JP6103705B2 - Secondary side open prevention device for current transformer - Google Patents

Description

  The present invention relates to a system for measuring the amount of electric power by detecting the voltage and current of a distribution line with a transformer (VCT), and when the transformer and the watt hour meter are separated, the secondary of the current transformer in the transformer. The present invention relates to a secondary side open prevention device for a current transformer that prevents a side terminal from being opened.

FIG. 8 is a configuration diagram of a system that measures the electric energy of the distribution line with an watt hour meter.
In FIG. 8, primary terminals 11 and 12 of the transformer 10 are connected to a distribution line (not shown), and an input terminal portion of the watt hour meter 30 is connected to the secondary terminal portion 13 via the wiring cable 20. 31 is connected. The worker M performs a meter reading of the electric energy by visually checking the display unit of the watt-hour meter 30.

  However, in this usage pattern, for the convenience of meter reading, the watt-hour meter 30 is often installed at a location away from the transformer 10, and the wiring cable 20 tends to be long. For this reason, an error may occur in the voltage and current input to the watt hour meter 30 due to a voltage drop of the wiring cable 20, and as a result, an error may occur in the measured value of the electric energy. Therefore, the transformer 10 is large in order to reduce power loss in the transformer 10 so as not to cause an error in the measured value of the electric energy.

On the other hand, the transformer 10 and the watt-hour meter 30 need to be replaced before the expiration date determined by laws and regulations, etc., and the work of separating the transformer 10 and the watt-hour meter 30 at the time of replacement is as follows. It is desirable that the distribution line can be performed in a live state.
Here, FIG. 9 is a circuit diagram of the VT (instrument transformer) 14 and the CTs (current transformers) 15a and 15b constituting the transformer 10, and the secondary side terminal portion 13 of the VT 14 and the CTs 15a and 15b. The input terminal portion 31 of the watt hour meter 30 is connected via the wiring cable 20.

As is well known, when the transformer 10 is in a live state and the wiring cable 20 is removed and the secondary terminals (secondary windings) of the CTs 15a and 15b are opened, a high voltage is generated between the secondary terminals. As a result, an arc may occur and an unexpected accident may occur.
Conventionally, various techniques have been proposed in order to prevent such opening of the secondary side of CT.

For example, FIG. 10 is a cross-sectional view showing a main part of a protection device for an alternating current input part described in Patent Document 1 described later, and FIG. 11 is an explanatory view showing a use state.
In this protective device, the measuring device 50 as an alternating current input device is attached to a socket 55 (see FIG. 11) connected in advance to the secondary terminal of the CT, whereby the secondary current of the CT is measured. AC current values and harmonics are measured from the input terminal.

  10 and 11, 51 is a stem fixed to the measuring instrument 50, and 51 a is an operation end portion thereof. Reference numeral 60 denotes a protective device fixed to the socket 55. Inside the protective device 60, conductors 61a and 61b that are electrically connected to the secondary terminal of the CT are arranged. In addition, a short-circuit conductor 63 having contact portions 63a and 63b at both ends is supported by a coil spring 62 inside the protective device 60. Reference numeral 63 c denotes an actuator that is integrally fixed to the central portion of the short-circuiting conductor 63.

  In a state where the measuring instrument 50 is mounted on the socket 55, as shown in FIG. 10A, the operation end 51a of the stem 51 presses the short-circuiting conductor 63 against the coil spring 62 via the actuator 63c. For this reason, the contact portions 63a and 63b of the short-circuiting conductor 63 are separated from the conductors 61a and 61b, so that the conductors 61a and 61b and thus the secondary terminals of the CT are not short-circuited. Therefore, a secondary current of CT is input to the input terminal of the measuring device 50 through the socket 55, and a predetermined measurement operation is executed.

  On the other hand, when the measuring instrument 50 is removed from the socket 55 for replacement or the like, the stem 51 is separated from the protective device 60 and the short-circuiting conductor 63 moves due to the restoring force of the coil spring 62 as shown in FIG. The contact parts 63a and 63b are connected to the conductors 61a and 61b, respectively, and the conductors 61a and 61b are short-circuited. As a result, the secondary terminals of the CT are also short-circuited, so that generation of a high voltage or arc between the secondary terminals can be prevented.

Patent Document 2 describes, as another conventional technique, connecting a protection device including a pair of diodes between a CT secondary side and a measuring instrument.
That is, in FIG. 12, 70 is a distribution line to be measured, 71 is a CT, 80 is a protective device, 90 is a measuring device, 91 is an auxiliary CT, and the protective device 80 is mutually reversed between the secondary terminals of the CT 71. It is composed of diodes 81 and 82 connected in parallel.

In this prior art, when the measuring device 90 is connected, only a voltage less than the forward drop voltage is applied to the diodes 81 and 82 of the protective device 80, so that no current flows through the diodes 81 and 82, and the measuring device 90 performs a normal measurement operation.
However, when the measuring instrument 90 is removed, the secondary voltage of the CT 71 rises, so that the diodes 81 and 82 become conductive, and current flows alternately to the diodes 81 and 82 every half cycle of the AC voltage of the distribution line 70. As a result, the voltage between the secondary terminals of CT71 is suppressed to the forward voltage drop of the diodes 81 and 82, and there is no possibility that a high voltage is generated between the secondary terminals of CT71.
The same protection device 80 as shown in FIG. 12 is also described in FIGS.

JP-A-5-288775 (paragraphs [0018] to [0023], FIGS. 4 to 6 etc.) JP-A-9-168231 (paragraphs [0003], [0004], FIG. 7 and the like)

The prior art described in Patent Document 1 is a mechanism in which the shorting conductor 63 is interlocked with the movement of the stem 51 integrated with the measuring instrument 50, and the secondary side of the CT is opened or short-circuited. The connection structure between the current input terminal and the CT secondary terminal in the socket 55 is not mentioned.
Further, when the measuring instrument 50 is detached from the socket 55 and the current input terminal on the measuring instrument 50 side and the CT secondary terminal are separated from each other, it is necessary that the state shown in FIG. However, even when the current input terminal on the measuring instrument 50 side and the CT secondary terminal are separated from each other due to an error in the dimensional accuracy of the parts or an error in the characteristics of the coil spring 62, the conductors 61a and 61b are completely connected by the short-circuit conductor 63. As a result, a high voltage may be generated between the secondary terminals of the CT without being short-circuited.

  In addition, the prior art described in Patent Document 2 has a simple configuration, but if a large current flows on the secondary side of the CT 71 for a long time with the measuring instrument 90 removed, the diode 81 in the protection device 80, 82 is overheated and its life is shortened. In the worst case, the diodes 81 and 82 may be burned out.

  Therefore, the problem to be solved by the present invention is that the current transformer and the transformer are separated from each other so that the secondary terminals of the CT are securely short-circuited, thereby improving the safety and reliability. It is in providing a secondary side open prevention device.

In order to solve the above-mentioned problem, the invention according to claim 1 is provided with an instrument transformer and a current transformer each of which is connected to each primary side terminal on the distribution line, and each of the instrument transformer and the current transformer is provided. A transformer in which the secondary terminal is arranged in the secondary terminal part;
A voltage input terminal and a current input terminal respectively connected to the secondary terminals of the instrument transformer and the current transformer when attached to the transformer; via these voltage input terminal and current input terminal; The power amount of the distribution line can be measured from the input voltage and current, and the watt hour meter is detachably formed with respect to the transformer.
When separating the transformer and the watt-hour meter, the secondary of the current transformer has a function of operating a short-circuit piece in the transformer to short-circuit between the secondary terminals of the current transformer. In the side opening prevention device,
The electricity meter includes a end surface S ₁ for joining the the transformer the secondary terminal end face S ₂ of when attached to, has a length L _b towards the short one-way from the end face S ₁ comprising a short-circuit piece drive unit and, with the current input terminal having a length L _c toward the secondary-side terminal of the current transformer,
The transformer, the secondary of the current transformer the jumper is driven by the short-circuit piece drive unit when the insertion length of the inserted from the end face S ₂ the jumper driver exceeds L _s It is formed to open between the side terminals,
The lengths L _b , L _c and L _s are
0 <L _b −L _s <L _c (L _b > 0, L _c > 0) is satisfied.

  According to the present invention, when the watt-hour meter and the transformer are exchanged for separation, the secondary terminals of the CT are reliably short-circuited to prevent the occurrence of high voltage or arc and safety. And can improve the reliability. Moreover, since there is no measurement error factor of the electric energy due to the length of the wiring cable, the transformer can be made smaller than before.

It is explanatory drawing which shows the use condition of embodiment of this invention. It is explanatory drawing which shows the basic composition of embodiment of this invention. It is a conceptual diagram which shows the basic composition of embodiment of this invention. It is a circuit diagram of the principal part of the transformer in FIG.2 and FIG.3. It is explanatory drawing of the dimensional relationship of each part in embodiment of this invention. It is explanatory drawing of the dimensional relationship of each part in embodiment of this invention. It is explanatory drawing of the dimensional relationship of each part in embodiment of this invention. It is a block diagram of the system which measures the electric energy of a distribution line. It is a circuit diagram of the principal part of the transformer in FIG. It is sectional drawing of the principal part of the prior art described in patent document 1. FIG. It is explanatory drawing which shows the use condition of the prior art of FIG. It is a circuit diagram which shows the prior art described in patent document 2.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, FIG. 1 is an explanatory view showing a use state of an embodiment of the present invention. In FIG. 1, 10A is a transformer composed of VT and CT, and 11 and 12 are primary terminals connected to a distribution line not shown. Reference numeral 16 denotes a secondary side terminal portion of the transformer 10A, which has built-in secondary side terminals of VT and CT.

100 is a watt-hour meter that can be attached to and detached from the secondary side terminal portion 16 of the transformer 10A in the direction of the arrow, and has a voltage input terminal and a current input terminal respectively connected to the secondary side terminals of VT and CT. I have.
The watt-hour meter 100 calculates the amount of power based on the voltage and current input from the secondary side terminal portion 16 of the transformer 10A, and stores, displays, or transmits the amount of power to the outside by wireless / wired communication. However, for the sake of convenience, description of a specific configuration for realizing these functions is omitted.

Next, FIGS. 2-4 is explanatory drawing which shows the basic composition of this embodiment.
In FIG. 2, the watt-hour meter 100 includes an input terminal (voltage input terminal and current input terminal) 101 connected to the secondary terminal 16a of the VT and CT of the transformer 10A, and a secondary side open / short circuit described later. 40 and a short-circuit piece drive section 102 for driving the short-circuit piece 17. Reference numerals 103 and 104 denote fixing portions made of bolts or the like for fixing the watt-hour meter 100 to the secondary side terminal portion 16.

  The secondary side terminal 16a on the side of the transformer 10A is composed of a total of seven terminals by the VT 14 and CTs 15a and 15b, for example, like the secondary side terminal part 13 in FIG. It is. Here, of the seven secondary terminals 16a shown in FIG. 2, any four terminals (for example, the four terminals on the right side) may be the secondary terminals of the CT, and these secondary terminals may be used. The four input terminals 101 on the watt-hour meter 100 side at the position corresponding to the terminals may be current input terminals.

  A secondary side open / short circuit portion 40 is disposed inside the transformer 10A. This secondary side open / short-circuit portion 40 has a drive portion 41 driven by the short-circuit piece drive portion 102, and a contact 18a, The short-circuit piece 17 which opens or short-circuits between 18b, and the coil spring 42 which always urges | biases the drive part 41 and the short-circuit piece 17 toward the short-circuit piece drive part 102 are provided.

FIG. 3 is a conceptual diagram assuming that the function shown in FIG. 2 is realized by, for example, a microswitch. In FIG. 3, reference numeral 19 denotes an actuator that operates in conjunction with the short-circuiting piece drive unit 102. The operation of the actuator 19 drives the short-circuiting piece 17 and opens or short-circuits the contacts 18a and 18b.
4 is a circuit diagram of a portion related to CT in the transformer 10A in FIGS. 2 and 3. Like FIG. 9, 15a and 15b are CT, and 17a and 17b are short circuits in FIGS. This is a short-circuit piece corresponding to the piece 17.

Here, the basic operation of the present embodiment will be described with reference to FIG.
In the state where the watt hour meter 100 is attached to the transformer 10A, the secondary terminal 16a on the transformer 10A side and the input terminal 101 of the watt hour meter 100 are connected as shown in FIG. 2 (a). The voltage and current output from the secondary side of the transformer 10 </ b> A are input to the watt-hour meter 100. At this time, the short-circuit piece drive unit 102 presses the drive unit 41 and the short-circuit piece 17 in the direction of the coil spring 42 against the restoring force of the coil spring 42, thereby opening the contacts 18a and 18b. Therefore, the secondary side of CT (15a, 15b in FIG. 4) of the transformer 10A is open.

  In a state where the watt hour meter 100 is detached from the transformer 10A, the short-circuit piece drive unit 102 of the watt hour meter 100 is separated from the secondary side terminal portion 16 as shown in FIG. For this reason, the drive unit 41 and the short-circuit piece 17 are restored by the restoring force of the coil spring 42, and the short-circuit piece 17 short-circuits the contacts 18a and 18b. That is, the secondary windings of CT15a and 15b in FIG. 4 are short-circuited by the short-circuit pieces 17a and 17b, respectively, and even if the distribution line is in a live line state, the There is no voltage or arcing.

Although the basic operation of the present embodiment is as described above, in this embodiment, each part of the CT is surely short-circuited when the watt-hour meter 100 and the transformer 10A are separated. The dimensions are set as follows.
In FIG. 5, S ₁ is an end face on which the input terminal 101 and the short-circuit piece drive unit 102 of the watt-hour meter 100 are implanted, and S ₂ is an end face on the watt-hour meter 100 side of the secondary side terminal part 16 of the transformer 10A. In the state where the watt-hour meter 100 is attached to the secondary terminal portion 16 and the input terminal 101 is connected to the secondary terminal 16a, both end faces S ₁ and S ₂ are joined.

Further, _{L b} is the length of the short bar driving unit 102 toward the short bar 17 the direction from the end face _{S 1, L c} is the length of the input terminal 101 from the end face _{S 1} toward the secondary-side terminal 16a, _{L s} a jumper 17 contacts 18a, when shorting between 18b, the length from the end face S ₂ of the driving portion 41 tip (i.e., the insertion length of the short bar driving unit 102 inserted from the end face S ₂ is L _s The length of the short-circuit piece 17 is driven by the short-circuit piece driving unit 102 when the distance exceeds the upper limit, and the secondary terminals of the CT are opened. These lengths L _b , L _c , and L _s are positive values in the direction of the arrows in FIG.
The length L _c of the input terminal 101, that the input terminal 101 when mounting the power meter 100 to the secondary-side terminal portion 16 is the length as securely connected to the secondary-side terminal 16a Needless to say.

In the present embodiment, the dimensional relationships of L _b , L _c , and L _s are set as the following formulas 1 to 3.
[Formula 1]
L _b > 0
[Formula 2]
L _c > 0
[Formula 3]
0 <L _b −L _s <L _c

By setting the dimensional relationships of L _b , L _c , and L _s as described above, before the input terminal 101 of the watt-hour meter 100 moves away from the secondary terminal 16a on the transformer 10A side, The distal end portion is separated from the distal end portion of the drive unit 41, and the short-circuit piece 17 short-circuits the contacts 18a and 18b. In other words, the input terminal 101 is always separated from the secondary side terminal 16a after the short-circuit piece 17 short-circuits between the contacts 18a and 18b, and the CT of the watt hour meter 100 and the transformer 10A is separated. The secondary terminals are never opened.

6 and 7 show the cases where the lengths L _b and L _s are different from those in FIG. 5. In these cases, the relationship of the above-described equations 1 to 3 is always maintained. Since the input terminal 101 is separated from the secondary side terminal 16a after the short-circuit piece 17 short-circuits between the contacts 18a and 18b, when the watt hour meter 100 and the transformer 10A are separated, the secondary side terminal of the CT is not connected. It will never be released.

  As described above, according to the present embodiment, compared with the prior art described in Patent Literature 1 and the like, the secondary terminal of the CT can be reliably connected with the watt-hour meter 100 and the transformer 10A separated. Therefore, safety and reliability can be improved by preventing high voltage and arc from occurring between the secondary terminals of the CT. Further, unlike Patent Document 2, there is no possibility that the diode constituting the protection circuit is overheated.

10A: Transformer (VCT)
11, 12: Primary side terminals 15a, 15b: CT
16: Secondary side terminal portion 16a: Secondary side terminals 17, 17a, 17b: Short-circuiting pieces 18a, 18b: Contact point 19: Actuator 40: Secondary side open / short-circuit portion 41: Drive portion 42: Coil spring 100: Electric energy meter 101: input terminal 102: short-circuit piece drive unit 103, 104: fixing section _S 1, _{S 2:} end face

Claims (1)

A transformer having an instrument transformer and a current transformer each connected to a primary line terminal on a distribution line, wherein each secondary terminal of the instrument transformer and the current transformer is arranged at a secondary terminal section When,
A voltage input terminal and a current input terminal respectively connected to the secondary terminals of the instrument transformer and the current transformer when attached to the transformer; via these voltage input terminal and current input terminal; The power amount of the distribution line can be measured from the input voltage and current, and the watt hour meter is detachably formed with respect to the transformer.
When separating the transformer and the watt-hour meter, the secondary of the current transformer has a function of operating a short-circuit piece in the transformer to short-circuit between the secondary terminals of the current transformer. In the side opening prevention device,
The electricity meter includes a end surface S ₁ for joining the the transformer the secondary terminal end face S ₂ of when attached to, has a length L _b towards the short one-way from the end face S ₁ comprising a short-circuit piece drive unit and, with the current input terminal having a length L _c toward the secondary-side terminal of the current transformer,
The transformer, the secondary of the current transformer the jumper is driven by the short-circuit piece drive unit when the insertion length of the inserted from the end face S ₂ the jumper driver exceeds L _s It is formed to open between the side terminals,
The lengths L _b , L _c and L _s are
0 <L _b −L _s <L _c (L _b > 0, L _c > 0)
The secondary side open prevention device of the current transformer characterized by satisfying the relationship

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