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Method and apparatus for determining a fault current portion in a differential current

A fault current and current technology, which is applied in the direction of circuit devices, emergency protection circuit devices, emergency protection devices with automatic disconnection, etc., can solve the problems that the AC fault current component cannot be determined, and the AC fault current component cannot be determined appropriately.

Active Publication Date: 2014-01-01
SMA SOLAR TECH AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The disclosed method can be applied in principle to a single-phase inverter, but it has been found that the AC fault current component of the difference current measured on a multi-phase inverter cannot be suitably determined in this way
Operating states also arise in the case of a single-phase inverter in which the AC fault current component of the measured differential current cannot be suitably determined with the known method

Method used

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  • Method and apparatus for determining a fault current portion in a differential current
  • Method and apparatus for determining a fault current portion in a differential current
  • Method and apparatus for determining a fault current portion in a differential current

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Embodiment Construction

[0035] figure 1 An inverter 1 is shown in , which is connected on the inlet side to a photovoltaic system 2 as a DC power source 3 . On the outlet side, the inverter is connected to a three-phase AC grid 4 . For this purpose, the inverter has a plurality of AC outputs 5 to 8 . In this case, the AC outputs 5 to 7 are provided for the outer conductors L1 to L3 and the AC output 8 is provided for the neutral line N of the three-phase AC network 4 . Correspondingly, the AC voltage u of the three phases of the AC grid 4 is staggered AC (t) is applied to the AC outputs 5 to 7 . The total current transformer 9 is set to detect the differential current i between all the AC output terminals 5 to 8 of the inverter 1 diff (t). Measuring device 10 detects three alternating voltages u AC (t) An alternating voltage on line 7 at the output. The difference current i diff (t) and the AC voltage u AC (t) is digitized in an analog / digital converter 11 and then fed to an evaluation devic...

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Abstract

When determining a fault current portion (IF) in a differential current (idiff(t)) measured at an inverter (1), an AC voltage (uAC(t)) applied to an AC output of the inverter (1) is measured and a periodic reference function (y(t)) of changing sign is generated on the basis of the measured AC voltage (uAC(t)) in order to determine an AC fault current portion (IFAC) in the differential current (idiff(t)). The differential current (idiff(t)) is multiplied by the periodic reference function (y(t)), and the product of the differential current (idiff(t)) and the reference function (y(t)) is averaged over an integral number of periods (T) of the reference function (y(t)). In this case, the reference function (y(t)) is generated, at least for one operating state of the inverter (1), with a predefined phase offset with respect to the measured AC voltage (uAC(t)) and / or with a frequency which is an integer multiple of the frequency of the measured AC voltage (uAC(t)).

Description

technical field [0001] The invention relates to a method for determining a fault current component of a differential current, which is measured at an inverter, and a device for carrying out such a method, wherein the method has an independent Characterized by the preamble of claim 1 , the device has the features of the preamble of the co-dependent independent claim 14 . [0002] The inverter particularly relates to an inverter for adjusting direct current supplied by a direct current power source into alternating current. The DC power supply may in particular be an optoelectronic device which, solely due to its spatially extended size, has a large leakage to ground These leakage quantities and potential displacements relative to ground occur during operation of the inverter, due to which leakage currents to ground arise. Said leakage currents are found in differential currents, which are generally monitored for quick recognition of the occurrence of fault currents. High le...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01R31/40H02H3/26
CPCH02H3/33G01R31/42H02M7/44
Inventor A·努斯C·博德W·格罗特
Owner SMA SOLAR TECH AG
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