JP2014183725A - Input conversion board for digital protection control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an input conversion board for holding information capable of achieving control corresponding to individual sensor characteristics of a hole element sensor adopted as an input converter.SOLUTION: An input conversion board for a digital protection control device of a power system includes: an input side primary circuit to which a current to be measured is inputted; a hole element sensor for detecting a current to be measured of the power system; a secondary circuit for outputting voltage generated in the hole element sensor corresponding to the current to be measured; a constant current source for supplying a constant current to the hole element sensor; a control circuit for controlling a value of the constant current; and a non-volatile memory for holding information about the control. A constant current value corrected by a correction value of the constant current obtained based on information about errors of sensor characteristics is set in the constant current source.

Description

  The present invention relates to a digital protection control device, and more particularly to an input conversion board in which a performance improvement and productivity improvement technique is applied to an input conversion unit in which an input transformer for measuring the amount of electricity in a power system is mounted.

  In a digital protection control device used for power system protection control, an input unit for taking in an output from an input transformer that measures the voltage and current of the power system, and protection control calculation by executing protection control calculation Each control unit configured to perform is configured as a separate unit. The input transformer in the above is mounted on the input conversion unit. However, because the input transformer is large and heavy, and because it requires multiple mounting, it has a large size, large mass, and many wires. It is a factor that increases the overall cost of the product. For this reason, the conventional input conversion unit uses an input transformer that uses a toroidal core with low leakage flux for the purpose of high-density mounting. It was difficult to make an input conversion unit.

  Therefore, as described in Patent Document 1, a Hall element sensor is used as an input transformer for measuring the current of the power system, thereby solving the above problem.

Japanese Patent No. 2552683 (Japanese Patent Laid-Open No. 1-83154)

  However, the Hall element sensor used as an input transformer for measuring the electric current of the power system is subject to individual variations such as the positional relationship between the ferromagnetic core and the Hall element itself and the characteristics of the Hall element itself. For this reason, variations occur in the relationship (sensor characteristics) between the current to be measured and the sensor output. In the protection control device that performs control based on the sensor output, it is necessary to perform correction on the sensor characteristics in order to eliminate this variation in solids. In particular, it is common to perform digital correction after A / D conversion, and it is necessary to store the correction value in the control unit on which the microcomputer is mounted, and the combination of the microcomputer mounting unit and the input converter unit may be fixed. It was necessary.

  Further, in the conventional input transformer, it is necessary to correct the sensor characteristics while satisfying the accuracy in a wide dynamic range and low frequency, which are required specifications of the protection control device.

  An object of the present invention is to provide an input conversion board holding information that enables control according to individual sensor characteristics of a Hall element sensor employed as an input transformer.

  The present invention comprises a Hall element sensor for detecting a measured current of a power system, a primary circuit on the input side and an output side secondary circuit of the Hall element sensor, and a constant current source for supplying a constant current to the Hall element sensor. The input conversion board includes a control circuit for controlling a constant current value and a non-volatile memory for holding information on the constant current value and sensor characteristics.

  The information held in the nonvolatile memory includes a gain determined by a ratio between the current value of the current to be measured that is input to the Hall element sensor and the voltage value that is the output of the sensor, and the current to be measured and the output voltage. Error information from the standard value regarding each of the phase differences, and information indicating the relationship between the constant current value and the detectable range (dynamic range) of the current value of the current to be measured are held.

  A digital protection control device used for protection control of the power system can perform control according to individual sensor characteristics of the Hall element sensor by referring to information held in the nonvolatile memory of the input conversion board.

It is a block diagram of the input conversion board | substrate which uses a Hall element sensor. It is explanatory drawing of the gain error of an input conversion board | substrate. It is explanatory drawing of a structure of the input conversion board | substrate which can respond | correspond to a some channel. It is a figure which shows the phase error of the input between channels. It is a figure which shows the operation principle of a Hall element sensor. It is a figure which shows the relationship between the constant current of a Hall element, and a dynamic range.

(Configuration of input conversion board)
FIG. 1 shows the configuration of an input conversion board in a digital protection control device for a power system in this embodiment. The input conversion board outputs the output voltage of the Hall element sensor 1 that detects the magnitude of the measured current of the power system, the primary circuit 2 that inputs the measured current on the input side of the Hall element sensor 1, and the output side sensor. Secondary circuit 3 that performs constant current source 4 that supplies a constant current to the Hall element sensor 1, a control circuit 5 that controls the value of the constant current, and a non-volatile that holds information on the value of the constant current and sensor characteristics The current to be measured is inputted from the input 7 and the voltage generated in the Hall element sensor 1 corresponding to the current to be measured is outputted from the output 8. As will be described later, the Hall element sensor 1 is provided in a current sensor that detects the magnitude of a current to be measured.

  The information held in the nonvolatile memory 6 includes a gain determined by the ratio between the current value of the current to be measured that is input to the Hall element sensor 1 and the voltage value that is the output of the sensor, and the current to be measured and the output voltage. And error information from the standard value for each of the phase differences between them and information indicating the relationship between the constant current value of the constant current source 4 and the detectable range (dynamic range) of the current value of the measured current. The

(Operational principle of Hall element sensor)
FIG. 5 is a diagram illustrating the operating principle of the Hall element sensor 1.

  Like the current sensor shown in FIG. 1 of Patent Document 1, the Hall element sensor 1 is provided in a part of the ring of the ring-shaped ferromagnetic core. When the magnetic field generated by the current to be measured passing through the center of the ring of the ring-shaped ferromagnetic core and penetrated by the ferromagnetic core penetrates the Hall element sensor 1, it corresponds to the current to be measured in a direction perpendicular to the magnetic field. Is output from the Hall element sensor 1. A constant current that supplies electric charges (electrons) that are the source of the output voltage is applied by the constant current source 4 in a direction perpendicular to the direction of the magnetic field and the direction of detection of the output voltage.

  FIG. 5 schematically shows the above operation. When the current to be measured flows in the direction of the arrow 18, a magnetic field is generated in the direction of the arrow 19 around the current to be measured. (●) indicates the direction of the magnetic field from the back side to the front side of the paper surface, and (×) indicates the direction of the magnetic field from the front side to the back side of the paper surface.

On the other hand, when a constant current is supplied from the constant current source 17 to the Hall element sensor in the direction of the solid arrow, and a charge is supplied to the Hall element sensor, a magnetic field is generated in the direction of the arrow 20 around the constant current. (Note that although FIG. 5 illustrates that a positive charge is supplied, in reality, negatively charged electrons are supplied from the opposite direction of the arrow in the sensor.)
As a result, both sides of the Hall element sensor close to the current to be measured strengthen each other and the other side weakens the magnetic field, so the path of the charge supplied to the sensor is bent in the direction opposite to the current to be measured. (Lorentz force known in electromagnetism). (Actually, the electrons supplied from the left side of FIG. 5 are bent toward the current to be measured.) As the charge path is bent, a positive charge is accumulated on the opposite side of the Hall element sensor from the current to be measured. (21) Negative charge accumulates on the opposite side (16), and this charge bias is output as the output voltage 22 of the Hall element sensor.

  The larger the current value of the current to be measured, the larger the magnetic field 19 generated around it, and the greater the degree of bending of the path of the charge supplied to the sensor, so the output voltage 22 of the Hall element sensor increases accordingly. . That is, an output voltage corresponding to the current value of the current to be measured is obtained by the Hall element sensor. The relationship between the current value of the constant current, the output voltage, and the current value of the current to be measured will be described later with reference to FIG.

(About gain and phase errors)
When the measured current I is an alternating current and I = I ₀ sinωt, the output V of the Hall element sensor output voltage 22 corresponding to the measured current I is generally expressed as V = V ₀ sin (ωt + φ). . Here, φ is a phase difference caused by variations in sensor characteristics and structures of the Hall element sensor itself. V ₀ / I ₀ is a gain indicating the sensitivity of the Hall element sensor, and this gain is also caused by variations in sensor characteristics and structures of the Hall element sensor itself.

  FIG. 2 is an explanatory diagram of the gain error of the input conversion board. The input conversion board has an error (10) due to the ability value of the object with respect to the ideal characteristic (9) of the input / output characteristics. For this reason, it is necessary to correct an error with respect to the ideal characteristic. This error correction value is stored in the non-volatile memory (6), and when the input conversion board is used, the error correction value is used on the CPU board or the like to obtain an ideal characteristic of the gain.

  FIG. 4 is a diagram showing a state in which the phases of the output voltages of the Hall element sensors corresponding to the respective channels become uneven when the currents to be measured are assigned to the plurality of channels, respectively. Each channel of the input conversion board has a phase characteristic depending on the actual value of the output voltage. Each channel has a phase characteristic.

  The purpose of the protection control device is to detect a minute abnormality in the power system. When the same input is input to a plurality of channels, it is necessary to make the phase characteristics and the gain characteristics the same. Therefore, it is necessary to correct the phase difference (14, 15) between the output waveform (11) of the reference channel and the output waveform (12, 13) of the other channel. This correction value is stored in the non-volatile memory (6), and when this input conversion board is used, the error correction value is used on the CPU board, etc. Thus, the same phase characteristic can be obtained.

(Relationship between constant current and dynamic range)
From equation Hall effect, magnetic flux density by the measured current _{I 0 B = μ 0 H =} I 0 μ 0 / (2πr), induced by the current _{I 0,} the electric field in the direction perpendicular to the current _{I 0 E} y = - _{eBτE x / m, i = ne} 2 τE x / m, V 0 = -dE y, d is the distance of the thickness of the perpendicular direction of the Hall element into a current _{I 0,} r is a current _{I 0} to the ferromagnetic core, n Is the electron density, m is the mass of the electron, μ ₀ is the magnetic permeability of the vacuum, e is the charge of the electron, and the constant k = (d / r) μ ₀ / (2πne), V ₀ = k · I ₀ · i Is obtained (sensor characteristics).

As a result, the output voltage V ₀ of the Hall element sensor is proportional to the measured current I ₀ and the constant current i (V ₀ = k · I ₀ · i). Therefore, by adjusting the constant current i, the sensitivity of detection of the current I _{0 to} be measured (the magnitude of the output voltage V ₀ ) can be adjusted.

  Here, since the constant k includes r and d related to the shape of the current sensor including the Hall element sensor, the sensitivity varies depending on r and d even if the constant current value is the same. That is, variations in sensor characteristics occur between individual current sensors.

On the other hand, in FIG. 5, when all of the constant current i injected into the Hall element is bent and gathered at the end of the element (in the direction perpendicular to the current to be measured), even if the value of the magnetic field H is increased (current to be measured). Even if I ₀ is increased), the magnitude of the electric field E _{y in} the direction (y direction) perpendicular to the current I ₀ does not change (saturated state), and therefore the output voltage V ₀ does not change. Further, the larger the constant current i, the faster the saturation state with respect to the magnetic field H. The upper limit value of the output voltage when this saturation state is reached is determined by the composition of the material constituting the Hall element.

The above explanation is about the average value of the constant current value. In fact, the velocity v _{x from} which the current value of the constant current is derived has a statistical mechanical distribution. Some of them reach the end of the element (saturated state) and others flow as current out of the element and return to the constant current source. The larger the constant current i and the larger the magnetic field H, the more saturated The proportion of charge that becomes a state increases.

Considering the sensor characteristics (V ₀ = k · I ₀ · i) and the upper limit value of the output voltage, the sensor characteristics of the Hall element sensor (the measured current I ₀ and the output voltage V using the constant current i as a parameter). (Relationship with ₀ ) is as shown in FIG. FIG. 6 also shows the range (dynamic range) of the detectable input (measured current I ₀ ) determined by the upper limit value of the output voltage.

As shown in FIG. 6, the Hall element shown in FIG. 5 has a characteristic that the dynamic range changes by increasing or decreasing the constant current value (23). When the constant current value is small, the dynamic range is small (24), and when the constant current value is large, the dynamic range is large (26). Thus, the dynamic range can be changed by controlling the constant current (4) input to the Hall element sensor (1) by the control circuit (5). The control value of the control circuit (5) is stored in the nonvolatile memory (6).
When using this input conversion board, it is possible to manage the dynamic range of each channel by using a constant current correction value (dynamic range correction value) on a CPU board or the like. In addition, the dynamic range can be arbitrarily changed by arbitrarily changing the constant current source.

However, as already described, since the constant k in the sensor characteristics (V ₀ = k · I ₀ · i) differs depending on the individual current sensors including the Hall element sensor, the dynamic range is managed for each current sensor. There is a need.

(Information held in the non-volatile memory 6)
As described above, individual current sensors including Hall element sensors have different sensor characteristics and dynamic ranges. Accordingly, the following parameters are measured for each individual current sensor, the obtained parameters are held in the nonvolatile memory 6 on the input board, and the protection control device refers to the parameters so that each current sensor is It is possible to perform control according to the variation of the.

(A) Gain (V ₀ / I ₀ )
(B) Phase φ
(C) Relationship between constant current value and dynamic range When a standard value of the above parameter is given in advance, an error from the standard value is stored in the nonvolatile memory 6 as a variation of each current sensor. You may keep it.

(Gain correction by constant current)
When the gain (V ₀ / I ₀ ) value of each current sensor including the Hall element sensor deviates from the reference value, the gain value is corrected to the reference value by correcting the constant current value. Control will be described. In other words, the gain error of each current sensor is held in the nonvolatile memory 6 in advance, and the control circuit 5 uses the error value to control the current of the constant current source 4, thereby Correct the value to the reference value. In the following calculation, secondary minute quantities are ignored.

From the relational expression V = k · I · i (V is an output voltage, k is a constant determined by the structure of the current sensor, I is a current to be measured, and i is a constant current value of a constant current source) The gain g is defined by g = V / I = k · i, and when the gain reference value g ₀ is g ₀ = k ₀ · i ₀ , the constant k is the reference value k when the constant current value is i _{0. It is} assumed that g ′ = (k ₀ + Δk) · i ₀ = g ₀ + Δg deviating from ₀ . However, Δg = Δk · i ₀ .

Therefore, when the condition that the gain g when the constant current value i is corrected to i ₀ + Δi is the same as the reference gain g ₀ (= k ₀ · i ₀ ) is obtained, g = (k ₀ + Δk) (i ₀ Since + Δi) = g ₀ = k ₀ · i ₀ , Δk ₀ · i ₀ + k ₀ · Δi = 0. As a result, when the correction value Δi of the constant current value is expressed using a gain error Δg, which is a known value held in the nonvolatile memory 6, Δi = Δk · i ₀ / k ₀ = − (Δg / g ₀ ) i ₀ . If the constant current value is corrected in the constant current source 4 by this value, it can be corrected to the original reference value even if the gain deviates from the reference value. At this time, (Δi / i ₀ ) + (Δg / g ₀ ) = 0 holds.

On the other hand, the maximum value I _m (dynamic range) of the measured current I determined by the maximum value V _m of the output voltage V is also changed by the deviation of the constant k from the reference value k ₀ when the constant current value is the reference value i _0. To do.

_Assuming that the dynamic range when the constant current value is the reference value i ₀ and the constant k is the reference value k ₀ is I _m0 , V _m = k · I _m · i = k ₀ · I _m0 · i ₀ is When k = k ₀ + Δk and i = i ₀ , the dynamic range in that case is expressed by using the gain reference value g ₀ and the gain deviation Δg, and I _m = I _m0 (k ₀ / k ) = I _m0 (1−Δg / g ₀ ), and the dynamic range changes.

Therefore, when the current value of the constant current source is corrected by the correction value Δi, the dynamic range I _m is I _m = I _m0 (k ₀ / k) (i ₀ / i) = I _m0 (1−Δg / g ₀ ) (1−Δi / i ₀ ) = I _m0 (1−Δg / g ₀ −Δi / i ₀ ) = I _m0, and the dynamic range I _m is corrected to the reference value I _m0 . That is, when the constant current value is corrected according to the gain deviation, both the gain and the dynamic range are corrected to the reference value.

(When constant k has dependency of current I to be measured)
When the constant k is dependent on the current I to be measured and there is a slight non-linear relationship (convex upward) between the current I to be measured and the output voltage V, the constant k is set to k (1-αI). If (where α is a minute amount), the deviation of the constant k is Δk = −k · α · I, and the deviation of the gain g is Δg = −k · α · I · i. Similarly to the above, the correction value Δi of the current value i of the constant current source for correcting the gain to the reference value is Δi / i ₀ = −Δg / g ₀ = αI. The gain is set to a reference value by this correction value Δi.

However, even if the current value i of the constant current source is corrected as described above, the dynamic range I _m becomes I _m = I _m0 (1 + αI _m0 ) using the reference value I _m0 of the dynamic range. Shift. That is, even if the current value of the constant current source is corrected, the gain and the dynamic range can be set to the reference values, and therefore there is a slight nonlinear relationship between the measured current I and the output voltage V. For each measured current I to be applied, the relationship between the gain and the dynamic range needs to be managed by the nonvolatile memory 6.

  When there is a slight non-linear relationship between the measured current I and the output voltage V, the gain error Δg is defined by defining the gain g as a differential coefficient dV / dI of the output voltage V with respect to the measured current I. , Δg = −2k · α · I · i, which is twice the value of Δg. Also in this case, it is necessary to manage the relationship of the gain g with respect to the measured current I to be applied by the nonvolatile memory 6.

(Multi-channel configuration)
FIG. 1 shows a configuration in which each of the input conversion boards is provided with a non-volatile memory 6 that holds variation parameters. A channel composed of the Hall element sensor 1, the primary circuit 2, the secondary circuit 3, the constant current source 4, and the constant control circuit 5 shown in FIG. A plurality of channels 1001, 1002, 1003,..., 100N may be mounted on the conversion substrate, and the variation parameter for the plurality of channels may be collectively held in one nonvolatile memory. That is, the input conversion board has a plurality of channels. Further, the correction value is stored in the nonvolatile memory for each channel.

  With the configuration shown in FIG. 3, variation parameters regarding individual currents to be measured can be collectively managed by one nonvolatile memory.

1: Hall element sensor, 2: Primary side circuit, 3: Secondary side circuit, 4: Constant current source,
5: Control circuit, 6: Non-volatile memory, 7: Input, 8: Output

Claims (6)

The input conversion board of the digital protection control device of the power system is
The primary circuit on the input side to which the current to be measured is input,
Hall element sensor that detects the measured current of the power system,
A secondary circuit that outputs a voltage generated by the Hall element sensor in response to the current to be measured;
A constant current source for supplying a constant current to the Hall element sensor;
An input conversion board of a digital protection control device, comprising: a control circuit that controls the value of the constant current; and a nonvolatile memory that holds information related to the control. The nonvolatile memory is
A gain determined by a ratio between a current value of the current to be measured that is an input to the Hall element sensor and a voltage value that is an output of the Hall element sensor;
Error information from a standard value for each of the phase differences between the measured current and the output voltage, and
2. The digital protection according to claim 1, wherein at least one piece of information indicating a relationship between a constant current value of the constant current source and a dynamic range which is a detectable range of the current value of the current to be measured is held. Input conversion board for the control device. The control circuit includes:
A correction value for the reference value of the constant current is obtained based on information on an error from the reference value of the gain held in the nonvolatile memory, and the corrected constant current value is set in the constant current source 3. The input conversion board of the digital protection control device according to claim 2, wherein The nonvolatile memory is
3. The input conversion board of the digital protection control device according to claim 2, wherein information relating to an error from a reference value of the gain is held corresponding to the value of the current to be measured. The input conversion board of the digital protection control device of the power system is
A plurality of channels corresponding to each of a plurality of currents to be measured;
Each of the plurality of channels is
The primary circuit on the input side to which the current to be measured is input,
Hall element sensor that detects the measured current of the power system,
A secondary circuit that outputs a voltage generated by the Hall element sensor in response to the current to be measured;
A constant current source for supplying a constant current to the Hall element sensor, and a control circuit for controlling the value of the constant current;
A non-volatile memory for holding information related to the control connected to each of the plurality of channels;
An input conversion board for a digital protection control device, comprising:   6. The input conversion board of a digital protection control device according to claim 5, wherein the nonvolatile memory collectively holds a parameter of variation in sensor characteristics for each of the plurality of channels.

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