JPS60113618A - Ground-fault detecting relay circuit - 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 [Technical Field of the Invention] The present invention relates to power supply equipment for supplying current to high inductance circuits, and particularly to a ground fault detection relay thereof.

[Prior art]

Conventionally, there has been a power supply facility as shown in the circuit diagram of FIG. 1 as a means of achieving this goal. In the figure, numeral 1 denotes a load coil, which has a large inductance and is composed of a resistance R that inevitably exists accordingly. 2 is a DC power supply equipment that can control voltage. Although the type of power supply equipment 2 is expressed as a semiconductor rectifier, this is not essential to the present invention, so there is no need to limit it to this type. Reference numeral 3 is a current shunt whose one end is connected to the ground bus and the other end is connected to the connection bus between the load coil 1 and the power supply equipment 2, thereby stabilizing the potentials of the load coil 1 and the power supply equipment 2. Further, 4 is a voltage relay for detecting a ground fault.

Note that 5 represents the ground fault resistance when insulation deterioration occurs.

Next, the operation of the circuit shown in FIG. 1 will be explained using the waveform diagram shown in FIG. 2. This figure 2 shows the current i flowing through the load coil 1,
This shows the waveform of the applied voltage V over time.
Time t. -1, period is the current rise period, V =
According to the relational expression L d i / d t + Ri, 1
==1. -16 in a short time, d i /
It is necessary to increase the current change rate expressed by dt, and therefore, when the inductance of the load coil 1 is large, it is necessary to apply a high voltage to the end of the load coil 1. On the other hand, 1=1. The period ˜t is a current flat period, and since the current change rate di/dt=o, ■=几i.If the resistance R of the load coil 1 is small, a low voltage is sufficient.

Next, 1=1. The period ~t is a current falling period, and like the current rising period, it is necessary to apply a high voltage in the reverse direction.

If the other four ends of the grounding side of the load coil l in Fig. 1 have a ground fault resistance Re represented by 5 and insulation deterioration occurs, and at this time the resistance of the shunt 2 is R5) I, the ground fault current ie, =
A current having the same waveform as V/(Re-4-Rsa) and having a different level from the t-pressure V in FIG. 2 flows. This ground fault current 1e is converted into voltage by a shunt 3 and then detected by a voltage relay 4 for ground fault detection.

However, in the conventional ground fault detection method consisting of this shunt 3 and voltage relay 4, when point A in Fig. 1 is completely grounded, Re = 0, so the terminal voltage of the load coil 1 is normally , because the current is limited only by the resistance RsH of the minute shunt 3,
When the voltage applied to the load coil 1 at the time of current rise and fall is large, a large ground fault current flows. Therefore, when setting to perform ground fault detection using this current, it is possible to detect a ground fault when the voltage of the load coil 1 is low during flat top or when the ground fault resistance Re becomes a relatively large value due to insulation deterioration, etc. In this case, the ie earth final current is small, the detection voltage of the shunt 3 is small, and it may be difficult to operate the earth fault detection relay 4. Furthermore, if the resistance value R5H of the shunt 3 is set to a large value so as to operate in a small current range, the voltage of the shunt 3 will increase in the event of a large current ground fault, and an overvoltage will be applied to the ground fault detection relay 4. , there is a possibility that the load coil 1 may be burnt out or the ground potential of the load coil 1 may rise.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional methods.In order to detect ground fault current, a saturable reactor type DC current transformer is used, and the ground fault current level is set to a predetermined value. It is possible to prevent a large level of current from appearing on the secondary side even if the current level exceeds The purpose is to provide a fault detection relay circuit.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 shows an embodiment of the present invention, in which the shunt 3 and ground fault detection voltage relay 4 in the conventional example of FIG. 1 are replaced by a DC transformer 6.
a and the ground fault detection control section 6b [replaced].

FIG. 4 is an external view showing an embodiment of a DC current transformer 6a according to the present invention, in which a central conductor 6C passing through the annular DC current transformer 6a is used as a primary winding, one end of which is grounded, and the other end of which is a primary winding. is connected to the load coil 1 and the power supply equipment 2, and a ground fault detection control section 6b is arranged near it.

FIG. 5 shows a detailed circuit diagram of one embodiment of the earth fault detection relay circuit of the present invention, in which a DC current transformer 6a is wound with secondary windings in opposite directions around two annular cores with low saturation magnetic flux density. A wire is provided and the center conductor 6c is inserted through it, and the number of primary windings is one.

The number of secondary turns is N times. The ground fault detection control section 6b is A
It consists of a leg restraint power supply voltage regulator 7 for supplying C control power, a rectifier 8, a load resistor 9, and a voltage relay 4 for ground fault detection. Note that the burden resistor 9 and the voltage relay 4 may be replaced with a current relay.

Note that the DC current transformer shown in this embodiment is called a saturable reactor type DC current transformer.

Next, the operation of the DC transformer 6a and the present invention will be explained with reference to FIG. FIG. 6A shows the relationship between the secondary voltage e of the power supply 7 and the magnetic saturation. When the iron core of the DC current transformer 6a is not saturated, the secondary current of the current transformer is determined by the law of equal ampere turns, as follows: 1e=N-ILI)Relationship teI'L=ie/
N, a secondary current proportional to the primary current of the current transformer flows, generating a voltage of V=IL-R,L in the load resistor 9, and energizing the voltage relay 4.

At the point when the positive and negative of the integral value (hunting part) of the difference between the control power source e and the burden resistance voltage x number of turns becomes equal, magnetic saturation occurs in the iron core of the DC current transformer 6a, the impedance becomes zero, and the p control # voltage e A current obtained by dividing the current by the burden resistance RL flows as shown by the hatched part in Figure 6B, but since this current is essentially useless for current detection, it is Using two sets of secondary coils and a control power supply phase of 18
By detecting the two sets of currents shown in Figure 6 B and C that differ by 0° and allowing the larger current to flow, it is possible to obtain a direct current proportional to the primary winding as shown in Figure 6. .

When a large current flows as the primary current ie, the iron core is saturated in a relatively short time and the DC current transformer impedance becomes zero, but the secondary current does not depend on the primary current and the control power supply phase V divided by the resistance value RL of burden resistor 9: IL=v/R
Since L is limited to the current rectified during all cycles, E in FIG. 6, no overcurrent flows to the secondary side, and no overvoltage is generated.

Therefore, when this invention is applied, by setting the ground fault detection level to a relatively low level, it is possible to detect a ground fault at any timing in the equipment where a large voltage difference as shown in Fig. 2 occurs. Even if a voltage occurs, it can always be detected, and it is also effective for voltages in the opposite direction due to the rectifier circuit 7.

Furthermore, since a DC transformer is used, it is possible to detect ground fault current with any waveform.

In addition, although the above-mentioned embodiment showed the case where it was applied to high inductance DC power supply equipment, the present invention is applicable to the type of load circuit,
It can be applied regardless of the type of AC or DC power source.

〔Effect of the invention〕

As described above, according to the present invention, since the saturable reactor type DC current transformer and the ground fault detection side are connected between the power supply load and between the top and the ground, relatively low level ground fault current can be generated. A ground fault detection relay circuit can be obtained which can detect a ground fault current of any waveform and withstand a large current ground fault current.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional ground fault detection relay, Fig. 2 is a current/voltage waveform diagram for explaining operation, Fig. 3 is a circuit diagram showing an embodiment of the present invention, Fig. 4 5 is a circuit diagram of an embodiment of the invention, and FIG. 6 is a waveform diagram showing the operation of an embodiment of the invention. In the figure, 1 is a load coil, 2 is a DC power supply equipment, 6a
is a DC current transformer, 6b is a first part of the ground fault detection side (3), and 6C is a primary conductor passing through the DC current transformer. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Patent applicant: Mitsubishi Electric Corporation Figure 1 Figure 2 t Time field Figure 3 Δ Figure 40 Figure 5 Ac Japanese Patent Application No. 58-221086 2, Title of the invention: Ground fault detection relay circuit 3, Representative of the person making the amendment: Katayuni Kata, Part 8, Section 5: Detailed explanation of the invention in the specification subject to the amendment, 6, Details of the content of the amendment. Correct the writing exactly as written.

Claims (1)

[Claims] In power supply equipment for supplying DC current to high-inductance loads, a saturable reactor-type DC current transformer includes a conductor that keeps one side of the power supply circuit for the high-inductance load at ground potential, and this conductor as a groove. 1. A ground fault detection relay circuit comprising: and a relay operated by the secondary output of the DC transformer, and the ground fault is detected by the operation of the relay.