Transmission & Distribution Technology
dead time. It stays closed if it was a temporary fault but trips again if the fault is permanent. Only customers on the spur line will be affected. If the recloser fails to trip on a fault, the upstream circuit breaker or feeder recloser has to operate, leaving all customers of the feeder affected by this spur line fault. When the recloser has cleared a permanent fault and changed to the lock-out stage, it will drop out and provide the line crews with a visible break at the site of the operation. It also offers rapid or sensitive fault protection to line crews so it enhances safety for live of line crews. Tese reclosers usually do not have internal fault memory to maintain a record of outage events. Tey also cannot be integrated into a network’s SCADA system and lack of remote control options. Te purchase price of a recloser with all its protection and communication equipment is rather high, which makes it difficult to justify this investment for spur lines.
wireless communication module is easily attached to each device allowing connection to the Siemens Connect software. Tis enables an operator to view live data of the status of each installed device, including the time, type and magnitude of the most recent fault. Event logs from multiple Fusesaver devices can be retrieved and analysed to determine the worst performing spur lines and allowing network owners to take preventative action in a cost effective manner. Furthermore, a utility can gather accurate, reliability data on their network performance for use in regulatory reporting, leading to financial savings. A proprietary, purpose-designed remote control unit is available, enabling this device to then be integrated into a network’s SCADA system, providing rapid access to data and remote access to devices from the central control center. Tis includes receiving fault alerts and gathering reliability data.
Conclusion
Fig. 3. The Fusesaver from Siemens: 1. Dead-end; 2 Fault-detection current transformer; 3. Vacuum interruptor; 4. Birdguard (optional); 5. Power current transformer; 6. Magnetic actuator; 7. Electronic module.
Live data Instead of all these solutions, a new, intelligent fuse-saving circuit breaker is an efficient and reliable alternative. Te Fusesaver device developed by Siemens is a self-powered, electronically controlled, single-phase fault-interrupting device that is installed in series with a fuse to protect it from transient faults. It detects, opens and clears a fault in as little as a half-cycle which, for most rural spur line faults, is less time that it takes for the fuse to melt. It then automatically closes after a configurable dead time. If the fault was transient, then only the spur line customers have experienced a momentary outage. If the fault is permanent, after closing, the fault current will flow again and the fuse will now operate to clear the fault. Te fuse drops down providing a visible flag to line crews of the permanently faulted line and electrical isolation. Again, only the customers on the faulted spur line experience an outage. Te Fusesaver device has on-board electronics with memory that contain an event history, including information on fault characteristics. A short-range
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A comparison of the performance capabilities of the various solutions show that Siemens Fusesaver is the only device that meets all of the criteria for the optimal protection of rural spur lines. Fuses, whilst the lowest cost option, are inadequate as they create a sustained outage for all faults when the majority of rural faults are transient. Drop-out sectionalisers require a much larger customer base to experience an outage to clear a spur line transient fault. Neither a fuse nor a sectionaliser has any smart grid functionality and certainly cannot be integrated into a SCADA system. One-phase recloser provide localised fault clearing but lack of events history and ability for SCADA integration. Furthermore, it is the most expensive option which can hardly be justified for spur lines. Te new Fusesaver device is the only technology that can improve rural performance and cost, whilst building an intelligent grid. It is the world’s fastest circuit breaker in the market and can be installed on an existing spur line to clear the fault before the fuse blows, saving a call-out, sustained outage and financial penalty. Installation is quite simple due to the fact, that the weight is just 5.5 kilograms per device. Te engineering and planning requires only a
short time because there is no need to modify the network protection scheme. Te characteristics of the installed fuse remains unchanged and will act in case of permanent failures as before. Te comprehensive history log provides data which the customer can additionally use for network improvements. Fusesaver addresses all of the key performance capabilities required for an achievable, improved rural network performance today and a financially sustainable future. ●
Stefan Kramer is with Siemens AG, Infrastructure & Cities Sector, Low and Medium Voltage Division. Erlangen, Germany.
www.siemens.com/powerdistribution
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