12593 Extended Parallel Operation

Because the closed transition transfer strategy has an overlap time limited to 100 ms, there is no need for protective relaying. The sources will be out of parallel before a protective relay can operate and before a recloser can reclose. When parallel operation extends beyond that very short period, the designer must evaluate how many and which protective relays will be needed and where they are to be applied. It has been suggested that the protective relaying scheme should be seen as two schemes. The first of these schemes is to prevent or permit an operating mode. The second is to terminate an operating mode. It has also been suggested that relays serving a permissive role can, and usually do, act as backup relays to those relays in the protective role.

The extent of the protective relay scheme, having met safety considerations, is affected somewhat by the length of time the sources operate in parallel. If the sources are to operate in parallel just long enough for the load to be shifted from one source to the other, thus eliminating loading transients, the sources need to be in parallel for less than two to three minutes. In theory, such operating strategies should not require as extensive a protective relaying scheme as would be required for continuous parallel operation of the sources.

Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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