JPS62236320A - Dc grounding detector - Google Patents

Abstract

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

Description

[Detailed description of the invention] [[1st object] of the invention (Industrial application field) The present invention relates to a DC ground fault detection device.

(Prior art) In a conventional DC ground fault detection circuit, a variable resistor is connected between both poles of a DC power supply, and the adjustment terminal of the variable resistor is grounded via a ground fault detection relay. The earth fault detection relay is rendered inoperable by adjusting the variable resistor to maintain the same potential between each pole and the ground, and by reducing the current flowing through the earth fault detection relay or the voltage between the adjustment terminal and the ground to zero. On the other hand, when a ground fault occurs, a ground fault voltage is generated between the adjustment terminal and the ground, and the ground fault has been detected by detecting a constant voltage or current using a ground fault detection relay.

(Problems to be Solved by the Invention) Such conventional methods rely on a device that detects a constant value of the voltage or current flowing through the ground fault detection relay, so it is not related to the voltage value of the DC power supply, and the There is a problem in that the ground fault detection sensitivity (ground fault detection voltage/DC power supply voltage) is not constant when the voltage value of the ground fault varies.

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive and simple DC ground fault detection device that can provide constant ground fault detection sensitivity even when the DC power supply voltage fluctuates.

[Structure of the invention]

(Means for Solving the Problems) The present invention includes a DC power supply, a DC power supply connected in parallel to the DC power supply,
Two variable resistors with adjustment terminals that can be divided into positive and negative electrodes, unidirectional elements connected to the adjustment terminals of these variable resistors in opposite directions, and this unidirectional element. This is a DC ground fault detection device characterized in that the other end is connected and a current detection device or voltage detection device is connected and grounded.

(Function) In a circuit configured in this way, the resistance value divided into the positive and negative poles is sufficiently small compared to the resistance between each pole and the ground during normal operation, and the ground fault resistance value in the event of a ground fault is Select it so that it is sufficiently large compared to . Also, the forward direction of the unidirectional element is connected to the ground, and the voltage applied between the negative electrode of the variable resistor and the unidirectional element.

Adjust the variable resistor so that the voltage is smaller than the voltage between this one-way element and ground. Similarly, for a variable resistor in which the forward direction of the unidirectional element is opposite to the ground, adjust so that the voltage between the positive electrode and the unidirectional element is smaller than the voltage between the positive electrode and the unidirectional element. Adjust each variable resistor as follows, during normal operation.

Since voltages in the opposite directions relative to ground are applied to each one-way element, current does not flow through the current detection device connected between the one-way element and ground, and the device does not operate. On the other hand, in this circuit, if the negative electrode has a ground fault, the ground fault resistance is sufficiently small compared to each voltage dividing resistor, so the ground potential becomes almost equal to the negative electrode potential, so the one connected from the positive electrode to the ground in the forward direction Since a current flows through the directional element, the current detection device operates, making it possible to detect a negative electrode ground fault. Similarly, when the positive electrode is grounded, current flows through the unidirectional element connected in the opposite direction from the positive electrode to the ground, making it possible to detect the grounding fault of the positive electrode. Further, since the current flowing into each unidirectional element is determined by the resistance ratio divided between the two poles, a constant ground fault detection level can be obtained regardless of fluctuations in the power supply voltage.

(Example) Next, one embodiment of the present invention will be described.

FIG. 1 shows two sets of adjustment resistors 2 and 4 connected in parallel to a DC power source 1, and unidirectional elements 6.7 connected in opposite directions to the adjustment terminals 3.5 of these adjustment resistors, respectively. A DC ground fault detection circuit consisting of a galvanometer 9 connected between the other end of the unidirectional and ground is shown.

Next, the operation of the present invention will be explained with reference to FIG.

Resistance RNt l RN2 indicates a resistance value divided into the positive and negative sides of adjustment resistor 2, respectively, and resistor RPt r
RP* indicates the resistance value divided into the positive electrode side and the negative electrode side of the adjustment resistor 4, respectively. Further, the resistances RP and RN are the resistance values between the positive electrode and the negative electrode, respectively, and the ground. It is assumed that each resistance value under normal conditions is selected and adjusted so that the following conditions are satisfied.

RP+ RN) IINL+ RN2+ RPt
w RPz When each resistance value is selected as above, voltages in opposite directions are applied to each unidirectional element 6, 7, so no current flows through the unidirectional elements 6, 7, so under normal conditions The galvanometer 9 becomes inactive.

Next, considering the case where a ground fault occurs on the negative electrode side, the resistance RN between the negative electrode side and the ground satisfies the relationship RN (RP* RNx + RN2), so the voltage between the negative electrode and the ground is equal to the power supply voltage E. Then you get the following.

In addition, the potential on the anti-ground side of the unidirectional element 7 is resistor RN1*
Since the value is divided into RN, it is as follows.

From the above, since a voltage is applied to the unidirectional element in the forward direction, a current flows through the galvanometer 9, and a ground fault of the negative electrode can be detected.

Similarly, when the positive electrode side is grounded, a forward voltage is applied to the unidirectional element 6 and a current flows to the galvanometer 9.

As explained above, according to the present invention, the current flowing through the galvanometer 9 depends on the resistance ratio determined by the ground faults of the positive and negative poles, so that the current flows at a constant level regardless of fluctuations in the power supply voltage. It becomes possible to obtain a ground fault detection level of Moreover, according to the present invention, the positive electrode side.

By changing the ground fault detection level on the negative electrode side or detecting the direction of the current flowing through the galvanometer, it is also possible to determine whether the ground terminal is present.

In the above description, a galvanometer was used as the ground fault detection device, but the same effect can be obtained even if voltage is detected. Furthermore, when a light emitting diode is used as the unidirectional element, the ground electrode can be determined without using a galvanometer, and a simpler DC ground fault detection device can be obtained.

〔Effect of the invention〕

According to the present invention, it is possible to obtain a constant ground fault detection level that is independent of fluctuations in power supply voltage6.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a DC ground fault detection circuit showing one embodiment of the present invention, and FIG. 2 is a configuration diagram showing another embodiment.
It is a diagram. 1... DC power supply 2... Variable resistor 3...
・Adjustment terminal 4...Variable resistor 5...Adjustment terminal 6...Unidirectional element 7...Unidirectional element 8...Load 9...Ground fault detection relay agent Patent attorney rules Ken Chika Yudo Hirofumi Mitsumata Figure 1 Figure 2

Claims (1)

[Claims] A DC power supply, two sets of variable resistors that are connected in parallel to this DC power supply and have adjustment terminals that can be divided into positive and negative pole values, and the adjustment terminals of these two sets of variable resistors are connected in opposite directions to each other. A DC ground fault detection device comprising: a unidirectional semiconductor element connected to the two sets of unidirectional semiconductor elements; and a current detection device whose one end is connected to these two sets of unidirectional semiconductor elements and whose other end is grounded.