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Earth fault detection method and device

A ground fault and fault range technology, which is applied in the direction of measuring devices, measuring electricity, measuring electrical variables, etc., can solve problems such as falling into ground faults, and achieve the effects of avoiding false alarms, reducing usage, and simple interface

Inactive Publication Date: 2017-04-12
SIEMENS SWITZERLAND
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

Assuming that, considering the voltage drop caused by the field wiring itself, it is very likely that the voltage at the far end of the field wiring is close to the set normal ground level, that is, it falls into the non-sensitive area of ​​ground fault detection, or the blind area

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  • Earth fault detection method and device
  • Earth fault detection method and device
  • Earth fault detection method and device

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Embodiment Construction

[0032] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation manners of the present invention will now be described with reference to the accompanying drawings.

[0033] Given figure 1 In view of the defects of the existing ground fault detection circuit shown, the inventors of the present invention propose to set the reference level Vref of the large site (EARTH) alternately at least two candidate levels under normal conditions, such as field connection The highest terminal voltage (about 24V) and the lowest terminal voltage on the line, that is, the reference ground (GND), instead of setting the ground reference level Vref under normal conditions at a fixed value. In order to reduce or avoid the occurrence of dead zones, at least two candidate levels need to be able to complement each other for the dead zone of ground detection, that is, the union of their respective corresponding fault ...

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Abstract

This invention discloses a method and a device for detecting earth faults in notifying equipment circuits, wherein the notifying equipment circuit comprises at least one filed wire return circuit. The method comprises: alternatively setting at least two candidate electric levels as earth reference electric levels (Vref) under a normal condition; detecting a practical grounding electric level (Vg) of a ground stud (GROUND_STUD) in the notification equipment circuit; and determining whether the practical grounding electric level (Vg) falls into a fault sub-range of any one of the candidate electric levels, wherein the union of all fault sub-ranges of the candidate electric levels covers the voltage range of the filed wire. If the fact that the practical grounding electric level (Vg) falls into any one of the fault sub-ranges is determined, a grounding fault indication (GS=1) is outputted, and if the fact that the practical grounding electric level doesn't fall into any one of the fault sub-ranges is determined, the non-grounding fault indication (GS=0) is outputted.

Description

technical field [0001] The present invention generally relates to field wire detection of notification equipment (for example, a fire alarm device), and particularly relates to a ground fault detection method and device for field wires. Background technique [0002] In a notification system such as a fire alarm system, the field wiring may be short-circuited to the ground due to careless installation or wear caused by long-term use. This short-circuit is called a ground fault (Ground Fault). Current safety standards (including UL: Underwriters Laboratories standards) generally require detection of ground faults, that is, require immediate reporting once a ground fault is detected. [0003] figure 1 A schematic diagram of an existing ground fault detection circuit 100 is exemplarily shown. Such as figure 1 As shown, the input terminal of the ground fault detection circuit 100 is connected to the field wire through the ground resistor R10, and the voltage on the field wire ...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G01R31/02
Inventor 宜帆
Owner SIEMENS SWITZERLAND