JPH0465990B2 - - Google Patents

Description

[Detailed Description of the Invention] <Technical Field> The present invention relates to an abnormality monitoring method for a single-point grounding system, and more specifically, the present invention relates to an abnormality monitoring method for a single-point grounding system, and more specifically, a method for monitoring abnormalities in a single-point grounding system that has multiple branches when a ground fault or short circuit occurs in each branch. This invention relates to a new abnormality monitoring method that can detect whether or not a problem is occurring.

<Prior art> Single-point grounding systems have traditionally been adopted in testing systems that use large amounts of power, systems that generate strong magnetic fields, etc., in order to maintain the system and prevent control system malfunctions. has been done. And a ground fault in the single point grounding system,
In order to constantly monitor whether a short circuit has occurred, for example, it detects the ground current, detects that the detected current value deviates from the normal value, and notifies that a ground fault or short circuit has occurred. That's what I do.

In the above test systems that use high power, if the system is operated with a ground fault or short circuit occurring, a large current will flow to the equipment where the ground fault or short circuit has occurred, causing damage to the equipment. Not only that, but also because a large current flows through the grounding cable, the potential of other equipment increases rapidly based on the inductance component of the grounding cable, causing problems such as damage to other equipment or malfunction. do.

Even if the above-mentioned detection method is adopted, it will not be a fundamental solution to such problems, and it is necessary to detect the location of the ground fault or short circuit before starting the system. There is a strong need for the development of a monitoring system that can eliminate ground faults and short circuits before they cause equipment damage. In addition, in such a monitoring system, a large current flows during operation,
Since there is a risk that the monitoring system may be damaged by the strong magnetic field generated during operation, there is a strong desire to develop a monitoring system that takes this point into consideration.

<Purpose> This invention was made in view of the above-mentioned problems, and is designed to prevent ground faults and
To provide an abnormality monitoring method for a single-point grounding system that can reliably detect whether an abnormality such as a short circuit has occurred and is free from any risk of damage during system operation.

<Structure> In order to achieve the above object, the abnormality monitoring method of the present invention is based on a path from each branch point to an adjacent branch point, and a path from each branch point to an open end of a grounding network consisting of a single point grounding system. , and the path to the ground point,
Install transformers, use some of the transformers as excitation transformers, and use the remaining transformers as current detection transformers. Based on the detection signal of the current detection transformers, check whether any abnormal conditions such as short circuits or ground faults have occurred. This system detects whether an abnormal state has occurred when the system is not in operation, and then cuts off the connection between the transformer and the main body of the monitoring device, and demagnetizes the transformer before performing the next monitoring operation. By cutting off the connection between the transformer and the monitoring device main body while the system is in operation, it is possible to prevent damage to the monitoring device main body, and to detect whether an abnormal state has occurred.

However, the presence or absence of an abnormal state can be detected by installing an excitation transformer and a current detection transformer in each path and calculating the loop impedance based on the detection signal from the current detection transformer. In this case, it is preferable to excite the excitation transformer using a low-frequency sine wave that is less susceptible to the capacitance and inductance components of the ground system. In addition, a current detection transformer is installed only on the path leading to the ground point, an excitation transformer is installed on the remaining paths, the excitation transformers are excited with signals of different frequencies, and the current detected by the current detection transformer is subjected to spectrum analysis. The presence or absence of an abnormal state may be detected by doing so.

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

FIG. 3 is a schematic diagram showing an embodiment of a single-point grounding system test system, in which power source 1 is connected to equipment 2,
3, 4, etc. are connected via power cables 12, 13, 14, and the casing 2 of each device 2, 3, 4, etc.
2, 23, 24 and the power source 1 are grounded at one point via grounding cables 31, 32, 33, 30. In addition, the attached devices 4a, 4b, 4c, etc.
These attached devices 4a,
4b, 4c casing 24a, 24b, 24c
are also connected to the ground cable 33 via ground cables 33a, 33b, and 33c. Then, the casing 23 of the device 3 and the attached device 4c
The casing 24c is 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.

FIG. 1 is a diagram showing the electrical configuration for implementing the abnormality monitoring method of a single-point grounding system, and includes each branch point (connection point with the casing, grounding point, etc.) of the grounding cables 30, 31, etc. 70, 71...7n, each pair of excitation transformers CT10, CT11...CT1n, and current detection transformers CT20, CT21...CT2n.
The output signals of the excitation oscillator 51 and the demagnetization oscillator 54 are selectively applied to the amplifier 52 by the switch 55, amplified, and applied to the switch 53, and the amplified signals are applied to the switch 53. 53, the voltage is sequentially applied to the excitation transformers CT10, CT11...CT1n via the switches 80, 81...8n. And the current detection transformer
The output signals of CT20, CT21...CT2n are transferred to the switch 53 via switches 90, 91...9n.
The output signal of the switch 61 is amplified to a predetermined level by the amplifier 62, converted to a digital signal by the A/D converter 63, and then sent to the central processing unit CPU.
is applied to the display device 6 by the central processing unit CPU.
I am trying to drive 4. And the switch 6
By installing a switch 65 between 1 and the amplifier 62, current detection transformers CT20 and CT2
1...The output signal of the degaussing transmitter 54 can also be applied to the CT2n, and each of the above switches 80, 81...8
n, 90, 91...9n, 55, 65 are switched and operated by the central processing unit CPU.
In addition, an operating state instruction signal from the measured system S (test system) is applied to the central processing unit CPU.

FIG. 2 is a flowchart showing the operation of monitoring an abnormal state.
5 to the detection operation side, the channels are switched by the switching devices 53 and 61 that operate in synchronization with each other in the step, and the amplified signal is applied to the selected excitation transformer CT1n in the step, thereby the grounding cable 7n is switched to the detection operation side. is excited, the signal from the current detection transformer CT2n is collected in the step, and the signal from the current detection transformer CT2n is sent to the central processing unit CPU in the step.
For example, calculate the effective value by applying
Convert to loop impedance in step. Next, in step, the impedance is compared with a reference loop impedance previously stored in a memory (not shown). If the impedance is smaller than the reference loop impedance, the grounding cable 7 is
An alarm indicating that a ground fault or short circuit has occurred is displayed at step n, and it is determined in step whether or not the system to be measured is operating. Then, if it is not operating, the determination and processing below the step is performed as is, but if it is operating, the switches 80, 81...8n, 90, 9 are activated at the step.
1...9n, 55, 65 are switched in the opposite direction to the detection operation side, wait until the measured system S becomes non-operating in step, and switch 80, 81...8n, 90, 91...9 in step
n only is switched to the detection operation side, and in step, the demagnetizing side oscillator 54 is activated to demagnetize the excitation transformers CT10, CT11...CT1n and the current detection transformers CT20, CT21...CT2n,
Thereafter, the determination and processing below the step is performed.

On the other hand, if the loop impedance is greater than or equal to the reference loop impedance, the determination and processing below the step is performed as is.

In summary, the loop impedances are sequentially calculated from the ground cable 70 to the ground cable 7n, and it is possible to display that a ground fault or short circuit has occurred only for the ground cables whose impedance is smaller than the reference loop impedance.

Therefore, for example, as shown in Figure 3, if a ground fault has occurred inside the device 2 (it has occurred in the history of the previous test, or it has occurred due to a human work error, etc.) (possible), ground cable 7
The impedance of the loop formed by 2 and 70 becomes small, and the current detection transformer CT22, CT2
Since the output signal of 0 becomes large, the display device 64 can be driven to display that a ground fault has occurred in the single-point grounding system test system, and the power source 1 can be activated in the ground fault state. Damage to equipment caused by this can be prevented.

In addition, as shown in FIG. 3, if the circuit return current is designed to flow through the grounding cable 32 of the device 3, and if this grounding cable 32 is in contact with the attached device 4c, the attached Equipment 4
An unexpected large current flows through the grounding cable 33c of c.
As a result, the potential of the attached device 4c will rise significantly due to the inductance component of the grounding cable 33c, which may damage the control device or cause it to malfunction.
The impedance of the loop formed by 78 becomes small, and current detection transformers CT24, CT25,
Since the output signals of CT27 and CT28 become larger,
The display device 64 can be driven to display that a short circuit has occurred in the single-point grounding test system, and in this case, the equipment associated with starting the power source 1 in the short-circuit condition can also be displayed. damage can be prevented.

The above detection operation is performed only when the measured system is not in operation, and during the period when the measured system is in operation, the connection between the excitation transformer, the current detection transformer, and the switching device is cut off, and then, Since the excitation transformer and current detection transformer are demagnetized before the next detection operation, large currents and
Damage caused by strong magnetic fields can be reliably prevented.

FIG. 4 is a diagram showing the electrical configuration of another embodiment, and shows the connections 71, 72 between each branch point (the concept is used to include the connection point with the casing) of the grounding cables 31, 32...3n. ...7n, one excitation transformer CT11, CT12...CT1n is attached, and a current detection transformer CT20 is attached to the path 70 leading to the ground point, and the excitation oscillators 511, 512...51n are connected to each other. Output signals f1, f2,...fn with different frequencies are sent to amplifiers 521, 52.
2...52n, and switches 81, 82...
8n, the excitation transformer CT11,
It is applied to CT12...CT1n. Then, the output signal of the current detection transformer CT20 is
The voltage is applied to the amplifier 62 via the switch 80, amplified to a predetermined level by the amplifier 62, converted to a digital signal by the A/D converter 63, and applied to the central processing unit CPU. I like to drive. A switch 55 is connected between the excitation oscillators 511, 512...51n and the amplifiers 521, 522...52n.
By connecting 1,552...55n, the signals from the excitation transmitters 511, 512...51n,
The signal from the degaussing oscillator 54 can be selectively applied to the excitation transformers CT11, CT12...CT1n, and the switch 80 and the amplifier 62
By connecting the switch 550 between the demagnetizing transmitter 54 and the current detecting transformer CT20, it is possible to apply the signal from the degaussing transmitter 54 to the current detecting transformer CT20.
The switching operation is performed by the central processing unit CPU. Furthermore, an operating state instruction signal from the system to be measured S is applied to the central processing unit CPU.

Therefore, in this embodiment, the signals from the excitation oscillators 511, 512...51n are simultaneously applied to the excitation transformers CT11, CT12...CT1n, and the current detection signal from the current detection transformer CT20 is subjected to spectrum analysis. By this, paths with abnormally low loop impedance are detected,
It is possible to detect that a ground fault has occurred on this path. After performing the above detection operation, the switches 80, 81...8n are switched to the opposite state to operate the system to be measured, and then,
Before performing the next detection operation, switch 8
0, 81...8n, 550, 551...55n to send the signal from the degaussing transmitter 54 to each transformer.
By applying voltage to CT20, CT11...CT1n, each transformer CT20, CT11...CT1n is demagnetized, and by repeating the above operation, the amplifier, central processing unit, etc. can be reliably removed without any risk of damage. Abnormal conditions can be monitored quickly and easily.

Although only the case where the present invention is applied to a test system has been described above, the present invention can be similarly applied 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 calculates the impedance between the branch points of the ground cable when the power source is not activated, and detects abnormalities such as ground faults and short circuits based on this impedance. This makes it possible to reliably prevent inconveniences such as damage to equipment, damage to control devices, and malfunctions caused by starting the power source when an abnormality is occurring. Since this is carried out only when the grounding system is inactive and the transformer is demagnetized before the detection operation is performed, it has the unique effect that detection can be carried out without error and without damage to the detection device.

[Brief explanation of drawings]

Figure 1 is a diagram showing the electrical configuration for implementing the abnormality monitoring method for a single-point grounding system, Figure 2 is a flowchart showing the operation for monitoring abnormalities, and Figure 3 is an outline of the single-point earthing system test system. FIG. 4 is a diagram showing the electrical configuration of another embodiment. 1... Power source, 2, 3, 4... Equipment, 4a, 4
b, 4c...attached equipment, 30, 31...3n, 7
0,71...7n...Ground cable, CT10,CT
11...CT1n, CT20, CT21...CT2n...
Transformer, 53, 61...Switcher, CPU...Central processing unit, 80, 81...8n, 90, 91...9
n, 55, 65, 510, 511...51n...switch.

Claims (1)

[Claims] 1. A transformer is installed in a path from each branch point to an adjacent branch point, a path from each branch point to an open end, and a path to a ground point of a grounding network consisting of a single point grounding system, A part of the transformer installed in each path is used as an excitation transformer, and the remaining transformer is used as a current detection transformer. Based on the detection signal of the current detection transformer, abnormal conditions such as short circuits and ground faults are detected. 1. An abnormality monitoring method for a single point grounding system, characterized by detecting whether or not the transformer is present, then cutting off the connection between the transformer and the main body of the monitoring device, and further demagnetizing the transformer before performing the next monitoring operation. 2 Attach an excitation transformer and a current detection transformer to each path, and sequentially excite the excitation transformer, detect the loop current of each path with the current detection transformer that pairs with the excitation transformer, and detect the loop current based on the loop current. An abnormality monitoring method for a single point grounding system according to claim 1, which detects whether or not a ground fault or short circuit has occurred by calculating loop impedance. 3. An abnormality monitoring method for a single-point grounding system according to claim 2, wherein the excitation transformer is excited by a low-frequency sine wave that is not easily affected by the capacitance and inductance components of the grounding system. 4 The transformer installed on the path leading to the ground point is used as a current detection transformer, the remaining transformers are used as excitation transformers, the excitation transformers are excited with signals of different frequencies, and the current flowing through the ground point is detected by the current detection transformer. 2. An abnormality monitoring method for a single point grounding system according to claim 1, which detects whether or not a ground fault has occurred by detecting the current flowing through the grounding point and performing spectrum analysis of the current flowing through the grounding point.