JPS61138178A - Ground fault detection device - Google Patents

Abstract

PURPOSE:To detect a ground-fault with high sensitivity and to specify an electric circuit where the ground-fault arises by installing a connection type ground-fault detector to a common DC electric circuit and installing through-type ground-fault detectors to plural branch electric circuits branched from the common DC electric circuit. CONSTITUTION:The generation of the ground-fault with all the branch electric circuits 2 including the common electric circuit 1 can be monitored by the connection type ground-fault detector 3 installed to the circuit 1. The circuits 2 are discretely monitored by the through-type ground-fault detectors 4 installed for each of the circuits 2. The detector 3 has the higher sensitivity than the sensitivity of the detector 4 and therefore even the ground-fault of the high resistance which is not detectable with the detectors 4 with all the circuits 1, 2 can be detected as well. The ground-fault is therefore detected with the high sensitivity by the detector 3 and the electric circuit where the ground-fault arises is specified by the detectors 4.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ground fault detection device for detecting a ground fault occurring in a DC power line of a DC power supply line for measurement in a plant or the like.

(Prior Art and Object of the Invention) Conventionally, as a device for detecting a ground fault occurring in a DC circuit, for example, as shown in Utility Application No. 175604 of 1981, a device is used that detects a ground fault that occurs in a DC circuit by detecting a ground fault on both sides of 91 pairs of resistors connected in series. The positive of the DC circuit,
A connected ground fault detector or a zero-phase current transformer is used, which connects each to the negative pole and connects the connected part to the ground via a variable resistance for setting, and compares the detection signals from the respective resistors to detect a ground fault. The former has the feature that it can detect ground faults with higher sensitivity than the latter, and its sensitivity is adjustable. By the way, a DC power line usually consists of a common line and multiple branch lines branching off from it, and it is difficult to determine in which part of these branch lines a ground fault has occurred. To know,
It is necessary to install ground fault detectors on all of these branch lines. However, in principle, connected type ground fault detectors can detect ground faults that occur at any point in the electrical circuits of the same system. It is impossible to use it to identify the electrical circuit where a short circuit has occurred. On the other hand, the through-type ground fault detector can be used in this way, that is, it can be installed for each of a plurality of branch electrical lines to be detected for ground faults, and ground faults can be detected for each corresponding electrical line. However, such penetrating ground fault detectors have relatively low detection sensitivity and it is difficult to adjust the sensitivity, so it is difficult to effectively detect ground faults and manage electrical circuits using only these. The purpose of this invention is to eliminate the conventional drawbacks of the conventional method and to enable highly sensitive ground fault detection and effective identification of a ground fault generating circuit.

(Structure of the Invention) The present invention aims to achieve all of the above-mentioned objects.
A pair of series-connected resistors are provided, each connected to the negative electrode, and a gold-plated grounding circuit is grounded from the connection point of the resistors through a variable resistor for setting. A connection-type ground fault detector for detecting faults is installed in a common DC line, and a pair of zero-phase current transformers' connected in series with opposite polarities are installed to penetrate the DC line. a through-type ground fault detector that detects a ground fault by comparing detection signals from the detector, installed in a plurality of branch circuits branching from the common DC circuit, and an output section of the plurality of through-type ground fault detectors; The gist is that the output section of the connected ground fault detector is connected to a common data collection alarm section through a multiplexer, and the details are as follows based on an example. .

In the figure, reference numeral 1 indicates a common DC circuit, and numeral 2 indicates a plurality of branch circuits branching off from this common circuit 1. Reference numeral 3 indicates a connection type ground fault detector, and the reference numeral 4 with a 0 indicates a through-type ground fault detector, in which this detector 3 is installed in the common electric line 1. Installed for each branch circuit 2. The output sections 5 of the plurality of through-type ground fault detectors 4 are connected to a common data collection alarm section 8 via a multiplexer 6, and the output section 7 of the connected ground fault detector 3 is connected to a common data collection alarm section 8. Here, the connection type ground fault detector 3 is connected to the positive and negative poles of the DC circuit, respectively.
A pair of resistors R1 and R2 connected in series is provided, and a setting variable resistor VRfc is connected from the connection point of the resistors R1 and l'h.
A grounding circuit 9t to be grounded through the ground is provided, and each of the resistors R1
, R2 to detect a ground fault. A specific configuration for detecting a ground fault by comparing detection signals is appropriate, such as the configuration shown in the above-mentioned Utility Model Application No. 1'75604 of 1982, for example. The through-type ground fault detector 4 also includes a pair of zero-phase current transformers 10.10 connected in series with opposite polarities through which a DC circuit passes through, and detects signals from these zero-phase current transformers 10.10. This is a configuration that detects ground faults by comparison. The configuration for detecting a ground fault by comparing the detection signals is to configure an AC bridge circuit with a pair of resistors Ra and IR4 as shown in the figure, and then perform appropriate operations such as differential amplification, positive and negative peak hold, addition, smoothing, etc. Although the configuration is such that a detection output is obtained through signal processing, other suitable configurations may be used. The data collection alarm unit 8 has specific functions such as data collection, display, printing, and alarm generation using a microcomputer, etc., based on the ground fault detection signals of the detectors 3 and 4. A desired function can be provided. Reference numeral 8' denotes a device such as a pre-receiver. It is possible to monitor the occurrence of a ground fault in the electrical circuit 2, and at the same time, the through-type ground fault detector 4 installed for each branch electrical circuit 2 can individually monitor those branch electrical circuits 2.

However, since the maximum sensitivity of the connection type ground fault detector 3 is higher than that of the through-type ground fault detector 4, all electrical circuits 1 and 2 have high A ground fault in a resistor can be detected. Therefore, it is possible to detect the possibility of a ground fault with a lower resistance occurring in the future, which is a problem, or to detect a high resistance ground fault, which is not a problem, at an early stage, making it possible to take prescribed countermeasures. can.

If a low-resistance ground fault occurs in the branch circuit 2, it can be detected by the through-type ground fault detector 4 installed in the branch circuit 2, and the branch circuit in which the ground fault has occurred can be detected. 2 can be specified. The output of the nine-through ground fault detector 4 installed in each branch circuit 2 is sent to the multiplexer 6.
Predetermined data is input to the data collection alarm unit 8 via
This data collection, etc. can be suitably performed using the detection output of the connection type ground fault detector 3 as a timing. That is, when the connection type ground fault detector 3 detects a ground fault, the multiplexer 6 is scanned and all data output from each of the through-type ground fault detectors 4 is collected.
It is possible to effectively collect and respond to the presence or absence of a ground fault in a ground fault.

In such a case, if the sensitivity of the connection type ground fault detector 3 is always maintained in a high sensitivity state, even if a high resistance ground fault occurs that the penetrating type ground fault detector 4 cannot detect, the branch will always be activated. Data regarding the electric circuit 2 will be collected, resulting in waste. However, in the present invention, in order to ensure that the detection sensitivity of the connected ground fault detector 3 is variable by the fully variable resistance VR, the first step is to constantly monitor the sensitivity as high sensitivity, and then When a ground fault occurs, as a second step, the sensitivity is lowered to the same level as the sensitivity of the all-penetrating ground fault detector 4, and the ground fault detected later by the connected ground fault detector 3 is monitored. A fault can also be detected by the penetrating ground fault detector 4, and in this way, it is possible to collect data and specify the branch circuit z in which a ground fault has occurred. In addition, even if a low resistance ground fault occurs while the connection type ground fault detector 3 is in a high sensitivity state, a ground fault occurs in the same manner and the connection type ground fault detector 3 is in a high sensitivity state.
Of course, it is possible to specify.

(Other Structures and Effects of the Invention) Next, as shown in FIG. ? [i- In addition, the through-type ground fault detector 4 is provided with an output direct holding switch 13 for selectively outputting the comparison output of the detection signal to the output value holding capacitor 12, and the capacitor 12 a comparator 14fc for detecting the ground fault by completely comparing the output value held in the output value with the comparison output, and the ground release switch 11;
By configuring the output value holding switch 13 to be operated intermittently in conjunction with the output value holding switch 13, the effects described below can be achieved. In the figure, reference numeral 15 is a differential amplification section, 16 and 16' are positive and negative peak hold sections, 17 is an addition section for obtaining the comparison output, and 18 is a subtraction circuit. This is the sample hold section. In the figure, the output value holding switch 13 is configured as a changeover switch, and is configured to selectively input the comparison output of the addition section 17 to the comparison section 14 directly via the capacitor 12. However, in addition to this, it may be configured as an ON-OFF switch, and there may be two paths from the addition section 17 to the comparison section 14, a direct path and a path via the capacitor 12t.

In the above configuration, the ground release switch 11 and the output value holding switch 13 are all interlocked by a timing control circuit configured in the data collection alarm section 8, etc., and when the switch 11 is open, the switch 13 is is connected to the capacitor 12 side, and when the switch 11 is closed, the switch 13 is connected to the comparator 14 side. However, switch 1
3 is connected to the capacitor 12 side, the capacitor 12 is charged with the comparison output voltage of the adder 17 at this time.

At this time, the switch 11 is open and the grounding circuit 9 is ungrounded, so the capacitor 12 is charged with the comparative output voltage when the electric path 1 is ungrounded.

When the switch 11 is closed and the grounding circuit 9 is grounded to achieve a predetermined detection state, the switch 13 closes the comparison section 1.
4 side, the comparator 14 compares the current comparative output voltage with the voltage of the capacitor 12, that is, subtracts it, and generates a ground fault detection output when a difference of more than a predetermined value occurs. , Through the above-described operations, predetermined data is collected and a response is taken.

In this way, the penetrating type ground fault detector 4 in this configuration serves as a comparison point in the comparison section 14 when the connected type ground fault detector 3 is ungrounded at predetermined time intervals and is in a steady state. As the voltage is updated to the capacitor 12, that is, it is initialized, and a ground fault is detected by comparing this voltage with the current comparison output voltage, the characteristics of each current transformer will differ and the voltage will change over time. Even if the state of the individual branch circuits 2, that is, the stray capacitance, electric field, magnetic field strength, etc., changes,
Stable ground fault detection can be performed without being affected by these factors.

(Effects of the Invention) As described above, the present invention is configured by combining a connecting type ground fault detector and a penetrating type ground fault detector in an extremely rational manner, so that it will be possible to prevent ground faults with low resistance from occurring in the future. It is possible to detect the possibility of a high-resistance ground fault occurring at an early stage when it is not a problem, and in this way, prescribed countermeasures can be taken. This has the effect of making it possible to reliably identify the electrical path where the occurrence occurred. Mano The present invention performs initialization in a very rational manner in relation to a grounding type ground fault detector when comparing detection signals from a pair of zero-phase current transformers in a penetrating type ground fault detector. As a result, there is a feature that deficient ground fault detection can be performed in a stable manner at all times without considering changes in the state of each electric circuit or changes in the characteristics of the zero-phase current transformer.

[Brief explanation of the drawing]

FIG. 1 is an overall schematic system explanatory diagram of the configuration of the present invention, FIG.
FIG. 3 is a more detailed system explanatory diagram of the configuration of the present invention. Code 1...Common electrical circuit, 2...Branch electrical circuit, 3...Connection type ground fault detector, 4...Penetration type ground fault detector, 5, 7...
・Output section, 6... Multiplexer, 8... Data collection alarm section, 9... Grounding circuit, 10.10... Zero-phase current transformer, 11... Grounding release switch, 12... Capacitor for holding output value, 13... Switch for holding output value,
14... Comparison unit, 15... Differential amplifier, 16, 1
6'...Positive, negative peak hold section, 17.../II
I calculation section, 18...sample hold section.

Claims (2)

[Claims] (1) A pair of series-connected resistors are provided, each connected to the positive and negative poles of the DC circuit, and a grounding circuit is provided that connects the resistors to ground via a setting variable resistor, and detects a detection signal from each of the resistors. A connection-type ground fault detector that detects ground faults by comparing the ground faults is installed in a common DC line, and a pair of zero-phase current transformers connected in series with opposite polarities that penetrate the DC line are installed. A through-type ground fault detector that detects a ground fault by comparing detection signals from a zero-phase current transformer is installed in a plurality of branch circuits branching from the common DC circuit, A ground fault detection device, characterized in that the output part of the detector is connected to a common data collection alarm part through a multiplexer, and the output part of the connected ground fault detector is connected to a common data collection alarm part. (2) A pair of series-connected resistors are provided which are connected to the positive and negative poles of the DC circuit, respectively, and a grounding circuit is provided which connects the resistors to the ground via a setting variable resistor, and the detection signal from each of the resistors is provided. A connection-type ground fault detector that detects ground faults by comparing the ground faults is installed in a common DC line, and a pair of zero-phase current transformers connected in series with opposite polarities that penetrate the DC line are installed. A through-type ground fault detector that detects a ground fault by comparing detection signals from a zero-phase current transformer is installed in a plurality of branch circuits branching from the common DC circuit, The output of the detector is connected through a multiplexer and the output of the connected ground fault detector is connected to a common data collection alarm part, and the connected ground fault detector has a ground release circuit connected to the ground circuit. In addition to providing a switch, the through-type ground fault detector includes an output value holding switch for selectively outputting the comparison output of the detection signal to an output value holding capacitor, and an output value held in the capacitor. and,
The ground fault is characterized in that a comparison section is provided to detect the ground fault by comparing the comparison output, and the grounding release switch and the output value holding switch are operated intermittently in conjunction with each other. Fault detection device.