08 autoreclosing

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Auto-Reclosing On Transmission Systems


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> Auto-Reclosing and System Stability January 20042 2

Fault Shunts (1)

ZF = Fault shunt

= Combined Impedance of -ve and zero sequencenetwork impedances for particular fault.

Z1

N1

F1

ZFE


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Fault Shunts (2)

/ E ZF = Z2 + Z0

/ ZF = Z2

/ / E ZF = Z2 . Z0

Z2 + Z0

3 ZF = 0 (short circuit)

Healthy ZF =

(open circuit)


4/24> Auto-Reclosing and System Stability January 20044 4

Use Of Power Angle Curves


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Comparative Power Angle Curves

3 Healthy

2 Healthy1 Tripped

/E Fault

//E Fault

3 Fault

3 Tripped

Load Angle ()

Power



Steady State

0

Power

Phase Angle

Difference

Normal HealthyOperation

P0

A

XY



During Fault

X Y

//E Fault

Power

0 Phase Difference

P0A

CB

1

P1

Normal

P0 - P1



Choice of Scheme

1AR or 3AR



1 Auto-Reclose Advantages (over 3 A/R)

1. Higher power transfer limit.

2. Reduced power swing amplitude.

3. Reduced switching overvoltages due to reclosing.

4. Reduced shock to generators.Sudden changes in mechanical output are less



Choice of Scheme (1)

1. Single transmission links.

2. 3 A/R.

3. 1 A/R for E/Fs

Lockout for multiphase faults.

4. 1 A/R for E/Fs

3 A/R for multiphase faults.

High Speed Auto-Reclose


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Choice of Scheme (2)

1. Densely interconnected systems.

Minimal power transfer level

reduction during dead time

2. Power swings due to fault and trippingallowed to decay

Less shock to system than with highspeed A/R

Delayed 3 Auto-Reclose


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1 Auto-Reclose Factors RequiringConsideration

1. Separate control of circuit breaker poles.

2. Protection must provide phase selection.

3. Mutual coupling can prolong arcing and require

de-ionising time.

4. Unbalance during dead time

(i) Interference with communications(ii) Parallel feeder protection may maloperate

5. More complex and expensive than 3 A/R

Hi h S d A t R l (H S A R ) (1)


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High Speed Auto-Reclose (H.S.A.R.) (1)

High speed < 2 cycles

Fast clearance at each line end.

Phase comparison

Distance schemes with signalling

Distance scheme with zone 1 extension

Direct intertrip

Phase selection required for 1 A/R

Protection

A t R l


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Auto-Reclose

Hi h S d A t R l (H S A R ) (2)


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High Speed Auto-Reclose (H.S.A.R.) (2)

Circuit breaker minimum open - closetime

200 - 300 msecs.

Same dead time at each line end.

De-ionising time

1 A/R longer special steps

Dead Time (short as possible)

Delayed Auto Reclosing (D A R ) (1)


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Delayed Auto-Reclosing (D.A.R.) (1)

Protection

High speed not critical for system stability

desirable to limit fault damage

improves probability of successful A/R

Dead Time

Allow for power swings and rotor oscillations todie down.

Different settings for opposite feeder ends.

Typically 5 to 60 secs.

Delayed Auto Reclosing (D A R ) (2)


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Delayed Auto-Reclosing (D.A.R.) (2)

Reclaim TimeAllow c.b. capacity to recover to full interrupting

value.

Number of Shots

1 (invariably)


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Check Synchronizing

Synchronism Check


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Synchronism Check

On interconnected systems - little chance of complete loss ofsynchronism after fault and disconnection of a single feeder.

Phase angle difference may change to cause unacceptable shock to

system when line ends are re-connected.

VL = 0

VB = live

Dead Line Charge

VB VL

Check Synchronising


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Check Synchronising

Used when system is non radial.

Check synch relay usually checks 3 things:

1) Phase angle difference

2) Voltage

3) Frequency difference


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Auto Isolation

Auto-isolation - Single Switch Substation


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Auto isolation Single Switch Substation

Transient Fault - Line 1 120/G1/Remote Open

120/Remote Reclose

T1 Energised

G1 Close After Time Delay

Persistent Line Fault

120/Remote Opens Again

103 Opens Automatically

120 Closes Followed By G1

T1/T2 Fed From Line 2

Transformer Fault

120/G1/Remote Trip

113 Auto Opens

G1 Lock Out

120/Remote Reclose

Line 1

G1 G2

Line 2

103 120 203

113 213

T1 T2


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08 autoreclosing

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