KR101645873B1 - Apparatus and method for detecting wrong wiring of watt-hour meter - Google Patents

Abstract

The present invention relates to an apparatus and a method for detecting the wrong wiring of a watt-hour meter. The apparatus includes a detection part which detects voltage and current signals from a three-phase three-wire watt-hour meter; a calculation part which calculates the effective and ineffective amount of power, and a phase angle for each phase and between phases based on the voltage and current signals; and a wrong wiring detecting part which detects the wrong wiring of the watt-hour meter based on the effective amount of power, a phase angle for each phase, the generation of a current value at non-active power metering, a period average power factor, and a phase difference between phases.

Description

TECHNICAL FIELD The present invention relates to an apparatus and a method for detecting miswiring in a watt-

The present invention relates to a miswiring detecting apparatus and method for a watt-hour meter, and more particularly, to a miswiring detecting apparatus and method for detecting a miswiring based on a voltage and a current signal detected from a watt-hour meter.

Generally, the power system has various transmission facilities for supplying electric power generated by the generator to the customer, and the electric power generated from the generator is supplied to the customer side through various transmission and transmission facilities in the middle.

On the customer side receiving the power supply, a watt-hour meter capable of measuring the amount of electricity received is to be installed. Watt-hour meters are generally divided into mechanical and digital (electronic), and current trends are dominated by digital watt-hour meters, which can acquire various information of supplied power.

This watt-hour meter can not measure the unacceptable high voltage and current like high pressure, so it is used in combination with a metering device such as MOF (Metering OutFit) or CT (Current Transformer) It is transformed into a low current and sent to the watt hour meter, and the watt hour meter weighs the denatured low voltage and low current.

In order to measure this in domestic three-phase four-wire supply system, the watt-hour meter consists of 10 current terminals, 3 current terminals, 3 voltage terminals, 1 voltage neutral terminal and 3 current return terminals. It has the structure that it is connected by the electric wire between the same transformer and the watt hour meter. At this time, if the connection between the transformer and the watt hour meter is wrong (in the case of a wrong connection), the phase displacement between the voltage and the current occurs, so that normal weighing can not be performed. In addition, it is impossible to infer the normal metering value because the abnormal metering due to such a miswiring varies at all times depending on the degree of load and the power factor state of the load.

An apparatus for integrating and storing information on the amount of power such as active power, reactive power, and power factor of the received power is referred to as a watt hour meter.

Therefore, although the electric power facilities are designed based on the normal electric power flow, when a fault occurs, there are various phenomena which cause a trouble to the customer such as overvoltage, undervoltage, overcurrent, frequency fluctuation, In the early stage, the failure must be removed to eliminate the fault.

In this connection, Korean Patent Laid-Open Publication No. 2004-0089155 discloses an electronic watt-hour meter having a false detection and alarm display function.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a three-phase three-wire watt- And a method of detecting a miswiring of a watt-hour meter by judging a case where a current value is generated when the average power factor is less than a predetermined range and a case where the phase difference between phases exceeds a predetermined angle It has its purpose.

According to an aspect of the present invention, there is provided an apparatus for detecting miswiring in a watt-hour meter, including: a detector for detecting a voltage and a current signal from a three-phase three-wire watt-hour meter; A calculating unit for calculating an effective and an ineffective power amount, phase and phase angle between phases based on voltage and current signals; And a miswiring detecting unit for detecting a miswiring of the watt hour meter based on an effective power amount, a phase angle with respect to each other, a current value at the time of no weighing, a period average power factor, and an in-phase difference.

Also, the calculating unit calculates an RMS (Root Mean Square) of each phase voltage, voltage and current over one period based on voltage and current signals converted into a digital signal through the converting unit, a phase voltage difference between phases, And calculates active power and reactive power for each phase based on the information.

In addition, the miswiring sensing unit may be configured such that when the effective power amount is negative, when the phase angle by phase is greater than a preset angle, when the current value occurs when the weight is not measured, when the period average power factor is less than a predetermined range, And the watt-hour meter determines that the watt-hour meter is broken if the watt-hour meter is at least one of the predetermined angles.

Also, the miswiring detection unit may include: an effective power amount sum value determination unit for determining whether the amount of active power is a negative value; Phase phase angle determiner for determining whether phase angles of any one of the three phases exceed ± 120 degrees; A weighing determination unit that determines whether a current value equal to or greater than a preset value is generated when the validity and the reactive power amount are '0'; A period average power factor determining unit for determining whether a period average power factor of a predetermined period is 50% or less; And an in-phase difference determination unit for determining whether the phase difference between phases exceeds ± 120 ° when the current values of the three phases are equal to or greater than a predetermined value.

Also, the active power amount sum value determining unit determines that the charged power amount is a negative value if the power factor phase difference is less than 50% due to a difference of ± 120 ° between the voltage and current phase angles.

The phase angle determining unit may determine that the phase difference of the voltage current falls within the range of -90 ° <θ <30 °, -30 ° <θ <90 ° in a balanced load, or the phase difference of the voltage current is 30 ° to 90 °, And when the phase angle falls within the range of 30 ° to -90 °, it is determined that the phase angle of each phase of any of the three phases exceeds ± 120 °.

If the phase difference between phases is more than 180 ° or the voltage phase difference of three phases is not more than ± 120 °, the weighing determination unit may set the starting current when the effective and reactive power amount is '0' Is present.

If the phase difference of the phase voltage falls within the range of 30 to 90 or -30 to -90 and the phase difference of the voltage and current does not exceed the range of +/- 120 DEG in any one of the phases, Or whether the period average power factor in the daytime is 50% or less.

When the phase difference of the phase voltage falls within the range of 30 ° to 90 ° or -30 ° to -90 ° and the voltage-current phase difference does not exceed ± 120 ° in any phase, And determines whether the phase difference between phases exceeds ± 120 °.

In addition, the miswiring detection unit senses miswiring of the watt-hour meter only when the watt-hour meter is a watt-hour meter.

Further, the present invention is characterized by further comprising a receiving power grasping unit for judging that the calculated active power amount is the received power when the amount is the backward effective power amount and recognizing that it is the power before the water repellency when the calculated amount is not the backward effective power amount.

According to an aspect of the present invention, there is provided a method for detecting miswiring in a watt-hour meter, comprising: detecting a voltage and a current signal from a three-phase three-wire watt-hour meter by a detecting unit; Calculating an effective and an ineffective power amount, a phase and an interphase phase angle based on the detected voltage and current signals by the calculating unit; And detecting the miswiring of the watt hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weight is measured, the period average power factor, and the phase difference between phases by the miswiring detection unit.

Further, after the step of calculating the effective and the reactive power amount, the phase and the phase angle between phases based on the detected voltage and current signals, it is determined that the effective power amount is the received power when the amount is the backward effective power amount, It is characterized by further comprising the step of determining that the power is the power.

The step of detecting the erroneous connection of the watt hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weighing, the period average power factor and the phase difference between phases is performed only when the watt- .

The step of sensing the erroneous wiring of the watt-hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weight is measured, the period average power factor and the phase difference between phases, When the current value is greater than the predetermined value, when the current value is greater than the predetermined value, when the current value is greater than the predetermined value, or when the current value is greater than the predetermined value, Is determined to be &quot;. &Quot;

The step of detecting the erroneous connection of the watt-hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weighing, the period average power factor, and the phase difference between phases includes: determining whether the active power amount is a negative value; Determining whether the phase angle by phase difference exceeds ± 120 ° on any one of the three phases; Determining whether a current value equal to or greater than a preset value is generated when the effective and reactive power amount is '0', determining whether the average period power factor of the predetermined period is 50% or less; And determining whether the phase difference between phases exceeds ± 120 ° when the current values of the three phases and the current values of the three phases are simultaneously set to a predetermined value or more.

The apparatus for detecting miswiring of the watt-hour meter according to the present invention having the above-described structure and the method of detecting the miswiring of the watt-hour meter based on the voltage and current signals detected from the watt-hour meter, It is possible to prevent an abnormal metering caused by an error in connection between the watt-hour meter and the terminal of the watt-hour meter, or a change in the internal voltage-current connection, and to perform a fair power transaction.

Fig. 1 is a view for explaining a normal wiring type of a three-phase three-wire watt-hour meter.
Figs. 2 to 7 are views for explaining a mis-wiring type of a three-phase three-wire watt-hour meter.
8 is a view for explaining a configuration of a miswiring detecting apparatus of a watt-hour meter according to the present invention.
9 is a view for explaining a detailed configuration of a miswiring detection unit employed in a miswiring detection apparatus of a watt-hour meter according to the present invention.
FIG. 10 is a flowchart for explaining a procedure of a miswiring detection method of a watt-hour meter according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings in order to facilitate a person skilled in the art to easily carry out the technical idea of the present invention. . First, in adding reference numerals to the constituent elements of the drawings, it should be noted that the same constituent elements are denoted by the same reference numerals whenever possible even if they are displayed on other drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the three-phase three-wire normal connection type is illustrated.

FIG. 1 is a view for explaining a normal wiring type of a 3-phase 3-wire watt-hour meter, and FIGS. 2 to 7 are views for explaining a mis-wiring type of a 3-phase 3-wire watt-hour meter.

Fig. 1 shows a normal wiring type of a three-phase three-wire watt-hour meter. In a normal connection, the phase angle of a three-phase three-wire type is as follows. When the load is balanced, when the ground power factor is 0 ~ 100%, the phase difference between voltage and current of one device is 30 ~ 120 ° and the phase difference of other device is -30 ~ 60 °. On the contrary, assuming that the load is in a state of phase, the difference between the voltage and current phase angles of one element is -30 ° to 120 ° when the power factor is 0 to 100%, and the other elements have a phase difference within the range of 30 to -60 ° will be. That is, the phase difference of the voltage current of one phase in the normal connection of the three-phase three-wire watt-hour meter can not exceed ± 120 ° (120 ° <θ <240 °, 120 ° <~ θ <-120 °).

In the following, mis-wiring types of three-phase three-wire are illustrated.

Fig. 2 is a graph showing the relationship between the voltage of the phase current of one phase and the phase of current of the other phase in the range of -90 DEG &lt; < The phase difference may exceed ± 120 °. Therefore, when the voltage-current phase difference of one phase exceeds 120 °, it can be judged as a mistake.

Fig. 3 shows a case where the load is in equilibrium, the phase difference between phases is 180 [deg.], And it is not measured, and if the phase difference of voltage and current does not exceed ± 120 [deg. It is not possible to judge whether or not there is a connection. Therefore, in such a case, when there is a starting current or a current value equal to or more than a predetermined value when there is no weighing, it can be judged as a wrong connection.

The following erroneous wiring types are used to judge the possibility of erroneous connection when the phase difference of the voltage current exceeds 30 ° ~ 90 ° or -30 ° ~ -90 ° and the voltage current phase difference does not exceed ± 120 ° And when the average power factor is less than 50% for a certain period of time, it is judged as a wrong connection. When the current value of all phases exceeds the predetermined value (more than the middle load), if the phase difference between phases exceeds ± 120 °, There is a way.

In the method of judging a misconnection when the average power factor of a period of time is 50% or less, FIG. 4 is a graph showing a case where the average power factor of the nighttime time period is 50% or less, P1 → P2 → P3 & 3S↔3L & 1S↔1L Type, and the customer who is usually overloaded in the night time, regardless of the load, usually uses light load (load less than 10% of the contracted power) for power factor compensation. Fig. 5 shows a case where the average power factor of the weekly time period is less than 50%, and P1 ~ P3 → P2 & 1S↔1L & 3S↔3L, And the ground power factor occurs even if a capacitor for power factor compensation is put into most of the load as a ground load.

In the case where the phase difference between the phases exceeds ± 120 ° when the current value of all phases is equal to or more than a predetermined value (heavy load or more) P1 → P2 → P3 & 1S↔1L are misconnected type, and FIG. 7 shows the type of misapplication of P1 → P3 → P2 & 3S → 3L when the average power factor of phase duration is 86.6% or less (120 degrees between phases).

Hereinafter, an apparatus and method for detecting miswiring of a watt-hour meter based on the above-mentioned three-phase three-wire mis-wiring type analysis result will be described.

8 is a diagram for explaining a configuration of a miswiring sensing apparatus 100 of a watt-hour meter according to the present invention.

8, a miswired sensing apparatus 100 of a watt-hour meter according to the present invention includes a detection unit 110, a conversion unit 120, a calculation unit 130, an electric power reception unit 140, And a sensing unit 150.

The detection unit 110 detects voltage and current signals from a three-phase three-wire type watt-hour meter.

The conversion unit 120 converts the detected analog signals, that is, voltage and current signals, into digital signals.

The calculation unit 130 calculates at least one of an effective and an ineffective power amount, a phase angle and an interphase phase angle based on the voltage and current signals. The calculating unit 130 calculates an RMS (Root Mean Square) of each phase voltage, voltage and current over one cycle based on the voltage and current signals converted into digital signals through the converting unit, a phase voltage difference between phases, Based on the sampling information, active power and reactive power are calculated for each phase.

The reception power grasp unit 140 grasps that the calculated active power amount is the reception power when the calculated amount is the backward transmission effective power and the reception power when the calculated amount is the backward transmission power.

The erroneous wire sensing unit 150 senses the erroneous connection of the watt-hour meter based on the active power amount, the phase angle with respect to each other, whether or not the current value is generated when the weight is unmeasured, the period average power factor, and the phase difference between phases. At this time, the miswiring sensing unit 150 senses miswiring of the watt-hour meter only when it is the watt-hour meter of the receiving power.

In the case where the effective power amount is a negative value, the phase angle is greater than a predetermined angle, the current value occurs when the weight is not weighted, the case where the period average power factor is less than a preset range, The watt-hour meter determines that the watt-hour meter is connected to the watt-hour meter.

Although not shown in the drawings, in the case of an AMI / AMR-based watt-hour meter, a notification unit for displaying mis-wiring notification information in a display window of a watt-hour meter when miswiring of the watt-hour meter is detected, And a transmission unit for transmitting the data.

9 is a view for explaining a detailed configuration of a miswiring detection unit employed in a miswiring detection apparatus of a watt-hour meter according to the present invention.

9, the miswiring detection unit 150 according to the present invention detects a miswiring of the watt-hour meter based on the active power amount, the phase angle per phase, whether or not the current value is generated when the weight is unmeasured, the period average power factor, Detection.

For this, the erroneous wire sensing unit 150 includes an active power amount sum determination unit 151, a phase angle determination unit 152, a weighing determination unit 153, a period average power factor determination unit 154, (155).

The active power sum value determination unit 151 determines whether the active power amount is a negative value.

The active power amount sum value determination unit 151 determines that the charged power amount is a negative value when the power factor phase difference is less than 50%

The phase angle determining unit 152 determines whether the phase angle of each of the three phases exceeds ± 120 degrees.

The phase angle determining unit 152 determines whether the phase difference of the voltage current falls within a range of -90 DEG <? &Lt; 30 DEG and -30 DEG < 90 DEG in a balanced load, When it falls within the range of -30 ° to -90 °, it is determined that the phase angle by phase difference in any one of the three phases exceeds ± 120 °.

The weighing determination unit 153 determines whether a current value equal to or greater than a preset value is generated when the effective and reactive power amount is '0'.

When the phase difference between phases is more than 180 ° or when the phase difference of voltage phase current of three phases does not exceed ± 120 °, the weighing determination unit 153 determines whether the starting current or the current Value is present.

The period average power factor determination unit 154 determines whether the period average power factor of the predetermined period is 50% or less.

When the phase difference of the voltage currents in the respective phases falls within the range of 30 ° to 90 ° or -30 ° to -90 ° and the voltage and current phase difference does not exceed ± 120 ° in any one of the phases, It is determined whether the period average power factor in the time or daytime is 50% or less.

Phase phase difference determination unit 155 determines whether the phase difference between phases exceeds ± 120 ° when the current values of the three phases are simultaneously set to a predetermined value or more.

When the phase difference of the phase voltage falls within the range of 30 to 90 or -30 to -90 and the phase difference of the voltage and current does not exceed the range of +/- 120 DEG in any phase, In this way, it is determined whether the phase difference between phases exceeds ± 120 °.

FIG. 10 is a flowchart for explaining a procedure of a miswiring detection method of a watt-hour meter according to the present invention.

Referring to FIG. 10, the miswiring detection method of the watt-hour meter according to the present invention uses the miswiring detection device of the watt-hour meter described above, and a repeated description will be omitted.

First, voltage and current signals are detected from a three-phase three-wire type watt-hour meter (S100).

Next, the detected voltage and current signals are converted into digital signals (S200).

Next, based on the voltage and current signals converted into the digital signals, the effective and reactive power amounts, phases, and phase angles are calculated (S300). In operation S300, the active power and the reactive power of each phase are calculated based on the RMS (Root Mean Square) of each phase voltage, voltage and current over one cycle, the phase of voltage and phase by phase, phase difference between phases, .

Next, it is determined whether the calculated active power amount is the reverse effective power amount (S400). It is determined that the received power is the received power when the amount is the backward effective power amount and the power before the water-repellent power when the amount is not the backward effective power amount.

Next, in the case of the receiving power, a miswiring of the watt hour meter is detected based on the active power amount, the phase angle with respect to each other, the occurrence of the current value when there is no weighing, the period average power factor and the phase difference between phases (S500). When the effective power amount is negative in step S500, the phase angle exceeds the preset angle, the current value occurs in the case of no weighing, the period average power factor is less than the predetermined range, (S600), the watt-hour meter determines that the watt-hour meter is misconnected.

As described above, according to the present invention, a miswiring detecting apparatus and method thereof detects a miswiring of a watt-hour meter based on a voltage and a current signal detected from the watt-hour meter, so that when the wattmeter is newly installed or replaced, It is possible to easily detect abnormality metering caused by a misjudgment or change of internal voltage and current connection and perform a fair power transaction.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but many variations and modifications may be made without departing from the scope of the present invention. It will be understood that the invention may be practiced.

100: Wrong wire detection device of watt hour meter
110:
120:
130:
140:
150:
151: Active power amount sum value determination unit
152: Phase angle determining unit
153:
154: Period average power factor determination unit
155:

Claims (16)

A detector for detecting a voltage and a current signal from a three-phase three-wire type watt hour meter;
A calculating unit that calculates at least one of an effective power amount, a reactive power amount, a phase angle by phase, and an interphase phase angle based on voltage and current signals; And
An erroneous wire sensing unit for sensing erroneous wiring of the watt hour meter based on an effective power amount, a phase angle for each phase, a current value generated when no weight is measured, a period average power factor and phase difference between phases;
Lt; / RTI &gt;
The erroneous wiring detection unit may include:
And a phase angle determining unit for determining that the watt-hour meter is misconnected when the phase angle of each phase of the three phases exceeds ± 120 °,
The miswiring detection unit
In the case where the phase angle of all of the three phases is ± 120 ° or less, the current value occurs when no weighing is performed, the case where the period average power factor is less than the preset range, and the case where the phase difference between phases exceeds the predetermined angle And if it is determined that the watt-hour is one, it is determined that the watt-hour meter is a mis-wiring. The method according to claim 1,
The calculating unit calculates an RMS (Root Mean Square) of each phase voltage, a voltage and a current, a voltage current phase by phase, a phase difference between phases, and current sampling information based on voltage and current signals converted into a digital signal through a converter And calculates the active power and the reactive power of each phase on the basis of the detected power consumption. delete The method according to claim 1,
The erroneous wiring detection unit may include:
An effective power amount sum value determining unit for determining whether the effective power amount is a negative value;
A weighing determination unit for determining whether or not the watt-hour meter is wired by determining whether the effective and reactive power amount is '0' and a current value equal to or greater than a preset value is generated when the phase angle of all of the three phases is ± 120 ° or less;
A period average power factor determining unit determining whether the watt-hour meter is misconnected by determining whether the period average power factor of the predetermined period is less than or equal to 50% when the phase angles of all of the three phases are equal to or less than 120 degrees; And
By judging whether the phase difference between phases on any one of the three phases exceeds ± 120 ° when the phase angle of each of the three phases is ± 120 ° or less and the current values of the three phases are simultaneously set to a predetermined value or more, An in-phase phase difference judging unit for judging whether or not a fault occurs;
Further comprising: an error detection unit for detecting an error in the watt-hour meter of the watt-hour meter. 5. The method of claim 4,
Wherein the effective power amount sum value determining unit determines that the charged power amount is a negative value when the voltage current phase angle is ± 120 ° and the power factor is less than 50%. 5. The method of claim 4,
The phase angle determining unit may determine that the phase difference of the voltage current falls within the range of -90 ° <θ <30 ° and -30 ° <θ <90 ° in a balanced load, or the phase difference of the voltage current is 30 ° to 90 ° or -30 ° To -90 degrees, it is determined that phase angles of any one of the three phases exceed ± 120 degrees. 5. The method of claim 4,
If the phase difference between phase differences exceeds 180 ° or the phase difference of voltage phase currents of three phases does not exceed ± 120 °, the weighing determination section determines whether there exists a starting current or a current value equal to or greater than a preset value when the effective and reactive power amount is '0' And judges whether the watt-hour meter is wired or not. 5. The method of claim 4,
When the phase difference of the phase voltage current falls within the range of 30 ° to 90 ° or -30 ° to -90 ° and the voltage and current phase difference does not exceed ± 120 ° in any one of the phases, And judges whether the period average power factor in time is 50% or less. 5. The method of claim 4,
The phase difference determining unit may determine that the phase difference of the phase voltage falls within the range of 30 ° to 90 ° or -30 ° to -90 ° and if the phase difference of voltage current does not exceed ± 120 ° in any phase, And determines whether or not the phase difference exceeds ± 120 °. The method according to claim 1,
Wherein the erroneous wiring sensing unit senses the erroneous wiring of the watt-hour meter only when it is a watt-hour meter of the received power. 11. The method of claim 10,
Further comprising an electric power detection unit for detecting that the calculated active power amount is the received power when the calculated effective power amount is the amount of backwired active power and that the measured power is the power before the water repellency when the calculated effective power amount is not the backward effective power amount. Detecting a voltage and a current signal from a three-phase three-wire watt-hour meter by a detecting unit;
Calculating at least one of an effective power amount, a reactive power amount, a phase angle by phase, and an interphase phase angle based on a voltage and a current signal by a calculation unit; And
Detecting an erroneous wiring of the watt hour meter based on an active power amount, a phase angle by phase, a current value occurrence when no weight is measured, a period average power factor, and an phase difference between phases by a miswiring detection unit;
Lt; / RTI &gt;
The step of detecting the erroneous connection of the watt-hour meter based on the active power amount, the phase angle with respect to each other, the generation of the current value when no weight is measured, the period average power factor,
Determining that the watt-hour meter is misconnected when the phase angle of each of the three phases exceeds ± 120 °; And
In the case where the phase angle of all of the three phases is ± 120 ° or less, the current value occurs when no weighing is performed, the case where the period average power factor is less than the preset range, and the case where the phase difference between phases exceeds the predetermined angle And judging that the watt hour meter is a miswiring if it corresponds to one
Wherein the power meter is connected to the power meter. 13. The method of claim 12,
After calculating the effective and reactive power amounts, the phases and the interphase phase angles based on the detected voltage and current signals,
Further comprising the step of: determining that the received power is the received power when the effective power amount is the amount of the backward transmission effective power and determining that the received power is the power before the water-repelling if not the backward-effective power amount. 13. The method of claim 12,
The step of detecting the erroneous connection of the watt hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weight is measured, the period average power factor and the phase difference between phases,
And the erroneous wiring of the watt-hour meter is detected only when the watt-hour meter is a watt-hour meter. delete 13. The method of claim 12,
The step of detecting the erroneous connection of the watt hour meter based on the active power amount, the phase angle by phase, the generation of the current value when no weight is measured, the period average power factor and the phase difference between phases,
Determining whether the effective power amount is a negative value;
Determining whether the watt-hour meter is misconnected by judging whether an effective and reactive power amount is '0' and a current value equal to or greater than a predetermined value is generated when phase angles of all three phases are equal to or less than ± 120 °;
Determining whether or not the watt-hour meter is misconnected by determining whether the period average power factor of the predetermined period is 50% or less when the phase angles of all of the three phases are ± 120 ° or less; And
By judging whether the phase difference between phases on any one of the three phases exceeds ± 120 ° when the phase angle of each of the three phases is ± 120 ° or less and the current values of the three phases are simultaneously set to a predetermined value or more, Judging whether a wrong connection is made;
And detecting a false connection of the watt-hour meter.

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