JP2012202844A - Current detector - Google Patents

Current detector Download PDF

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JP2012202844A
JP2012202844A JP2011068070A JP2011068070A JP2012202844A JP 2012202844 A JP2012202844 A JP 2012202844A JP 2011068070 A JP2011068070 A JP 2011068070A JP 2011068070 A JP2011068070 A JP 2011068070A JP 2012202844 A JP2012202844 A JP 2012202844A
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resistance
resistor
input
transformer
burden
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Keigo Adachi
圭吾 足立
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Mitsubishi Electric Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a current detector capable of accurately performing temperature compensation of a secondary winding resistance.SOLUTION: The current detector includes a transformer 1, a load resistance 2 connected between secondary-side terminals of the transformer 1, a voltage amplifier 5 which amplifies a voltage developed across the load resistance 2, an input resistance 3 connected to one secondary-side terminal of the transformer 1 in parallel with the load resistance 2, and a feedback resistance 4 which determines an amplification factor of the voltage amplifier 5 together with the input resistance 3. The input resistance 3 is constituted including a thermistor and compensates for temperature characteristics of a winding resistance 11 of the transformer 1.

Description

この発明は、電力系統を保護する目的で設置される保護リレー装置に用いられる電流検出装置に関するものである。   The present invention relates to a current detection device used in a protection relay device installed for the purpose of protecting a power system.

保護リレー装置に用いられる電流検出装置は変成器を用いる方式が一般的である。電流検出装置では、変成器の2次巻線の両端に負担抵抗を接続し、負担抵抗に発生する電圧を測定することにより1次巻線に流れる電流を測定することが出来る。しかし、1次巻線、2次巻線に流れる電流等により変成器の温度が変化すると変成器の2次巻線抵抗が変化し、電流を正確に測定することが困難となる問題があった。この問題を解決するために、負担抵抗と直列に2次巻線抵抗の温度変化を打ち消すようにサーミスタを挿入する方法が提案されている(特許文献1参照)。   The current detection device used for the protection relay device is generally a system using a transformer. In the current detector, a current flowing in the primary winding can be measured by connecting a burden resistor to both ends of the secondary winding of the transformer and measuring a voltage generated in the burden resistance. However, when the temperature of the transformer changes due to the current flowing in the primary winding and the secondary winding, the secondary winding resistance of the transformer changes, which makes it difficult to accurately measure the current. . In order to solve this problem, a method has been proposed in which a thermistor is inserted so as to cancel the temperature change of the secondary winding resistance in series with the burden resistance (see Patent Document 1).

特開平5−34376号公報JP-A-5-34376

上記のように、従来の電流検出装置では、2次巻線抵抗の温度変化を打ち消すように負担抵抗と直列にサーミスタを挿入している。しかしながら、この場合、サーミスタに負担電流が流れるため、この負担電流によりサーミスタ自体が発熱しサーミスタの抵抗値が変化する。このため、2次巻線抵抗の温度補償を正確に行うことが困難になるという問題があった。   As described above, in the conventional current detection device, the thermistor is inserted in series with the burden resistance so as to cancel the temperature change of the secondary winding resistance. However, in this case, since a burden current flows through the thermistor, the thermistor itself generates heat due to this burden current, and the resistance value of the thermistor changes. For this reason, there is a problem that it is difficult to accurately perform temperature compensation of the secondary winding resistance.

この発明は、上記に鑑みてなされたもので、正確に2次巻線抵抗の温度補償をすることができる電流検出装置を提供することを目的とする。   The present invention has been made in view of the above, and an object of the present invention is to provide a current detection device capable of accurately compensating the temperature of the secondary winding resistance.

上述した課題を解決し、目的を達成するために、本発明に係る電流検出装置は、1次巻線に入力された1次電流に対して前記1次巻線と2次巻線との巻数比に応じた2次電流を前記2次巻線に発生させて出力する変成器と、この変成器の2次側の端子間に接続された負担抵抗と、この負担抵抗の両端に生ずる電圧を増幅する電圧増幅器と、この電圧増幅器の増幅率を決定する入力側の抵抗であって、前記負担抵抗と並列に前記変成器の2次側の一方の端子に接続された入力抵抗と、この入力抵抗とともに前記電圧増幅器の増幅率を決定する帰還抵抗と、を備え、前記入力抵抗は、サーミスタを含んで構成され、かつ、前記変成器の2次巻線抵抗の温度特性を補償するものであることを特徴とする。   In order to solve the above-described problems and achieve the object, the current detection device according to the present invention is configured such that the number of turns of the primary winding and the secondary winding with respect to the primary current input to the primary winding. A transformer that generates and outputs a secondary current corresponding to the ratio to the secondary winding, a burden resistor connected between the terminals on the secondary side of the transformer, and a voltage generated across the burden resistor. A voltage amplifier to be amplified, an input-side resistor for determining an amplification factor of the voltage amplifier, an input resistor connected in parallel to the burden resistor to one terminal on the secondary side of the transformer, and the input And a feedback resistor that determines the amplification factor of the voltage amplifier together with a resistor, and the input resistor includes a thermistor and compensates for the temperature characteristics of the secondary winding resistance of the transformer. It is characterized by that.

この発明によれば、負担抵抗の両端に発生する電圧を測定するための電圧増幅器の入力抵抗をサーミスタとして温度補償を実施することにより、正確に変成器の2次巻線抵抗の温度補償を行うことができる、という効果を奏する。   According to the present invention, the temperature compensation of the secondary winding resistance of the transformer is accurately performed by performing the temperature compensation by using the input resistance of the voltage amplifier for measuring the voltage generated at both ends of the burden resistance as a thermistor. There is an effect that it is possible.

図1は、実施の形態1に係る電流検出装置の構成図である。FIG. 1 is a configuration diagram of a current detection device according to the first embodiment. 図2は、変成器1の巻線抵抗11及び負担抵抗2の端子間電圧の温度特性の一例を示す図である。FIG. 2 is a diagram illustrating an example of the temperature characteristics of the inter-terminal voltage of the winding resistor 11 and the burden resistor 2 of the transformer 1. 図3は、入力抵抗3のサーミスタ抵抗値及び電圧増幅器5のゲインの温度特性の一例を示す図である。FIG. 3 is a diagram illustrating an example of temperature characteristics of the thermistor resistance value of the input resistor 3 and the gain of the voltage amplifier 5. 図4は、実施の形態2に係る電流検出装置の構成図である。FIG. 4 is a configuration diagram of the current detection device according to the second embodiment. 図5は、変成器1の巻線抵抗11及びサーミスタ抵抗の温度特性の一例を示す図である。FIG. 5 is a diagram illustrating an example of temperature characteristics of the winding resistance 11 and the thermistor resistance of the transformer 1. 図6は、変成器1の巻線抵抗11、抵抗とサーミスタの組合せた電圧増幅器5の入力抵抗3及び負担抵抗2の端子間電圧の温度特性の一例を示す図である。FIG. 6 is a diagram illustrating an example of temperature characteristics of the inter-terminal voltage of the winding resistor 11 of the transformer 1, the input resistor 3 of the voltage amplifier 5 and the burden resistor 2 in combination of the resistor and thermistor. 図7は、従来の電流検出装置の構成図である。FIG. 7 is a configuration diagram of a conventional current detection device.

以下に、本発明に係る電流検出装置の実施の形態を図面に基づいて詳細に説明する。なお、この実施の形態によりこの発明が限定されるものではない。   Embodiments of a current detection device according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

実施の形態1.
図1は、本実施の形態に係る電流検出装置の構成図である。図1において、本実施の形態に係る電流検出装置は、変成器1、負担抵抗2、電圧増幅器5、電圧増幅器5の入力抵抗3、及び電圧増幅器5の帰還抵抗4を備えて構成される。
Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a current detection device according to the present embodiment. In FIG. 1, the current detection device according to the present embodiment includes a transformer 1, a burden resistor 2, a voltage amplifier 5, an input resistor 3 of the voltage amplifier 5, and a feedback resistor 4 of the voltage amplifier 5.

変成器1は、1次巻線20と2次巻線21とを備え、1次巻線20に入力された1次電流I1に対して1次巻線20と2次巻線21との巻数比に応じた2次電流I2を2次巻線21で発生させて出力する。巻線抵抗11は、変成器1の2次巻線抵抗である。変成器1の2次側の両端子間には負担抵抗2が接続されている。即ち、2次巻線の両端には負担抵抗2が接続されている。2次電流I2は負担抵抗2の両端に電圧VLを発生する。   The transformer 1 includes a primary winding 20 and a secondary winding 21, and the number of turns of the primary winding 20 and the secondary winding 21 with respect to the primary current I 1 input to the primary winding 20. A secondary current I2 corresponding to the ratio is generated by the secondary winding 21 and output. The winding resistance 11 is a secondary winding resistance of the transformer 1. A burden resistor 2 is connected between both terminals on the secondary side of the transformer 1. That is, the burden resistor 2 is connected to both ends of the secondary winding. The secondary current I2 generates a voltage VL across the burden resistor 2.

電圧増幅器5は、その入力側が負担抵抗2の両端に接続され、電圧VLを増幅して出力する。電圧増幅器5はオペアンプであり、入力抵抗3及び帰還抵抗4とともに反転増幅回路30を構成する。電圧増幅器5は二つの入力端子と一つの出力端子を備える。電圧増幅器5の一方の入力端子である反転入力端子(−)には入力抵抗3が接続され、入力抵抗3は変成器1の2次側の一方の端子及び負担抵抗2の一端に接続されている。入力抵抗3は、負担抵抗2と並列に、変成器2の2次側の一方の端子と接続されている。電圧増幅器5の他方の入力端子である非反転入力端子(+)はグランドに接続されている。電圧増幅器5の反転入力端子(−)と非反転入力端子(+)との間には帰還抵抗4が接続されている。この電流検出装置では、電圧VLを電圧増幅器5で増幅することにより1次電流I1に応じた電圧信号を得ることが出来る。電圧増幅器5は、そのゲイン(電圧増幅率)が入力抵抗3と帰還抵抗4の比で決まる。   The voltage amplifier 5 has its input side connected to both ends of the burden resistor 2, and amplifies and outputs the voltage VL. The voltage amplifier 5 is an operational amplifier and constitutes an inverting amplifier circuit 30 together with the input resistor 3 and the feedback resistor 4. The voltage amplifier 5 has two input terminals and one output terminal. The input resistor 3 is connected to the inverting input terminal (−) which is one input terminal of the voltage amplifier 5, and the input resistor 3 is connected to one terminal on the secondary side of the transformer 1 and one end of the burden resistor 2. Yes. The input resistor 3 is connected to one terminal on the secondary side of the transformer 2 in parallel with the burden resistor 2. The non-inverting input terminal (+) which is the other input terminal of the voltage amplifier 5 is connected to the ground. A feedback resistor 4 is connected between the inverting input terminal (−) and the non-inverting input terminal (+) of the voltage amplifier 5. In this current detection device, a voltage signal corresponding to the primary current I1 can be obtained by amplifying the voltage VL by the voltage amplifier 5. The gain (voltage amplification factor) of the voltage amplifier 5 is determined by the ratio of the input resistor 3 and the feedback resistor 4.

ここで、2次電流I2自体は温度特性を持たないが、変成器1の巻線抵抗11が図2のような温度特性を持っている。図2は、変成器1の巻線抵抗11及び負担抵抗2の端子間電圧VLの温度特性の一例を示す図である。図2では、横軸を温度T(℃)、縦軸を巻線抵抗(Ω)又は端子間電圧(V)とし、変成器1の巻線抵抗11の抵抗値をRで示し、負担抵抗2の端子間電圧をVLで示している。この温度特性が出力に影響しないようにするには、変成器1の励磁インピーダンスを巻線抵抗11と負担抵抗2の和に比べて十分大きくなるように設計すれば良いが、励磁インピーダンスを大きくすると、大きな1次電流I1が流れた場合に変成器1が飽和する問題がある。このため、保護リレー装置に用いられるような広いダイナミックレンジで用いられるような変成器1の場合は、励磁インピーダンスを巻線抵抗11と負荷抵抗2の和に比べて十分大きく出来ないため、負担抵抗2の両端に発生する電圧VLも巻線抵抗2の温度特性に影響され、図2のように温度特性を持つことになる。例えば保護リレー装置に用いられる変成器1についてこれらの抵抗値の一例を挙げれば、負担抵抗2の抵抗値〜20(Ω)、巻線抵抗11の抵抗値(温度20℃の場合)〜70(Ω)、変成器1の励磁インピーダンス〜350(Ω)であり、巻線抵抗11と負担抵抗2の抵抗値の和と変成器1の励磁インピーダンスとの比は〜0.26であり、十分に小さいとはいえない。実際、この場合、負担抵抗2に発生する電圧VLは温度が10℃変化すると〜0.2%変動する。従って、保護リレー装置の使用温度範囲:−10〜50℃では〜1.2%変動することになるが、要求性能を例えば0.5%以下とすると、かかる温度変動を補償する必要がある。   Here, the secondary current I2 itself does not have temperature characteristics, but the winding resistance 11 of the transformer 1 has temperature characteristics as shown in FIG. FIG. 2 is a diagram illustrating an example of the temperature characteristics of the inter-terminal voltage VL of the winding resistor 11 and the burden resistor 2 of the transformer 1. In FIG. 2, the horizontal axis represents temperature T (° C.), the vertical axis represents winding resistance (Ω) or inter-terminal voltage (V), the resistance value of the winding resistance 11 of the transformer 1 is indicated by R, and the burden resistance 2 The voltage between the terminals is indicated by VL. In order to prevent this temperature characteristic from affecting the output, the excitation impedance of the transformer 1 may be designed to be sufficiently larger than the sum of the winding resistance 11 and the burden resistance 2, but if the excitation impedance is increased, There is a problem that the transformer 1 is saturated when a large primary current I1 flows. For this reason, in the case of the transformer 1 that is used in a wide dynamic range such as that used in the protective relay device, the exciting impedance cannot be made sufficiently larger than the sum of the winding resistance 11 and the load resistance 2, so that the burden resistance The voltage VL generated at both ends of 2 is also affected by the temperature characteristics of the winding resistance 2, and has temperature characteristics as shown in FIG. For example, with respect to the transformer 1 used in the protection relay device, if one example of these resistance values is given, the resistance value of the burden resistance 2 to 20 (Ω), the resistance value of the winding resistance 11 (when the temperature is 20 ° C.) to 70 ( Ω), the excitation impedance of the transformer 1 to 350 (Ω), and the ratio of the sum of the resistance values of the winding resistance 11 and the load resistance 2 to the excitation impedance of the transformer 1 is about 0.26, It's not small. In fact, in this case, the voltage VL generated in the burden resistor 2 varies by 0.2% when the temperature changes by 10 ° C. Therefore, the temperature range of the protective relay device varies by ˜1.2% at −10 to 50 ° C. If the required performance is 0.5% or less, for example, it is necessary to compensate for such temperature variation.

そこで、本実施の形態では、この負担抵抗2の両端に発生する電圧VLの温度特性を補償するために、電圧増幅器5の入力抵抗3をサーミスタにする。電圧増幅器5のゲイン(G)は入力抵抗3と帰還抵抗4の比で決まるが、入力抵抗3を負担抵抗2の電圧VLの温度特性を打ち消すような温度特性を持つサーミスタとすることにより、電圧増幅器5のゲイン(G)を図3のように負担抵抗2の電圧VLの温度特性を打ち消すようにすることができる。ここで、図3は、入力抵抗3のサーミスタ抵抗値及び電圧増幅器5のゲインの温度特性の一例を示す図である。図3では、横軸を温度T(℃)、縦軸をサーミスタ抵抗値(Ω)又は電圧増幅率(ゲイン)Gとし、入力抵抗3の抵抗値をRTで示し、電圧増幅器5のゲインをGで示している。図2と図3の比較から明らかなように、入力抵抗3の抵抗値RTは巻線抵抗11の抵抗値Rの温度特性を相殺するように温度の増加とともに減少する。よって、電圧増幅器5のゲイン(G)は負担抵抗2の電圧VLの温度特性を相殺するように温度の増加とともに増加する。このように電圧増幅器5の入力抵抗3をサーミスタにすることにより、電流検出装置の温度特性が改善できる。   Therefore, in this embodiment, in order to compensate for the temperature characteristics of the voltage VL generated at both ends of the burden resistor 2, the input resistor 3 of the voltage amplifier 5 is a thermistor. The gain (G) of the voltage amplifier 5 is determined by the ratio of the input resistor 3 and the feedback resistor 4. By making the input resistor 3 a thermistor having a temperature characteristic that cancels the temperature characteristic of the voltage VL of the burden resistor 2, The gain (G) of the amplifier 5 can cancel the temperature characteristic of the voltage VL of the burden resistor 2 as shown in FIG. Here, FIG. 3 is a diagram illustrating an example of temperature characteristics of the thermistor resistance value of the input resistor 3 and the gain of the voltage amplifier 5. In FIG. 3, the horizontal axis represents temperature T (° C.), the vertical axis represents thermistor resistance value (Ω) or voltage amplification factor (gain) G, the resistance value of the input resistance 3 is represented by RT, and the gain of the voltage amplifier 5 is represented by G. Is shown. As is clear from the comparison between FIG. 2 and FIG. 3, the resistance value RT of the input resistor 3 decreases as the temperature increases so as to cancel out the temperature characteristic of the resistance value R of the winding resistor 11. Therefore, the gain (G) of the voltage amplifier 5 increases as the temperature increases so as to cancel out the temperature characteristics of the voltage VL of the burden resistor 2. Thus, by making the input resistance 3 of the voltage amplifier 5 a thermistor, the temperature characteristic of the current detection device can be improved.

また、電圧増幅器5の入力インピーダンスは負担抵抗2に比べて非常に高くすることができる。通常、負担抵抗2は数百Ω程度であるが、電圧増幅器5の入力インピーダンスは1MΩ以上ある。即ち、負担抵抗2は電圧増幅器5の入力インピーダンスの1/1000以下とすることができる。このため、負担抵抗2に直列にサーミスタを追加した場合に比べて、サーミスタを電圧増幅器5の入力抵抗3とした場合、サーミスタに流れる電流は1/1000以下になる。そのためサーミスタを流れる電流による発熱は抑えられ、正確に負担抵抗2の電圧VLの温度補償を行うことができる。   Further, the input impedance of the voltage amplifier 5 can be made very high compared to the burden resistor 2. Usually, the burden resistor 2 is about several hundred Ω, but the input impedance of the voltage amplifier 5 is 1 MΩ or more. That is, the burden resistor 2 can be set to 1/1000 or less of the input impedance of the voltage amplifier 5. For this reason, when the thermistor is used as the input resistor 3 of the voltage amplifier 5 compared to the case where the thermistor is added in series with the burden resistor 2, the current flowing through the thermistor is 1/1000 or less. Therefore, heat generation due to the current flowing through the thermistor is suppressed, and temperature compensation of the voltage VL of the burden resistor 2 can be performed accurately.

なお、図7は、従来の電流検出装置の構成図である。図7では、図1と同一の構成要素には同一の符号を付している。入力抵抗7は、サーミスタとは異なる通常の抵抗である。従来の電流検出装置では、サーミスタ6が、負担抵抗2と直列に、変成器1の2次側の一方の端子に接続されている。即ち、負担抵抗2と直列にサーミスタ6を挿入することにより、2次巻線抵抗の温度変化を打ち消すようにしている。しかしながら、この構成では、サーミスタ6に2次電流I2が流れるので、サーミスタ6自体が発熱し、サーミスタ6の抵抗値が変化することとなる。このため、従来の構成では、2次巻線抵抗の補償を正確に行うことが困難であった。   FIG. 7 is a configuration diagram of a conventional current detection device. In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. The input resistor 7 is a normal resistor different from the thermistor. In the conventional current detection device, the thermistor 6 is connected in series with the load resistor 2 to one terminal on the secondary side of the transformer 1. That is, by inserting the thermistor 6 in series with the burden resistor 2, the temperature change of the secondary winding resistance is canceled out. However, in this configuration, since the secondary current I2 flows through the thermistor 6, the thermistor 6 itself generates heat, and the resistance value of the thermistor 6 changes. For this reason, in the conventional configuration, it is difficult to accurately compensate the secondary winding resistance.

以上のように、本実施の形態によれば、電圧増幅器5の入力抵抗3をサーミスタにすることにより正確に負担抵抗2の電圧VLの温度補償を行うことができるという効果がある。また、電圧増幅器5の入力インピーダンスは負担抵抗2に比べて非常に高いので(負担抵抗2は電圧増幅器5の入力インピーダンスの例えば1/1000以下)、電圧増幅器5の入力電流は非常に小さくなる。そのためサーミスタの発熱は抑えられ、正確に2次巻線抵抗の温度補償を行うことができる。従って、本実施の形態によれば、電流検出装置の電流検出精度が向上する。   As described above, according to the present embodiment, the temperature resistance of the voltage VL of the burden resistor 2 can be accurately compensated by using the input resistor 3 of the voltage amplifier 5 as a thermistor. Moreover, since the input impedance of the voltage amplifier 5 is very high compared to the burden resistor 2 (the burden resistor 2 is 1/1000 or less of the input impedance of the voltage amplifier 5), the input current of the voltage amplifier 5 becomes very small. Therefore, the heat generation of the thermistor is suppressed, and the temperature compensation of the secondary winding resistance can be performed accurately. Therefore, according to the present embodiment, the current detection accuracy of the current detection device is improved.

本実施の形態は、例えば保護リレー装置に用いられる変成器1のように、変成器1の励磁インピーダンスを巻線抵抗11と負担抵抗2の和に比べて十分大きく設定することが困難な構成においても負担抵抗2の電圧VLの温度補償を実施することができる。例えば(負担抵抗2+巻線抵抗11)/(励磁インピーダンス)が0.1以上となり、2次巻線抵抗の温度補償の実施が必要となる構成に対して好適である。   In the present embodiment, for example, in a transformer 1 used in a protection relay device, it is difficult to set the excitation impedance of the transformer 1 sufficiently larger than the sum of the winding resistance 11 and the burden resistance 2. In addition, temperature compensation of the voltage VL of the burden resistor 2 can be performed. For example, (burden resistance 2 + winding resistance 11) / (excitation impedance) is 0.1 or more, which is suitable for a configuration that requires temperature compensation of the secondary winding resistance.

実施の形態2.
図4は、本実施の形態に係る電流検出装置の構成図である。なお、図4では、図1と同一の構成要素には同一の符号を付している。実施の形態1では、電圧増幅器5の入力抵抗3を単一のサーミスタにするようにしたが、この実施の形態2では、電圧増幅器5の入力抵抗3を図4のように抵抗とサーミスタの組合せとするようにしたものである。
Embodiment 2. FIG.
FIG. 4 is a configuration diagram of the current detection device according to the present embodiment. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals. In the first embodiment, the input resistor 3 of the voltage amplifier 5 is a single thermistor. However, in the second embodiment, the input resistor 3 of the voltage amplifier 5 is a combination of a resistor and a thermistor as shown in FIG. It is made to do.

具体的には、入力抵抗3は、抵抗60と、抵抗60に直列に接続されたサーミスタ61と、抵抗60及びサーミスタ61と並列に接続された抵抗63と、抵抗60及びサーミスタ61と直列に接続された抵抗62と、を備えて構成される。また、図4では、抵抗60の抵抗値をR1で、サーミスタ61の抵抗値をRT1で、抵抗62の抵抗値をR3で、抵抗63の抵抗値をR2で表している。また、入力抵抗3の抵抗値はRinで表している。   Specifically, the input resistor 3 includes a resistor 60, a thermistor 61 connected in series to the resistor 60, a resistor 63 connected in parallel to the resistor 60 and the thermistor 61, and a resistor 60 and the thermistor 61 connected in series. And configured resistor 62. In FIG. 4, the resistance value of the resistor 60 is represented by R1, the resistance value of the thermistor 61 is represented by RT1, the resistance value of the resistor 62 is represented by R3, and the resistance value of the resistor 63 is represented by R2. The resistance value of the input resistor 3 is represented by Rin.

図5は、変成器1の巻線抵抗11及びサーミスタ抵抗の温度特性の一例を示す図である。巻線抵抗11の温度特性(R)は図5のように温度に比例するが、一般に入手しやすいサーミスタは図5のように対数的な温度特性(RT)を持っている。なお、実施の形態1のサーミスタは図3のように線形的な温度特性(RT)を持っている。   FIG. 5 is a diagram illustrating an example of temperature characteristics of the winding resistance 11 and the thermistor resistance of the transformer 1. The temperature characteristic (R) of the winding resistor 11 is proportional to the temperature as shown in FIG. 5, but a generally available thermistor has a logarithmic temperature characteristic (RT) as shown in FIG. The thermistor of the first embodiment has a linear temperature characteristic (RT) as shown in FIG.

このような例えば対数的な温度特性を持つサーミスタを用いて温度補償をするためには、図4のようにサーミスタ61と抵抗60,62,63を組合せて入力抵抗3を構成し、図6のように入力抵抗3の抵抗値Rinを巻線抵抗11の温度特性(R)を打ち消すような抵抗60,62,63とサーミスタ61の組合せとすることにより可能となる。入力抵抗Rinは次の式で求められる。
Rin=1/(1/(R1+RT1)+1/R2)+R3
ここで、R1,R2,R3の値を適切に選べば、図6のように入力抵抗3の抵抗値を巻線抵抗11の温度特性Rを打ち消すようにすることができる。なお、図6は、変成器1の巻線抵抗11、抵抗とサーミスタの組合せからなる入力抵抗3及び負担抵抗2の端子間電圧の温度特性の一例を示す図である。図6では、横軸を温度T(℃)、縦軸を抵抗(Ω)又は電圧(V)としている。V0は、負担抵抗2の端子間電圧を表している。入力抵抗3をサーミスタ61と複数個の抵抗60,62,63で構成する方法は図示例に限定されないが、図示例は最も簡素かつ十分な構成を与える。
In order to perform temperature compensation using such a thermistor having a logarithmic temperature characteristic, for example, the input resistor 3 is configured by combining the thermistor 61 and the resistors 60, 62, 63 as shown in FIG. As described above, the resistance value Rin of the input resistor 3 can be set by combining the thermistor 61 with resistors 60, 62, and 63 that cancel the temperature characteristic (R) of the winding resistor 11. The input resistance Rin is obtained by the following equation.
Rin = 1 / (1 / (R1 + RT1) + 1 / R2) + R3
Here, if the values of R1, R2, and R3 are appropriately selected, the resistance value of the input resistor 3 can be canceled by the temperature characteristic R of the winding resistor 11 as shown in FIG. FIG. 6 is a diagram illustrating an example of temperature characteristics of the inter-terminal voltage of the winding resistance 11 of the transformer 1, the input resistance 3 composed of a combination of resistance and thermistor, and the burden resistance 2. In FIG. 6, the horizontal axis represents temperature T (° C.) and the vertical axis represents resistance (Ω) or voltage (V). V 0 represents the voltage between the terminals of the burden resistor 2. Although the method of configuring the input resistor 3 with the thermistor 61 and the plurality of resistors 60, 62, 63 is not limited to the illustrated example, the illustrated example provides the simplest and sufficient configuration.

このようにすれば、一般に入手しやすいサーミスタを用いることが可能となるため安価に温度補正を実施することができる。また、電圧増幅器5のゲインの温度特性を、抵抗60,62,63を用いて微調整することができるため、より正確に温度補正をすることが出来るという効果がある。なお、本実施の形態のその他の効果は、実施の形態1と同様である。   In this way, it is possible to use a thermistor that is generally available, so that temperature correction can be performed at low cost. Further, since the temperature characteristic of the gain of the voltage amplifier 5 can be finely adjusted using the resistors 60, 62, 63, there is an effect that the temperature can be corrected more accurately. Other effects of the present embodiment are the same as those of the first embodiment.

上記説明では、この発明の用途として電力系統を保護する目的で設置される保護リレー装置に用いる電流検出装置の場合を例に説明したが、その他の変成器を用いて電流検出する装置にも利用できる。   In the above description, the case of the current detection device used for the protection relay device installed for the purpose of protecting the power system as an application of the present invention has been described as an example. However, the present invention is also used for a device for detecting current using other transformers. it can.

本発明は、電力系統を保護する目的で設置される保護リレー装置に適用できる電流検出装置として有用である。   The present invention is useful as a current detection device applicable to a protection relay device installed for the purpose of protecting a power system.

1 変成器
2 負担抵抗
3 入力抵抗
4 帰還抵抗
5 電圧増幅器
11 巻線抵抗
20 1次巻線
21 2次巻線
30 反転増幅回路
60,62,63 抵抗
61 サーミスタ
DESCRIPTION OF SYMBOLS 1 Transformer 2 Burden resistance 3 Input resistance 4 Feedback resistance 5 Voltage amplifier 11 Winding resistance 20 Primary winding 21 Secondary winding 30 Inversion amplification circuit 60, 62, 63 Resistance 61 Thermistor

Claims (5)

1次巻線に入力された1次電流に対して前記1次巻線と2次巻線との巻数比に応じた2次電流を前記2次巻線に発生させて出力する変成器と、
この変成器の2次側の端子間に接続された負担抵抗と、
この負担抵抗の両端に生ずる電圧を増幅する電圧増幅器と、
この電圧増幅器の増幅率を決定する入力側の抵抗であって、前記負担抵抗と並列に前記変成器の2次側の一方の端子に接続された入力抵抗と、
この入力抵抗とともに前記電圧増幅器の増幅率を決定する帰還抵抗と、
を備え、
前記入力抵抗は、サーミスタを含んで構成され、かつ、前記変成器の2次巻線抵抗の温度特性を補償するものであることを特徴とする電流検出装置。
A transformer that generates and outputs a secondary current corresponding to a turns ratio of the primary winding and the secondary winding to the primary current input to the primary winding;
A burden resistor connected between the terminals on the secondary side of the transformer;
A voltage amplifier that amplifies the voltage generated at both ends of the burden resistor;
An input-side resistor for determining an amplification factor of the voltage amplifier, the input resistor being connected to one terminal on the secondary side of the transformer in parallel with the burden resistor;
A feedback resistor that determines the amplification factor of the voltage amplifier together with the input resistor;
With
The current detection device is characterized in that the input resistance includes a thermistor and compensates for temperature characteristics of the secondary winding resistance of the transformer.
前記入力抵抗は、単一のサーミスタから構成されていることを特徴とする請求項1に記載の電流検出装置。   The current detection device according to claim 1, wherein the input resistance is constituted by a single thermistor. 前記入力抵抗は、単一のサーミスタと複数個の抵抗から構成されていることを特徴とする請求項1に記載の電流検出装置。   The current detection device according to claim 1, wherein the input resistance includes a single thermistor and a plurality of resistors. 前記負担抵抗は前記電圧増幅器の入力インピーダンスの1/1000以下であることを特徴とする請求項1〜3のいずれか1項に記載の電流検出装置。   The current detection apparatus according to claim 1, wherein the burden resistance is 1/1000 or less of an input impedance of the voltage amplifier. 前記負担抵抗と前記2次巻線抵抗の抵抗値の和は、前記変成器の励磁インピーダンスの0.1倍以上であることを特徴とする請求項1〜4のいずれか1項に記載の電流検出装置。   5. The current according to claim 1, wherein a sum of resistance values of the burden resistance and the secondary winding resistance is 0.1 times or more of an excitation impedance of the transformer. Detection device.
JP2011068070A 2011-03-25 2011-03-25 Current detector Pending JP2012202844A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104835639A (en) * 2015-05-12 2015-08-12 林纪秋 Cable cross-core all-shield electronic current transducer
CN106843355A (en) * 2017-03-01 2017-06-13 广州今闰能源科技有限公司 A kind of zero current secondary voltage drop dynamic compensating device
CN109596926A (en) * 2018-12-30 2019-04-09 国网北京市电力公司 The modification method and device of transformer test temperature

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Publication number Priority date Publication date Assignee Title
JPH0534376A (en) * 1991-07-30 1993-02-09 Matsushita Electric Works Ltd Current detector
JPH10294628A (en) * 1997-04-21 1998-11-04 Mitsubishi Electric Corp High frequency amplifier
JP2001249152A (en) * 2000-03-07 2001-09-14 Matsushita Electric Ind Co Ltd Selection level measuring apparatus

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0534376A (en) * 1991-07-30 1993-02-09 Matsushita Electric Works Ltd Current detector
JPH10294628A (en) * 1997-04-21 1998-11-04 Mitsubishi Electric Corp High frequency amplifier
JP2001249152A (en) * 2000-03-07 2001-09-14 Matsushita Electric Ind Co Ltd Selection level measuring apparatus

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104835639A (en) * 2015-05-12 2015-08-12 林纪秋 Cable cross-core all-shield electronic current transducer
CN106843355A (en) * 2017-03-01 2017-06-13 广州今闰能源科技有限公司 A kind of zero current secondary voltage drop dynamic compensating device
CN109596926A (en) * 2018-12-30 2019-04-09 国网北京市电力公司 The modification method and device of transformer test temperature

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