JPH07146321A - Circuit for detecting ground fault of battery of uninterruptible power unit - Google Patents

Abstract

PURPOSE:To easily and accurately discover the occurrence of the ground fault of a battery constituting an uninterruptible power unit due to a leakage liquid from the battery. CONSTITUTION:An earth leakage breaker 11 is installed to the AC input circuit of a rectifier 3 constituting an uninterruptible power unit as an AC ground-fault current detecting means or the breaker 11 is installed to the input circuit of a battery 6 as an AC ground-fault current detecting means. In either case, one line of the AC input circuit of the rectifier 3 is connected to the ground through a grounding capacitor when an AC power source 2 is of a non- grounding system. When the battery 6 causes a ground fault due to a leakage liquid, the ground-fault current flowing between the ground-fault point and the grounding section 2E of the power source 2 or between the ground-fault point and grounding capacitor flows to the breaker 11 as an unbalanced current. Therefore, the ground fault of the battery 6 can be easily and accurately detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an uninterruptible power supply for an uninterruptible power supply device which is constructed by connecting a rectifier, an inverter and a storage battery to a DC intermediate circuit, and which detects a ground fault due to leakage of the storage battery. The present invention relates to a storage battery ground fault detection circuit of a device.

[0002]

2. Description of the Related Art FIG. 5 is a circuit diagram showing a state in which a storage battery, which is a component of a general uninterruptible power supply, leaks liquid to cause a ground fault, and one end of an AC power supply is grounded. The case is shown. The uninterruptible power supply device is composed of a rectifier 3 (configured by connecting four diodes 3U, 3V, 3X, 3Y in a single-phase bridge), a smoothing capacitor 4, an inverter 5, and a storage battery 6, and the rectifier 3 is an AC power supply. The AC power from 2 is converted into DC power, and the smoothing capacitor 4 absorbs and removes the ripple component contained in this DC power. The inverter 5 converts the smoothed DC power into AC power having a desired voltage and frequency and supplies it to the load 7. A storage battery 6 is connected to a DC intermediate circuit that connects the DC side of the rectifier 3 and the DC side of the inverter 5, and the rectifier 3 supplies DC power to the inverter 5 and charges the storage battery 6 with charging power. Is being supplied. Therefore, if the AC power supply 2 fails, the storage battery 6 is replaced by the inverter 5 instead of the AC power supply 2.
Since DC power is supplied to the load 7, the load 7 can continue to operate even if the AC power supply 2 fails. Incidentally, 2E is a power source grounding section.

In recent years, a large number of information processing devices such as small computers have been introduced for the purpose of rationalizing various operations and improving efficiency, but the functions of these information processing devices are impaired even during a power failure for an extremely short time. There is a drawback that it will be. Therefore, the power failure is avoided by supplying AC power to each information processing apparatus via the uninterruptible power supply apparatus shown in FIG. In the maintenance of this uninterruptible power supply,
In the past, maintenance of storage batteries that backed up power failure was difficult, but in recent years, sealed storage batteries have been developed, and maintenance-free operation of uninterruptible power supplies has become possible.

However, if the sealed storage battery is also used for a long time, the storage battery case may be cracked due to the deformation of the internal electrodes and the electrolyte may leak out. This leakage causes the storage battery to become a ground fault. The circuit diagram of FIG. 5 shows a state in which the storage battery 6 causes a ground fault via the ground resistance 8 due to this leakage.

[0005]

The uninterruptible power supply is provided with overcurrent detection means in case the input current or output current becomes excessive, so that each device of the uninterruptible power supply is protected from damage. We are preventing it. However, FIG.
When a storage battery ground fault as shown in Fig. 2 occurs, the input current and output current of the uninterruptible power supply will not become excessive, so the above-mentioned overcurrent detection means cannot detect the storage battery ground fault. . When a ground fault occurs due to liquid leakage, the charging current to the storage battery 6 decreases and does not reach a full charge state contrary to the above. Therefore, when the AC power supply 2 fails, the storage battery 6 cannot back up this power failure and the load 7 However, such an inconvenience cannot be identified unless the AC power supply 2 actually fails. In other words, if the ground fault due to liquid leakage cannot be detected, the above-mentioned problems will occur.
When a ground fault occurs, an arc discharge may occur to ignite the storage battery 6, or a ground fault may cause an electric shock accident due to the voltage of the AC power supply 2 or the DC electromotive force of the storage battery 6.

Therefore, in an uninterruptible power supply for backing up a power failure of an important device, for example, a DC current detecting means composed of a hall element is installed on the input side of the storage battery 6 to detect a ground fault accident from an imbalance of charging currents. However, Hall current transformers have the disadvantages of poor sensitivity and high price. Therefore, an object of the present invention is to make it possible to easily and accurately find out that a storage battery constituting an uninterruptible power supply device has leaked and a ground fault has occurred.

[0007]

In order to achieve the above-mentioned object, the storage battery ground fault detection circuit of the uninterruptible power supply of the present invention comprises an AC power supply whose one end is grounded, and an AC power supply connected to this AC power supply. A rectifier that converts electric power to DC power, an inverter that converts DC power output by the rectifier to AC power, and a storage battery that is connected to a DC intermediate circuit that connects the DC side of the rectifier and the DC side of the inverter. In an uninterruptible power supply comprising, the AC side of the rectifier is provided with an AC ground fault current detecting means for detecting an AC ground current, or an AC circuit is connected between the DC side of the rectifier and the storage battery. AC ground fault current detection means for detecting the ground fault current is provided.

Alternatively, an ungrounded AC power source, a rectifier that is connected to the AC power source to convert the AC power into DC power, an inverter that converts the DC power output by the rectifier into AC power, and a DC of the rectifier. An uninterruptible power supply device having a storage battery connected to a DC intermediate circuit that connects the DC side of the inverter to the DC side of the inverter, and connects the AC line of the rectifier to the AC line of the AC circuit. A grounding capacitor and an AC grounding current detecting means for detecting an AC grounding current are provided, or a grounding capacitor is provided on the AC side of the rectifier to connect between one wire of this AC circuit and ground.
An AC ground fault current detection means for detecting an AC ground fault current is provided in a circuit connecting the DC side of the rectifier and the storage battery.

[0009]

The present invention is directed to an AC ground fault that detects an AC ground fault current when one end of an AC power supply for supplying an AC power to an uninterruptible power supply composed of a rectifier, an inverter and a storage battery is grounded. The current detecting means is inserted into either the AC input circuit of the rectifier or the circuit connecting the DC side of the rectifier and the storage battery. When the AC power supply is not grounded, one wire of the AC input circuit of the rectifier is grounded via a grounding capacitor and the AC ground fault current detecting means is either the AC input circuit of the rectifier or the DC side of the rectifier. Insert the battery into one of the circuits that connect it to the storage battery. With such a circuit configuration, if a ground fault occurs due to leakage of the storage battery, an unbalanced AC current will flow to the installation point of the AC ground fault current detection means. This unbalanced AC current can be easily and accurately detected by the AC ground fault current detection means.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a circuit diagram showing a first embodiment of the present invention, which corresponds to claim 1. The AC power supply 2 and the power source grounding portion shown in the first embodiment circuit of FIG. 2E, name / application of rectifier 3, smoothing capacitor 4, inverter 5, storage battery 6, load 7, and grounding resistor 8 consisting of a single-phase bridge connection
Since the function is the same as that of the conventional circuit described above with reference to FIG. 5, the description thereof will be omitted.

In the circuit of the first embodiment, the earth leakage breaker 11 as an AC ground fault current detecting means is installed on the AC input side of the rectifier 3, and this earth leakage breaker 11 has a current interruption portion.
A current transformer part for detecting an imbalance of an alternating current flowing through the earth leakage breaker 11, and an operation signal generating part for sending an interruption signal to the current interruption part when the degree of the imbalance of the alternating current exceeds a predetermined value. It consists of and.

When the storage battery 6 leaks and a ground fault occurs, an AC ground fault current flows through the path shown by the dotted line. That is, the AC power supply 2 → the power supply grounding section 2E → the grounding resistance 8 → a part of the storage battery 6 → the diode 3X → one circuit of the earth leakage breaker 11 → the AC electricity supply 2, but the ground fault current at this time is the earth leakage breaker 11 It flows only to one circuit and not to the other circuit. That is, the currents flowing through the earth leakage breaker 11 become unbalanced. If the polarity of AC power supply 2 is reversed, AC power supply 2 →
One circuit of the earth leakage breaker 11 → diode 3U → part of the storage battery 6 → ground resistance 8 → power source grounding section 2E → AC power source 2
Although the AC ground fault current flows through the path of, the ground fault current does not flow in the other circuit of the earth leakage breaker 11 in this case as well. That is, the AC current flowing through the earth leakage breaker 11 becomes unbalanced when a ground fault occurs due to the leakage of the storage battery 6. The current transformer portion of the earth leakage breaker 11 detects this unbalanced current, and if the degree of unbalance exceeds a predetermined value, the circuit is cut off by the cutoff command from the operation signal generation portion.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention, which corresponds to claim 2. The second embodiment circuit of FIG. 2 has an AC ground fault on the input side of the storage battery 6. 1 is different from the circuit of the first embodiment described above in FIG. 1 in that an earth leakage breaker 12 as a current detecting means is installed, but other than that, it is the same as the circuit of the first embodiment in FIG. Therefore, the description of the names, uses, and functions of the illustrated devices will be omitted.

Similar to the case of the first embodiment circuit described above,
When a ground fault occurs in the storage battery 6 due to liquid leakage, an unbalanced AC current flows through the input circuit of the storage battery 6 (the current path is the same as in the first embodiment circuit of FIG. 1). The earth leakage breaker 12 detects this unbalanced current and shuts off the circuit. FIG. 3 is a circuit diagram showing a third embodiment of the present invention, which corresponds to claim 3, but in the third embodiment circuit, the AC power supply 2 is not grounded. When the power source is not grounded, no current flows even if a ground fault occurs in the storage battery 6. Therefore, grounding capacitor 13
Of the grounding capacitor 13 is connected to the ground, and the other end of the grounding capacitor 13 is connected to the ground to form a grounding circuit. At the AC input side of the rectifier 3, an earth leakage breaker 11 is installed as an AC grounding current detecting means. . The third embodiment circuit of FIG. 3 configured as described above is different from the first embodiment circuit of FIG. 1 in that the ground capacitor 13 is connected instead of removing the power source grounding portion 2E. Everything else is the same. Therefore, the description of the names, uses, and functions of the devices illustrated in the circuit of the third embodiment will be omitted.

In the circuit of the third embodiment of FIG. 3, the storage battery 6
The path of the alternating current that flows when a ground fault occurs in the following is as follows (however, not shown). That is, AC power supply 2 →
Ground capacitor 13 → Ground resistance 8 → Part of storage battery 6 →
The diode 3X → one circuit of the earth leakage breaker 11 → the AC power supply 2. At this time, the ground fault current flows only in one circuit of the earth leakage breaker 11 and does not flow in the other circuit, so that the AC current flowing in the earth leakage breaker 11 becomes unbalanced. If the polarity of the AC power supply 2 is reversed, an AC ground fault current is generated in the path of the AC power supply 2 → one circuit of the earth leakage breaker 11 → diode 3U → a part of the storage battery 6 → grounding resistance 8 → grounding capacitor 13 → AC power supply 2. It flows, but also in this case, the earth leakage breaker 11
The ground fault current flows only in one circuit and does not flow in the other circuit. That is, the AC current flowing through the earth leakage breaker 11 becomes unbalanced when a ground fault occurs due to the leakage of the storage battery 6. The current transformer part of the earth leakage breaker 11 detects this unbalanced current and shuts off the circuit if the degree of unbalance exceeds a predetermined value.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention, which corresponds to claim 4. The circuit of the fourth embodiment of FIG. 4 is a leakage current as an AC ground fault current detecting means. Circuit breaker 1
2 is installed on the input side of the storage battery 6 is different from the circuit of the third embodiment described above in FIG. 3, but is otherwise the same as the circuit of the third embodiment of FIG. 3, Descriptions of names, uses, and functions of the illustrated devices are omitted.

Similar to the case of the third embodiment circuit described above,
When a ground fault occurs in the storage battery 6 due to liquid leakage, an unbalanced AC current flows in the input current of the storage battery 6 (the current path is the same as in the third embodiment circuit of FIG. 3). The earth leakage breaker 12 detects this unbalanced current and shuts off the circuit. In each of the circuits of the above-described embodiments, the case where the earth leakage breaker is used as the AC ground fault current detecting means is illustrated, but other means for detecting an AC unbalanced current instead of the earth leakage breaker, for example, zero phase change. Of course, there is no problem in encountering a configuration in which the sink and the circuit opening / closing means are combined.

[0018]

[Effects of the Invention] Even if the storage battery constituting the uninterruptible power supply leaks to cause a ground fault, the input and output quantities of the uninterruptible power supply do not change significantly. Therefore, there is an inconvenience that such a ground fault is usually not detected. Therefore, there are cases where a hall element is used in the input circuit of the storage battery to provide a means for detecting the imbalance of DC current.
This has a drawback in that the detection accuracy is difficult and the apparatus is expensive.

On the other hand, according to the present invention, the AC ground fault current detecting means is installed on the AC input side of the rectifier constituting the uninterruptible power supply or on the input side of the storage battery. At this time, if the AC power supply is a non-grounded system, one
The line and ground are connected via a grounding capacitor. With such a circuit configuration, if the storage battery leaks and a ground fault occurs, a ground fault occurs between the ground portion of the AC power supply and the ground fault point, or between the ground capacitor and the ground fault point. An AC ground fault current flows between the two. That is, since this AC ground fault current flows through the place where the AC ground fault current detecting means is installed, it is possible to easily detect the ground fault. Since this AC ground fault current detecting means has been widely used in AC circuits, it is possible to obtain an effect that a ground fault can be detected much more easily and accurately than an apparatus using a hall element.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention.

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 5 is a circuit diagram showing a state in which a storage battery, which is a component of a general uninterruptible power supply, leaks liquid to cause a ground fault.

[Explanation of symbols]

 2 AC power supply 2E Power supply grounding part 3 Rectifier 4 Smoothing capacitor 5 Inverter 6 Storage battery 7 Load 8 Ground resistance 11 Earth leakage breaker 12 Earth leakage breaker 13 Earthing capacitor

Claims (4)

[Claims] 1. An AC power supply whose one end is grounded, a rectifier that is connected to this AC power supply to convert AC power into DC power, and an inverter that converts DC power output from this rectifier into AC power. In an uninterruptible power supply device comprising a storage battery connected to a DC intermediate circuit that connects the DC side of the rectifier and the DC side of the inverter, an AC ground fault current detection that detects an AC ground fault current on the AC side of the rectifier. A storage battery ground fault detection circuit for an uninterruptible power supply, characterized in that means is provided. 2. An AC power supply whose one end is grounded, a rectifier which is connected to the AC power supply to convert AC power into DC power, and an inverter which converts DC power output from the rectifier into AC power. In an uninterruptible power supply comprising a storage battery connected to a DC intermediate circuit that combines the DC side of the rectifier and the DC side of the inverter, an AC ground is connected to the circuit connecting the DC side of the rectifier and the storage battery. A storage battery ground fault detection circuit for an uninterruptible power supply, comprising an AC ground fault current detection means for detecting a fault current. 3. An ungrounded AC power supply, a rectifier that is connected to this AC power supply to convert AC power into DC power, an inverter that converts DC power output from this rectifier into AC power, and a DC of the rectifier. Side and a storage battery connected to a DC intermediate circuit that connects the DC side of the inverter, in the AC side of the rectifier, between the line 1 of this AC circuit and ground A storage battery ground fault detection circuit for an uninterruptible power supply, comprising a grounding capacitor and an AC ground fault current detection means for detecting an AC ground fault current. 4. An ungrounded AC power supply, a rectifier that is connected to this AC power supply to convert AC power into DC power, an inverter that converts DC power output from this rectifier into AC power, and a DC of the rectifier. Side and a storage battery connected to a DC intermediate circuit that connects the DC side of the inverter, in the AC side of the rectifier, between the line 1 of this AC circuit and ground A storage battery ground fault detection of an uninterruptible power supply device, characterized in that a grounding capacitor is provided, and an AC ground fault current detection means for detecting an AC ground fault current is provided in a circuit connecting the DC side of the rectifier and the storage battery. circuit.