JP2000074972A - Method for detecting open phase of neutral conductor at distribution line of single-phase three-wire system, and detector used therein - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make detectable an open phase speedily in various cases by connecting a voltage detector with an incorporated abnormal voltage detection load in each point of a distribution line and detecting an abnormal voltage generated between a neutral conductor and the other line. SOLUTION: The neutral conductor open-phase detector 1 used for judging an open phase of a neutral conductor at a distribution line of a single-phase three-wire system has, for example, terminals T1-T3 for connecting the detector to the distribution line, and voltage detection loads R1, R2 for restricting an abnormal voltage as a result of generation of an open phase of the neutral conductor within a range of, e.g. 120-135 V. A resistor or capacitor is used as the voltage detection load and set so that the abnormal voltage is within a predetermined range. When a voltage-detecting part detects the abnormal voltage, an abnormal voltage-judging part compares the voltage with a set value and outputs a warning signal indicating that the distribution line is an open-phase state, flickering a lamp or sounding a buzzer, or the like. It is preferred so as to detect an intermittent open phase if the inspection result is displayed continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a neutral phase loss in a single-phase three-wire distribution line and a detector used for the method.

[0002]

2. Description of the Related Art At present, a single-phase three-wire system is widely used as a power distribution system for general households in terms of high efficiency such as efficient supply to both large-capacity loads such as air conditioners and general loads such as lights. The power distribution system has become common. In this case, as shown in FIG.
AC200V is supplied from the wires on both sides of the wire, and AC100V is supplied from a neutral wire and a wire on one side to a general load. Here, it is known that an abnormal voltage is generated when the neutral line of the three lines is out of phase and the general load is not balanced. It is difficult to keep the load balance of this single-phase three-wire distribution line even at all times, and when the neutral conductor is disconnected due to poor connection, etc., the general household equipment connected to this distribution line is abnormal. Voltage is applied, causing damage to general household equipment.

Therefore, in order to prevent damage due to abnormal voltage, a leakage breaker with open-phase protection is installed on a distribution board of a customer connected to the distribution line. When an abnormal voltage is generated in a distribution line, the leakage circuit breaker with open-phase protection detects the abnormal voltage (normally, a voltage of 135 V or more) by a detection unit, and cuts off the distribution line at a high speed. Although it stops power transmission, it does not check the location of the occurrence of neutral phase loss, etc., so it is unknown at this location where the neutral wire was cut with this earth leakage breaker with phase loss protection. After the circuit breaker was operated, it was necessary to immediately search for a portion where the phase was lost.

[0004] The open phase of the neutral wire includes a permanent open phase caused by disconnection or the like, and an intermittent phase generated temporarily or intermittently by loosening of a screw or the like. If the neutral phase is a permanent phase loss, it is possible to check the distribution line by breaking it with a circuit breaker on the customer side and measuring it with a tester, etc. In this case, there is no other way but to check the connection points one by one until the open phase point is found in a state where the power supply is shut off. Furthermore, if the neutral phase is an intermittent phase, it returns to its original state after a while after the neutral phase is lost, so it cannot be detected by the tester. There is no current situation.

[0005]

SUMMARY OF THE INVENTION In view of the above-mentioned situation, the present invention provides a single-phase three-wire distribution line that can be used not only when the neutral phase is a permanent phase but also when it is an intermittent phase. It is an object of the present invention to provide a detection method capable of detection.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a voltage detector having a built-in load for detecting abnormal voltage is connected at various points in a single-phase three-wire distribution line to generate a voltage between a neutral wire and another wire. Detecting an abnormal voltage and determining the occurrence of open phase of the neutral line, and detecting the open phase of the neutral line in the single-phase three-wire system distribution line, and connecting to the single-phase three-wire system distribution line, respectively. Each terminal and the abnormal voltage due to the occurrence of open phase of neutral
A voltage detecting load for suppressing the voltage to a voltage within the range of ~ 135V, a voltage detecting unit for detecting the suppressed voltage, and an abnormal voltage determining unit for outputting an alarm signal when the detected voltage is 120 to 135V. And an alarm display unit for displaying an alarm in accordance with the alarm signal.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The present invention detects an abnormal voltage generated on the load side of a neutral line in a single-phase three-wire system distribution line, and determines the occurrence of a phase loss of the neutral line. The mechanism of the abnormal voltage generation is as follows.

In the state where the neutral line is not open, as shown in FIG. 2, the voltage between the neutral line N and the voltage line L1 and the voltage between the neutral line N and the voltage line L2 are , 100V. However, if the neutral wire breaks due to disconnection or poor connection,
A voltage is applied only to the point a of the voltage line L1 and the point b of the voltage line L2 in FIG. 3, and the resistance value of the electric equipment of the general load between the neutral line N and the voltage line L1, the neutral line N and the voltage The voltage distribution is proportional to the resistance value of the general load electric device between the line L2 and the line L2.

Therefore, the electric equipment between the neutral line N and the voltage line L1 is a 500 W microwave oven (20 ohm), and the electric equipment between the neutral line N and the voltage line L2 is a 50 W fluorescent lamp ( 200 ohm)
Then, the voltage distribution is as follows: Va = 200 × 20 / (200 + 20) = 18V Vb = 200 × 200 / (200 + 20) = 182V Therefore, a voltage of 182V is applied to the fluorescent lamp, Therefore, the transmission from the distribution line must be interrupted immediately when the neutral line loses phase. Therefore, as described above, the abnormal voltage (usually a voltage of 135 V or more) is detected by the earth leakage breaker with phase loss protection, and the distribution line is cut off at high speed. Need to be repaired.

According to the present invention, an abnormal voltage generated between a neutral wire and another wire is detected by connecting a voltage detector having a built-in load for detecting an abnormal voltage at various points of a single-phase three-wire system distribution line,
This is to determine the occurrence of the phase loss of the neutral line. As shown in FIG. 1, the neutral line open phase detector 1 used for the determination of the open phase of the neutral line has terminals T1 and T1 for connecting to the single-phase three-wire system distribution lines L1, N and L2, respectively. T2, T3, voltage detection loads R1, R2 for suppressing the abnormal voltage due to the occurrence of neutral phase loss to a voltage in the range of 120 to 135V, and a voltage detection unit for detecting the suppressed voltage, An abnormal voltage determining unit that outputs an abnormal voltage signal when the detected voltage is 120 to 135 V;
An alarm display unit for displaying an alarm based on the abnormal voltage signal.

When the terminals T1, T2 and T3 of the neutral line open phase detector 1 are connected to the three lines L1, N and L2 of the distribution line, respectively, different voltage detections set in the neutral line open phase detector are set. Load R1, R2
The voltage Va between the L1 and N and the voltage Vb between the L2 and N according to the above are detected by the voltage detector. A resistor or a capacitor can be used as the voltage detection load. here,
The description will be made assuming that the capacitors C1 and C2 are adopted by using capacitors. Va = V × ωC2 / (ωC1 + ωC2) Vb = V × ωC1 / (ωC1 + ωC2) where ω = 2πf. These voltage detection loads ωC2, ωC1
It is desirable to satisfy both the conditions of displaying as an abnormal voltage that is easy to confirm and that we do not want to generate too much high voltage that may damage the equipment. , L1-N voltage
One of Va and L2-N voltage Vb is 120-135V
Is selected so as to have an abnormal voltage within the range. For example, if the voltage detection load ratio is set to be about 1: 2,
The abnormal voltage can be set to 200 × 2/3 = 133V.

When each of the voltage detectors of the neutral-phase open-phase detector detects an abnormal voltage in the above range, the abnormal-voltage determiner compares the set value with an alarm indicating that the distribution line is in an open-phase state. A signal is output, and an alarm is displayed by the alarm display unit. As the alarm display unit, various means such as displaying the presence of an abnormal voltage on a blinking lamp, a sound of a buzzer, or the like, an alarm display board, or the like are employed. If the neutral phase is a permanent phase, the status at the time of the test is immediately displayed,
In particular, a buzzer or the like, whose results are easy to understand at the time of the test, is preferable.If the neutral phase is an intermittent phase, the temporary phase result during the test period is displayed, so the test result is displayed continuously. A warning display plate is suitable. The alarm display panel is, for example, a display panel having different colors on the front and back sides, and is turned over when an abnormal voltage is detected, and the state is maintained.

When the neutral phase is a permanent phase,
By performing the above-described inspection on the three distribution lines in each part of the single-phase three-wire system distribution line, it is possible to detect a permanent open phase portion. If the open phase of the neutral line is an intermittent phase, install a neutral line open phase detector at each location such as a branch point of a single-phase three-wire system distribution line or a customer's switchboard, and display an alarm. By displaying the occurrence of the abnormal voltage on the plate, it is possible to detect the location of the intermittent phase. That is, when an intermittent phase occurs at a certain branch point, an intermittent phase also occurs at a subsequent branch point or switchboard, so that an intermittent phase is generated by detecting an intermittent phase at a plurality of points. The location can be specified.

According to the present invention, an unbalanced load state is created in a single-phase three-wire distribution line by using the voltage detection load circuit formed in the voltage measuring device as described above, and the abnormal voltage due to the open phase of the neutral line is confirmed. You can do it. As described above, the present invention relates to a method and an apparatus for detecting an open phase of a neutral line. However, the apparatus of the present invention is provided with a load (such as a variable load) that generates an abnormal voltage at which an earth leakage breaker can operate. It is also possible to test whether the earth leakage breaker with open-phase protection operates normally with respect to abnormal voltage by arranging circuits having in parallel and switching as necessary.

[0015]

According to the present invention, there is provided a detection method capable of quickly detecting a neutral phase loss in a single-phase three-wire system distribution line, and a neutral phase loss detector used for the method. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one example of a neutral-line open-phase detector of the present invention.

FIG. 2 is an explanatory diagram showing a normal voltage state in a single-phase three-wire system distribution line.

FIG. 3 is an explanatory diagram showing a state of an abnormal voltage in a single-phase three-wire system distribution line.

[Explanation of symbols]

 1 Neutral line open phase detector T1, T2, T3 terminals R1, R2 Voltage detection load S switch

Claims (2)

[Claims] 1. A voltage detector having a built-in load for detecting abnormal voltage is connected at various points in a single-phase three-wire system distribution line, and a voltage is generated between the neutral wire and another wire when the neutral wire loses phase. A method for detecting a neutral phase loss in a single-phase three-wire system distribution line, comprising detecting an abnormal voltage and determining occurrence of a neutral phase loss phase. 2. Terminals for connecting to a single-phase three-wire system distribution line, and an abnormal voltage caused by the occurrence of an open phase of a neutral line.
A voltage detecting load for suppressing the voltage to a voltage within a range of 0 to 135 V, a voltage detecting unit for detecting the suppressed voltage, and an abnormal voltage determining unit for outputting an alarm signal when the detected voltage is 120 to 135 V And a warning display unit for displaying a warning in accordance with the warning signal.