6.1-Busbar protection.pdf

6.1 BusBar protection

6.1 BusBar protection

BUSBAR PROTECTION

BUSBAR PROTECTION

Ref : APP14

Ref : APP14

Issue B1 Last Release : October 2010

Issue B1 Last Release : October 2010

Schneider Electric - Jean Marmonier - 20/01/2011


Program g

Program g

PART 1 : GENERALITY

PART 1 : GENERALITY

PART 2 : OPERATING PRINCIPLES

PART 2 : OPERATING PRINCIPLES

PART 3 : OTHER SUBSTATION TOPOLOGIES

PART 3 : OTHER SUBSTATION TOPOLOGIES

Advantages / Disadvantages


PART 4 : HIGH IMPEDANCE DIFFERENTIAL PROTECTION –

PART 4 : HIGH IMPEDANCE DIFFERENTIAL PROTECTION –

PRINCIPLE

PRINCIPLE

PART 5 : LOW IMPEDANCE PROTECTION – PRINCIPLE

PART 5 : LOW IMPEDANCE PROTECTION – PRINCIPLE

PART 6 : FRAME LEAKAGE PROTECTION - PRINCIPLE

PART 6 : FRAME LEAKAGE PROTECTION - PRINCIPLE

PART 7 : BLOCKING SCHEME PROTECTION

PART 7 : BLOCKING SCHEME PROTECTION

PART 8 : OTHER APPLICATIONS

PART 8 : OTHER APPLICATIONS


2


2

PART 1 : Generality

PART 1 : Generality

PART 2 : Operating Principle


PART 3 : Other Substation Topologies




PART 4 : High Impedance Differential


p Protection – Principle

p Protection – Principle

PART 5 : Low Impedance Protection – Principle


PART 6 : F Frame L Leakage k P Protection t ti - Principle Pi i l

PART 6 : F Frame L Leakage k P Protection t ti - Principle Pi i l

PART 7 : Blocking Scheme Protection


PART 8 : Other Applications

PART 8 : Other Applications 3


Busbar protection

Busbar protection

Objective : Clear a fault inside a substation as quickly as possible

A

Objective : Clear a fault inside a substation as quickly as possible

B

A

C

To Protect : - The operator and workers - HV equipment - Global Network Stability Schneider Electric - Jean Marmonier - 20/01/2011

3


B

C

To Protect : - The operator and workers - HV equipment - Global Network Stability 4


4

Busbar protection

Busbar protection

Zone protected by distance protection

Zone protected by distance protection

XX

XX

21

21

X

X

X

X

Zone p protected By the Transformer Differential protection

X

The final protection method will depend on the substation topology and complexity

XX

87T

X

X

Zone p protected By the Transformer Differential protection

Zone protected By the busbar protection X

Zone protected By the busbar protection

The final protection method will depend on the substation topology and complexity

XX

87T

X

X

The distance protection will see a busbar fault in reverse zone ( time delayed ) the transformer differential protection will not see the busbar fault, except by back-up protection

The distance protection will see a busbar fault in reverse zone ( time delayed ) the transformer differential protection will not see the busbar fault, except by back-up protection 5


Busbar protection B1

5


Busbar protection B2

B1 Zone 1

L1

Zone 1

L1

Zone 2

X

B2

Zone 2

X

L2

L2

X

X

L3

L3 X

X

L4

L4

X

X

L5

L5 X

X

X

X

C Schneider Electric - Jean Marmonier - 20/01/2011

C 6


6

Differential Protection

Differential Protection

● When a differential protection is recommended ?

● When a differential protection is recommended ?

● The grading between overcurrent protections is difficult to guarantee or impossible

● The grading between overcurrent protections is difficult to guarantee or impossible

● The max clearance time is critical for HV equipment or network stability ● Applicable for :

● The max clearance time is critical for HV equipment or network stability ● Applicable for :

● Generators, ● Transformers, Transformers ● Overhead lines, ● Underground cables, ● busbars, ● Motors. Schneider Electric - Jean Marmonier - 20/01/2011

● Generators, ● Transformers, Transformers ● Overhead lines, ● Underground cables, ● busbars, ● Motors. 7


Busbar Faults Are Usually Permanent

Busbar Faults Are Usually Permanent

Causes of Busbar Faults :

Causes of Busbar Faults :

● Falling debris

● Falling debris

● Insulation failures

● Insulation failures

● Circuit breaker failures

● Circuit breaker failures

● Current transformer failures

● Current transformer failures

● Isolators switchs operated on load or outside their ratings

● Isolators switchs operated on load or outside their ratings

● Safety earths left connected

● Safety earths left connected

Therefore :

Therefore :

● Circuit breakers should be tripped and locked out by busbar protection ( l i mustt b (reclosing be d done after ft installation i t ll ti check) h k)

● Circuit breakers should be tripped and locked out by busbar protection ( l i mustt b (reclosing be d done after ft installation i t ll ti check) h k)


8


7

8

Busbar Protection must be

Busbar Protection must be

●

●

RELIABLE ● Failure to trip could cause widespread damage to the substation

●

● Failure to trip could cause widespread damage to the substation

STABLE

●

● False tripping can cause widespread interruption of supplies to possible p power system y instability y customers / p

●

DISCRIMINATING

●

DISCRIMINATING ● Should Sh ld ttrip i th the minimum i i number b off b breakers k tto clear l th the ffault lt

FAST

●

● To limit damage and possible power system instability Schneider Electric - Jean Marmonier - 20/01/2011

STABLE ● False tripping can cause widespread interruption of supplies to possible p power system y instability y customers / p

● Should Sh ld ttrip i th the minimum i i number b off b breakers k tto clear l th the ffault lt

●

RELIABLE

FAST ● To limit damage and possible power system instability

9


Protection Methods

Protection Methods

● Differential Protection

● Differential Protection

● High Impedance ● Low Impedance ● Medium Impedance with Bias Characteristic (no more used)

● High Impedance ● Low Impedance ● Medium Impedance with Bias Characteristic (no more used)

● Frame Leakage Protection (Detection of leakage currents)

● Frame Leakage Protection (Detection of leakage currents)

● Directional Comparison Protection (Blocking Scheme)

● Directional Comparison Protection (Blocking Scheme)


9

10


10

PART 1 : Generality

PART 1 : Generality









Protection – Principle




PART 6 : Frame Leakage Protection - Principle


PART 7 : Blocking g Scheme Protection

PART 7 : Blocking g Scheme Protection




Biased Differential Scheme I2

I1

Biased Differential Scheme I2

I1

I1 - I2

Differential Current

I2

I1

I1 - I2


HI

I1 - I2

11


I1 - I2


LI

I1 - I2

I1 - I2


HI

I1 - I2

LI

I1 - I2

Trip

Trip

no Trip

no Trip

Trip

Trip

no Trip

no Trip

Mean Through I + I 2 1 Current Schneider Electric - Jean Marmonier - 20/01/2011

I2

I1

2

Mean Through I + I 2 1 Current

2

12

Mean Through I + I 2 1 Current Schneider Electric - Jean Marmonier - 20/01/2011

2

Mean Through I + I 2 1 Current

2

12

Biased Differential Scheme Differential Current


I1 - I2

I1 - I2

Trip

Trip

no Trip

no Trip

Mean Through Current


I1 + I2

I1 + I2

2

2

13



13



I1 - I2

Trip

Trip

no Trip


I1 + I2


I1 + I2 2

no Trip


I1 + I2


I1 + I2


I1 + I2 2

2

Differential Current = 2 X Mean Through Current Schneider Electric - Jean Marmonier - 20/01/2011

I1 - I2


I1 + I2 2

Differential Current = 2 X Mean Through Current 14


14

Protective Zone definitions

Protective Zone definitions

Bus Section / Bus Disconnector

Bus Section / Bus Disconnector

BS

BS

Z Zone 1

Zone 2

Z Zone 1

Zone 2

Zone 3

Zone 4

Zone 3

Zone 4

BC1

BC2

F1

F2

F3

BC1

F4

F1

15


No Busbar Protection

F3

F4

15


●Advantages

F1

● There are fewer faults on busbars than on other parts of the power system. ● No risk of dislocation of system due to accidental operation of busbar protection.

F2

●Drawbacks

F1

F2

●Drawbacks

● Slow fault clearance. Busbar faults at F1 and F2 are cleared by remote t time ti delayed d l d protection t ti on circuits i it feeding the faults: Time Delayed Overcurrent or Time Delayed Distance Protection (Zone 2) Schneider Electric - Jean Marmonier - 20/01/2011

F2

No Busbar Protection

●Advantages ● There are fewer faults on busbars than on other parts of the power system. ● No risk of dislocation of system due to accidental operation of busbar protection.

BC2

● Slow fault clearance. Busbar faults at F1 and F2 are cleared by remote t time ti delayed d l d protection t ti on circuits i it feeding the faults: Time Delayed Overcurrent or Time Delayed Distance Protection (Zone 2) 16


16

With Busbar Protection ZONE

● Fast clearance by tripping of all breakers at the busbars

● Fast Tripping but only for the Cirscuit breakers of the selectied zone

With Busbar Protection F1

ZONE 1

ZONE 2 F1

F2

17


With Busbar Protection 1/2

SS 1

SS 2

87BB

● Fast Tripping but only for the Cirscuit breakers of the selectied zone


F1

ZONE 1

ZONE 2 F1

F2

17


With Busbar Protection 1/2

SS 3

SS 1

SS 2

87BB

87BB

21

ZONE

● Fast clearance by tripping of all breakers at the busbars

SS 3

87BB

21

21

18


21

18

With Busbar Protection

With Busbar Protection

2/2

2/2

21

87BB

87BB

87BB

87BB

21

21

19


Without Busbar Protection

21

19



1/2

1/2

21

21


21

21

21

21

21

20


21

21

21

20



2/2

2/2

21

21

21

21

21

21

21

With Busbar protection

21 Schneider Electric - Jean Marmonier - 20/01/2011

21

21


With Busbar protection

87BB

87BB

87BB

87BB

21

21

Without Busbar protection p

21

21

21

21


21

21

21

Without Busbar protection p

21

21

21

21 22


21

21

21 22

PART 1 : Generality

PART 1 : Generality



PART 3 : Other Substation Topologies Advantages / Disadvantages




Protection – Principle p

Protection – Principle p










Topology & Architecture of the HV network and HV subtations Single breaker - Single bus


23


Topology & Architecture of the HV network and HV subtations Single breaker - Single bus

Most basic, simple and economical bus design design.

Most basic, simple and economical bus design design.

Main use : - distribution, - lower transmission voltages

Main use : - distribution, - lower transmission voltages

Drawback : - Lack of flexibility for bus faults - maintenance

Drawback : - Lack of flexibility for bus faults - maintenance

Generaly G l nott protected t t d by b a busbar protection if one or two infeeds exist.

Generaly G l nott protected t t d by b a busbar protection if one or two infeeds exist.

24


24

Topology & Architecture of the HV network and HV subtations Single S g e buses co connected ected with t bus ttie e

Topology & Architecture of the HV network and HV subtations Single S g e buses co connected ected with t bus ttie e

Generally used when a large number of circuits exist.

Generally used when a large number of circuits exist.

Main use : - Distribution networks, - Industrial substations with or without co-generation.

Main use : - Distribution networks, - Industrial substations with or without co-generation.

Advantages : - Flexibility, specially when the substation is fed by two separate t power supplies li (generators). - A bus fault only causes the loss of half a bar

Advantages : - Flexibility, specially when the substation is fed by two separate t power supplies li (generators). - A bus fault only causes the loss of half a bar

25


25


Double breaker - Double bus

2 Busbars ; 2 Circuit Breakers

2 Busbars ; 2 Circuit Breakers

Drawback : - The line p protection must be connected to both CTs. Schneider Electric - Jean Marmonier - 20/01/2011

X

X

X

Advantage : - Increased operating flexibility, - Both busbars are independent, specially from a protection point of view. view - All switch disconectors are normally closed and no bus couplor is used. - The loss of one bus dos not affect th transmitted the t itt d power.

X

Generally used in HV substations (500 kV)

X

X

X

X

X

X

Double breaker - Double bus

Generally used in HV substations (500 kV) Advantage : - Increased operating flexibility, - Both busbars are independent, specially from a protection point of view. view - All switch disconectors are normally closed and no bus couplor is used. - The loss of one bus dos not affect th transmitted the t itt d power. Drawback : - The line p protection must be connected to both CTs.

26


26

Main and transfer buses with single breaker


Main

Main

Reserve / Transfer By-pass Isolator

Reserve / Transfer By-pass Isolator

By-pass Isolator

27



27



Main

Main

Reserve T Transfer f

By-pass Isolator

Reserve Transfer CB

Transfer CB

T Transfer f

Be carefull to the CT ocation on the Bus Transfer, in order to clearly defined the protected zone Schneider Electric - Jean Marmonier - 20/01/2011

Transfer CB

Transfer CB

Be carefull to the CT ocation on the Bus Transfer, in order to clearly defined the protected zone 28


28

Breaker and a half bus arrangement

Breaker and a half bus arrangement

Widely used for larger multicircuit and higher voltage systems

Widely used for larger multicircuit and higher voltage systems

Advantage : - High flexibility flexibility, - Line faults trip two circuit breakers but does not cause loss of services of other lines and busbars.

Advantage : - High flexibility flexibility, - Line faults trip two circuit breakers but does not cause loss of services of other lines and busbars.

87

87

Zone to protect separately

Zone to protect separately

87

87

29


Other Busbar Topologies

Other Busbar Topologies Common for Higher voltages (US) No busbar

OHL FEEDER

X

X

X

Drawback : - If the ring is opened, a fault on a line y separate p the other lines and the may bus. Schneider Electric - Jean Marmonier - 20/01/2011

X

X

X

X

X

X

X

X

X

OHL FEEDER

X

Advantage : - One circuit breaker for two lines, - No busbar is required (not applicable) as the bus protection is already performed by the line protection themselves. - The ring can be opened without loss of power.

X

X

Advantage : - One circuit breaker for two lines, - No busbar is required (not applicable) as the bus protection is already performed by the line protection themselves. - The ring can be opened without loss of power.

Ring Bus

X

Ring Bus Common for Higher voltages (US) No busbar

29


Drawback : - If the ring is opened, a fault on a line y separate p the other lines and the may bus.

TRANSF. FEEDER

30


TRANSF. FEEDER

30

Mesh Busbar

F1

Mesh Busbar

F3

F1

F3

T1

T3

T1

T3

T4

T2

T4

T2

F4

F2

F4 31


Mesh Busbar Protection 87 R1

F1

F2 31


Mesh Busbar Protection F3

87 R1

87 R3

F1

F3 87 R3

T1

T3

T1

T3

T4

T2

T4

T2

87 R4

87 R2

F4 Schneider Electric - Jean Marmonier - 20/01/2011

87 R4

F2

87 R2

F4 32


F2 32

Importance of CT Location and Number

Importance of CT Location and Number

33


Effect of CT location on the global P t ti Performance Protection P f

33


Effect of CT location on the global P t ti Performance Protection P f

Bus

Bus

Feeder Protection Feeder Protection Bus Protection Bus Protection

CT Overlap

Feeder Protection

51 Feeder Protection

Bus Protection Bus Protection

All CTs on Bus side

CT Overlap

Feeder Schneider Electric - Jean Marmonier - 20/01/2011

Feeder Protection

Bus Protection

51

All CT CTs on liline side id

51 Feeder Protection Bus Protection

51

All CT CTs on liline side id

All CTs on Bus side

Feeder 34


34

PART 1 : Generality

PART 1 : Generality



PART 3 : Other Substation Topologies p g

PART 3 : Other Substation Topologies p g














35


Single Bus Substation


35



P1

S1

P1

S1

P1

S1

P1

S1

P1

S1

P1

S1

P2

S2

P2

S2

P2

S2

P2

S2

P2

S2

P2

S2


36


36




37




37


38


38




39

Double Bus Substation



39


40


40


Double Bus Substation Bus A

Bus A

Bus B

Bus B

P1 S1

P1 S1

P2 S2

P2 S2

P1

S1

P1

S1

P1

S1

P2 S2

P1

S1

P1

S1

P1

S1

P2 S2

P2

S2

P2

S2

P2

S2

P1 S1

P2

S2

P2

S2

P2

S2

P1 S1

a b

Current

41



a b


Bus B


41


Bus A

a b

Current

Bus B

Current

42

a b


Current

42



Bus A

Bus B

Bus B

Current

a b

43




Bus B


43


Bus A

a b

Current

a b

Bus B

Current

44

a b


Current

44



Bus A

Bus B

Bus B

Current

a b

45




Bus B


45


Bus A

a b

Current

a b

Bus B

Current

46

a b


Current

46



Bus A

Bus B

Bus B

Tripping a b a Current b


Tripping a b a Current b

47




●Interposing CTs are not acceptable

●Interposing CTs are not acceptable

● Main CT must be identical ● Current C t switching it hi via i auxilliary illi relay l iis nott acceptable. t bl ● Requirement of number of position contact (Disconnector switch) is high


47

● Main CT must be identical ● Current C t switching it hi via i auxilliary illi relay l iis nott acceptable. t bl ● Requirement of number of position contact (Disconnector switch) is high

48


48



●No auxiliary contact must be used for current switching g

●No auxiliary contact must be used for current switching g

● Supplementary delay on current switching ● Reliabiliby

● Supplementary delay on current switching ● Reliabiliby

●Auxiliary relays must be designed so that :

●Auxiliary relays must be designed so that :

● They get closed before the bus disconnector is closed get open p after ● Theyy g the bus disconnection is open

● They get closed before the bus disconnector is closed yg get open p after ● They the bus disconnection is open

49


Check Zone Supervision

Bus B

Bus B

Trip Bus A

Trip Bus B

Bus A

Trip Bus A

Bus A

Zone A Zone B


Trip Bus B


49


Zone A Zone B

50


50

Bus B

Bus B

Currentt C switching failure

Trip Bus B

Bus A

Trip Bus A

Bus A

Currentt C switching failure

Zone A Zone B

Zone A Zone B

False Tripping

False Tripping 51


51



Bus B

Bus B

Trip Bus A

Trip Bus B

Bus A

Trip Bus A

Bus A

Zone A Zone B

Zone A Zone B

Check Zone

Check Zone 52


Trip Bus B



Trip Bus B


Trip Bus A


52


Bus B

Bus B

Trip Bus A

Trip Bus B

Bus A

Trip Bus A

Bus A

Zone A Zone B

Zone A Zone B

53


53



Bus B

Bus B

Trip Bus A

Trip Bus B

Bus A

Trip Bus A

Bus A

Check Zone

Trip Bus B



Trip Bus B


Check Zone 54


54

Protection Sensitivity

Protection Sensitivity

55


Stability for External Faults RCT

2RL

M

2RL

A

ZM

Stability for External Faults RCT

RCT

ZM

2RL

M

2RL

A

ZM

RCT

RCT

ZM

RCT 2RL

2RL M


55


2RL

M RCT 56


2RL

RCT 56

External Fault with CT Saturation RCT

2RL

2RL

M

A

ZM

External Fault with CT Saturation

RCT

RCT

ZM=0

M

2RL

ZM=0

CT Saturation

2RL M

RCT

2RL

TC saturé

External Fault with CT Saturation RCT

2RL

2RL

M

57


External Fault with CT Saturation

RCT

RCT

2RL

RCT

RS

A

ZM=0

A

ZM

Stabilizing Resistance

ZM=0

Stabilizing Resistance

RCT

RCT 2RL

2RL M

2RL

M RCT

Saturated CT Schneider Electric - Jean Marmonier - 20/01/2011

2RL

M

RS ZM

RCT

TC saturé 57


RCT

Unwanted Tripping

RCT

CT Saturation

2RL

2RL

M

A

ZM

Unwanted Tripping

RCT

2RL

2RL

RCT

Saturated CT 58


58

Impact of CT Saturation - Remind


High Increase

High Increase

of IM

VS

of IM

VS

Knee point Voltage

Knee point Voltage

Above Knee Point Voltage :

Small increase

Small increase

● IM increase highly

of IM

● => Zm zero

Above Knee Point Voltage : ● IM increase highly

of IM

can be considered equal to

● => Zm zero

IM

IM 59


Impact of CT Saturation - Remind RC

2R

T

L

2R

RC

L

T

RS

ZM

59



VS

ZM

A

can be considered equal to

RC

2R

T

L

2R

RC

L

T

RS

ZM

VS

ZM

A

IM

IM

Before saturation

RC

2R

T

L

2R

RC

L

T

RS

ZM

Before saturation

A

VS

ZM=0

RC

2R

T

L

L

T

A

VS

ZM=0

During saturation IM


RC

RS

ZM

During saturation

2R

IM 60


60

Stability for Internal Fault RCT

2RL

2RL

M

Stability for Internal Fault RCT

RCT

2RL

RS ZM

RCT

A

ZM

RCT 2RL

RCT 2RL

2RL

2RL M

Vset

Vset

61


Insulation requirements 2RL


M

61


RCT

RCT

2RL

ZM

RCT

A

ZM

RCT

ZM

RCT

2RL

RCT 2RL

M

2RL M

=> Very High Risk of Over Voltages across Protection Terminals

=> Very High Risk of Over Voltages across Protection Terminals Vset


RCT

RS

A

2RL

2RL

M

RS ZM

ZM

RCT

M

RCT

RCT

RS

A

ZM

2RL

M

Vset

62


62

Insulation requirements RCT

2RL


M

RCT

RCT

2RL

RS

A non linear resistance can be g required to limit the voltage across terminals (Secondary circuit withstand voltage)

RCT 2RL

ZM

A

ZM

A non linear resistance can be g required to limit the voltage across terminals (Secondary circuit withstand voltage)

RCT

M

2RL

M

RCT 2RL

63

2RL

saturation 2RL

M

63


Internal Fault with CT

RCT

RCT

2RL

saturation

ZM=0

RCT

ZM=0

●To avoid a non-tripping of the protection:

● The relay must have fast detection and tripping ● CTs must be designed to avoid saturation for internal faults RCT


A

ZM

●To avoid a non-tripping of the protection:

● The relay must have fast detection and tripping ● CTs must be designed to avoid saturation for internal faults RCT

ZM = 0

M

2RL

M RS

A

2RL

2RL

M

RS ZM

RCT

Vset


RCT

ZM

M

Vset

Internal Fault with CT

RCT

RS

A

ZM

2RL

M

2RL

(TC “short-circuited" )

Vset 2RL

M RCT

64


ZM = 0 (TC “short-circuited" )

Vset 2RL

RCT

64

CT Wiring Supervision Requirements

CT Wiring Supervision Requirements

65


CT Wiring Supervision (2)

65


CT Wiring Supervision (2)

I1 CT1 V Super vision relay l

RST

I1

I2 R

ZM2

ZM3

I3

CT1

I4

V

ZM4

Super vision relay l

RR

RST

I2 R

ZM2

ZM3

RR I1

Voltage measured by supervision relay V  1 (R // Z M2 // Z M3 // Z M4 )

Voltage measured by supervision relay V  1 (R // Z M2 // Z M3 // Z M4 )

If supervision relay setting  VSP

If supervision relay setting  VSP

Out - of - balance current to operate the supervision relay

Out - of - balance current to operate the supervision relay

VSP V V V  SP  SP  SP R Z M2 Z M3 Z M3

 

Alarm is Generally time delayed (3 sec. sec typ.) typ )


I4

ZM4

I1

 

I3

VSP V V V  SP  SP  SP R Z M2 Z M3 Z M3

Alarm is Generally time delayed (3 sec. sec typ.) typ ) 66


66

Differential Relay Circuit

A B C N

Differential Relay Circuit Zone bus wires

95X

95X

Bus wire short contacts

95X Supervision relay

95

Stabilising resistors

v 87

Metrosil resistors 87


v

v 87

67

High Impedance Protection Synthesis

v 87

87


67

High Impedance Protection Synthesis

● Stability is entirely due to a stabilising resistor in the circuit.. ● It is a simple, simple reliable and circulating current scheme ● The CTs must have the same ratio & must be of high accuracy (low magnetizing current) - class X ● The Th CT knee k point i voltage l needs d to b be relatively l i l hi high h ● The magnetising current can desensitise the scheme ● The scheme can be very fast ● Isolator contacts are needed to switch the full CT secondary current between the zones. ● There are risks to open the secondary side of CTs ● Extending the scheme is quite simple (if CTs not too old) ● Metrosil and Buswire supervision is required ● Maintenance M i t rules l are strict ti t Schneider Electric - Jean Marmonier - 20/01/2011

Supervision relay

Stabilising resistors

v 87

Bus wire short contacts

95X 95

v

Zone bus wires

95X

95X

Metrosil resistors

A B C N

● Stability is entirely due to a stabilising resistor in the circuit.. ● It is a simple, simple reliable and circulating current scheme ● The CTs must have the same ratio & must be of high accuracy (low magnetizing current) - class X ● The Th CT knee k point i voltage l needs d to b be relatively l i l hi high h ● The magnetising current can desensitise the scheme ● The scheme can be very fast ● Isolator contacts are needed to switch the full CT secondary current between the zones. ● There are risks to open the secondary side of CTs ● Extending the scheme is quite simple (if CTs not too old) ● Metrosil and Buswire supervision is required ● Maintenance M i t rules l are strict ti t 68


68

One Breaker and a Half Substation Requirements for the Tee zone

One Breaker and a Half Substation Requirements for the Tee zone

69


One and Half Circuit Breaker Systems Bus A P1 S1

S1

P1

S2

P2

P2 S2


One and Half Circuit Breaker Systems Bus B

P2

P1

S2

S1

69


Bus A P1 S1

S1

P1

S2

P2

P2 S2

Bus B P2

P1

S2

S1

●Use of one additional Protection

●Use of one additional Protection

● High Impedance Differential relay ● Low Impedance Differential relay (3 winding transformer relay)

● High Impedance Differential relay ● Low Impedance Differential relay (3 winding transformer relay) 70


70

One and Half Circuit Breaker Systems Bus A


Bus A

71




Bus B

71



Bus A

72


Bus B

72



Bus A

73




Bus B

73



Bus A

74


Bus B

74

One and Half Circuit Breaker Systems


Bus A

Bus B

Bus A

75



Bus B

75



Bus A

Bus B

Bus A

Bus B

P1

P2

P2

P1

P1

P2

P2

P1

S1

S2

S2

S1

S1

S2

S2

S1

P1

P2

P2

P1

P1

P2

P2

P1

S1

S2

S2

S1

S1

S2

S2

S1


76


76

PART 1 : Generality

PART 1 : Generality

PART 2 : O Operating ti Principle Pi i l


PART 3 : Other Substation Topologies Ad Advantages t / Disadvantages Di d t


PART 4 : High Impedance Differential Protection Pi i l Principle


PART 5 : Low Impedance Protection Principle

PART 5 : Low Impedance Protection Principle

PART 6 : F Frame Leakage L k P Protection t ti - Principle Pi i l

PART 6 : F Frame Leakage L k P Protection t ti - Principle Pi i l






GENERAL SCHEME

GENERAL SCHEME

BB1a

BB1b

Peripheral Unit

Peripheral Peripheral Peripheral Unit Unit Unit

Peripheral Units

Optical Fibres


BB1a

BB1b

Peripheral Unit

Unité Centralle

77


Peripheral Unit

Peripheral Unit

Optical Fibres

Peripheral Unit

Peripheral Unit

Peripheral Units

78

Peripheral Peripheral Peripheral Unit Unit Unit

Peripheral Units

Optical Fibres


Peripheral Unit

Unité Centralle

Peripheral Unit

Optical Fibres

Peripheral Unit

Peripheral Unit

Peripheral Units

78

Bias Characteristic Principle

Bias Characteristic Principle

idiff (t)

idiff (t) Tripping pp g Area

X

X

i1 X

X i3

X

Tripping pp g Area

X

i2

in

ID>2 IS ID>1

X

Blocking Area

X

i1 X i3

X

i2

in

ID>2 IS ID>1

Blocking Area

ibias (t)

Differentail Current: idiffnoeud (t) = i1 + i2 + i3 + … + in Operating p gQ Quantity: y idiff ((t)= ) |i| diffnoeud ((t)| )| = |  in| Bias Quantity: ibias(t) = |i1|+ |i2|+ | i3| + … + |in| =  |in| Schneider Electric - Jean Marmonier - 20/01/2011

Differentail Current: idiffnoeud (t) = i1 + i2 + i3 + … + in Operating p gQ Quantity: y idiff ((t)= ) |i| diffnoeud ((t)| )| = |  in| Bias Quantity: ibias(t) = |i1|+ |i2|+ | i3| + … + |in| =  |in| 79

INTEGRATED FUNCTIONS


79

INTEGRATED FUNCTIONS

●Peripheral Units Objective


● Local Current Acquisition ● Local Signal Processing (magnitude, angle, saturation detection ) ● Local Back-up Protections (Max I)

● Local Current Acquisition ● Local Signal Processing (magnitude, angle, saturation detection ) ● Local Back-up Protections (Max I)

●Central Unit objective


● Automatic Adaptation p of zone number ● Differential Calculation Element for each zone ● Differential Calculation Element « Check Zone » ● Communication management CU < <--> > PU ● Circuitry Fault Control for each Differential Element


ibias (t)

● Automatic Adaptation p of zone number ● Differential Calculation Element for each zone ● Differential Calculation Element « Check Zone » ● Communication management CU < <--> > PU ● Circuitry Fault Control for each Differential Element

80


80

OTHER INTEGRATED FUNCTIONS

OTHER INTEGRATED FUNCTIONS



● Pole Discrepency Supervision, for circuit breakers and bus disconnectors ● CT Supervision S i i ● Inter-Tripping management in case of Internal Bus Fault ● Circuit Breaker Failure : ReTrip order (stage 1) or Zone Tripping (stage 2)

● Pole Discrepency Supervision, for circuit breakers and bus disconnectors ● CT Supervision S i i ● Inter-Tripping management in case of Internal Bus Fault ● Circuit Breaker Failure : ReTrip order (stage 1) or Zone Tripping (stage 2)



● Circuit Breaker Failure– Definition of zones to be tripped ● Maintenance modes management (per zone differential blocking)


● Circuit Breaker Failure– Definition of zones to be tripped ● Maintenance modes management (per zone differential blocking)

81


Current Circuitry Fault Supervision

Current Circuitry Fault Supervision

● Under ideal operating conditions idiff = 0

● Under ideal operating conditions idiff = 0

● Under normal operating conditions idiff  0

● Under normal operating conditions idiff  0

● => use of a circuitry fault alarm threshold so that : 1.2 x idiff (normal operation)  (ID>1))  0.8 x Ifeeder (min (min. load)

● => use of a circuitry fault alarm threshold so that : 1.2 x idiff (normal operation)  (ID>1))  0.8 x Ifeeder (min (min. load)

● => Affected zone blocking (option depending on manufacturer)

● => Affected zone blocking (option depending on manufacturer)


82


81

82



●The Check Zone Element does not take into account the status g to bus A or B)) of busbar disconnections ((assignment

●The Check Zone Element does not take into account the status g to bus A or B)) of busbar disconnections ((assignment

Total Idiff = Sum of current node idiff idiff(t) CZ =  idiff =  ( i) 

Total Idiff = Sum of current node idiff idiff(t) CZ =  idiff =  ( i) 

●Under pole discrepency condition on a circuit breaker or a bus disconnector the differential current in the check zone remains disconnector, nil, preventing any maloperation of the busbar protection,

●Under pole discrepency condition on a circuit breaker or a bus disconnector the differential current in the check zone remains disconnector, nil, preventing any maloperation of the busbar protection,

●=> A trip will be issued only if the differential current measured by y the check zone has reached the tripping pp g threshold.

●=> A trip will be issued only if the differential current measured byy the check zone has reached the tripping pp g threshold.


83


Tripping Threshold Conditions

Tripping Threshold Conditions

● No Blocking due to Circuitry Fault

● No Blocking due to Circuitry Fault

● Differential Current detected by the Check Zone Element

● Differential Current detected by the Check Zone Element

● Differential Current above the Tripping Threshold, generaly set so that :

● Differential Current above the Tripping Threshold, generaly set so that :

1,2 x I_highest loaded feeder  (ID>2)  0.8 x I” Min. shortshort-

1,2 x I_highest loaded feeder  (ID>2)  0.8 x I” Min. shortshort-

Circuit

Circuit

● Fault point inside the Characteristic Operating Area


83

● Fault point inside the Characteristic Operating Area

84


84

Use of only 1 CT on the Bus Coupler

Use of only 1 CT on the Bus Coupler

●Pole Discrepency on the bus coupler Circuit Breaker :

●Pole Discrepency on the bus coupler Circuit Breaker :

Zone 1

BB1

Zone 2

BB2

ILOAD across CB CB.

Zone 1

BB1

EN

EN

IdiffZ2 = + ILOAD

IdiffZ1= 0

Peripheral Unit

IdiffZ2 = + ILOAD

IdiffZ1= 0

CB CLOSED but given Status is OPEN

Peripheral Unit

CB CLOSED but given Status is OPEN

Central Unit Peripheral Unit

Peripheral Unit

Zone 2

BB2

ILOAD across CB CB.

Central Unit

Check zone Idiff =  idiff = idiffZ1+ idiffEN1 + idiffZ2 =0

Peripheral Unit

Peripheral Unit

Peripheral Unit

● The protection remainS stable

Peripheral Unit

Check zone Idiff =  idiff = idiffZ1+ idiffEN1 + idiffZ2 =0

Peripheral Unit

Peripheral Unit

● The protection remainS stable 85


85


Use of 2 CTs on the Bus Coupler

Use of 2 CTs on the Bus Coupler

●Bus Coupler CB closed and fault on the Bus coupler

●Bus Coupler CB closed and fault on the Bus coupler

Zone 1

BB1

IdiffZ3 = IFault VZ

IdiffZ1= 0

Zone 2

BB2

Zone 1

IdiffZ2 = 0

Peripheral Unit

Check zone Idiff =  idiff = idiffZ1+ idiffZ3 + idiffZ2 =iFault

IdiffZ2 = 0


Peripheral Unit

●In case of Fault on the Bus Coupler, the relay will generally trip both zones, BUT, a two stage trip is possible depending on :

Peripheral Unit

Peripheral Unit

Check zone Idiff =  idiff = idiffZ1+ idiffZ3 + idiffZ2 =iFault

Peripheral Unit

Peripheral Unit

●In case of Fault on the Bus Coupler, the relay will generally trip both zones, BUT, a two stage trip is possible depending on :

●The fault current level level, ●The required max clearance time (stability criteria) Schneider Electric - Jean Marmonier - 20/01/2011

Zone 2

BB2

Peripher. Unit

Peripher. Unit


IdiffZ3 = IFault VZ

IdiffZ1= 0

Peripher. Unit

Peripher. Unit

BB1

●The fault current level level, ●The required max clearance time (stability criteria) 86


86

Dead Zone

Dead Zone

●Feeder’s CB open : Fauklt between CT and CB

●Feeder’s CB open : Fauklt between CT and CB

idiff

idiff

Trip

EN

EN

ID>2 IS ID>1

Restrain

● No zone trip but intertrip to the remote end 87

Typical Tripping Scheme Peripheral Unit

idiff(t) > k2 . ibias (t )

Local confirmation I>BB or IN>BB*

CZ

idiff(t) > [IDCZ>2 ] I  0 in more than 1 feeder No CT saturation detected

Local confirmation or V0>*

V<

Zone & CZ

Peripheral Unit

idiff(t) > k2 . ibias (t )

Local confirmation I>BB or IN>BB*

idiff(t) > kCZ . ibias CZ(t ) idiff(t) > [IDCZ>2 ] I  0 in more than 1 feeder

Local L l signal i l processing i

No CT saturation detected

5

No broken sec.y CT detected


Central Unit (87 BB)

idiff(t) > [ID>2 ]

3 & 4

87


Typical Tripping Scheme

Central Unit (87 BB)

2

ibias

●Fixe current threshold or ●Current linked to the zone differential current, to avoid any pole discrepency problem on the CB status


idiff(t) > kCZ . ibias CZ(t )

Restrain

● The relay detects the fault b y using a current criteria

● No zone trip but intertrip to the remote end

1

ID>2 IS ID>1

ibias

●Fixe current threshold or ●Current linked to the zone differential current, to avoid any pole discrepency problem on the CB status

idiff(t) > [ID>2 ]

Idiff EN = I Défaut Ibias EN = I Défaut

Idiff EN = 0 Ibi Ibias EN = 0

● The relay detects the fault b y using a current criteria

Zone

EN

EN

Idiff EN = I Défaut Ibias EN = I Défaut

Idiff EN = 0 Ibi EN = 0 Ibias

Trip

1 2

Local confirmation or V0>*

V<

&

3 & 4

L Local l signal i l processing i

5

No broken sec.y CT detected

88


88

Low Impedance Protection Synthesis

Low Impedance Protection Synthesis

 Stability S bili iis entirely i l d due to the h bi bias characteristic h i i off the h scheme. Metrosils and Stabilizing resistors are not required,

 Stability S bili iis entirely i l d due to the h bi bias characteristic h i i off the h scheme. Metrosils and Stabilizing resistors are not required,

 CTs can have different ratios

 CTs can have different ratios

 Scheme bias characteristic can cater for lesser accuracy CTs (class 5P), instead of Class X CTs,

 Scheme bias characteristic can cater for lesser accuracy CTs (class 5P), instead of Class X CTs,

 CTs with moderate knee point voltages can be used used, because the relay can manage the saturation effects,

 CTs with moderate knee point voltages can be used used, because the relay can manage the saturation effects,

CTs can be shared with other protection, due to low burden,

CTs can be shared with other protection, due to low burden,

 Number of // circuits does not affect he primary operating current

 Number of // circuits does not affect he primary operating current

 Fast ast Tripping pp g ttime e ((Decision ec s o bet between ee 3 to 5 ms) s)

 Fast ast Tripping pp g ttime e ((Decision ec s o bet between ee 3 to 5 ms) s)

 Isolator contact are not needed to switch heavy currents,

 Isolator contact are not needed to switch heavy currents,

 Extending the scheme is simple,

 Extending the scheme is simple,

 Self supervision and breaker fail protection is easier to integrate,

 Self supervision and breaker fail protection is easier to integrate,


89


PART 1 : Generality

PART 1 : Generality









PART 6 : Frame Leakage Protection Principle

PART 6 : Frame Leakage Protection Principle






90


89

90

Frame Leakage Busbar Protection


●Principle and Limitations

●Principle and Limitations

● Limited to Medium Voltage BusBar applications ● Can detect only earth faults ● Means that the fault current betwwen circuit breaker cells and earth must be measured :

● Limited to Medium Voltage BusBar applications ● Can detect only earth faults ● Means that the fault current betwwen circuit breaker cells and earth must be measured :

●=> Switchgear must be insulated from earth (by standing on concrete plinth), li th) ●=> Only one single earth conductor allowed on switchgear, ●=> All cable glands must be insulated from the cell’s earth, ●=> Only O l one single i l phase h CT iis used, d b between t earth th conductor d t and d an instantaneous overcurrent relay.

●=> Switchgear must be insulated from earth (by standing on concrete plinth), li th) ●=> Only one single earth conductor allowed on switchgear, ●=> All cable glands must be insulated from the cell’s earth, ●=> Only O l one single i l phase h CT iis used, d b between t earth th conductor d t and d an instantaneous overcurrent relay.

● In case of several sections (with couplers), Switchgear sections must be insulated.


● In case of several sections (with couplers), Switchgear sections must be insulated.

91



91


>I

>I

Insulation


Insulation

92


92



>I


>I

93


93


>I



>I

94


94


>I


>I

>I

95



>I

95



Confirmation by Transformer Neutral protection


False Operation because induced loop

False Operation because induced loop

>I

>I

(Insulation Fault)

(Insulation Fault) >I


Tripping is confirmed by the relay, to avoid false trip

>I

96


Tripping is confirmed by the relay, to avoid false trip

96





>I

>I

>I

>I

97






>I

>I

>I


97


>I

98


98

Blocking Scheme Busbar Protection >II

>II

>II

>II

>II

Blocking Scheme Busbar Protection

BUSBAR PROTECTION LOGIC

>II

99




>II

>II

>II

>II

>II

>II

>II

>II


99




>II

100


>II

>II

>II

>II


100


>II

>II

>II

>II




>II

101

>II

>II

>II

>II



PART 1 : Generality

PART 1 : Generality





PART 4 : High Impedance Differential Protection – Principle











102


101

102

Busbar Blocking Protection

Busbar Blocking Protection

● Fault at F1

● Fault at F1

● Tripping of the Feeder Relay Only ● Blocking of the Incommer Relay

● Tripping of the Feeder Relay Only ● Blocking of the Incommer Relay

Incomer

● Fault at F2

O/C Relay

BLOCK

● Fault at F2

● No Blocking of the Incomer Relay ● Time Delayed tripping of the Incomer and Fault Clearance IF2 O/C Relay

Incomer O/C Relay

BLOCK

● No Blocking of the Incomer Relay ● Time Delayed tripping of the Incomer and Fault Clearance IF2 O/C Relay

O/C Relay

O/C Relay

O/C Relay

IF1


O/C Relay

O/C Relay

O/C Relay

IF1

103


PART 1 : Generality

PART 1 : Generality
















104


103

104

Bus Protection - other application


●Other Application commonly used for ‘’Oil & Gas’’

●Other Application commonly used for ‘’Oil & Gas’’

● Use of a Partial BusBar relay ● The 51∆ Relay is limited to the load current of each half section

● Use of a Partial BusBar relay ● The 51∆ Relay is limited to the load current of each half section

I_pilote=I_incomer-I_coupler

I_pilote=I_incomer-I_coupler

●Same scheme than previously

●Same scheme than previously

●Advantage

●Advantage

● Protection of BB1 even if TA is in maintenance

● Protection of BB1 even if TA is in maintenance

105


105




●Protection by Transformer Differential Relay

●Protection by Transformer Differential Relay

● Can be used in case of 4 feeders max ● No Bus Coupler or Bus Disconnector

● Can be used in case of 4 feeders max ● No Bus Coupler or Bus Disconnector 87T


87T

106


106

6.1-Busbar protection.pdf

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