JPH0555078U - Measuring device - Google Patents

Abstract

(57) [Summary] [Purpose] While reducing the secondary load on the current transformer for meters,
Provided is a compact measuring device capable of reducing the open circuit accident of the secondary circuit and enhancing the reliability of a protective relay circuit attached to the secondary circuit. [Structure] A feed-through current detector 12 for detecting the secondary current is attached to a secondary circuit of an instrument current transformer 3 for detecting a main circuit current, and an amplifier 14, which amplifies a current signal from the detector 12, A measuring instrument 13 including a computing section 15 for computing the measurement values of various measurement items based on the amplified signal from the amplifier 14 and the voltage signal of the main circuit voltage from the instrument transformer, and a display section 16 for displaying each measurement value. To provide.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to a measuring device in a power receiving and transforming facility.

[0002]

[Prior Art]

 Conventionally, in the power receiving and transforming equipment, when various measured values related to the main circuit are obtained, various instruments are directly connected to the secondary circuit of the current transformer for instrument installed in the conductor of the main circuit.

For example, as shown in FIG. 2, an instrument current transformer (hereinafter referred to as CT) 3 is attached to the load side of the circuit breaker 2 of the main circuit conductor 1, and a protective relay circuit 4 is attached to the secondary circuit of this CT 3. When connected, the power converter (W / TD) 5, power meter (W) 6, power factor converter (PF / TD) 7, power factor meter (PF) 8, current converter ( A / TD) 9, and then the ammeter (A) 11 is sequentially connected via the ammeter selector switch (AS) 10, while the secondary from the transformer for meters (hereinafter referred to as PT) for detecting the main circuit voltage. The voltage is input to the power converter 5, the power meter 6, the power factor converter 7, and the power factor meter 8. Further, the outputs from the converters 5, 7, 9 are extracted as transmission output signals.

[0004]

[Problems to be solved by the device]

 In the above-mentioned prior art, since each meter 6, 8, 11 and each converter 5, 7, 9 etc. are directly connected to the secondary circuit of CT3 which is the same as the protection relay circuit 4, the connection point There is a problem that the reliability of the protective relay circuit 4 becomes low, and if these connection points become open, damage to the CT3 itself and the accompanying accident spread can be expected. There is a problem that the possibility of such an accident is high.

Further, since not only the protective relay circuit 4 but also the meters 6, 8, 11 and the converters 5, 7, 9 are connected to the secondary circuit of CT3, the secondary load of CT3 is increased, and As a result, the detection accuracy in the large current region at the time of the main circuit failure is lowered, and the stability and reliability of the operation of the protective relay circuit 4 are lowered.

Further, since the various instruments 6, 8, 11 and the converters 5, 7, 9 are individually installed, there is a disadvantage that these are mixed and the wiring is very large, resulting in an increase in size of the entire apparatus. Yes, and when additional instruments or converters are additionally installed, or when the CT3 current change ratio is changed, hard measures such as wiring of additional instruments or replacement of instruments must be taken. , There is a very troublesome problem.

The present invention has been made in view of the above problems of the conventional technology. The purpose of the present invention is to significantly reduce the secondary burden of CT and to reduce CT 2 An object of the present invention is to provide a compact measuring device capable of improving the reliability of the protective relay circuit provided in the next circuit.

[0008]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, in the measuring device of the present invention, a feedthrough type current detection unit which is attached to the secondary circuit of CT for detecting the main circuit current and detects the secondary current of CT, and Measuring instrument equipped with an amplifier that amplifies the current signal, a computing unit that computes the measured values of various measurement items by the amplified signal from the amplifier and the voltage signal of the main circuit voltage from PT, and a display unit that displays each measured value It is equipped with and.

[0009]

[Action]

 In the measuring device with the above-mentioned configuration, a weak current signal of the main circuit current is detected by the penetrating current detector attached to the secondary circuit of the CT without contact, and this is amplified by the amplifier of the measuring instrument. After that, the voltage signal from the PT is input to the calculation unit, and the measured values of various measurement items are calculated and displayed on the display unit.

In this case, in the secondary circuit of CT, there is no connection point related to the measuring device, and since the measuring device has a built-in function of amplifying the current signal from the detecting unit, the detecting unit is It suffices if the secondary current is detected as a weak current element, and the secondary load of CT is extremely small. Furthermore, adding measurement items or changing the CT current ratio can be easily dealt with by adding or changing settings in the calculation unit.

[0011]

【Example】

 An example will be described with reference to FIG. Attach CT (measuring device current transformer) 3 to the load side of the circuit breaker 2 of the main circuit conductor 1 at the substation, connect the protective relay circuit 4 to the secondary circuit of CT 3, and connect the secondary circuit to this secondary circuit. A current detection unit (auxiliary CT) 12 is attached for each phase to detect the secondary current of CT3 in a non-contact manner. The current signal from each detection unit 12 is input to the measuring instrument 13 of the microcomputer configuration together with the voltage signal from the PT (measuring transformer).

The measuring instrument 13 includes an amplifier 14 that amplifies a weak current signal from each detection unit 12, and an amplifier 14 that is based on preset measurement items, current transformation ratio, transformation ratio, and the like. An arithmetic unit 15 for calculating various kinds of measured values of current, voltage, electric power, power factor and the like by an amplified signal from PT and a voltage signal from PT, and a display unit 16 for displaying each of the obtained measured values are provided. The calculation unit 15 has a function of converting and outputting the calculated measurement value according to a preset conversion output item, and the conversion output is output from the measuring instrument 13 as a transmission measurement signal.

In such a configuration, the secondary current of CT3 detected by each detection unit 12 is amplified by the amplifier 14 and then input to the calculation unit 15 together with the voltage element from PT. Various measurement values are calculated at the place and displayed on each display unit 16, and the transmission output of each measurement value output from the calculation unit 15 is transmitted from this substation to the sales office, central control station, etc. To be done.

In this case, the secondary current of CT3 is detected by the detection unit 12 in a non-contact manner, and the secondary circuit of CT3 has no connection point related to this type of measuring device, so that the reliability of the protective relay circuit 4 is improved. Is significantly improved, and the risk of damage to the CT3 or the spread of accidents due to the secondary opening of the CT3 is reduced. Moreover, the measuring device 13 has an amplifying function, and the secondary current of the CT3 is a weak current from the detection unit 12. As a result, the secondary load on the CT3 is reduced, the operation of the protective relay circuit 4 in the event of a main circuit failure is stabilized, and the reliability is increased.

In addition, since one measurement device 13 calculates and displays various measured values based on the current signal obtained by the detection unit 12 and the voltage signal from PT, the wiring amount becomes smaller than in the conventional case, and The device can be made compact, and the addition and change of measurement and conversion items can be done simply by changing the setting in the calculation unit 15, which is so-called software-based, which makes it easy to add or change these. You can do it.

[0016]

[Effect of the device]

 Since the present invention is configured as described above, it has the following effects. The secondary current of the current transformer for the meter that detects the main circuit current is detected by the non-contact type current detector, and the detected current is amplified and calculated in the measuring section to obtain the measured values of various measurement items. Since the configuration is displayed, the connection point to the current transformer secondary circuit can be eliminated for measurement, and the secondary load can be significantly reduced, and the operation of the protective relay circuit connected to this secondary circuit can be reduced. This not only improves stability and reliability, but also reduces accidents due to opening of the secondary circuit.

Moreover, since various measured values can be calculated and displayed by one measuring instrument, the apparatus can be made compact, and the measurement items can be added or changed only by changing the setting in the calculation section. It can be carried out and these measures can be easily taken.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a measuring device according to the present invention.

FIG. 2 is a configuration diagram of a conventional example.

[Explanation of symbols]

 3 Current transformer (CT) for measuring instrument 12 Penetration type current detecting section 13 Measuring instrument 14 Amplifier 15 Computing section 16 Display section

Claims (1)

[Scope of utility model registration request] 1. A current transformer for an instrument for detecting a main circuit current, comprising:
A through-type current detection unit attached to the next circuit for detecting the secondary current of the current transformer, an amplifier for amplifying a current signal from the detection unit, an amplified signal from the amplifier and a main circuit from an instrument transformer A measuring device comprising: a calculator that calculates measured values of various measurement items based on a voltage signal of a voltage; and a measuring instrument that includes a display unit that displays the measured values.