A method for monitoring the line impedance of a protective earth (PE) conductor is provided. The method injects a small stimulus current at a frequency much higher than the grid frequency. The stimulus current circulates in the loops between a grid-connected device and a grid source, creating small voltage drops in the grid conductors, resulting in a common mode voltage which can be measured. The method then includes measuring the common mode voltage and the residual current at a point of common coupling (PCC). The method then includes monitoring the resistive and reactive parts of the line impedance. For example, the method can monitor the line impedance and report a broken PE conductor or a high PE resistance, beyond a given threshold where safety becomes a concern.

A method for monitoring the line impedance of a protective earth (PE) conductor is provided. The method injects a small stimulus current at a frequency much higher than the grid frequency. The stimulus current circulates in the loops between a grid-connected device and a grid source, creating small voltage drops in the grid conductors, resulting in a common mode voltage which can be measured. The method then includes measuring the common mode voltage and the residual current at a point of common coupling (PCC). The method then includes monitoring the resistive and reactive parts of the line impedance. For example, the method can monitor the line impedance and report a broken PE conductor or a high PE resistance, beyond a given threshold where safety becomes a concern.

In one aspect, a charging station is provided. The charging station includes a controller, a direct current (DC) power source configured to provide a charging power for charging an electric vehicle, a charging cable with a connector configured to electrically contact a vehicle inlet of the electric vehicle, a connector holder with a station inlet configured to electrically contact the connector when the connector is inserted into the connector holder, and a contact resistance sensor electrically connected to the station inlet. The contact resistance sensor configured to measure a resistance of at least one electrical contact formed between the connector and the station inlet. The controller is configured to cause the DC power source to provide a measuring power while the connector is inserted into the connector holder so that a measuring current flows between the connector and the station inlet, and receive a resistance value from the resistance sensor.

The present system includes an instrument configured to couple to a device under test, where the instrument is coupled to a local ground and an earth ground, the instrument having: a signal source; a relay coupled to the local ground; a impedance between the first signal source and the relay; and one or more processors configured to execute code that causes the one or more processors to: operate the relay to either connect or disconnect the earth ground to the local ground; measure quality of a first connection to the earth ground and quality of a second connection to the local ground using the instrument, the first signal source, and the first impedance; and determine whether to continue operating the relay to either keep the earth ground connected to or disconnected from the local ground based on the quality of the first connection and the quality of the second connection.

The present system includes an instrument configured to couple to a device under test, where the instrument is coupled to a local ground and an earth ground, the instrument having: a signal source; a relay coupled to the local ground; a impedance between the first signal source and the relay; and one or more processors configured to execute code that causes the one or more processors to: operate the relay to either connect or disconnect the earth ground to the local ground; measure quality of a first connection to the earth ground and quality of a second connection to the local ground using the instrument, the first signal source, and the first impedance; and determine whether to continue operating the relay to either keep the earth ground connected to or disconnected from the local ground based on the quality of the first connection and the quality of the second connection.

In accordance with an embodiment, a method for determining a first contact resistance or a second contact resistance that includes: performing a first measurement using both a first measurement path and a second measurement path coupled to a device under test (DUT) by supplying a predefined measurement current to the DUT via the first measurement path, and measuring a first voltage at an input node of internal circuitry of the DUT to which the first and second measurement paths are coupled; and performing at least one of: a second measurement using only the first measurement path coupled to the DUT for determining the first contact resistance, or a third measurement using only the second measurement path coupled to the DUT for determining the second contact resistance.

The present invention relates to a method (400) for determining a grounding impedance (210) of a grounding device (120) of a power engineering installation (110). The method comprises determining (406, 412) at least two impedance values on the grounding device (120), while the grounding device (120) is electrically connected to at least one further grounding device of at least one further power engineering installation (170, 180). Each of the at least two impedance values is determined with a respective test current at a specified frequency. The frequencies of the respective test currents are different. The method further comprises determining (414) at least one parameter of a model (500), which represents the grounding device (120) and the at least one further grounding device, as a function of the at least two impedance values. The at least one parameter comprises an approximate value for the grounding impedance (210) of the grounding device (120).

The present invention relates to a method (400) for determining a grounding impedance (210) of a grounding device (120) of a power engineering installation (110). The method comprises determining (406, 412) at least two impedance values on the grounding device (120), while the grounding device (120) is electrically connected to at least one further grounding device of at least one further power engineering installation (170, 180). Each of the at least two impedance values is determined with a respective test current at a specified frequency. The frequencies of the respective test currents are different. The method further comprises determining (414) at least one parameter of a model (500), which represents the grounding device (120) and the at least one further grounding device, as a function of the at least two impedance values. The at least one parameter comprises an approximate value for the grounding impedance (210) of the grounding device (120).

The invention relates an electric measuring arrangement (10) and to a measuring method both for monitoring a ground connection for an insulation monitoring device (4), which is connected to at least one active conductor (L1, L2) of an ungrounded power supply system (2) and a ground terminal (PE) of an electric installation (3), with an active loop measurement device (20), which is connectable between a ground-connection clamp (E) of the insulation monitoring device (4) and the ground terminal (PE) and has an independent excitation voltage source (U.sub.gEKE) for quantitatively determining a ground resistance (R.sub.EKE) of the ground connection (6) between the insulation monitoring device (4) and the ground terminal (PE).

Furthermore, the invention relates to an insulation monitoring device (30) having an electric measuring arrangement (10) according to the invention.

The invention relates an electric measuring arrangement (10) and to a measuring method both for monitoring a ground connection for an insulation monitoring device (4), which is connected to at least one active conductor (L1, L2) of an ungrounded power supply system (2) and a ground terminal (PE) of an electric installation (3), with an active loop measurement device (20), which is connectable between a ground-connection clamp (E) of the insulation monitoring device (4) and the ground terminal (PE) and has an independent excitation voltage source (U.sub.gEKE) for quantitatively determining a ground resistance (R.sub.EKE) of the ground connection (6) between the insulation monitoring device (4) and the ground terminal (PE).

Furthermore, the invention relates to an insulation monitoring device (30) having an electric measuring arrangement (10) according to the invention.