1. RT3b – André Smit, Siemens USA
U.S. Distribution Feeder Automation Pilot Project
We have developed a peer-to-peer feeder automation system using WiMAX and IEC61850
During the project we needed to develop new protection settings for the feeder
We found that conventional settings of coordinated overcurrent relays was not possible 
The relay setting groups could not be adapted to all the different operating scenarios we faced 
We needed to find a solution that was less complicated with better performance

2. Traditional Feeder Operation
Overcurrent protection operate and trip
Utility receives a fault notification from a customer experiencing an outage
Trouble desk dispatches a line crew to locate and isolate the fault
Crew restores service to unaffected sections of line
Crew effects repairs and restores feeder to normal operation
Outage time could be measured in hours
André Smit – U.S. – RT3b

3. Automation of the Distribution Feeder
FLISR
Fault Location, Isolation, and Service Restoration
Circuit Breaker
Recloser
Switch

4. Feeder Automation Pilot Project

5. Automating the Distribution Feeder
Operational Features to Consider
Change open point based on loading
Isolate line sections for maintenance
Transfer to healthy source
Circuit Breaker
Recloser

6. Different curve shapes to deal with
Relay protecting power transformer does not have same shape curve as fuse designed to protect small distribution feeder load

7. Affect when lowering the Isc
The effect of moving 50 setting to indicate what happens when Isc is low.
Little room to coordinate with 51 element. Cannot coordinate with 50 element
as a higher Isc will cross both lines and both relays will trip.

8. Affect without low Isc being a factor
If low Isc not a factor, more space to coordinate with 51 element and still stay above fuse.

9. 3 Reclosers with Tolerance Affect
Typical TCC curve showing high and low tolerances. (Used ±5% on pickup & time.)
Not considering CT tolerance. Illustrates need for space between curves.

10. 1 Recloser
Only one recloser easy to fit between max fuse and feeder main breaker.
Better coordination (more space) between all four devices.

11. One set of TCC curves of 16 sets Using four total setting groups
51 pickup markers
Match curves
to data
by color
Largest downstream fuse
Feeder main breaker and three reclosers
Upstream Transformer or Bus Main Breaker
50 active only during reclose

12. One set of TCC curves of 16 sets Using four total setting groups
51 pickup markers
Match curves
to data
by color
Largest downstream fuse
Feeder main breaker and three reclosers
Upstream Transformer or Bus Main Breaker
50 active only during reclose

13. Difficulties in Coordinating Feeder
Reclosers are in series on feeder and not located on branches
Segments have different types of loads
Curves for transformers are not as steep
Demand changes by time of day and season and differently for each segment
Melt/time characteristics for distribution fuses do not fit closely with substation transformer protection upstream
Original system designed without new switching points

14. Difficulties in Coordinating Feeder
High source impedance + long line = very low fault currents
Substations located at the ends of the line, so source impedance is usually high; a long feeder—the best candidate for automation—adds to the impedance
Severe limits caused by existing minimum current settings and low short circuit current (Isc)
Low available Isc limits use of 50, or 50 with definite time
Must include considerable allowance for high-impedance branch line faults causing Isc to be even lower
Inrush current could be five times nominal current, therefore precluding the use of 50 element when Isc is low

15. How do we deal with these difficulties to protect an Automated Feeder?
Setting Sheets

16. Our Solution
Detect and isolate faults with a differential (87L) function
Activate a 50/51 overcurrent curve on one device end and reclose on fault
Diff Zone
Diff Zone
Primary
Switch 1
Primary
Switch 2
Primary
Switch 3 87 87 87 87 87 87
Relay 1
Relay 2
Relay 3

17. Performance
Direct Fiber
WiMAX
30 msec
80 msec

18. Automating the Distribution Feeder
Locate using 87L
Isolate using 87L & Restore
Reclose using 50/51
Restore

19. New Protection for Automated Feeders
Fast
Selective
Uncomplicated
Minimal Disruption for customers
Reclosers
Feeder Breaker
Transformer

20. Questions