Siemens Aktiengesellschaft

Joerg Meyer

Peter Schegner

Karsten Wenzlaff

Stefan Widmann

A Rogowski coil is used for determining the magnitude of the electrical current of a conductor of a low-voltage AC circuit, which outputs an analogue voltage which is equivalent to the magnitude of the electrical current of the conductor. The Rogowski coil is connected to an analogue integrator, which is followed by an analogue-digital converter, which converts the integrated analogue voltage into a digital signal which is further processed by a microprocessor in such a way that the phase shift generated by the Rogowski coil and the components connected downstream of the Rogowski coil is compensated such that there are in-phase current values for the detection of error situations in order to protect the low-voltage AC circuit, in particular for a low-voltage power switch or an arc fault detection unit.

Low-voltage power switch and arc fault detection unit

Low-voltage power switch and arc fault detection unit with compensation due to phase shifting

A fault-arc identification unit for an electric circuit, includes at least one voltage sensor, for the periodic determination of electric voltage values; and at least one current sensor, for the periodic determination of electric current variables of the circuit. Both sensors are connected to an evaluation unit, designed such that: electric voltage values are fed to a first fault-arc identification function which carries out a first fault-arc identification based upon a signal profile of the voltage, and emits a first fault-arc identification signal upon a first threshold value being exceeded; electric voltage values and current variables are fed to a second fault-arc identification function which carries out a second fault-arc identification based upon the voltage values and current variables, and emits a second fault-arc identification signal upon a second threshold value being exceeded. The fault-arc identification signals are fed to an inclusive disjunction function, to emit a fault-arc identification signal.

Arc fault detection unit

An arc fault identification unit for an electrical three-phase alternating current circuit with three phase conductors and a neutral conductor. The identification unit includes voltage sensors to periodically determine phase/neutral conductor voltage values and phase/phase voltage values current sensors to periodically determine phase conductor current variables which are used to determine the phase conductor current value and a value for the change in the electrical current over time per phase, and an evaluation unit connected to the voltage and current sensors. A current root mean square is compared with a current threshold value in each case and an excess current signal is emitted if the threshold value is exceeded; arc voltages are calculated and are compared with threshold values, with the result that arc fault identification signals are output.

Arc fault identification unit

An arc fault detection unit for an electrical low-voltage circuit, includes at least one voltage sensor assigned to the circuit, for periodically determining electrical voltage values of the circuit, and at least one current sensor assigned to the circuit, for periodically determining electrical current magnitudes of the circuit, both of which are connected to an evaluation unit. The sensors being embodied such that value pairs, having a voltage value and a current magnitude are determined continuously, a value set including a plurality of value pairs. Further, an arc voltage, compared to a first threshold value, is calculated from three value sets and in response to the first threshold value being exceeded, an arc fault detection signal is output.

Accidental arc detection unit and method thereof

An embodiment relates to an arc fault detection unit for an electrical low-voltage circuit including, connected to an evaluation unit, a voltage sensor assigned to the circuit, for periodically determining electrical voltage values of the circuit; and a current sensor assigned to the circuit, for periodically determining electrical current values. They are embodied such that pairs of a voltage and a current value are determined continuously at a point in time. In each case, a first value pair of a voltage and of a current value is present at a first point in time, a second value pair is present at a second point in time, and a third value pair is present at a third point in time. An arc voltage, which is compared to a threshold value, is calculated from the three value pairs. If the threshold value is exceeded, an arc fault detection signal is output.

An arc fault detection unit is disclosed for a low-voltage electrical circuit. The arc fault detection unit includes at least one voltage sensor, for periodically determining electrical voltage values of the electrical circuit, connected to an evaluation unit. The evaluation unit is designed such that a first half of a first number of voltage values is continuously summed to form a first partial sum and the second half of the voltage values is continuously summed to form a second partial sum and a difference of the two partial sums is calculated. Either as one alternative the difference or the amplitude of the difference is compared with a first threshold value and if the value is exceeded, an arc fault detection signal is output; or as a second alternative the difference is compared with a second threshold value and if the value is undershot, an arc fault detection signal is output.

A method is disclosed for selectively triggering circuit breakers in the event of a short circuit, wherein an upstream circuit breaker and at least one downstream circuit breaker on the output side are provided. In at least one embodiment, the upstream circuit breaker monitors as to whether the or one of the downstream circuit breakers is already in the process of opening the switch contacts thereof to interrupt the circuit on the output side, while forming a switch arc. In order to reliably determine whether a downstream circuit breaker is already in the process of opening, according to at least one embodiment of the invention the upstream circuit breaker, so as to detect a switch arc on the output side, checks whether the ohmic resistance of the short circuit loop produced by a short circuit has an exponential curve over time in that an exponent is continually computed and based on the computer exponent the switch arc is determined if the computed exponent exceeds a threshold.

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Dresden, Germany

Joerg Meyer