new smart multi -ended line current differential solution...

New Smart Multi-Ended Line Current Differential

Solution for Power Networks

Joao Jesus, Simon Richards, Sankara Subramanian, Hengxu Ha GE Grid Solutions UK

2017 Texas A&M Conference for Protective Relay Engineers

Introduction

• Utility power networks are evolving to transport power in ever more complex ring and meshed networks.

• Line/cable differentia l protection becomes increasingly a ttractive, with its inherent ability to address grading/selectivity challenges and scalable for multi-terminal circuits able to accommodate many connections of distributed generation along the line.

• For circuits which neighbour the coast , or other potentia l windfarm locations, there is a lways the possibility that those will be candidates for tee infeed’s to evacuate renewable energy.

• Previously circuits would have two or three ends only, whereas five or more ends are becoming common.

Why Multi-Ended Protection?

Why Multi-Ended Lines?• Lines become just a mechanical/electrical highway to

evacuate power…

• Or to tee-off supplies from existing lines to expanding urban areas

End 3

End 2

End 1End 4

End 5

End 6

Off shore windfarm

On shore windfarm

Solar farm

Line Differential Principle (2 Ended)

End 1 End 2

IEnd1 IEnd2

Communication Link

IF

Differential definition:IEnd1 + IEnd2 = 0 HealthyIEnd1 + IEnd2 ≠ 0 (= IF) Fault

Line Differential Principle (6 Ended)

Differential definition:IEnd1 + IEnd2 + IEnd3 + IEnd4 + IEnd5 + IEnd6 = 0 HealthyIEnd1 + IEnd2 + IEnd3 + IEnd4 + IEnd5 + IEnd6 ≠ 0 (= IF faulty)

New Multi-Ended Line Differential

Operating characteristic

Multi-ended Line Differential algorithm• Same characteristic, innovative sample-based

algorithm• Sub cycle operating time, up to 4 ends • Max. Total Propagation Delay, up to 64 ms • Immune to CT Saturation, algorithm reduces CT

requirements, reduces $$• Capacitive Current Compensation, voltage

input used• Fault locator operating multi-ended (S1 Agile)

End 1 End 6

End 5

End 3

End

2

End

4

Differential trip logic

Capacitive current compensation

CT Saturation(internal/external fault)

CT Supervision

Phase Differential

Differential Trip

CT & VT

Send to remote end

AND

Receipt from Remote ends

48 samples/cycle ADC

Internal fault

Data alignment(synchronization)

CT Saturation algorithm activates only if Ibias > IbiasThres fulfilled

Capacitive Current Compensation (1)

The capacitive current of the transmission lines should be eliminated, especially for the lines that are longer than 50km, or for cables longer

than 10km

• The objective for the capacitive current calculation is to calculate the current a t terminal N based on the voltage and current a t terminal M;

• The mathematical model for calculating the capacitive current of a transmission line that is used here is distributed parameter line model, which is more accurate than the lumped model;


• New algorithm based on samples with distributed parameter line model (or underground cables);

• Only the impedance and admittance per unit are required;• The function has been transposed from the frequency domain to the

time domain so that it can be applied to a sample based input;• More accurate especially for topologies with long lines. The error of the

calculation is less than 1% even considering transients in the a lgorithm.

IchL IchR

IRIL

VL VR

ZL


Junct ion

IEnd1’ IEnd2’

I End

3’

IEnd1‘, IEnd2‘, IEnd3‘ = calculated junction currents after charging current compensation

• Based on local measurement of the current & voltage input a t End1, End2, End3, each relays can remove capacitive charging current from local to the junction and calculate the voltage and current a t the junction IEnd1‘, IEnd2‘, IEnd3‘ .

• These IEnd1‘, IEnd2‘, IEnd3‘ current vector (with charging current removed) are sent to remote end for differentia l calculation.

CT Saturation (1)

IPOS

INEG

𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅𝑅 =𝐼𝐼𝑃𝑃𝑃𝑃𝑃𝑃 + 𝐼𝐼𝑁𝑁𝑁𝑁𝑁𝑁𝐼𝐼𝑃𝑃𝑃𝑃𝑃𝑃 − 𝐼𝐼𝑁𝑁𝑁𝑁𝑁𝑁

ExternalFault

InternalFault

Ratio < RThres

Ratio < RThres

CT saturation detection works by calculating the ra tio of Ipos and Ineg. If the saturation is in phase then the fault is within the protected zone, if the saturation is out of phase then the fault is external to the protected zone.

New CT saturation technique reduces CT dimensioning requirements

CT Saturation (2)

• The signatures of IPOS, INEG and Ratio of transient phase comparison for external to internal (evolving) fault

• Diagram 1: original waveform received at the relay

• Diagram 2: relay derived Iposand Ineg

• Diagram 3: relay internal fault detection

• Diagram 4: normalization for stability

CT Saturation (3)The signatures of IPOS, INEG and Ratio

of transient phase comparison for external to internal (evolving) fault

The signatures of IPOS, INEG and Ratio of transient phase comparison for internal to external (evolving) fault

Unique Address• Avoids maloperation should multiplexers misdirect data messages• Range of addresses for 2 terminal applications

1A, 1B; 2A, 2B; _ _ _ _ _ 32A, 32B• Range of addresses for 6 terminal applications

1A, 1B to 1F; 2A to 2F; _ _ _ _ _32A to 32F

6 Ended Communication Configuration

Ch2Rx

Tx

Ch1Tx

Rx

Ch2Tx

Rx

Ch1Rx

Tx

Fixed configuration6 ends is ALWAYSRing connection

Please noteCh1 and Ch2 allocation

A

D

C

B

E

F

Communication Configuration (1)

Terminal 2

Terminal 3

Terminal 1

Terminal 4

Four Terminal Scheme

Terminal 2 Data Terminal 3 Data Terminal 4 Data

Terminal 1 DataTerminal 3 DataTerminal 4 Data

Term

inal

3 D

ata

Terminal 4 Data

Terminal 1 Data

Term

inal

2 D

ata

Terminal 1 Data

Terminal 4 Data

Term

inal

2 D

ata

Terminal 3 Data

Terminal 4 Data

Term

inal

1 D

ata

Terminal 2 Data

Terminal 3 Data

Terminal 3 Data Terminal 2 Data Terminal 1 Data

Terminal 4 DataTerminal 1 DataTerminal 2 Data

Ch2Tx

Rx

Ch1Rx

Tx

Ring connection provides redundant connection

If one communication leg is broken, the communication will automatically reroute and protection continues

Ch2Rx

Tx

Ch1Tx

Rx

A

D

C

B

E

F


Traffics on 6-ends Closed Ring• Multi-ended Line Differential

• C37.94, 12x64kbps

• Max. Total Propagation Delay, up to 64 ms

• (trip t ime increase, unavoidable, but protection continue!)

Reconfiguration Feature

Ch2Tx

Rx

Ch1Rx

Tx

Ring connection provides Reconfiguration

If one relay is out of service, the communication will automatically

reconfigure the system and protection continues

Ch2Rx

Tx

Ch1Tx

Rx

A

DC

B

E

F

out of servicefor maintenanceProtection out of service

for maintenanceBUT

communication continue!

No interruption to the Ring communication

Reconfiguration 4 ends to 3 ends

Relay End B Relay End C

Relay End D

Relay End A

Protected zone

out of servicefor maintenance

Relay End B Protectionout of service for maintenance

BUTcommunication continue!

Open the CB at End B

No interruption to the protection communication ring

1

2

3

4

Any relay(Reconfiguration command can be sent from any relay,The relay will get ‘reconfiguration confirmation’)

Conclusions

Mult i-terminal line diff.for SONET and MPLS

… without reliance on GPS

Reduced primary CTcost and size

Optimum overall protection scheme costreduction in CT dimensioning

Subcycle line different ialFor renewable gen. ride-throughGreater power system stability

Limit touch/step potential exposure

Mult i-ended accuratefault locat ion (S1 Agile)

Pinpoint the fault locationDispatch maintenance crews

with precision

Fault136.4 km

Thank You

Questions?

new smart multi -ended line current differential solution...

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