JPS6318918A - Dc leakage alarm device - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Purpose of the Invention (Field of Industrial Application) The present invention is directed to a control DC power supply circuit that is installed in a factory, transformer power plant, etc. and has circuit branches for multiple loads. This invention relates to a DC earth leakage alarm device that detects and alarms line grounding faults.

(Prior Art) This type of DC leakage alarm device generally includes a grounding detector that detects the occurrence of a grounding fault, a ground leakage detector that is installed in each branch circuit and detects the leakage current of that branch circuit, and a grounding detector that detects the occurrence of a grounding fault. It consists of a grounding detector and a ground leakage alarm that warns or displays a grounding accident based on signals from the ground leakage detector.

FIG. 6 shows the configuration of a conventional DC S lightning warning device in a control DC power supply circuit.

1 is a DC power supply. 2+, 22. ..., 2n detects the difference current flowing through the line of each branch circuit branched into multiple branches from the DC power source (1), and outputs the corresponding voltage. Second. . . . is the n-th earth leakage detector. Reference numeral 3 denotes a grounding detector installed immediately after the DC power supply 1 to detect a line grounding fault. 4 is each earth leakage detector 21.22.・
..., input the output signal from 2n (hereinafter referred to as earth leakage detection o2 when one is shown as a representative) and the output signal from the grounding detector 3, and determine in which branch circuit a grounding fault occurs. This is an earth leakage alarm that displays an alarm to indicate whether something has happened.

FIG. 7 shows the logic circuit inside this 'JA electric alarm device 4.

The same functional parts as in FIG. 6 are given the same reference numerals.

Reference numeral 5 denotes an earth leakage detection circuit which inputs the output signal from the earth leakage detector 2 and outputs a signal when the output signal exceeds a set value. af
The logic circuit of the fi alarm 4 is an AND 6 of the output signal from the earth leakage detection circuit 5 and the output signal from the grounding detector 3 which outputs a signal when one line is grounded. A
The reason for using the ND circuit is to detect grounding faults more accurately, and if there is only a leakage in each branch circuit, then the
Although it is possible to detect electrical leakage using only one sensor, a dual detection mechanism is used to prevent false detections.

With the above configuration, DC! The operation of the lightning warning device is as follows.

In FIG. 6, point A in the diagram of the first branch circuit is defined as the line ground fault point. When point A is grounded, a current flows from the positive pole of DC power supply l, through the positive side of the line of first earth leakage detector 21, and from point A to the negative pole of DC power supply 1, through grounding detector 3, as shown by the solid arrow. increases. At this time, the first leakage fti detector 21 detects and outputs a current difference that occurs in the line of the first branch circuit. Further, the grounding detector 3 detects grounding current and outputs a corresponding signal. and,
When signals are output from both the earth leakage detector 21 and the earthing detector 3, the electric alarm 4 will display an alarm according to the logic circuit shown in FIG.

Hereinafter, in the operation 1i'' of ``H'', if a line ground fault point occurs on the negative side of the line, the same applies to the gate, and an alarm display of the leakage point is performed via the earth leakage alarm 4.

(Problems to be Solved by the Invention) However, recently, a capacitor grounding circuit 7 for surge voltage protection is increasingly provided in a part of one branch circuit. Therefore, when the point A is grounded, the capacitor is charged 11! as shown by the two-dot chain arrow in the figure. In addition to the first earth leakage detector 2I of the branch circuit through which the current flows and the fault has occurred, there is also another earth leakage detector 2n that detects a difference current, such as the n-th earth leakage detector 2n. As a result, when a line grounding fault occurs, alarms are output from multiple branch circuits, making it impossible to determine which branch circuit the grounding fault occurred in, which hinders prompt recovery from the accident. was there.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a DC earth leakage alarm device that can reliably detect a branch circuit where an accident has occurred in the event of a line grounding accident.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a current detector in each branch circuit for determining whether more current flows on the positive side or the negative side of the line, and A grounding detector is installed to determine whether the positive side or negative side of the line is grounded, and the logic for comparing each grounding judgment and displaying an alarm when it is determined that they are the same ground, but not displaying an alarm when it is determined that the ground is reversed. It is equipped with a circuit.

(Function) In the branch circuit where the line grounding fault occurred and the branch circuit where the capacitor grounding circuit is installed, the magnitude relationship of the current flowing to the positive and negative sides of the line is opposite, so the grounding fault occurs. An alarm will be displayed only for the branch circuit that has failed, and no alarm will be displayed for other normal branch circuits. Thereby, it is possible to reliably display an alarm only for the branch circuit in which a line grounding accident has occurred.

(Embodiment) FIG. 1 shows the configuration of a DC earth leakage alarm device in a control DC ffi source circuit according to an embodiment of the present invention.

To simplify the diagram, only two branch circuits are shown: a branch circuit with point A grounding and a branch circuit with a capacitor grounding circuit. Components with the same names as those in FIG. 6 are given the same reference numerals. 2+ and 2n are conventional earth leakage detectors. Reference numeral 3 denotes a grounding detector that outputs a signal corresponding to the positive or negative polarity of the ground line when the line is grounded.

8 and 8n determine the magnitude of the current flowing in the line of each branch circuit and output the corresponding signal. This is the n-th current detector (hereinafter, when one of the current detectors 81°8n is represented, it will be referred to as current detector 8).

FIG. 2 shows the configuration of this current detector 8. 9p.

9++ are shunt resistors inserted on the positive side and negative side of the line of one branch circuit, respectively. 10 is shunt resistance 9
Input the voltages Ss and S2 generated from P and 9N.

As α≧1, α(IS+ 1-1521) is the signal S3
This is a comparison amplifier circuit that outputs as follows.

11 inputs the signal S3, and if the signal S3 is positive, outputs a signal S4 indicating that the current on the positive side of the line of the branch circuit is large;
Conversely, if the signal S3 is negative, the output circuit outputs a signal S5 indicating that the current on the negative side of the line of the branch circuit is large, and if the signal S3 is zero, it outputs nothing.

Reference numeral 4 denotes an electric alarm which receives signals from the main detectors 2+ and 2n, the earth detector 3, and the current detectors 8+ and 8n and outputs an alarm when a grounding accident occurs.

A logic circuit within this earth leakage alarm 4 is shown in FIG.

A grounding detector 3 monitors all branch circuits and outputs a signal Sp to the earth leakage alarm 4 when the positive side of the line is grounded, and a signal SN when the negative side of the line is grounded.

Reference numeral 8 denotes the aforementioned current detector, which outputs a signal S4 when the current on the positive side of each branch circuit line is large, and outputs a signal S5 when the current on the negative side of the line is large. The logic circuit in the earth leakage alarm 4 uses the signal Sp output from the grounding detector 3, the signal S4 output from the current detector 8, and the earth leakage detection circuit 5.
AND16 of each output signal of the signal S7 outputted from the grounding detector 3, the signal S5 outputted from the current detector 8, and the signal S5 outputted from the current detector 8 and the earth leakage detection circuit 5.
A N D 1 of each output signal of the signal S7 output from
This is a logic circuit that takes 0R18 of the output signal of each AND16 and 17 and displays an alarm.

Next, the operation of the DC earth leakage alarm device will be explained with further reference to the time charts of FIGS. 4 and 5.

Normally, as shown in FIG. 4, the signals S+ to S5 of the current detector 8 are all 0 (v) before the load is activated at the TL point. When the load is activated at point TL, shunt resistance 9p, 9
Load current flows through ++, (-B St is positive voltage, signal S
2 is a negative voltage. At this time, each shunt resistor 9p, 9
The magnitude of the current flowing through ++ is the same, and the comparison amplifier circuit 10
The output signal S3 remains at 0(v).

Therefore, even when the load is activated, the discrimination output circuit 11 does not output the signals S4 and S55. Further, the signals SP and SN are not outputted from the grounding detector 3 either. Therefore, if the line is normal according to the internal logic circuit, the alarm will not be displayed.

Next, as shown in FIG. 5, when a grounding fault occurs at the TA time after the load is activated at the TL time, the grounding detector 3 outputs a signal Sp based on the grounding of the positive line. On the other hand, in the current detector 8I of the branch circuit where the fault occurred, a large current flows through the shunt resistor 9P on the positive side of the line, and the signal St increases. On the other hand, since the change in the current flowing from the load through the shunt resistor 9++ can be ignored compared to the change in the current flowing through the shunt resistor 9P, it can be considered that the signal S2 does not change. Therefore, since l5II 1321>O, the comparison amplifier circuit 10 outputs a positive signal S3. As a result, the discrimination output circuit 11 outputs the signal S4 as the output of the current detector 8 since the signal S3 is positive. Further, the earth leakage detection circuit 5, which receives the signal S6 from the earth leakage detector 2 that has detected the earth leakage, also outputs the signal S7. These three signals SP, S4. AND16 which inputs S7 becomes active and displays an alarm via 01118 for the branch circuit where the accident has occurred.

On the other hand, in the current detector 82 of the branch circuit having the capacitor grounding circuit 7, the current on the negative side of the line is greater than the positive side of the line due to the capacitor charging/discharging current, and the current is 15+ I -1521
In contrast to the current detector 81 where <0 and an accident occurred, the signal S
Outputs 5. However, the signal S++ from the ground detector 3
is not output.

Since the output of AND17 cannot be activated and, of course, the output of AND16 is not output, no alarm is displayed in the branch circuit having the capacitor grounding circuit 7.

The above operation is the same even when the negative side of the line is grounded.

In this way, when the earth leakage detector 2 is activated, by comparing the direction of the grounding current detected by the earthing detector 3 and the current detector 8, it is possible to ensure that only the branch circuit where the -a earthing fault has occurred is detected. An alarm can be displayed.

[Effects of the Invention] As described above, according to the present invention, when a line grounding accident occurs in a control DC power supply circuit that is branched into multiple circuits, the grounded branch circuit can be reliably detected even if there is a capacitor grounding circuit. Accident detection and recovery work can be carried out quickly.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a DC earth leakage alarm device in a control DC power supply circuit according to an embodiment of the present invention, Fig. 2 is a block diagram of the current detector of Fig. 1, and Fig. 3 is a block diagram of the earth leakage alarm of Fig. 1. Logic circuit diagram of the device, Figure 4 is a time chart of each signal in Figure 2 when normal, Figure 5 is a time chart of each signal in Figure 2 when point A is grounded, Figure 6 is for conventional control. FIG. 7 is a block diagram of a DC earth leakage alarm device in a DC power supply circuit, and FIG. 7 is a logic circuit diagram of the earth leakage alarm device of FIG. 6. 1... DC power supply, 2.2 +, 2 x, 2n...
Earth leakage detector. 3... Earthing detector, 4... Earth leakage alarm, 5... Earth leakage detection circuit, 7... Capacitor grounding circuit, 8h8 +
182...Current detector, 9P, 9N...
Shunt resistor, 10... Comparison amplifier circuit, 11...
Discrimination output circuit. l/゛-1, Figure 1 Figure 2 M Figure 3 L Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] A DC earth leakage alarm system that monitors earth leakage in a control DC power supply circuit that is branched into multiple circuits includes a grounding detector that detects whether the positive or negative side of the line is grounded when a single line grounding accident occurs; A current detector detects the direction of the leakage current in the branch circuit, and the outputs of the grounding detector and the current detector are input, and if the directions of the leakage current detected by each detector match, an alarm is output, A DC earth leakage alarm device characterized by being provided with a logic circuit that does not output an alarm in the opposite case.