New Smart Multi-Ended Line Current Differential Solution for Power Networks

Transcription

1 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

2 Introduction Why Multi-Ended Protection? Utility power networks are evolving to transport power in ever more complex ring and meshed networks. Line/cable differentia l protection becomes increa singly a ttra ctive, with its inherent ability to address grading/selectivity challenges and scalable for multi-termina l circuits a ble to a ccommodate many connections of distributed generation along the line. For circuits which neighbour the coast, or other potential windfa rm locations, there is a lwa ys the possibility tha t 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.

3 Why Multi-Ended Lines? Lines become just a mecha nical/electrical highwa y to evacuate power Or to tee-off supplies from existing lines to expanding urban areas End 6 On shore windfarm End 1 End 4 Off shore windfarm End 3 End 2 End 5 Solar farm

4 Line Differential Principle (2 Ended) End 1 End 2 Communication Link I End1 I End2 I F Differential definition: I End1 + I End2 = 0 Healthy I End1 + I End2 0 (= I F ) Fault

5 Line Differential Principle (6 Ended) Differential definition: I End1 + I End2 + I End3 + I End4 + I End5 + I End6 = 0 Healthy I End1 + I End2 + I End3 + I End4 + I End5 + I End6 0 (= I F faulty)

6 New Multi-Ended Line Differential End 2 End 4 End 1 End 6 End 3 Multi-ended Line Differential algorithm Same characteristic, innova tive sa mple-based a lgorithm 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 5 Operating characteristic

7 Differential trip logic Send to remote end CT & VT 48 samples /cycle ADC Capacitive current compensation Phase Differential Receipt from Remote ends Data alignment (synchronization) CT Supervision AND Differential Trip CT Saturation (internal/external fault) Internal fault CT Saturation algorithm activates only if Ibias > IbiasThres fulfilled

8 Capacitive Current Compensation (1) The objective for the capacitive current calcula tion is to calcula te the current a t terminal N based on the voltage and current at terminal M; The ma thema tical model for calcula ting the capacitive current of a transmission line that is used here is distributed pa ra meter line model, which is more accurate than the lumped model; 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

9 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 algorithm. IL ZL IR VL IchL IchR VR

10 Capacitive Current Compensation (3) I End1 I End2 Junction I End3 IEnd1, IEnd2, IEnd3 = calcula ted junction currents after charging current compensation Based on local measurement of the current & voltage input at End1, End2, End3, each relays can remove capacitive charging current from local to the junction and calculate the voltage and current at the junction IEnd1, IEnd2, IEnd3. These IEnd1, IEnd2, IEnd3 current vector (with charging current removed) are sent to remote end for differential calculation.

11 CT Saturation (1) I POS Ratio < R Thres External Fault RRRRRRRRRR = II PPPPPP + II NNNNNN II PPPPPP II NNNNNN I NEG Ratio < R Thres Internal Fault CT saturation detection works by calculating the ratio 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

12 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 Ipos and Ineg Diagram 3: relay internal fault detection Diagram 4: normalization for stability

13 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

14 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

15 6 Ended Communication Configuration A Ch1 Ch2 B F Fixed configuration 6 ends is ALWAYSRing connection E Ch2 Please note Ch1 and Ch2 allocation Ch1 D C

16 Terminal 1 Data Terminal 2 Data Communication Configuration (1) Four Terminal Scheme Terminal 1 Terminal 4 Data Terminal 2 Data Terminal 3 Data Terminal 3 Data Terminal 1 Data Terminal 4 Data Terminal 2 Terminal 2 Data Terminal 3 Data Terminal 4 Data Terminal 3 Data Terminal 1 Data Terminal 4 Data Terminal 1 Data Terminal 2 Data Terminal 3 Data Terminal 4 Data Terminal 4 Terminal 2 Data Terminal 3 Data Terminal 1 Data Terminal 2 Data Terminal 4 Data Terminal 1 Data Terminal 3

17 Communication Configuration (2)

18 Communication Configuration (3) A Ch1 Ch2 B F Ring connection provides redundant connection If one communication leg is broken, the communication will automatically reroute and protection continues C E Ch2 Ch1 D

19 Traffics on 6-ends Closed Ring Multi-ended Line Differential C37.94, 12x64kbps Max. Total Propagation Delay, up to 64 ms (trip time increase, unavoidable, but protection continue!)

20 Reconfiguration Feature Protection out of service for maintenance BUT communication continue! A Ch1 out of service for maintenance Ch2 B No interruption to the Ring communication Ring connection provides Reconfiguration F If one relay is out of service, the communication will a utoma tically reconfigure the system and protection continues E Ch2 Ch1 D C

21 Reconfiguration 4 ends to 3 ends 4 1 Open the CB at End B Relay End B out of service for maintenance Relay End C 2 Protected zone 3 Relay End B Protection out of service for maintenance BUT communication continue! Relay End A No interruption to the protection communication ring Any relay (Reconfiguration command can be sent from any relay, The relay will get reconfiguration confirmation ) Relay End D

22 Conclusions Subcycle line differential For renewable gen. ride-through Greater power system stability Limit touch/step potential exposure Mult i-terminal line diff. for SONET and MPLS without reliance on GPS Fault km Mult i-ended accurat e fault location (S1 Agile) Pinpoint the fault location Dispatch maintenance crews with precision Reduced primary CT cost and size Optimum overall protection scheme cost reduction in CT dimensioning

23 Thank You Questions?