JPH09218234A - Short circuit detector for ac electric circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a short circuit detector for Ac electric circuit suitable for the inspection work of circuit in a power receiving/distributing facility and an AC electric circuit having a large number of feeders. SOLUTION: The short circuit detector comprises an impedance 14A for detecting short circuit, and an indicating light (or buzzer) 12 with rectifier 11. An AC power supply 10 is connected through the impedance 14A with an AC electric circuit 4 as a power supply for detecting short circuit. The indicating light 12 with rectifier 11 is connected in parallel with the AC electric circuit 4. When the circuit 4 is not short-circuited (a switch 6 is opened), a voltage is applied to the rectifier 11 and the indicating light 12 is lighted. When the circuit 4 is short-circuited (the switch 6 is closed), no voltage is applied to the rectifier 11 and the indicating light 12 is unlighted thus indicating the presence of short circuit. The interconnecting impedance 14A may be replaced by a transformer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-circuit detecting device for an AC electric circuit, and more particularly to a short-circuit detecting device suitable for inspection work of power receiving and distributing equipment and AC electric circuits having a large number of feeders.

[0002]

2. Description of the Related Art FIG. 6 illustrates an AC electric circuit of a power receiving and distributing facility as a circuit to be inspected to which short circuit detection is applied.

In FIG. 6, 1 is an AC power source for power distribution equipment, 2 is a bus bar, 3 and CB are circuit breakers, 4 and T are transformers, and 5 and M are electric motors. This type of AC electric circuit is mainly configured by branching from a bus bar 2 and connecting a circuit breaker (CB) 3, a transformer (T) 4, an electric motor (M) 5 and the like in multiple stages. FIG. 7 is a part (A part) in FIG.
Is shown in a double-line diagram, and the case of a single phase is shown in order to simplify the diagram.

As shown in FIG. 7, when detecting the presence or absence of a short circuit in such a power receiving / distributing circuit, generally, as a simple method, a tester 7, an insulation resistance meter 8, a Wheatstone bridge 9, etc. are measured. Vessels are used. In the figure, reference numeral 6 or S is a switch equivalently representing a short circuit of the transformer 4 to be inspected.

Any one of these measuring instruments 7, 8 and 9 is used, or a plurality of measuring instruments are used together as required. Of these, the equivalent circuits using the tester 7 are shown in FIGS.
FIG. 8 shows a state in which the circuit is not short-circuited,
FIG. 9 shows a short-circuited state.

In any of these methods, the power source E for detecting a short circuit is a DC power source, and if the internal resistance of the circuit 4 to be short-circuited is rT, the inductive reactance is xT, and the short-circuit resistance is rs, it is non- Tester current I in case of short circuit
_N is I _N = E / rT, and the tester current Is when short-circuited is represented by Is = E / rso (rso is rs
It is the combined resistance of o and rT).

[0007]

[Problems to be Solved by the Invention] Maintenance of an AC electric circuit,
In inspection work, short-circuit inspection at the completion of work is an important task.

In all of the above-mentioned conventional short-circuit detecting devices, the power source for short-circuit detection is a DC power source, so that the AC electric circuit to be inspected mainly has an inductive reactance like a transformer or a transformer. In the case of a short circuit or an incomplete short circuit, it is difficult to distinguish between the short circuit and the internal resistance, and skill is required to judge the short circuit situation.

Further, in equipment having a large number of branch circuits such as power receiving and distributing equipment, a method of using a plurality of measuring instruments together or subdividing the measuring circuits is used if necessary, but it is simple. Was lacking in. In particular, since the instructions of the existing measuring instruments are analog, skilled judgment is required for each measurement. Although high-grade circuit measuring devices have been developed, they are expensive and lack in simplicity.
It was unsuitable.

Furthermore, the existing measuring instrument requires a dedicated or special power source, and it is necessary to prepare the power source in advance, so that it is inconvenient to use it on site or in the field.

The present invention has been made in view of the above circumstances, and an object thereof is a device in which it is difficult to determine the presence or absence of a short circuit in an existing measuring instrument (for example, an AC electrical device mainly having an inductive reactance such as a transformer). It is an object of the present invention to provide a short-circuit detection device which can easily detect a short circuit by a simple means even for a circuit or a circuit in which an incomplete short circuit occurs.

Further, a short-circuit detection device for an AC electric circuit, which can easily detect a short circuit even in a power receiving / distributing facility or an AC electric circuit having a large number of feeders, and which is convenient for on-site and on-site inspections. To provide.

[0013]

In order to achieve the above object, the present invention is basically connected to an AC electric circuit to be inspected and detects the presence or absence of a short circuit in the AC electric circuit. The apparatus is provided with an impedance used for short-circuit detection, and an AC power supply can be connected to the AC electric circuit as a power supply for short-circuit detection through this impedance (this is referred to as problem solving means 1).

Further, as a specific mode of such a short-circuit detection device, a display device with a rectifier (for example, an indicator lamp, a buzzer, etc.) is provided in addition to the impedance, and the short-circuit detection of the AC power source is performed through the impedance. It can be connected to the AC electric circuit as a power supply for, and the display with the rectifier is connected in parallel with the AC electric circuit at the time of connecting the AC power supply / AC electric circuit, and whether there is a short circuit through the display. The AC electric circuit is provided with a distinguishable one (this is referred to as problem solving means 2), a transformer used for short circuit detection, and an indicator with a rectifier, and an AC power source is used as a power source for short circuit detection through the transformer. The display with rectifier is connected in parallel with the AC electric circuit when the AC power supply / AC electric circuit is connected. The AC electric power supply is provided with a device capable of discriminating the presence or absence of a fault (this is referred to as problem solving means 3), a transformer used for short circuit detection, and a relay, and the AC power source is used as a power source for short circuit detection via the transformer. Circuit is connected, the relay is connected to the primary side of the transformer, and the coil of the relay has an operating voltage when the AC electric circuit connected to the secondary side of the transformer is short-circuited. It is proposed that the device is configured to be applied and has an indicator that operates through this relay (this will be referred to as problem solving means 4).

These functions will be described in the section of the next embodiment.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. The AC electric circuit (transformer) 4 to be inspected shown in FIGS. 1 to 6 is the same as that of FIGS. 6 to 9 described above, and the same reference numerals used in the drawings are the same or common. Indicates the element to do.

FIG. 1 is an embodiment showing the principle configuration of the present invention and corresponds to the problem solving means 1.

In FIG. 1, when performing a short circuit inspection,
AC electric circuit (transformer here) to be inspected
An AC power source (E) 10 is connected to the relay unit 4 via a relay short-circuit detection impedance 14A. Impedance 14
A is for short circuit detection and is also displayed as Zo.
By appropriately selecting the impedance 14A, a normal electric lamp power source can be connected to the AC electric circuit 4 as the power source 10 for detecting a short circuit. The switch (S) 6 is equivalent to a short circuit as described above, and its short circuit impedance is rs.

The present invention basically has an impedance of 1.
The presence or absence of a short circuit in the AC electric circuit, for example, the transformer 4, is detected by the magnitude of the current flowing through 4A.

Since the internal impedance ZT of the transformer 4 is composed of the resistance rT and the inductive reactance xT, the current I flowing in the circuit is represented by the equation (1) in the non-short-circuited state, and is in the short-circuited state. Then, it becomes a formula (2).

[0021]

[Equation 1]

[0022]

[Equation 2]

Since rs << ZT in general, I
S»I _N becomes, from the relationship between the Is and I _N, can be easily determined whether or not a short circuit. According to such a short-circuit detection method, even in an AC electric circuit such as a transformer mainly having an inductive reactance or an AC electric circuit having an incomplete short circuit, the relay impedance 14A during non-short circuit and short circuit
Since there is a noticeable difference in the currents flowing through, it is possible to easily determine the presence or absence of a short circuit.

On the other hand, in the principle of the existing DC power supply type measuring instrument shown in FIGS. 8 and 9, I _N and Is are (3)
In general, it is not clear which of rs and rT is larger. Therefore, in the conventional method,
Magnitude relationship Is and I _T is also unknown, it is difficult to determine the presence or absence of a short circuit of an AC electric circuit exclusively circuitry inductive reactance as described above.

[0025]

(Equation 3)

[0026]

(Equation 4)

Next, various embodiments applying the above principle will be described with reference to FIGS.

The embodiment shown in FIG. 2 corresponds to the problem solving means 2.

In this embodiment, an AC power source 10 used for short circuit detection, a relay impedance 14A, a rectifier 11 (RE).
The display 12 with CT) is provided. As the display 12,
An indicator light (also indicated by PL) is used. Rectifier 11
For example, a bridge rectifier circuit is used, and the indicator lamp 12 is inserted and connected in the bridge rectifier circuit.

In the short-circuit detecting device herein, the AC power source 10 can be connected to the AC electric circuit (transformer) 4 as a power source for detecting a short circuit through the impedance 14A. The indicator light 12 with the rectifier 11 is set to be connected in parallel at the time of connection.

According to this example, when the transformer 4 is not short-circuited, the voltage proportional to the impedance Zo of the power supply voltage E is applied to the rectifier 11 in the circuit of the indicator lamp 12. The lamp 12 is turned on. In the short-circuited state (the switch 6 is closed), no voltage is applied to the rectifier 11, and the light is turned off. Therefore, the presence / absence of a short circuit can be easily determined through the indicator lamp 12.

The embodiment of FIG. 3 corresponds to the problem solving means 3.

This embodiment is a modification of the embodiment shown in FIG. 2, and the impedance 14 is used as a relay means for detecting a short circuit.
This is an example in which a transformer 14B is interposed instead of A.

That is, the transformer 14B used for detecting a short circuit.
And the indicator light 12 with the rectifier 11 are provided.
The AC power supply 10 can be connected to the AC electric circuit (transformer) 4 as a power supply for detecting a short circuit via the. The rectifier 11 and the indicator lamp 12 are connected in parallel with the AC electric circuit 4.

In this example, as in the first and second embodiments, it is possible to use a normal lamp power supply as the AC power supply 10, and this can be converted into an AC power supply for short circuit detection by the transformer 14B. From a different point of view, the transformer 14B serves as an AC power source / impedance element for detecting a short circuit.

When the AC electric circuit 4 is not short-circuited, the voltage of the AC power source set by the transformer 14B is applied to the indicator light 12 with the rectifier 11 and the AC electric circuit 4, and the indicator light 12 is turned on. In the short-circuited state (the switch 6 is closed), no voltage is applied to the rectifier 11, and the light is turned off. Therefore, the presence / absence of a short circuit can be easily determined through the indicator lamp 12.

In the present embodiment, similarly to the first and second embodiments, the presence / absence of a short circuit can be easily and easily detected even for an AC power supply circuit in which it is difficult to determine the presence / absence of a short circuit with an existing DC power system type short-circuit detector. It has the effect of being able to detect, and also being able to insulate the AC power supply 10 from the measuring device for detecting a short circuit, which is convenient in actual use.

The embodiment shown in FIG. 4 is a modified example of the third problem solving means.

The short-circuit detecting device of FIG. 4 is provided with a test switch 15 (also shown as PB) in addition to the above-described transformer 14B for short-circuit detection and the indicator light 12 with the rectifier 11. The test switch 15 is set to be connected in parallel with the rectifier 11, and by closing the switch 15, the short circuit of the AC electric circuit 4 can be simulated.

According to the present embodiment, simplification of short circuit detection,
In addition to improving ease, the following effects are achieved. Prior to the short-circuit inspection, it is confirmed whether the short-circuit detection device normally operates in advance by checking whether the test switch 15 is closed and the indicator lamp 12 is turned off or the switch 14 is opened and turned on. can do.

The embodiment of FIG. 5 corresponds to the problem solving means 4.

In this embodiment, the buzzer 17 (B
(Indicated by Z). A transformer 14B for detecting a short circuit and a relay 16 are provided.

The transformer 14B for detecting a short circuit is the same as that shown in FIGS. Further, the relay 16 is connected in series with the primary coil of the transformer 14B on the primary (AC power supply 10) side of the transformer 14B. The circuit of the buzzer (display) 17 is connected in parallel with the circuit of the primary coil of the transformer 14B, and the contact 19 of the relay 16 and the push button switch 18 (also indicated by the symbol PB) are inserted in series in this buzzer circuit. It is connected.

When the AC electric circuit 4 is not short-circuited,
That is, when the switch 6 is in the open state, most of the power supply voltage E is shared by the transformer 14B, so that the voltage applied to the coil of the relay 16 is set to be equal to or lower than its operating voltage, and the contact 19 of the relay 16 is opened and the buzzer is opened. 17 does not ring. When the circuit is short-circuited, that is, when the switch 6 is closed, the secondary side of the transformer 14B is short-circuited, so most of the power supply voltage E is applied to the coil of the relay 16. Since this applied voltage is set to be equal to or higher than the operating voltage of the relay 16, the contact 19 of the relay 16 is closed and the buzzer 17
Sounds and the short-circuit status is displayed. Here, the push button switch 18 inserted in series with the buzzer 17 is
Is to stop.

In order to perform the display surely and easily,
The examples shown in FIGS. 1 and 2 may be used together. In addition, in FIGS. 1 to 5, the short circuit detection device 13, 13A, 1 in which the power supply voltage E of the AC power supply 10 is indicated by a box D surrounded by a chain double-dashed line
3B, 13C, and 13D are arranged outside the figure, but this is because a normal electric lamp power source can be used. It is also possible to use a portable generator power supply in addition to this normal electric light source, and when the portable generator power supply is enabled, work at the site and in the field is facilitated. For the components such as the transformer 14B and the relay 16, analog components can be selected, and by this proper selection, it is possible to use an electric light source that is easily available on-site and on-site.

Furthermore, the indicator for displaying the presence or absence of a short circuit is
It is also possible to use a buzzer and an indicator light together.

[0047]

According to the problem solving means 1, since the AC power source can be used as the power source for detecting the short circuit through the impedance of the relay, for example, the AC electric circuit mainly having the inductive reactance or the incomplete short circuit. Even with such an AC electric circuit, it is possible to easily and surely determine the presence or absence of a short circuit in the circuit by a simple measuring means without requiring skill.

According to the problem solving means 2 to the problem solving means 4, in addition to the above-mentioned effects, since the display device for displaying the result of the judgment of the presence or absence of the short circuit is provided, the recognition of the short circuit inspection result is facilitated. Therefore, even when a plurality of measuring instruments are used together, or when the circuits to be measured are separated or subdivided, the efficiency of the inspection work is improved.

Further, according to the above-mentioned first to fifth means for solving the problems, the impedance for short-circuit detection and the transformer are appropriately selected to be used as a power supply for short-circuit detection (measurement power supply) normally on site or in the field. Since it is possible to use the electric lamp power supply that is used, it is possible to use the short-circuit detection device locally or in the field.

[Brief description of drawings]

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

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

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

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

FIG. 5 is a configuration diagram showing a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a circuit of a power receiving and distribution facility showing an example of an application target of the present invention.

FIG. 7 is a double-track diagram showing in detail part A of FIG.

FIG. 8 is an explanatory diagram when a tester is used as a conventional short-circuit detection device.

FIG. 9 is an explanatory diagram when a tester is used as a conventional short-circuit detection device.

[Explanation of symbols]

1 ... AC power source of power distribution equipment, 2 ... Bus of power distribution equipment, 3
... Circuit breaker, 4 ... Transformer, 5 ... Electric motor, 6 ... Short circuit switch, 7 ... Tester, 8 ... Insulation resistance meter, 9 ... Wheatstone bridge, 10 ... AC power supply, 11 ... Rectifier, 12 ... Indicator, 13, 13A ~ 13D ... short circuit detection device, 14A ...
Impedance, 14B ... Transformer, 15 ... Pushbutton switch, 16 ... Relay, 17 ... Buzzer, 18 ... Pushbutton switch, 19 ... Relay contact.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuo Nakauchi 3-2-2 Sachimachi, Hitachi City, Ibaraki Prefecture Hitachi Engineering Service Co., Ltd.

Claims (7)

[Claims] 1. An apparatus which is connected to an AC electric circuit to be inspected and detects the presence or absence of a short circuit in the AC electric circuit, has an impedance used for detecting a short circuit, and detects an AC power supply through the impedance. A short circuit detection device for an AC electric circuit, wherein the AC electric circuit is connectable to the AC electric circuit as a power source. 2. An apparatus for detecting the presence / absence of a short circuit in an AC electric circuit, which is connected to an AC electric circuit to be inspected, is provided with an impedance used for detecting a short circuit and an indicator with a rectifier, and through the impedance. An AC power supply can be connected to the AC electric circuit as a power supply for short circuit detection, and the indicator with the rectifier is connected in parallel with the AC electric circuit when the AC power supply / AC electric circuit is connected. A short-circuit detection device for an alternating-current electric circuit, characterized in that it is possible to determine the presence or absence of a short-circuit through the circuit. 3. An apparatus for detecting the presence or absence of a short circuit in an AC electric circuit to be inspected by connecting to the AC electric circuit to be inspected, comprising a transformer used for short circuit detection, an indicator with a rectifier, and the transformer. Via the AC power supply as a power supply for short-circuit detection through the AC electric circuit can be connected, the display with the rectifier is connected in parallel with the AC electric circuit at the time of connecting the AC power supply / AC electric circuit, A short-circuit detecting device for an AC electric circuit, which is capable of discriminating the presence or absence of a short-circuit through a display. 4. An apparatus for detecting the presence or absence of a short circuit in an AC electric circuit, which is connected to an AC electric circuit to be inspected, is provided with a transformer and a relay used for detecting a short circuit, and the AC is provided via the transformer. A power source is connectable to the AC electric circuit as a power source for short circuit detection, the relay is connected to the primary side of the transformer, and the coil of the relay is connected to the secondary side of the transformer. A short-circuit detecting device for an AC electric circuit, which is configured to apply an operating voltage when the AC electric circuit is short-circuited, and has an indicator which operates via the relay. 5. The short circuit detection device for an AC electric circuit according to claim 2, wherein the indicator is at least one of an indicator lamp and a buzzer. 6. The short-circuit detection device for an AC electric circuit according to claim 1, wherein a normal lamp power supply and a portable generator power supply can be used as the AC power supply. 7. The short circuit detection device for an AC electric circuit according to claim 1, further comprising a test switch circuit capable of simulating a short circuit of the AC electric circuit.