GE Grid Solutions - Universal Relay Family · 2000. 10. 17. · Power Management The Universal Relay Features • Protection: – Low-impedance biased differential protection •

Universal Relay FamilyUniversal Relay Family

B30B30

Bus Differential RelayBus Differential Relay

Power Management The The Universal RelayUniversal Relay

Contents...Contents...

Features

CT Saturation Problem

Theory of Operation

Dynamic Bus Replica

Operation Examples (link)

Q&As (link)

Benefits


FeaturesFeatures

•• Configuration:Configuration:

– up to 5 feeders with bus voltage

– up to 6 feeders without bus voltage


FeaturesFeatures

•• Protection:Protection:

– Low-impedance biased differential protection

• CT saturation immunity

• sub-cycle tripping time

• dynamic 1-out-of-2 or 2-out-of-2 operation

– Unbiased differential protection

– Dynamic bus replica

– CT trouble monitoring

– Undervoltage (2 elements)

– Phase Overcurrent (2 elements)


FeaturesFeatures

•• Metering:Metering:

– Oscillography

– Event Recorder

– Phasors / true RMS


CT saturation problemCT saturation problem

• During an external fault

– fault current may be supplied by a number of

sources

– the CTs on the faulted circuit may saturate

– saturation of the CTs creates a current

unbalance and violates the differential principle

– a conventional restraining current may not be

sufficient to prevent maloperation

• CT saturation detection and a directional

principle enhance through-fault stability


differential

restraining

DIFFERENTIAL – RESTRAINT PointDIFFERENTIAL – RESTRAINT Point

Externalfault: ideal

CTs

DIF – differential

RES – restraining

t0

– fault inception

t2

– fault conditions

t0

t2


differential

restraining


Externalfault: ratio

mismatch


RES – restraining

t0

– fault inception

t2


t0

t2


differential

restraining


Externalfault: CT

saturation


RES – restraining

t0

– fault inception

t1

– CT starts to saturate

t2


t0

t1

t2


differential

restraining


Internalfault: high

current


RES – restraining

t0

– fault inception

t2


t0

t2


differential

restraining


Internalfault: low

current


RES – restraining

t0

– fault inception

t2


t0

t2


differential

restraining


Externalfault:

extreme CTsaturation


RES – restraining

t0

– fault inception

t1


t2


t0

t1

t2


Operating principlesOperating principles

•• Combination ofCombination of

–– low-impedance low-impedance biased differentialbiased differential

–– directionaldirectional (phase comparison)(phase comparison)

•• Adaptively switched betweenAdaptively switched between

–– 1-out-of-2 operating mode1-out-of-2 operating mode

–– 2-out-of-2 operating mode2-out-of-2 operating mode

•• byby

–– Saturation DetectorSaturation Detector


Biased Characteristic: Biased Characteristic: Restraining CurrentRestraining Current

•• Restraining Current is a “maximum of”Restraining Current is a “maximum of”

the bus zone currents :the bus zone currents :

– better stability on external faults (as compared

to the “average of” definition)

– better sensitivity on internal faults (as compared

to the “sum of” definition)


Biased Characteristic: Biased Characteristic: ShapeShape

• Two breakpoints

• Two slopes

– both slopes provide TRUE percentage restraint,

i.e. they are represented by straight lines

crossing the origin of the differential-

restraining plane

– if the slopes are different, discontinuity of the

characteristic occurs

– the discontinuity issue is solved by a smooth

“gluing” function


Biased Characteristic: Biased Characteristic: ShapeShape

0 2 4 6 8 10 120

1

2

3

4

5

6

7

8

RESTRAINING, pu

DIF

FE

RE

NT

IAL

,pu

LOW BPNT HIGH BPNT

HIGH SLOPE

LOW SLOPE

PICKUP


Biased Characteristic: Biased Characteristic: Two distinctive regionsTwo distinctive regions

• low currents

• saturation possible

due to dc offset

• saturation very

difficult to detect

• more security

required

differential

restrainingA

B1

K2

K1

B2

DIF1


Biased Characteristic: Biased Characteristic: Two distinctive regionsTwo distinctive regions

• large currents

• quick saturation

possible due to

large magnitude

• saturation easier

to detect

• security required

only if saturation

detected

differential

restrainingA

B1

K2

K1

B2

DIF2


LogicLogic

DIF1

DIR

SAT

DIF2

OR

AND

OR

TRIP

AND


LogicLogic

differential

restrainingA

B1

K2

K1

B2

1-out-of-2 (DIF) if no saturation

2-out-of-2 (DIF+DIR) if saturation

detected

2-out-of-2

(DIF+DIR)


LogicLogic

DIF1

DIR

SAT

DIF2

OR

AND

OR

TRIP

AND


Directional principleDirectional principle

•• Internal faultsInternal faults - all currents approximately

in phase



•• External faultsExternal faults - one current approximately

out of phase



• Check all the angles

• Select the maximum current contributor and

check its position against the sum of all the

remaining currents

• Select major current contributors and check

their positions against the sum of all the

remaining currents



"contributor"

(phasor)

differential less

"contributor"

(phasor)

BLOCK

TRIP

TRIP

BLOCK

BLOCK



BLOCK

OPERATE

BLOCK

− pD

p

II

Ireal

− pD

p

II

Iimag

Ip

ID - I

p

External Fault Conditions

OPERATE



BLOCK

BLOCK

− pD

p

II

Ireal

− pD

p

II

Iimag

Ip

ID - I

p

Internal Fault Conditions

OPERATE

OPERATE


LogicLogic

DIF1

DIR

SAT

DIF2

OR

AND

OR

TRIP

AND


Saturation DetectorSaturation Detector

• differential-restraining trajectory

• dI/dt

differential

restraining

External

fault: CTsaturation

t0

t1

t2

t0

– fault inception

t1


t2




0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fe

eder

1

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fe

eder

2

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der3

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der4

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der5

Time, sec

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fe

eder

1

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fe

eder

2

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der3

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der4

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-40-20

02040

Fee

der5

Time, sec

Sample External

Fault on Feeder 1

(Case 1)

Sample External

Fault on Feeder 1

(Case 1)


0 5 10 15 20 25 30 350

5

10

15

20

25

30

35D

iffer

ent

ial[

A]

Restraining [A]

12 3 4 56

789

101112

13

1415

16171819

2021222324252627282930313233

Phase A (Infms)

0 5 10 15 20 25 30 350

5

10

15

20

25

30

35D

iffer

ent

ial[

A]

Restraining [A]

12 3 4 56

789

101112

13

1415

16171819

2021222324252627282930313233

Phase A (Infms)


Analysis of the DIF-

RES trajectory enables

the B30 to detect CT

saturation (Case 1)

Analysis of the DIF-

RES trajectory enables


saturation (Case 1)



0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20F

eede

r1

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fe

eder

2

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der

3

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der4

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der

5

Time, sec

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20F

eede

r1

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fe

eder

2

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der

3

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der4

0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45-20

0

20

Fee

der

5

Time, sec

Sample External Fault

on Feeder 4 - severe

CT saturation after

1.5msec (Case 2)

Sample External Fault

on Feeder 4 - severe

CT saturation after

1.5msec (Case 2)


0 5 10 15 200

5

10

15

20

Diff

ere

ntia

l[A

]

Restraining [A]

12

3

4

5 6

7

8

91011121314

15

16

1718

19

20

2122

23

24252627282930

313233

Phase A (Infms)

0 5 10 15 200

5

10

15

20

Diff

ere

ntia

l[A

]

Restraining [A]

12

3

4

5 6

7

8

91011121314

15

16

1718

19

20

2122

23

24252627282930

313233

Phase A (Infms)


dI/dt principle enables


saturation (Case 2)

dI/dt principle enables


saturation (Case 2)


Saturation Detector: Saturation Detector: State MachineState Machine

NORMAL

SAT := 0

EXTERNAL

FAULT

SAT := 1

EXTERNAL

FAULT & CT

SATURATION

SAT := 1

The differential

characteristic

entered

The differential-

restraining trajectory

out of the differential

characteristic for

certain period of time

saturation

condition

The differential

current below the

first slope for

certain period of

time



•• Operation:Operation:

– The SAT flag WILL NOT set during internal

faults whether or not the CT saturates

– The SAT flag WILL SET during external faults

whether or not the CT saturates

– The SAT flag is NOT used to block the relay

but to switch to 2-out-of-2 operating principle


ExamplesExamples

• The oscillograms on the next two slides

were captured from a B30 relay under test

on a real-time digital power system

simulator


B30 Bus Differential Relay: B30 Bus Differential Relay: External Fault ExampleExternal Fault Example

0.06 0.07 0.08 0.09 0.1 0.11 0.12-200

-150

-100

-50

0

50

100

150

200

~1 ms

The bus differential

protection element

picks up due to heavy

CT saturation

The CT saturation flag

is set safely before the

pickup flag

Despite heavy CTsaturation the

external fault currentis seen in theopposite direction

The

directional flag

is not set

The element

does not

maloperate


B30 Bus Differential Relay: B30 Bus Differential Relay: Internal Fault ExampleInternal Fault Example

The bus differential

protection element

picks upThe saturation

flag is not set - no

directional

decision required

The element

operates in

10ms

All the fault currents

are seen in one

direction

The

directional

flag is set


Dynamic Bus ReplicaDynamic Bus Replica

• The dynamic bus replica mechanism is

provided by associating a status signal with

each current of the differential zone

• The status signal is a FlexLogicTM operand

• The status signals are formed in

FlexLogicTM – including any filtering or

extra security checks – from the positions of

switches and/or breakers


Dynamic Bus ReplicaDynamic Bus Replica

BUS SECTION 2

F1

U7a

SOURCES

SRC 1

FLEXLOGICTM

Cont Ip 1 On BUS

Z1

BUS ZONE 1A STATUS

BUS ZONE 1A SOURCE

BUS SECTION 1


Dynamic Bus Replica: Dynamic Bus Replica: ExampleExample

NORTH BUS

SOUTH BUS

CT-8

B-5

B-6

CT-5

CT-6

S-5

S-6

B-4CT-4

S-3

S-4

B-3CT-3

S-1

S-2

B-2CT-2

CT-1

B-1

C-1 C-2 C-4

C-3 C-5

CT-7

B-7



NORTH BUS

SOUTH BUS

CT-7

CT-8

B-7

B-5

B-6

CT-5

CT-6

S-5

S-6

B-4CT-4

S-3

S-4

B-3CT-3

S-1

S-2

B-2CT-2CT-1

B-1

C-1 C-2 C-4

C-3 C-5

B30 #1



NORTH BUS

SOUTH BUS

CT-7

CT-8

B-7

B-5

B-6

CT-5

CT-6

S-5

S-6

B-4CT-4

S-3

S-4

B-3CT-3

S-1

S-2

B-2CT-2CT-1

B-1

C-1 C-2 C-4

C-3 C-5

B30 #2


Dynamic Bus Replica: Dynamic Bus Replica: ZoningZoning

NORTH BUS

SOUTH BUS

CT-8

B-5

B-6

CT-5

CT-6

S-5

S-6

B-4CT-4

S-3

S-4

B-3CT-3

S-1

S-2

B-2CT-2

CT-1

B-1

C-1 C-2 C-4

C-3 C-5

CT-7

B-7

B30 #2

B30 #1D60 #1


BenefitsBenefits

• Sensitive settings are possible

• Very good through-fault stability

• Fast operation:

– fast form-C contacts and FlexLogicTM

operands: typically 10-12ms

– form-A trip rated contacts: typically 13-15ms

• Benefits of the UR platform (metering and

oscillography, event recorder, FlexLogicTM,

fast peer-to-peer communication, etc.)

Documents

GE Grid Solutions - Universal Relay Family · 2000. 10. 17. · Power Management The Universal Relay Features • Protection: – Low-impedance biased differential protection •