Eds coordination system protectives device ppt

Audisankara
College
of
Engineering
and
Technology(A)::Gudur,AP.
Department of EEE
Topic: CO-ORDINATION OF
PROTECTIVE DEVICES
Subject name: EDS
Year/Section: IV-B.Tech-EEE A(VIIISEM)
P.Sudhakiran
Associate.professor
Department of EEE

CO-ORDINATION OF PROTECTIVE DEVICES
Introduction to coordination:-
• The process of selecting the over current protection devices
with certain time current Characteristics and their appropriate
arrangement in series along in a distribution circuit in order to
clear faults from the lines and operates according to a preset
sequence of Operations is known as coordination
Audisankara
College
of
Engineering
and

Basic concept of Co-ordination
 Here the device which is set to operate first to isolate the
fault (or interrupt the fault current) is defined as protecting
device .
 It is usually located very closer to the fault
 The device which provide backup protection but operates
only when the protecting device is fails to operate to clear the
fault is define as protected device.
Audisankara
College
of
Engineering
and

Need for coordination
 Coordination of the protective devices improves the overall performances of
the system .
 The following are the basic objectives in distribution system

Need for coordination
 Coordination of the protective devices improves the overall performances of
the system.
 The following are the basic objectives in distribution system due to
coordination of protective devices .
 To eliminate the service interruptions due to temporary faults.
 To minimize the extent of faults in order to reduce the number of customers
affected.
 To locate the fault ,thereby minimizing the duration of service outage.
 As the coordination is primarily the selection of protective devices and their
Settings to develop zones that provide protection against the temporary faults
And outage area to the minimum size possible if fault is permanent.
Audisankara
College
of
Engineering
and

Data required for the coordination of
protective devices
• To coordinate the protective devices in general the
distribution system engineer must assemble the following
data.
1. Scaled feeder circuit configuration (complete map of the
distribution circuit)
2. Location of existing protecting devices
3. Time –current Characteristics (TCC) of protective devices
4. Load currents (under normal& emergency operating
conditions )
5. Fault currents and short circuit MVA (under Minimum and
Maximum generation conditions )at every point where the
protective devices might be located .
Audisankara
College
of
Engineering
and

Types of coordination
Audisankara
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• The following the major coordination schemes for the
protecting devices
1. Fuse to Fuse coordination
2. Recloser to Recloser coordination
3. Recloser to Fuse coordination
4. Fuse to circuit Breaker coordination
5. Recloser to circuit Breaker Coordination

1.Fuse –Fuse coordination
Audisankara
College
of
Engineering
and

Con--
• The selection of a fuse rating to provide sufficient protection
to the circuit beyond its location is based on several factors
• The selected fuse must be able to carry the expanded load
current
• At the same time, it must be sufficiently selective
(coordinated) with other protective apparatus in series
• It must have the capability to clear a minimum fault current
within its zone in predetermined time duration.
Audisankara
College
of
Engineering
and

Con---
Audisankara
College
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and

Con--
• In the first method two fuses are connected in series as
shown in figure
• The coordination of these devices is achieved by comparing
the total clearing time –current curve (TCC) of the “protecting
fuse”that is fuse B with the damaging curve of “protected fuse
"that is fuse A.
• Here 75% of fuse A minimum melting time of protected fuse
• The 25% margin has been selected to take into account some
of the operating variables ,such as preloading, ambient
temperature and the into account some of the operating
variables ,such as preloading, ambient temperature and the
partial melting of fuse link due to fault current of short
duration
Audisankara
College
of
Engineering
and

Con--
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2.Recloser –Recloser Coordination
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College
of
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Recloser –Recloser Coordination
• A recloser is an over- current protective device which trips and recloses
manually or automatically a preset number of times
• It recloses the for clearing either the temporary faults of for isolating the the
permanent faults.
A recloser can be operated in five different modes they are:
I. Two instantaneous (Trip and Reclose) operations followed by two time –
delay trip operations prior to lockout.
II. One instantaneous plus three time –delay operations
III. Three instantaneous plus one time –delay operations
IV. Four instantaneous operations
V. Four time –delay operations
Audisankara
College
of
Engineering
and

Recloser to Fuse coordination
Audisankara
College
of
Engineering
and

Con--
• The recloser is an over current protecting device ,which trips and recloses
the circuit from overloading for a preset number of operating sequence .
• Fuse is also an over current protecting device but it blown out to trip the
faulted segment when the excessive current flowing through it
The above two curves of fuses ‘A’ is coordinated with below two curves of
tripping characteristics of Auto recloser “R”
I. Delayed auto recloser opening characteristics
II. Instantaneous auto recloser opening characteristics
 The following can be concluded for the operating sequence of selective
devices from the above characteristics
 If the fault current is less than ‘p’ the recloser operates with delayed opening
time
 If the fault current is less than ‘Q’ the recloser operates with instantaneous
opening time
 Beyond the current ‘Q’ the fuse ‘A’ operates
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4.Circuit Breaker to fuse coordination
• Circuit breaker is tripped by over current phase fault protection .Total
fault clearing time is equal to relay time plus circuit breaker time.
• The coordination between the circuit breaker and fuse can be limited
to two cases
I. Fuse is the main protective device and circuit breaker is a backup
device
II. Circuit breaker is the main protective device and fuse is backup
device
Audisankara
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of
Engineering
and

3.Circuit Breaker to fuse coordination
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College
of
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5.Circuit Breaker to Auto-Recloser Coordination
• An Auto reclose is a protective device used to protect the
distribution system due to over current faults
• When recloser is used as main protecting device, it will
coordinate with other protective devices in the distribution
circuit
• Here the coordination of recloser with the circuit breaker is
described for Short circuit fault .
In this circuit breaker provide backup protection (Protected
device)
Audisankara
College
of
Engineering
and

5.Circuit Breaker to Auto-Recloser Coordination
Audisankara
College
of
Engineering
and

24
THANK YOU
Audisankara
College
of
Engineering
and

Eds coordination system protectives device ppt

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