new smart multi -ended line current differential solution...
TRANSCRIPT
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;
Capacitive Current Compensation (2)
• 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
Capacitive Current Compensation (3)
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
Communication Configuration (2)
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
Communication Configuration (3)
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?