Handbook - elec-engg.com

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AutoreclosingProtection Application

Handbook

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Autoreclosing

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AutoreclosingAuto reclosing Cycle

Fast

simultaneous

Fault clearing

OH-lines

High fault-rate

(80-90%)

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AutoreclosingAUTORECLOSING CYCLE

OH-lines

Intermittent faults

(80-90%)

Successful

AR-rate :

High (80-90%)

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Autoreclosing

Auto reclosing principles

95% of faults are transient type

3 Ph autoreclosing synchrocheck is used

Helps verify phase angles are not out of phase e.g: due to

heavy power swing

1 Ph autoreclosing needs identification of faulty phase

Phase identification is difficult for high resistance faults

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Autoreclosing

Auto reclosing principles

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AutoreclosingAutoreclosure in a Line

bay

AR- Autorecloser

BFR- Breaker failure

relay

COM- Communication

COND-CB condition

DLC SC-Dead line check

and synchronism check

LP- Line protection

MAN- Manual CB control

PD- Pole discordance

relay

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Autoreclosing

Auto reclosing principles Protections that start autoreclosing

Main 1 protection

Main 2 protection

Protections that block autoreclosing

CB fail detected by Breaker fail relay & Pole discrepancy relay

CB not ready

Delayed tripping ( Zone2 or3 of distance relay , Back up relay)

Manual CB operation

Communication fail

Direct transfer trip receive , BB protection , O/V protection, Reactor protection

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Autoreclosing

Circuit-breaker Contact Travel

Con

tact

pos

itio

n

Time

Closed

Open

Closed

t t t t

tt 2 6

5431

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AutoreclosingDead time for Automatic Reclosing Equipment

A B

Time

Con

tact

po

siti

on

t2 B

t2 A

t6 A

t6 B

t1 A

t1 B

t0

A

B

F

Open

Open

Closed

ClosedDead time

Interruption time

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Autoreclosing

Single-pole Reclosing

A B C A B C

Single-Pole Reclosing

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AutoreclosingTemporal Description of Automatic Reclosing

0.1 1 10 100 s

TD

3

HSR = High-Speed Automatic Reclosing

DR = Delayed Automatic Reclosing

R = Automatic Reclosing

SR = Slow Automatic Reclosing

R SR

DR

HSR

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Autoreclosing

Classical Three-pole Reclosing

A B

Time

Con

tact

po

siti

on

t2 B

t2 A

t6 A

t6 B

t1 A

t1 B

t0

A

B

F

Open

Open

Closed

Closed

Dead time

Interruption time

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Autoreclosing

Factors affecting extinction of Primary Arc

Fault current magnitude

Fault clearance time

Coupling from energized conductors

Closing or opening of resistors

Magnitude of reenergizing voltage

Point of wave for reenergizing

Magnetic forces on the fault current

Length of insulating string

Weather conditions

Shape of grading ring

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AutoreclosingMinimum Dead Time (IEEE)

System Voltage Minimum deionization time [ms]

kV Based on Field and

Laboratory Tests

Based on Operating

Experience

23 110 180

46 120 200

69 130 210

115 150 230

132 160 240

230 210 280

345 260 340

400 280 370

500 330 420

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AutoreclosingMinimum Dead Time for Three-pole Reclosing

Minimum Dead Time

Three-Pole Reclosing

System Voltage

100 200 300 400 500 600 kV

500

400

300

200

100

ms

Based on Opera-

ting Experience

Based on Field and

Laboratory Tests

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Autoreclosing

Double Fault on a Double-circuit Line

L R

A B CA B CL1

L2

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AutoreclosingCapacitive Coupling and Single-pole Tripping

L R

A B C A B CC p

C p C p

Ce

Ce

Ce

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Secondary arc

Secondary arc is phasor sum of currents maintained by

capacitive and inductive coupling from the energised

phase conductors

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Critical Line Lengths for Single-pole Reclosing

System Voltage Critical Line Length [miles]

kV Successful Range Doubtful Range

230 0-300 300-500

345 0-140 140-260

500 0-60 60-100

765 0-50 50-80

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Autoreclosing

Artificial extinction of secondary arc

Where high-speed automatic reclosing is to be implemented,

secondary arcs must be artificially extinguished since they would

otherwise last too long.

There are several methods to extinguish artificially the secondary

arc:

Fixed Four-Reactor Scheme

Switched Four-Reactor Scheme

High speed Earthing Switch Scheme

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AutoreclosingFixed Four-reactor Scheme

L R

A B C A B C

L p L p L p

L n

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AutoreclosingSecondary Arcing Time (Haubrich)

s Tsa

Is

A50 100 150

0.5

1.0

1.5

2.0

Secondary Arcing Time

Haubrich 1971

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Autoreclosing

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AutoreclosingAuto reclosing in one and a half breaker

system

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AutoreclosingAuto reclosing in one and a half breaker

system

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Special problems

Memory Circuit

Priority circuit

Autoreclosure out of service

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Autoreclosing

ULine UBus

SYNC-BLOCK

UBus

ULine

Fuse fail

1-ph

3-ph (or 1-ph)

UBus

ULineUHigh > 50-120% Ur

ULow < 10-100% Ur

PhaseDiff < 5-75

UDiff < 5-50% Ur

FreqDiff < 50-300 mHzo

Synchronism and Energizing check

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Auto ReclosingCBIP manual on Protection

of Generators, generator

transformers and 220kV

and 400 kV networks

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Autoreclosing1.0 GENERAL

• The auto-reclosing of power lines has become a generally accepted

practice.

• Reports from different parts of the world show that in

certain networks in region subject to a high lightening intensity only

about 5% of the faults are permanent.

• Auto reclosing therefore provides significant advantages.

• Outage times will be short compared to where station personnel

have to re-energize the lines after a fault.

• In interconnected networks auto-reclosing helps in maintaining

system stability

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Autoreclosing1.1 Recommendations for provisions of auto-reclosing

• Presently 1 phase high speed auto-reclosure (HSAR) at 400kV and

220kV level is widely practised including on lines emanating from

Generating Stations and the same is recommended for adoption.

• If 3-phase auto-reclosure is adopted in future the application of the

same on lines emanating from generating stations should be studied

and decision taken on case to case basis.

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Autoreclosing2.0 SETTING CRITERIA

2.1 Dead Time

• Auto- reclosing requires a dead time which exceeds the de-ionising

time

• Time required for the de-ionising of the fault path depends on:- arcing

time, fault duration, wind conditions, circuit voltage, capacitive

coupling to adjacent conductors, etc.

• Single phase dead time of 1.0 sec is recommended for both 400kV

and 220kV system.

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Autoreclosing2.2 Reclaim Time

• The time during which a new start of the auto-reclosing equipment is

blocked.

• If reclosing shot has been carried out and the line is energized and a

new fault occurs before the reclaim time has elapsed, the auto-reclosing

equipment is blocked and a signal for definite tripping of the breaker is

obtained.

• After the reclaim time has elapsed, the auto-reclosing equipment

returns to the starting position and a new reclosing sequence can occur.

• The reclaim time must not be set to such a low value that the intended

operating cycle of the breaker is exceeded, when two faults incidents

occur close together.

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Autoreclosing• If the breaker is closed manually, the auto reclosing equipment is

blocked and cannot start again until the reclaim time has elapsed.

• For the breaker to be used for auto-reclosing, it is essential that it

has the operating mechanism and breaking capacity necessary for

it to be able to perform the auto-reclosing sequences required.

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Autoreclosing2.3 Circuit Breaker Requirement

• According to IEC Publication 56.2, a breaker must be capable of

withstanding the following operating cycle with full rated breaking

current:

O + 0.3 s + CO + 3 min + CO

• The recommended operating cycle at 400kV and 220kV is as per the

IEC standard.

• Reclaim time of 25 sec is recommended.

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