A measuring apparatus includes: N pairs of probes that are respectively connected to a positive electrode and an external member of N rechargeable batteries that have a capacitance connected in parallel between the positive electrode and the external member; a scanner that selectively switches to one pair of probes out of the N pairs; a measuring apparatus that measures the voltage between the selected probes; and a controller. A plurality of resistance configurations to be connected between each pair of probes are provided. After a standby time has elapsed in a state where the N pairs of probes are connected to the positive electrodes and external members of the N rechargeable batteries, the controller outputs control signals to the scanner to successively switch to each pair of probes and causes the measuring apparatus to measure the voltage between the selected probes every time switching is performed.

A system may include a resistive-inductive-capacitive sensor, a driver configured to drive the resistive-inductive-capacitive sensor at a driving frequency, a measurement circuit communicatively coupled to the resistive-inductive-capacitive sensor and configured to measure phase information and amplitude associated with the resistive-inductive-capacitive sensor, and a noise detection circuit communicatively coupled to the measurement circuit and configured to determine a presence of external interference in the system based on at least one of the phase information and the amplitude information.

An insulation resistance detection circuit and method are disclosed. The circuit includes a controller configured to: open a first relay, and close second relays, or switch an on/off status of at least one of the second relays; determine, based on a first measurement value between a positive input terminal of an inverter circuit and an earthing point, whether the positive input terminal of the inverter circuit is short-circuited or has low resistance to protective earthing; and determine, based on a second measurement value between a negative input terminal of the inverter circuit and the earthing point, whether the negative input terminal of the inverter circuit is short-circuited or has low resistance to protective earthing, where the first relay is one of in M relays and is connected to at least one impedor in parallel, and the second relays are relays other than the first relay in the M relays.

The invention relates to a method and a device for identifying arc faults in an ungrounded power supply system. This object is attained by detecting a displacement voltage to ground at an active conductor or at a neutral point of the ungrounded power supply system; by providing a value of an operating frequency occurring in the power supply system; and by analyzing a frequency spectrum of the detected displacement voltage by calculating and assessing Fourier coefficients at the locations of the operating frequency and its harmonics. Due to the broadband detection of the displacement voltage interacting with the “quick” generation of the basic functions by means of a DDS generator, arc faults can be identified reliably in an ungrounded power supply system.

A method for a single-fault-tolerant determination of an isolation resistance of a photovoltaic system including an inverter and a solar generator connected thereto is disclosed. The isolation resistance is determined as a function of a test voltage drop in a resistor network, wherein the resistor network is connected to a variable voltage source by way of a first terminal, to a first pole of the solar generator by way of a second terminal and to a ground terminal of the inverter via an isolation relay by way of a third terminal. A capacitor is disposed between the ground terminal and the first pole of the solar generator. The method includes a) applying a first DC voltage value to the first terminal when the isolation relay is closed using the variable voltage source, b) applying a second DC voltage value to the first terminal when the isolation relay is closed using the variable voltage source, c) generating an AC voltage at the first terminal using the variable voltage source when the isolation relay is closed, d) generating the AC voltage at the first terminal using the variable voltage source when the isolation relay is open, and e) testing a function of the isolation relay by comparing an amplitude of the test voltage between the acts c) and d).

A testing apparatus and a method for detecting insulation resistance of an unshielded high voltage line are provided. The testing apparatus has a voltage source for providing a measurement voltage for the high voltage line, an accommodating device for accommodating the high voltage line and for connecting the high voltage line to the voltage source, an insulation tester for detecting the insulation resistance on the basis of the measurement of a leakage current via the insulating sheath, two electrically conductive half shells which, when combined, form hollow cylindrical sheathing for the high voltage line, and two contact probes which can be electrically connected to the sheathing and to an inner conductor of the high voltage line. The insulation tester is designed to measure a current between the contact probes as the leakage current.

An insulation resistance measurement apparatus includes a first resistance unit having one end connected to an anode of a battery and the other end connected to ground, and variably having a first resistance value or a second resistance value greater than the first resistance; a second resistance unit having one end connected to a cathode of the battery and the other end connected to ground, and variably having a third resistance value or a fourth resistance value greater than the third resistance value according to control; a voltage measurement unit configured to measure a voltage across the first or second resistance unit; and an insulation resistance calculation unit configured to calculate a first insulation resistance value between the anode of the battery and ground and a second insulation resistance value between the cathode of the battery and ground by using the first to fourth resistance values and the measured voltage.

A method and a test apparatus for determining the elements of a dielectric equivalent circuit diagram for an insulation of an electric system and to an insulation monitoring device. All data points of the system's step response are stored for a measuring period T.sub.m, and fault resistance R.sub.f and an initial value C.sub.e0 of leakage capacitance C.sub.e are calculated. After this determination of fault resistance R.sub.f and initial value C.sub.e0, the elements of absorption element R.sub.a and C.sub.a and leakage capacitance C.sub.e are determined by numeric signal processing by using an approximation algorithm which continuously simulates the recorded step response. For simulating the step response, a transfer function G(s) modelled by the equivalent circuit diagram having equivalent circuit diagram elements R.sub.f, C.sub.e, R.sub.a, C.sub.a and measurement resistance R.sub.m is formed analytically and the output signal is calculated, which is described using transfer function G(s), by means of the step function.

A measurement device with improved electrical strength comprises an input for receiving an input signal as well as a measurement circuit connected with the input. The measurement circuit has at least one component. The measurement device also comprises an electrical interface provided in addition to the input. The measurement device further comprises at least one internal enclosure that encloses the component within the measurement device, thereby improving the electrical strength of the measurement device.

A power converter between an AC side and DC of the power converter is disclosed. The AC side is connected to an AC supply grid and the DC side is connected to a DC grid. The power converter includes a bridge circuit connected to the AC side of the power converter via AC switches and connected to the DC side of the power converter via circuit breakers, wherein a DC link circuit of the power converter is chargeable from the AC supply grid via an AC precharging circuit. The power converter has an insulation monitor to measure the insulation resistance of the DC side when the AC precharging circuit is connected to the DC link circuit. The disclosure also includes a related method.