JP2001218309A - Distribution board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distribution board having a current transformer, capable of measuring primary currents over a wide range. SOLUTION: An amplifier 6, that amplifies the output of auxiliary current transformers, is provided to set current which transforms ratio by controlling the amplifying rate of an amplifier in a distribution board provided with current transformers 2a, 2b inserted in a main circuit, the auxiliary current transformers 4a, 4c that transform the output currents of the current transformers, and an operation processing device 7 that measures the current flowing in the main circuit, by measuring the output current of the auxiliary current transformer and protects and controls the main circuit, based on the measured current values.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switchboard, and more particularly to a switchboard provided with a current transformer capable of measuring a wide range of primary current.

[0002]

2. Description of the Related Art JP-A-63-249410 discloses that
It is shown that a relay auxiliary unit is connected to the output side of an instrument transformer and a current transformer connected to a main circuit, and an electronic compound protection relay or a measurement control unit is connected via the relay auxiliary unit. The auxiliary relay unit includes an auxiliary transformer for reducing the output level of the instrument transformer and the current transformer to a predetermined value, an auxiliary current transformer, and the like, and outputs the output reduced to the predetermined value by the relay auxiliary unit. It is shown to supply an electronic compound protection relay or a measurement control unit. Further, it is disclosed that the auxiliary relay unit, the electronic composite protection relay, and the measurement control unit are installed in a switchboard.

[0003]

SUMMARY OF THE INVENTION The above-mentioned JP-A-63-24
In the conventional switchboard disclosed in No. 9410, a relay auxiliary unit, an electronic composite protection relay, a measurement control unit, and the like are dispersedly arranged in the switchboard. For this reason, a cable for connecting them and a cable connection work are required. Also, the rating of the instrument transformer and current transformer to be connected to the main circuit needs to be appropriately selected according to the capacity of the load connected to the main circuit. For example, it is necessary to select a current transformer that takes out a current signal proportional to the main circuit current from its secondary side and has a primary current rated according to the load.
However, it takes time to determine the rated primary current, and the workability is reduced.

When an operational amplifier or the like is used to supply a signal from the relay auxiliary unit to an electronic composite protection relay or a measurement control unit, a DC component is mixed in the signal, and the protection relay or the measurement control unit malfunctions. There is a fear.

The present invention has been made in view of the above problems, and provides a switchboard provided with a current transformer capable of measuring a wide range of primary current. Further, the present invention provides a switchboard provided with a current transformer that does not malfunction due to a DC component.

[0006]

The present invention employs the following means in order to solve the above-mentioned problems.

A current transformer inserted in the main circuit, an auxiliary current transformer for transforming an output current of the current transformer, and a current flowing in the main circuit by measuring an output current of the auxiliary current transformer A power distribution panel having an arithmetic processing unit for protecting and controlling the main circuit based on the measured current value, comprising an amplifier for amplifying an output of the auxiliary current transformer, and controlling an amplification factor of the amplifier to generate a current Set the ratio. The output of the auxiliary current transformer is A / D
After the conversion, it can be supplied to an arithmetic processing unit. Further, a digital filter for blocking a direct current component can be inserted on the output side of the A / D converter.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a diagram showing a circuit configuration of a switchboard according to an embodiment of the present invention. In the figure,
Reference numeral 1 denotes a main circuit conductor, which comprises an a-phase conductor 1a, a b-phase conductor 1b, and a c-phase conductor 1c. 2a and 2c are a
Phase and c-phase current transformers.
A current proportional to the phase current is sent to its secondary side. Reference numeral 3 denotes a protection control unit that measures and displays a main circuit current based on the current signal transmitted from the current transformer 2 and controls the main circuit device. Reference numerals 4a and 4c denote a-phase and c-phase auxiliary current transformers which transform the output currents of the current transformers 2a and 2c, and reduce the output currents of the current transformers 2a and 2c to predetermined values suitable for the operational amplifier. To the operational amplifiers 5a and 5c. 5
a and 5c are a-phase and c-phase operational amplifiers. The gains of the operational amplifiers 5a and 5c can be controlled by the gain control circuit 8. 6 is an A / D converter,
The output of the operational amplifier 5 is converted into a digital signal. 7 is M
An arithmetic processing device configured by a PU or the like, which performs arithmetic processing on the digital signal based on the amplification factor set by the gain control circuit 8 to display various measurement results, output a protection signal, output a control signal, etc. Perform control. A gain control circuit 8 adjusts the amplification factor of the operational amplifier 5 and converts the level of the output signal of the auxiliary current transformer 4 to an optimum voltage level. Reference numeral 9 denotes a memory which stores the value of the amplification factor set by the gain control circuit 8. 10
Denotes a display unit, which displays a measurement result calculated by the arithmetic processing unit 7. Reference numeral 11 denotes an output unit which sends out a trip signal based on the result of the arithmetic processing by the arithmetic processing unit 7.

FIG. 2 is a diagram showing the structure of a switchboard according to an embodiment of the present invention. In the figure, 1A and 1B are the lead-in cables drawn into the switchboard 12, 12 is the switchboard, 1
3 is a circuit breaker inserted in the cable 1A side of the bus 14;
Is a circuit breaker inserted on the cable 1B side of the bus 15, and 15 is a bus composed of bus conductors 15a, 15b, 15c.

Reference numeral 20 denotes a current transformer inserted into the conductor of the cable 1A, and reference numeral 21 denotes a current transformer inserted into the conductor of the cable 1B. Reference numeral 30 denotes a protection control unit which is connected to the current transformer 20 to measure a current flowing through the cable 1A, and
The protection control of the side circuit is performed. A protection control unit 31 is connected to the current transformer 21 to measure a current flowing through the cable 1B and perform protection control of a circuit on the cable 1B side.

FIG. 3 is a diagram showing the accuracy compensation range of the current transformer. 3 to no I ₁ in (a) shows the I _n the precision coverage of a conventional current transformer drawing, FIG. 3 (b) is a diagram showing the relationship between the primary current and the secondary current of the current transformer. As shown in the figure, the accuracy compensation range of the current transformer differs for each rated primary current of the current transformer. In other words, the rated one shown in _{I 1} primary current 40A
Precision coverage of current transformer is 1～40A, precision coverage of current transformer rated primary current 600A shown in I _n is 40
~ 600A. Therefore, in order to measure the main circuit current fluctuating in the range of 1 to 600 A, it is necessary to use at least a current transformer having a rated current of 40 A and a current transformer having a rated current of 600 A in combination.

Ix in FIG. 3A is a diagram showing an accuracy compensation range of the current transformer according to the present embodiment. As shown in the figure, in the current transformer according to the present embodiment, the precision compensation range can be expanded to 1 to 600 A by suppressing the load on the current transformer using an operational amplifier or the like, and one current transformer It is possible to measure the main circuit current over the range of 1 to 600 A using only the device.

FIG. 4 is a diagram showing a procedure for adjusting the gain of the operational amplifier 5 by the gain control circuit. First, supply to the main circuit a reference current I ₁ in step 1. In step 2, an internal constant (A) is initially set as the amplification factor of the operational amplifier. In step 3, the reference current _{I 1} 'detects the _{I 1'} A / D converter output values _{I 1} at feeding calculates the product _{I 1} '· A of the A and the _{I 1} is I
It is determined whether it is larger than ₁ '· A. The _{I 1} is I
If it is larger than ₁ ′ · A, the process proceeds to step 4; otherwise, the process proceeds to step 5. In step 4, A
Substitute +1 for A and go to step 3. In step 5, the I ₁ is equal to or smaller than I ₁ '· A. If I ₁ is smaller than I ₁ ′ · A, proceed to step 6; otherwise, proceed to step 7. In step 6, A-1 is substituted for A, and the process proceeds to step 3. In step 7, the internal constant (A) is
Is stored in the memory 9 as the amplification factor. This procedure is performed for each a-phase circuit including the current transformer 2a, the auxiliary current transformer 4a, and the operational amplifier 5a, and for each c-phase circuit including the current transformer 2c, the auxiliary current transformer 4c, and the operational amplifier 5c. , Operational amplifier 5
a and the amplification factor of the operational amplifier 5c are optimally adjusted. By adjusting the amplification factor for each of the operational amplifiers 5a and 5c in this manner, it is possible to correct variations in the characteristics of the current transformers 2a and 2c, the auxiliary current transformers 4a and 4c, and the operational amplifiers 5a and 5c. it can. The operational amplifiers 5a, 5a
c, the load on the current transformers 2a and 2c and the auxiliary current transformers 4a and 4c can be minimized. For this reason, the accuracy compensation range of the current transformer can be expanded.

FIG. 5 is a diagram showing output characteristics of a band-pass filter inserted into a measurement circuit of each phase including a current transformer, an auxiliary current transformer, and an operational amplifier. As shown in the figure, the filter is a band-pass filter having a commercial frequency (50 Hz or 60 Hz) pass band, and can block a direct current component mixed in the measurement circuit. This filter can be configured as a digital filter by the arithmetic processing unit 7.

FIG. 6 is a diagram showing a modification of the current transformer according to the present embodiment. In the figure, 2b is a b-phase current transformer, 4b
Is a b-phase auxiliary current transformer, and 5b is a b-phase operational amplifier.
In the drawing, the same portions as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this example, the b-phase current can be directly measured. Further, since the current of each phase is directly measured, it is possible to protect against a ground fault or the like in which a zero-phase current occurs.

As described above, according to the present embodiment, the current transformer 2
The protection control unit that measures, displays, and controls the main circuit devices based on the current signals sent from the TEC is integrated into a single unit, reducing wiring materials and increasing wiring efficiency. it can. In addition, since the operational amplifier capable of adjusting the amplification factor is used, the adjustment work of the protection control unit can be simplified. Further, since the accuracy compensation range of the current transformer is expanded and the number of parts can be reduced, the manufacturing process of the switchboard can be shortened.

[0017]

As described above, according to the present invention, it is possible to provide a switchboard having a current transformer that can measure a wide range of primary current and does not malfunction due to a DC component.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a switchboard according to an embodiment of the present invention.

FIG. 2 is a diagram showing a structure of a switchboard according to the embodiment of the present invention.

FIG. 3 is a diagram showing an accuracy compensation range of a current transformer.

FIG. 4 is a diagram showing a procedure for adjusting the gain of the operational amplifier.

FIG. 5 is a diagram illustrating output characteristics of a band-pass filter.

FIG. 6 is a diagram showing a modified example of the current transformer in the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main circuit conductor 1A, 1B Lead-in cable 2 2a, 2b, 2c Current transformer 3, 30, 31 Protection control unit 4a, 4c Auxiliary current transformer 5a, 5c Operational amplifier 6 A / D converter 7 Arithmetic processing unit 8 Gain Control circuit 9 Memory 10 Display unit 11 Output unit 12 Switchboard 13, 14 Circuit breaker 15 Busbar

Continuing from the front page (72) Inventor Fukahiro Sato 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Within Kokubu Works, Hitachi, Ltd. (72) Katsunori Kojima 1-1-1, Kokubuncho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd. Kokubu Office (72) Inventor Toru Tanimizu 1-1-1, Kokubuncho, Hitachi, Ibaraki F-term (Reference) 2G035 AA09 AB08 AC01 AC03 AC16 AD19 AD20 AD26 AD28 AD55 AD65 5G042 BB02 BB13

Claims (4)

[Claims] A current transformer inserted in a main circuit, an auxiliary current transformer for transforming an output current of the current transformer, and a current flowing in the main circuit by measuring an output current of the auxiliary current transformer. And a distribution panel having an arithmetic processing unit for protecting and controlling the main circuit based on the measured current value, wherein the distribution panel includes an amplifier for amplifying an output of the auxiliary current transformer, and controls an amplification factor of the amplifier. A switchboard characterized by setting a current transformer ratio. 2. An apparatus according to claim 1, further comprising an A / D converter for A / D converting the output of the amplifier, and supplying the output of the A / D converter to the arithmetic processing unit. switchboard. 3. The switchboard according to claim 1, wherein a digital filter for removing a DC component is provided on an output side of the A / D converter. 4. The current transformer and the amplifier according to claim 1, wherein the current transformer and the amplifier are provided in at least two phases of a main circuit, and an amplification factor of the current transformer can be set for each phase. A switchboard characterized by the following.