Siemens Reyrolle 7SR45 Argus Device Manual

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Time-Delayed Measured Earth Fault Protection (51G)Overview of the Function (51G)The time-delayed measured earth fault protection is used to provide:• Detection of earth current in electrical equipment• Backup or emergency protection in addition to other protection functions or devices• Coordinated operation with other devices using time graded settingsStructure of the Function (51G)The time-delayed measured earth fault protection element has group dependent settings. These settings canbe different in each settings group – group numbers (Gn) 1 and 2.The function monitors the primary system current using the earth fault CT input for example CT4.The basic time‑delayed measured earth fault protection function (51G) is summarized as follows:• Current measurement is based on the fundamental current.• A number of time/current operate curves are selectable based on IEC and ANSI standards.• Alternatively, the 51G elements can operate with a definite time lag (DTL) characteristic.• LED operations are provided for earth fault. A general pickup and 51G‑n output are also provided.Logic of the Function (51G-n)[lo_7sr45_51G_TimeDelayedMeasuredEFFn, 2, en_US]Figure 3-7 Logic Diagram of Time-Delayed Measured E/F Protection (51G)The following characteristic curves are supported by 51G-n:3.7Functions3.7 Time-Delayed Measured Earth Fault Protection (51G)Reyrolle, 7SR45, Device Manual 61C53000-G7040-C101-2, Edition 09.2020