KR20220167130A - PT Fault Detection Device of 3-Phase Integrated MOF and 3-Phase Integrated MOF Fault Detection Apparatus - Google Patents

Abstract

A PT failure detection device of a three-phase integrated MOF of the present invention may include: a voltage measurement unit for measuring voltages of secondary side voltage terminals of the MOF; a current measurement unit for measuring currents of secondary side current terminals of the MOF; a current vector calculation unit for calculating a three-phase current vector from the current values measured by the current measurement unit; a voltage vector calculation unit for calculating the three-phase voltage vector from the voltage values measured by the voltage measurement unit; and a PT failure determination unit for determining whether the PT of the MOF has failed from the three-phase current vector and the three-phase voltage vector.

Description

PT Fault Detection Device of 3-Phase Integrated MOF and 3-Phase Integrated MOF Fault Detection Apparatus}

The present invention relates to a method and apparatus for detecting a failure of a three-phase integrated MOF PT using secondary side voltage and current of the MOF PT.

In the distribution system, MOF (Metering OutFit, hereinafter referred to as MOF) is also called an instrument transformer. It has an insulated form, and a meter is installed on the secondary side of the terminal block of the MOF to measure the total amount of power.

1 is a photograph showing a state in which PTs and CTs are embedded in an inflow-type three-phase integrated MOF frame.

2 is a photograph showing a case of PT failure (wire breakage) in the MOF.

3 is a photograph showing the external appearance of PT and CT of an inflow-type three-phase integrated MOF.

4 is a photograph showing the appearance of a PT having a three-phase integrated iron core of an inflow-type three-phase integrated MOF.

High voltage customers who receive power with a voltage of 229kV use MOF (Metering OutFit, hereinafter referred to as MOF), an instrument transformer composed of an instrument transformer and current transformer, in an oil-immersed type and a molded type. Among the two MOF types, the inflow type is mostly used in the field. In the case of an oil-immersed MOF, as shown in FIG. 1, a PT, an instrument transformer, and a CT, a current transformer, are embedded in a steel cover. It is weighed.

If the CT is out of order, it is possible to determine whether or not it is out of order by measuring the current ratio in the live wire state with the ‘MOF ratio error meter’, and also, it is possible to negotiate a rate for the under-metered part.

However, in the case of a PT failure, there is no way to determine the failure in the current live wire state. This means that in order to determine the PT failure, the detection unit must be directly contacted with the high-voltage side terminal and the detection device is also heavy and bulky. However, this is because it is difficult to carry heavy equipment in order to determine whether or not there is a failure, and it is difficult to carry out when considering the safety aspect of the work to directly contact the detection device to the high-voltage side terminal.

On the other hand, it was thought that most of the MOF exploded when a PT failure occurred inside the MOF due to the influence of a fault current, etc., but as a result of confirmation, there was no abnormality on the outside of the MOF, but as shown in FIG. It was confirmed that there are many.

In this case, if the secondary side voltage of the phase connected to the failed PT is 0, it can be inferred whether the PT is out of order, but a voltage similar to or slightly lower than 110V is measured on the secondary side. This is because in the case of the oil-immersed MOF, the iron core of the PT is a three-phase integral type as shown in FIG. 4, so even if the voltage of one phase is disconnected from the primary side, the voltage appears in the phase where the PT is broken by the induced current (magnetic flux) of the other two phases through the integral iron core. . In this case, since the primary side voltage of the phase in which the PT is out of order is not transferred to the secondary side of the MOF, an error occurs in weighing.

Therefore, an appropriate method for determining whether a PT as well as a CT in an oil-immersed MOF is out of order is desired.

Republic of Korea Publication No. 10-2021-0051887

An object of the present invention is to provide a PT failure detection device of a three-phase integrated MOF and an MOF failure detection device that can check whether a PT built into an oil-immersed MOF has a failure.

An apparatus for detecting a PT failure of a three-phase integrated MOF according to an aspect of the present invention includes a voltage measurement unit for measuring voltages of secondary side voltage terminals of the MOF; a current measuring unit for measuring currents of secondary side current terminals of the MOF; a current vector calculation unit calculating a three-phase current vector from the current values measured by the current measurement unit; a voltage vector calculation unit calculating a three-phase voltage vector from the voltage values measured by the voltage measurement unit; and a PT failure determination unit determining whether or not the PT of the MOF has failed, based on the three-phase current vector and the three-phase voltage vector.

Here, the current vector calculation unit may estimate the three-phase current vector sum from the current value measured at the video terminal of the MOF.

Here, the voltage vector calculation unit calculates the reactive power and active power of each phase from the measured voltage values of the voltage measuring unit and the measured current values of the current measuring unit, and the ratio of reactive power to active power for each phase. The voltage phase of each phase can be estimated from

Here, the voltage vector calculation unit may obtain a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the voltage measurement unit for more than half a period of a power frequency.

Here, the current vector calculation unit may obtain a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the current measurement unit for more than half a period of a power frequency.

Here, the PT failure determination unit determines that the PT is normal due to the 3-phase load balance when both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, and the 3-phase voltage vector sum and 3-phase current vector sum are both 0. Otherwise, if the PT is determined to be normal due to load imbalance in the three phases, the vector sum of the three phase voltages is 0, and the vector sums of the three phase currents are all non-zero, the PT failure may be determined.

Here, a user interface for notifying an operator of a failure determination result of the PT failure determination unit may be further included.

A three-phase integrated MOF failure detection device according to another aspect of the present invention includes a voltage measurement unit for measuring voltages of secondary side voltage terminals of the MOF; a current measuring unit for measuring currents of secondary side current terminals of the MOF; a current vector calculation unit calculating a three-phase current vector from the current values measured by the current measurement unit; a voltage vector calculation unit calculating a three-phase voltage vector from the voltage values measured by the voltage measurement unit; a CT failure determining unit for determining whether the MOF has a CT failure; and a PT failure determination unit determining whether or not the PT of the MOF has failed, based on the three-phase current vector and the three-phase voltage vector.

Here, the CT failure determining unit may compare current values measured in the primary-side line of each phase of the MOF with current values measured in the secondary-side current terminals of the MOF to determine whether the CT is out of order.

Here, the PT failure determination unit determines that the PT is normal due to the 3-phase load balance when both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, and the 3-phase voltage vector sum and 3-phase current vector sum are both 0. Otherwise, if the PT is determined to be normal due to load imbalance in the three phases, the vector sum of the three phase voltages is 0, and the vector sums of the three phase currents are all non-zero, the PT failure may be determined.

Here, the voltage vector calculation unit calculates the reactive power and active power of each phase from the measured voltage values of the voltage measuring unit and the measured current values of the current measuring unit, and the ratio of reactive power to active power for each phase. The voltage phase of each phase can be estimated from

Here, the voltage vector calculation unit may obtain a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the voltage measurement unit for more than half a period of a power frequency.

Here, the current vector calculation unit may obtain a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the current measurement unit for more than half a period of a power frequency.

Here, the CT failure determining unit may determine that the CT is out of order when the pattern of the voltage vector and the pattern of the current vector of each phase are not similar and the PT is determined to be normal.

If the PT failure detection device and/or the MOF failure detection device of the three-phase integrated MOF according to the spirit of the present invention having the above configuration is implemented, it is easy to check whether the PT built in the oil-immersed MOF has a failure at low pressure (secondary side). There are benefits to being able to

The PT failure detection device and/or MOF failure detection device of the three-phase integrated MOF of the present invention has an advantage of supporting rate normalization by converting under-metering due to PT failure of the MOF to normal metering.

The PT fault detection device and/or MOF fault detection device of the three-phase integrated MOF of the present invention has the advantage of reducing the probability of safety accidents because it measures and judges on the secondary side (low voltage) rather than the primary side (high voltage) of the MOF. .

1 is a photograph showing a state in which PTs and CTs are embedded inside an inlet-type three-phase integrated MOF frame.
Figure 2 is a photograph showing a case of PT failure (wire break) in the MOF.
Figure 3 is a photograph showing the appearance of the PT and CT of the inflow-type three-phase integrated MOF.
4 is a photograph showing the appearance of a PT having a three-phase integrated iron core of an inflow-type three-phase integrated MOF.
5 is a block diagram illustrating an embodiment of a PT failure detection device of a three-phase integrated MOF according to the spirit of the present invention.
6 is a conceptual diagram illustrating a connection structure between a PT failure detection device of the three-phase integrated MOF of FIG. 5 and a MOF terminal block;
Figure 7 is a block diagram showing an embodiment of a three-phase integrated MOF failure detection device according to the spirit of the present invention.

In describing the present invention, terms such as first and second may be used to describe various components, but the components may not be limited by the terms. Terms are only for the purpose of distinguishing one element from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention.

When a component is referred to as being connected or connected to another component, it may be directly connected or connected to the other component, but it may be understood that another component may exist in the middle. .

Terms used in this specification are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions may include plural expressions unless the context clearly dictates otherwise.

In this specification, the terms include or include are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features or numbers, It can be understood that the presence or addition of steps, operations, components, parts, or combinations thereof is not precluded.

In addition, shapes and sizes of elements in the drawings may be exaggerated for clearer description.

5 is a block diagram illustrating an embodiment of a PT failure detection device of a three-phase integrated MOF according to the spirit of the present invention.

The PT failure detection device 100 of the illustrated three-phase integrated MOF includes a voltage measuring unit 110 for measuring voltages of secondary side voltage terminals of the MOF; a current measurement unit 120 for measuring currents of secondary side current terminals of the MOF; a current vector calculation unit 140 that calculates a three-phase current vector (vectors or vector sum of each phase) from the current values measured by the current measuring unit; a voltage vector calculation unit 130 that calculates a three-phase voltage vector (vectors or vector sum of each phase) from the voltage values measured by the voltage measurement unit; and a PT failure determining unit 160 that determines whether or not the PT of the MOF has failed from the three-phase current vector and the three-phase voltage vector.

Depending on implementation, a user interface 180 for notifying an operator of a failure determination result of the PT failure determination unit 160 may be further included.

In order to detect a PT failure according to the spirit of the present invention, it is first necessary to know the sum (vector sum) of the current vectors of each phase of the three phases with respect to the secondary side current terminals of the MOF. For this purpose, the current vector calculation unit 140 is provided. .

Depending on the implementation, the current vector calculation unit 140 may apply various current vector calculation methods.

As described in the prior art, considering that the CT of the MOF is regularly inspected by the 'MOF ratio error meter', the current vector calculation unit 140 according to a simple implementation is the current value measured at the video terminal of the MOF. The three-phase current vector sum can be estimated from In this case, it is assumed that the vector sum of three-phase currents is zero if zero phase current does not exist.

The current vector calculation unit 140 according to a complex implementation may obtain a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the current measurement unit for more than half a cycle of the power frequency. This follows the method used in precision measurement equipment such as an oscilloscope. In this case, each three-phase current vector calculated by the current vector calculation unit 140 is used for cross-checking the inspection result of the 'MOF specific error measuring instrument'. may be

Depending on the implementation, the voltage vector calculation unit 130 may also apply various voltage vector calculation methods.

For example, in a method used in a general metering device, the voltage vector calculator 130 calculates each voltage from the voltage values measured by the voltage measurement unit 130 and the current values measured by the current measurement unit 120. Reactive power and active power of each phase can be calculated, and the voltage phase of each phase can be estimated from the ratio of reactive power to active power for each phase.

Alternatively, in a method used in precision measurement equipment, the voltage vector calculation unit 130 observes the pattern of instantaneous voltage values of each phase measured by the voltage measurement unit 110 for more than half a cycle of the power frequency, The phase difference for the phase can be obtained.

The user interface 180 is most simply implemented as an LED/buzzer that is turned on/off and lit/pronounced according to a PT failure or normal determination result, or each of a three-phase voltage vector (with a three-phase voltage vector) It can be implemented as a display showing a pattern on a frequency axis, a time axis, or a phasor.

The illustrated PT failure determination unit 160 determines that the PT is normal with the 3-phase load balance when both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, and the 3-phase voltage vector sum and the 3-phase current vector sum are 0. If all are not 0, it is determined that the PT is normal due to 3-phase load imbalance, and if the 3-phase voltage vector sum is 0 and the 3-phase current vector sum is not all 0, it can be determined that the PT is out of order.

6 is a conceptual diagram illustrating a connection structure between a PT failure detection device of the three-phase integrated MOF of FIG. 5 and a MOF terminal block. The principle of the failure determination method of the PT failure determination unit 160 of FIG. 5 will be described with reference to FIG. 6 .

Oil-immersed MOF uses a PT with a three-phase integral iron core, and when one phase PT fails, the voltage of the fault phase appears due to the induced current (magnetic flux) of the other two phases.

In case of a normal real field, it is common that the three-phase vector sum of voltage and current is not balanced respectively. That is, Va+Vb+Vc≠0, Ia+Ib+Ic≠0.

If the primary of the Va winding is disconnected, the secondary voltage by Va is not created in the case of a single iron core. On the other hand, in the case of an integrated triangular iron core, Va is created by Vb and Vc, and the built-in PT of the oil-immersed MOF is also the same.

That is, -Va=Vb+Vc, ⇒ Va+Vb+Vc=0. But Ia+Ib+Ic≠0.

Therefore, when Va+Vb+Vc=0 and Ia+Ib+Ic≠0, failure of the built-in PT can be expected.

In summary, it can be divided into the following three cases.

1) Va+Vb+Vc=0, Ia+Ib+Ic=0 ⇒ Normal (3 top load balance)

2) Va+Vb+Vc≠0, Ia+Ib+Ic≠0 ⇒ normal (unbalanced 3 upper loads)

3) Va+Vb+Vc=0, Ia+Ib+Ic≠0 ⇒ PT failure (unbalanced upper 3 loads)

Therefore, a method of determining a PT failure of an MOF having a three-phase integrated PT can be efficiently performed by determining that Va+Vb+Vc=0 and Ia+Ib+Ic≠0 when vector synthesis is performed.

FIG. 6 illustrates a connection configuration between the MOF terminal block and the voltage measuring unit 110 and the current measuring unit 120 of FIG. 5 for a method of utilizing the above-described method for determining a PT failure.

7 is a block diagram illustrating an embodiment of a three-phase integrated MOF failure detection device according to the spirit of the present invention.

The illustrated three-phase integrated MOF failure detection device 200 includes a voltage measuring unit 210 for measuring voltages of secondary side voltage terminals of the MOF; a current measurement unit 220 for measuring currents of secondary side current terminals of the MOF; a current vector calculation unit 240 that calculates a three-phase current vector from the current values measured by the current measurement unit 220; a voltage vector calculator 230 that calculates a three-phase voltage vector from the voltage values measured by the voltage measurer 210; a CT failure determining unit 250 that determines whether the MOF has a CT failure; a PT failure determining unit 260 that determines whether or not the PT of the MOF has failed from the three-phase current vector and the three-phase voltage vector; and a user interface 180 for notifying an operator of failure determination results of the CT failure determination unit 250 and the PT failure determination unit 260 .

7 is similar to the PT failure detection device of the three-phase MOF of FIG. That is, the functions of the illustrated voltage measurement unit 210, current measurement unit 220, current vector calculation unit 240, voltage vector calculation unit 230, and PT failure determination unit 260 are almost the same as in the case of FIG. can be the same

For example, the PT failure determining unit 260 determines that the PT is normal due to the 3-phase load balance when both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, and the 3-phase voltage vector sum and 3-phase current vector sum If all of these are not 0, it is determined that the PT is normal due to 3-phase load imbalance, and if the sum of 3-phase voltage vectors is 0 and all 3-phase current vectors are not 0, it can be determined that the PT is out of order.

The CT failure determination unit 250 may determine whether a CT failure occurs in various ways.

For example, in a method used in precision measurement equipment, the voltage/current vector calculators 230 and 240 convert the pattern of instantaneous voltage/current values of each phase measured by the voltage/current measurement units 210 and 220 to power When the voltage/current vector of each phase is obtained by obtaining the phase difference with respect to the reference phase of each phase by observing more than a half cycle of the frequency, the CT failure determination unit 250 determines that the pattern of the voltage vector and the pattern of the current vector of each phase If it is not similar and the PT is determined to be normal, it can be determined that the CT is out of order.

Alternatively, the current values measured in the primary-side line of each phase of the MOF are measured by a method and measuring equipment similar to the conventional 'MOF specific error measuring instrument', and the CT failure determination unit 250 measures the primary-side line of each phase of the MOF. It is possible to determine whether a CT is out of order by comparing the current values measured at the MOF with the current values measured at the secondary side current terminals of the MOF.

The user interface 180 notifies the operator of not only PT failure information but also CT failure information. Accordingly, the three-phase integrated MOF failure detection device of this embodiment can be used to replace the existing 'MOF specific error measuring instrument' or to cross-check the inspection results of the 'MOF specific error measuring instrument'.

Those skilled in the art to which the present invention pertains should understand that the embodiments described above are illustrative in all respects and not limiting, since the present invention can be embodied in other specific forms without changing the technical spirit or essential characteristics thereof. only do The scope of the present invention is indicated by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. .

100: PT failure detection device of 3-phase integrated MOF
110, 210: voltage measuring unit
120, 220: current measuring unit
130, 230: voltage vector calculator
140, 240: current vector calculator
160, 260: PT failure determining unit
180, 280: user interface
200: 3-phase integrated MOF fault detection device
250: CT failure determination unit

Claims (14)

a voltage measurement unit for measuring voltages of secondary side voltage terminals of the MOF;
a current measuring unit for measuring currents of secondary side current terminals of the MOF;
a current vector calculation unit calculating a three-phase current vector from the current values measured by the current measurement unit;
a voltage vector calculation unit calculating a three-phase voltage vector from the voltage values measured by the voltage measurement unit; and
PT failure determining unit for determining whether the PT of the MOF has failed from the 3-phase current vector and the 3-phase voltage vector
PT failure detection device of a three-phase integrated MOF comprising a.
According to claim 1,
The current vector calculator,
A PT fault detection device of a 3-phase integrated MOF that estimates the 3-phase current vector sum from the current value measured at the video terminal of the MOF.
According to claim 2,
The voltage vector calculator,
Calculating reactive power and active power of each phase from the measured voltage values of the voltage measuring unit and the measured current values of the current measuring unit, and estimating the voltage phase of each phase from the ratio of reactive power and active power for each phase PT failure detection device of 3-phase integrated MOF.
According to claim 1,
The voltage vector calculator,
A PT failure detection device of a three-phase integrated MOF that obtains a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the voltage measurement unit for more than half a cycle of the power frequency.
According to claim 1,
The current vector calculator,
A PT fault detection device of a three-phase integrated MOF that obtains a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the current measuring unit for more than half a cycle of the power frequency.
According to claim 1,
The PT failure determining unit,
If both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, PT is judged normal with 3-phase load balance,
If both the 3-phase voltage vector sum and 3-phase current vector sum are not 0, the 3-phase load unbalance is determined as PT normal,
A PT failure detection device of a three-phase integrated MOF that determines a PT failure when the three-phase voltage vector sum is 0 and the three-phase current vector sum is not all zero.
According to claim 1,
User interface for notifying the operator of the failure determination result of the PT failure determination unit
A PT failure detection device of a three-phase integrated MOF further comprising a.
a voltage measurement unit for measuring voltages of secondary side voltage terminals of the MOF;
a current measuring unit for measuring currents of secondary side current terminals of the MOF;
a current vector calculation unit calculating a three-phase current vector from the current values measured by the current measurement unit;
a voltage vector calculation unit calculating a three-phase voltage vector from the voltage values measured by the voltage measurement unit;
a CT failure determining unit for determining whether the MOF has a CT failure; and
PT failure determining unit for determining whether the PT of the MOF has failed from the 3-phase current vector and the 3-phase voltage vector
A three-phase integrated MOF fault detection device comprising a.
According to claim 8,
The CT failure determining unit,
A three-phase MOF fault detection device that compares current values measured in the primary-side line of each phase of the MOF with current values measured in the secondary-side current terminals of the MOF to determine whether a CT has failed.
According to claim 8,
The PT failure determining unit,
If both the 3-phase voltage vector sum and the 3-phase current vector sum are 0, PT is judged normal with 3-phase load balance,
If both the 3-phase voltage vector sum and 3-phase current vector sum are not 0, the 3-phase load unbalance is determined as PT normal,
A three-phase integrated MOF failure detection device that determines a PT failure when the sum of three-phase voltage vectors is 0 and all three-phase current vector sums are not 0.
According to claim 8,
The voltage vector calculator,
Calculating reactive power and active power of each phase from the measured voltage values of the voltage measuring unit and the measured current values of the current measuring unit, and estimating the voltage phase of each phase from the ratio of reactive power and active power for each phase 3-phase integrated MOF fault detection device.
According to claim 9,
The voltage vector calculator,
A three-phase integrated MOF fault detection device for obtaining a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the voltage measurement unit for more than half a cycle of the power frequency.
According to claim 12,
The current vector calculator,
A three-phase integrated MOF fault detection device for obtaining a phase difference with respect to a reference phase of each phase by observing a pattern of instantaneous voltage values of each phase measured by the current measuring unit for more than half a cycle of the power frequency.
According to claim 13,
The CT failure determining unit,
A three-phase integrated MOF fault detection device that determines that the CT is faulty when the pattern of the voltage vector and the pattern of the current vector of each phase are not similar and the PT is determined to be normal.

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