A Protection Scheme using Ultra-fast Circuit Breakers for Wildfire

Mitigation and Reliability Improvement for Rural

Distribution

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Headline News

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Rural Network Challenges

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• Rural lateral lines are long, have few customers generating little revenue and frequent faults incurring high operating costs and reliability penalties to the network operator.

• Rural lateral lines in hot, dry and windy locations with large amounts of vegetation means these lines represent a considerable risk in electrical faults causing ignition of wild fires.

Network operators are therefore trapped between the conflicting requirements of minimising investment, optimising reliability and yet responsibly managing the network to eliminate the risk of electrical faults igniting wild fires.

Reliability Protection Objectives

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Criteria 1. Transient faults should not result in

sustained outages that require a line crew to attend site.

2. The minimum number of customers should be impacted by a transient fault.

3. The minimum number of customers should be impacted by a permanent fault.

4. Permanent faults should be sectionalised at the protection device immediately upstream of the fault.

Typical Strategies to meet criteria • reclosing to clear transient faults

• reclosing at lateral line level rather than feeder line

• Automatically sectionalise permanent faults at the lateral line level

Wild Fire Mitigation Objectives

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[1] D. Coldham. A. Czerwinski and T Marxsen, "Probability of Bushfire Ignition from Electric Arc

Faults," HRL Technology Pty Ltd., Melbourne, VIC., Australia, Tech. Rep. HRL/2010/195, 2011.

Criteria

1. Ensure no fuses blow that can expel arc products capable of igniting a fire.

2. Clearing time for faults should be less than 20ms, preferably 10ms.

3. On extreme fire risk days the protection time-current curve of the key protection devices can be changed to ultra-fast mode via a SCADA control.

4. Reclose function must be disabled via SCADA control

Ultra-fast Fusesaving Circuit Breaker

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• The Fusesaver is a self-powered, electronically controlled, single-phase fault interrupting device that is installed in series with a fuse to protect that fuse from transient faults.

• Add the Siemens Remote Control Unit (RCU) and interface Fusesaver with a SCADA system to provide remote access to Fusesavers throughout your rural network.

Core Functionality

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• Temporary Faults

• Permanent Faults

Half Cycle Interruption

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• To be able to save fuses effectively the Fusesaver has an ultra-fast protection capability. It can detect, open and clear a fault in as little as a half-cycle.

• This speed also means faults can be prevented from igniting wild fires

Models and Ratings

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Reliability Optimisation

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Feeder Line

Fusesaver & RCU “A”

25T Fuse

Sub-Spur Line

Fusesaver “B”

12T Fuse

Spur Line Sub-Spur Line

Sub-Spur Line

This approach satisfies ALL

reliability criteria

Wild Fire Mitigation

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Feeder Line

Fusesaver & RCU “A”

25T Fuse

Sub-Spur Line

Fusesaver “B”

12T Fuse

Spur Line Sub-Spur Line

Sub-Spur Line

This approach satisfies ALL

wild fire mitigation criteria

Conclusion

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Ultra-fast Fusesaving Circuit Breakers with SCADA connectivity provides optimal reliability performance and robust wild fire mitigation at a price point that is appropriate for use on rural networks with few customers.