so-called an electromagnet
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Types of relay:
- Electromechanical relay
- Static relay- Digital relay
- Numerical relay
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Electromagnetic Relay
convert a magnetic flux generated by the
application of a low voltage electrical control
signal either AC or DC across the relay terminals,
into a pulling mechanical force which operatesthe electrical contacts within the relay.
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- Electromechanical relay construction
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Relay contact types
Electrical relays can be made up of one or moreindividual switch contacts with each "contact"
being referred to as a "pole
Description of the contact types:
SPST - Single Pole Single Throw
SPDT - Single Pole Double Throw
DPST - Double Pole Single Throw
DPDT - Double Pole Double Throw with the action of the contacts being described as
"Make" (M) or "Break" (B)
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- Relay Contact Configuration
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- Relays at Jimah MV Switchgear
Example of Protection relays at Jimah electrical
system:
- Lockout relay
- Power relay
- Thermal overload relay
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Power relay:
- 11kV & 3.3kV switchgear panel uses MM type
OMRON Power relay for control circuits.
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Case study: CX-M relay operation in VCB
control circuit
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Lockout relay
- Protect our main system and safeguard our
personnel with the industry standard for
safety and reliability. This lockout relay
applied for protection of:
Generator Transformer & Generator
Unit Auxliary transformer (UAT)
Excitation Transformer
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3. Current Transformer ( CT) & Voltage
Transformer (VT)
CT Principle:
- The alternating currentflowing in the primary
produces a magnetic field in the core, which then
induces a current in the secondary winding
circuit.
http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Alternating_current -
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CT symbol:
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- CT types applied for medium voltage system
Window or Ring type CT
Bar type CT
Bushing Type Or Busduct
Current Transformers ( BCT )
Wound type Primary CT
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VT Principle:
- to produce the system votlages, accurately at low
voltage suitable for the operation of measuring
instruments
- The primary winding is connected across the
supply voltage and low range voltmeter (0-110V)
is connected across the secondary windingterminals.
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- VT types applied for medium voltage system
Cast iron in-resin VT
Capacitor VT
Electromagnetic VT
Cast iron VT with Build-in Fuse type
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4. Relation between Relay and CT/VT
The relays are connected to the power system
through the CT and VT.
CT and VT are used to measure the current
and voltage in a circuit of the order of
hundreds of amperes and volts respectively.
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- Basic configuration of protection relay in a circuit
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- Basic scheme of protection relay and circuit breaker
When current exceeds the normal value, torque produced
will overcome the spring tension to rotate the disc about a
vertical spindle to which a long arm is attached.
The arm moves in the anticlockwise direction till it closes
the terminals 1& 2, and completes the circuit comprising
of a battery and the trip coil of the circuit breaker.
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5. I.D.M.T Overcurrent relay
In inverse definite minimum time (IDMT) relay its
operating is inversely proportional to fault
current and also a characteristic of minimum
time after which this relay definitely operates.
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- Relay coordination
a. whenever possible, use relays with the same
operating characteristic in series with each other
b. make sure that the relay fastest from the
source has current settings equal to or less than
the relays behind it.
using either time or overcurrent, or a
combination of both.
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IEC 60255 defines a number of standard
characteristics as follows:
- Standard Inverse (SI)
- Very Inverse (VI)
- Extremely Inverse (EI)
- Definite Time (DT)
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- Relay characteristics & equations
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- Relay Time Grading Margin (GM)
The time interval that must be allowed between
the operation of two adjacent relays in order to
achieve correct discrimination between them.
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The grading margin depends on a number of
factors:
the fault current interrupting time of the circuit
breaker
relay timing errors
the overshoot time of the relay
CT errors
final margin on completion of operation
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- Important terms for I.D.M.T relay setting
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The important parameters required for relay setting are
such as:(i) Pick-up current- It is the minimum current in the
relay coil at which the relay starts to operate
[ Pickup current = Rated secondary current of CT
x Current setting]
(ii) Current settingIt is often desirable to adjust
the pickup current to any value.
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(iv) Plug setting (P.S.M)- determines the current at
which the relay will start to operate.
(v) Time-setting multiplier (T.M) - controls the
relays disc movement. The position of the
moving contact is usually adjusted by turning
the time multiplier knob, which ranges from 0.1
to 1.0. Calculated by multiplying the time
setting multiplier with the time obtained from
time/ p.s.m curve of the relay.