KR100907566B1 - 4CT Combination Portable Earth Leakage Measuring Device and Method - Google Patents

Abstract

The present invention relates to a 4CT combined portable earth leakage measuring apparatus and method, and in particular, the leakage current of a three-phase four-wire distribution line that cannot be measured by one zero current transformer (ZCT) is divided into four individual current transformers (Current). Current is measured by Transformer (CT), and the current measured by four individual current transformers is calculated through a predetermined calculation formula, and the result is displayed on a monitor, and the result is transmitted to the central control panel using wireless communication for analysis in real time. The present invention relates to a 4CT combined portable earth leakage measuring apparatus and method that can monitor current and prevent accidents caused by leakage current.

Image Current Transformer (ZCT), Current Transformer (CT), Leakage Current, Underground Line, Multi Switch Unit, DMM / ADC

Description

Portable measuring apparatus and method for the electric leakage of 4CT combination

1 is a block diagram of a 4CT combination portable earth leakage measuring apparatus and method according to the present invention;

2 is a flow chart showing a 4CT combination portable short-circuit measuring method according to the present invention;

3 is a graph illustrating phases of R, S, and T phases of a sensor input unit in FIG. 1 as a plane vector.

Explanation of symbols on the main parts of the drawings

1: power supply 2: sensor input

3: multi-switch section 4: DMM / ADC section

5: CPU 6: memory

7: LCD screen 8: Key operation panel

9: USB

The present invention relates to an earth leakage measuring apparatus and method, in particular, by measuring the leakage of the low-medium-low voltage line to check the leakage and the size of the low-voltage circuit by 4CT combination portable to be suitable for preventing the electric shock accident by a short and accurate short circuit An earth leakage measuring apparatus and method are provided.

In general, in the case of an electric cable installed under the ground because the exposure on the ground is not desirable, when an electric leakage occurs in the cable, it is impossible to pinpoint the electric leakage position due to invisibility and lack of suitable equipment. It has been implemented as a work.

On the other hand, when an earth leakage occurs in the underground cable, a high voltage pulse current is forced through the earth leakage line, and then a current leak is detected by detecting a current leaked to the ground through the earth leakage point, thereby identifying a short circuit. It provides an economical repair method that can reduce the material and time loss by finding the exact leakage location without replacing the entire surface.

However, this method can reduce material and time losses, but is not suitable for measuring leakage currents in three to four wire underground low voltage lines.

In addition, underground low-voltage lines are usually 3 ~ 4 wire type, so large current transformers with a diameter of more than 300mm are required to measure leakage current, but the products developed at home and abroad were limited to 100mm. In particular, large current transformers are not only inconvenient to handle, but also expensive, and the demand is limited to special purposes.

Accordingly, the present invention has been proposed to solve the conventional problems as described above, the object of the present invention is to detect the leakage of the underground low-voltage line in the live state in the live state to check the leakage and the size of each low-voltage circuit leakage and quickly and accurately The present invention provides a 4CT combination portable earth leakage measuring apparatus and method which can prevent an electric shock accident.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a 4CT combined portable earth leakage measuring apparatus and method according to the present invention, and as shown, a power supply unit 1 to which power is applied; A sensor input unit 2 to which R, S, T, and N phases are input when power is applied from the power source unit 1; A multi-switch unit 3 which receives the R, S, T and N phase sensor signals from the sensor input unit 2 and sends them to the DMM / ADC unit; A DMM / ADC unit 4 for converting the sensor signal of each phase received from the multiple switch unit 3 into a digital signal (22 bit ADC = about 4 million counters) and sending it to the CPU; A CPU 5 which periodically measures the digital signal received from the DMM / ADC unit 4 for 0.3 seconds and calculates measurement data of each phase; A memory (6) for storing a result of calculating measurement data of each phase in the CPU (5); An LCD screen 7 which shows the calculated leakage current calculated by the CPU 5 and the measured current of each phase; A key operation unit 8 for controlling the CPU through key operation; It is characterized by consisting of a USB (9) that can easily move data.

In addition, data stored in the memory 6 can be transmitted in real time to a central control panel (not shown) by wireless communication.

Figure 2 is a flow chart illustrating a 4CT combined portable short-circuit measuring method according to the present invention, as shown in the 4CT combination portable short-circuit measuring method, the current measurement to measure the current of the phases input to the current transformer of the sensor input when power is applied Step ST1; A signal conversion step (ST2) of converting the current measurement value into a digital signal and transmitting it to the CPU after the current measurement step (ST1); A data calculation step (ST3) of calculating measurement data of each phase in a CPU after the signal conversion step (ST2); A result display step (ST4) of storing the result value in a memory and displaying it on an LCD screen after the data operation step (ST3); A measurement completion step (ST5) of terminating the measurement if the leakage current is not measured after the result display step (ST4); If it is confirmed that the leakage current is measured after the result display step ST4, take immediate action and report to the central control panel (not shown) and report step ST6.

In addition, a method of measuring leakage current by calculating data in the data operation step ST3 is as follows.

3 is a graph illustrating phases of R, S, and T phases of a sensor input unit in FIG. 1 as a plane vector.

FIG. 3 is a graph showing the phases of the R, S, and T phases of the sensor input unit as a plane vector in FIG. 1, and as shown, the phases of the R, S, and T phases differ by exactly 120 ° from each other.

Therefore, when the effective value currents are the same and the N-phase current is 0, the sum is always zero when the instantaneous value of the three-phase (R, S, T) current is calculated with a 120 ° phase difference.

Equation 1 below is a formula for calculating the leakage current of the three-phase four-wire.

[식 1]

[Equation 1]

By using Equation 1, the synthesized value of the current flowing in the R, S, and T phases is obtained, and the measured N value is subtracted from the synthesized value to become the leakage current value.

However, when the current phase difference of the R, S, and T phases is not 120 degrees, the values of the R, S, and T phases are slightly complicated in decimal units in [Equation 1], but the form of the overall equation does not change.

As described in detail above, in the prior art, it is necessary to check whether there is a short circuit for each low voltage circuit in order to detect a ground line leakage, and when three to four circuits are newly established, it cannot be measured by one image current transformer. It is possible to display by integrating the measured current by measuring the leakage current even when 3 ~ 4 circuits are newly established.It also monitors the leakage current in real time for each distribution line. There is an effect that can prevent accidents in advance.

Claims (2)

In the 4CT combination portable leakage current measuring device for three-phase four-wire underground cable low voltage line of R, S, T, N, A power supply unit 1 to which power is applied; A sensor input unit having four separate image current transformers of R, S, T, and N phases, into which phases of the current transformer are input when power is applied from the power source unit 1; A multi-switch unit 3 which receives a sensor signal of a current transformer from the sensor input unit 2 and sends the sensor signal to a DMM / ADC unit; A DMM / ADC unit 4 for converting the sensor signal of each phase received from the multiple switch unit 3 into a digital signal (22 bit ADC = about 4 million counters) and sending it to the CPU; A CPU 5 which periodically measures the digital signals of each phase received from the DMM / ADC unit 4 and calculates the measurement data of each phase, the CPU using the digital signals input and processed from the four separate current transformers The CPU (5) which obtains a synthesized value of the currents flowing on the R, S, and T from [Equation 1], and calculates a leakage current value by adding or subtracting the value of the N phase measured from the synthesized value; A memory (6) for storing a result of calculating measurement data of each phase in the CPU; An LCD screen 7 which shows the calculated leakage current calculated by the CPU 5 and the measured current of each phase; A key operation unit 8 for controlling the CPU through key operation; And 4CT combination portable earth leakage measuring apparatus including USB (9) which can carry data easily.

[Equation 1] In the 4CT combination portable leakage current measuring method for three-phase four-wire underground cable low voltage line of R, S, T, N, A current measuring step (ST1) of measuring current of phases input to a current transformer of a sensor input unit having four individual image current transformers of R, S, T, and N phases when power is applied; A signal conversion step (ST2) of converting the current measurement value into a digital signal and transmitting it to the CPU after the current measurement step (ST1); After the signal conversion step (ST2) as a data calculation step (ST3) for calculating the measurement data of each phase in the CPU, R, S and by using [Equation 1] of the measured values of the R, S, T and N phases measured Calculating the synthesized value of the current flowing in the T phase, and subtracting the measured N-phase value from the synthesized value is a leakage current value; A result display step (ST4) of storing the result value in a memory and displaying it on an LCD screen after the data operation step (ST3); A measurement completion step (ST5) of terminating the measurement if the leakage current is not measured after the result display step (ST4); If it is confirmed that the leakage current is measured after the result display step (ST4), take immediate action and report to the central control panel (not shown) and reporting step (ST6), portable short-circuit measuring method combined.

[Equation 1]

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