JPS6212879A - System for monitoring earth of one-point earthing system - Google Patents

Abstract

PURPOSE:To detect whether earth is generated or not precisely in the non- working status of a system by detecting current in a path up to an earth point and executing the spectrum analysis of data. CONSTITUTION:Exciting transformers CT11-CT1n are connected to respective paths 80-8n from respective branch points to their adjacent branch points and from respective branch points to opened terminals. The transformers CT 11-CT1n connected to respective paths 80-8n are excited with signals having different frequency respectively, current flowing into the earth point is detected by a current detecting transformer CT20 connected to the path connected to the earth point and the current flowing into the earth point is analyzed with spectrum to discriminate whether earth is generated or not. An earth generating position can be also discriminated on the basis of a frequency component obtained by the spectrum analysis.

Description

[Detailed Description of the Invention] Technical Field> This invention relates to a ground fault monitoring method for a single point grounding system.
More specifically, the present invention relates to a novel ground fault monitoring method that can determine whether a ground fault has occurred in a single point grounding system having multiple branches.

<Prior art> Conventionally, single-point grounding systems have been adopted for test systems that use large amounts of electric power, systems that generate strong magnetic fields, etc. in order to maintain the system and prevent control system malfunctions. has been done. In order to constantly monitor whether or not a ground fault has occurred in the single point grounding system, for example, the ground current is detected, and if the detected current value deviates from the normal value, it is detected that a ground fault has occurred. I'm trying to let you know what happened.

In test systems and the like that use high power as described above, if the system is operated with a ground fault occurring, a large current will flow to the equipment where the ground fault has occurred, not only damaging the equipment but also causing damage to the equipment. When a large current also flows through the ground cable, the potential of other devices increases rapidly based on the inductance component of the ground cable, causing problems such as damage to other devices or malfunctions.

Even if the above-mentioned detection method is adopted, it will not be a fundamental solution to such problems. There is a strong need for the development of a monitoring system that can eliminate this.

Purpose> This invention was made in view of the above problems,
An object of the present invention is to provide a ground fault monitoring method for a single point grounding system that can reliably detect whether or not a ground fault has occurred when the system is not in operation.

<Structure> In order to achieve the above object, the ground fault monitoring system of the present invention detects the path from each branch point to an adjacent branch point, and from each branch point to an open end of a ground network consisting of a single point grounding system. One excitation transformer is attached to each route leading to the ground, and the excitation transformers attached to each route are excited with signals of different frequencies, and the current detection transformer attached to the route leading to the ground point is used to connect the By detecting the current flowing through a point and analyzing the spectrum of the current flowing through the grounding point, it is possible to detect whether or not a ground fault has occurred.Since the loop current is inversely proportional to the loop impedance, For example, by detecting the current at a point and analyzing the spectrum using a discrete Fourier transform method on a data string obtained by sampling this current at a predetermined interval, it is possible to detect abnormalities in the loop between the ground fault path and the grounding point. can be determined.

Since the ground fault occurrence point is the farthest position from the grounding point in the above-mentioned loop, the grounding fault occurs on the path furthest from the grounding point among the paths corresponding to the frequency components obtained by the above spectrum analysis. It can also be determined that this is occurring.

<Example> Hereinafter, embodiments will be described in detail with reference to the accompanying drawings showing examples.

Figure 3 is a schematic diagram of a single-point grounding system test system, in which devices 21 (31 (41, etc.) are connected to the power source (1) via power cables (12) (13H14), and each device (2) (3) (4) etc. casing (22) (23)
H24) and power source (1), and ground cable (31)
It is grounded at one point via (32), (33), and (30).

In addition, attached equipment (4aH4b) (4c) etc. are equipment (4).
are connected to these attached devices (4a) (4
b) (4c) Ke] Thing (24a) (24bH24
c) also ground cape/L/ (33a)(33b)(3
3c) to the ground cable (33). The casing (23) of the device (3) and the casing (24c) of the accessory device (4c) are connected via a control cable (44c). A start signal from a control device (not shown) is applied to the power source (1), and the power source (1) is activated by intermittently applying a start signal from the outside.

Figure 1 is a diagram showing an electrical diagram for implementing a ground fault monitoring method for a single point grounding system.
) (32) ... (3n), between each branch point (used as a concept including the connection point with the casing) (81
)(82)...(8n), one excitation transformer (CT11)(CT12)...-(CTln)
) on the route (80) leading to the grounding point.
Install the current detection transformer (CT20) and connect the transmitter (
51)(52)--(5n) output signals f1. f2.・・・・・・fn,
Amplifiers (61) (62)... (6n) amplify the excitation transformers (CT11) (CT1), respectively.
2) It is applied to (CTln). Then, the output signal of the current detection transformer (CT20) is amplified to a predetermined level by the amplifier (11),
converted into a digital signal by an A/D converter (12),
Central processing unit (CPU)
u) is used to drive the display device (73).

FIG. 2 is a flowchart showing the operation of monitoring ground faults, and in step (3) the transmitter (51052)...
...(5n) is activated to activate the excitation transformer (crin)
The path (8n) of each grounding cable is excited by applying the amplified signal to ) is applied to the central processing unit (CPU) for spectrum analysis. Then, in step (■), the input resistance value corresponding to each spectral component is converted into a resistance value, and in step (2), the input resistance value is compared with that of each recognition device, and in step (2), an abnormality in the spectrum component is determined. Among the routes corresponding to a certain frequency component, determine the route (8n) that is the most distant from the grounding point, and proceed to step ■
At , an alarm indicating that a ground fault has occurred on the route (8n) is displayed, and the determination and processing from step ① is performed again. On the other hand, if there is no abnormality, just step
Perform the following determination and processing.

Thus, for example, as shown in FIG.
If a ground fault has occurred inside (it may have occurred in the history of the previous test or may have occurred due to human work error), route (80) (83) (85) (86)
Since the impedance of the loop made up of 3. f5. Since f6 increases, it is possible to determine that a ground fault has occurred, and it is also possible to determine that a ground fault has occurred on the path (86) that is the farthest from the grounding point, so the display device (7
3) to display the occurrence of a ground fault in a single-point grounding test system and the location of the ground fault, and to start the power source (1) in the state where a ground fault has occurred. It is possible to prevent damage to equipment caused by ground faults, and also to take prompt measures at locations where ground faults occur.

The above description has only been made regarding the case where the present invention is applied to a test system, but it is also possible to apply the present invention to a system other than a test system, as long as it is a single point grounding system.

<Effects> As described above, the present invention detects the current in the path leading to the ground point based on the mutually different frequency components that are excited for each branched path when the power source is not activated. Since it is determined whether or not a ground fault has occurred based on the frequency components obtained by spectrum analysis of this data, it is possible to start the power source while a ground fault has occurred, Damage to equipment, damage to control equipment,
This has the unique effect of reliably preventing inconveniences such as malfunctions.

Further, it is more preferable to make it possible to determine the location where a ground fault has occurred based on the obtained frequency components, because countermeasures against the ground fault can be taken quickly.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the electrical configuration for actually implementing the ground fault monitoring method for a single-point grounding system. Figure 2 is a flowchart showing the operation for monitoring ground faults. Figure 3 is a test system for a single-point grounding system. Schematic diagram.

Claims (1)

[Scope of Claims] 1. One excitation transformer is installed in each path from each branch point to an adjacent branch point and from a branch point to an open end of a grounding network consisting of a single point grounding system, The excitation transformers attached to each route are excited by signals with different frequencies, and the current flowing through the ground point is detected by the current detection transformer attached to the route leading to the ground point, and the current flowing through the ground point is detected. A ground fault monitoring method for a single point grounding system, which is characterized by determining whether or not a ground fault has occurred by performing spectrum analysis. 2. The single-point grounding system according to claim 1, which detects the point farthest from the grounding point as the ground fault occurrence point among the paths corresponding to the frequency components obtained by spectrum analysis. Ground fault monitoring method.