Earth measuring isolator
An earth measuring isolator (EMT) is a piece of equipment used in electrical power supply systems, primarily in low-voltage networks with protective earthing (e.g., TN systems or TT systems). It serves to separate the earthing system of an electrical installation from the earthing system of the network operator in a measurable and testable manner.
Normal operation (closed connection)
The two earth electrodes (the grid operator's operating earth electrode and the system earth electrode) are electrically connected to each other. This ensures that the earthing system has a consistently low impedance and guarantees personal protection, functional earthing, and lightning protection.
Measuring operation (separate connection)
The separation point is opened for tests (e.g., measurement of the grounding resistance according to DIN VDE 0100-600 or DIN VDE 0105-100). This allows the system grounding electrode to be measured in isolation from the operational grounding electrode. A safe, defined connection remains possible during the measurement, as the separation point is usually designed so that measuring devices can be connected.
Once the measurement is complete, the connection is closed again.
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