JPH0451465Y2 - - Google Patents

Description

[Detailed description of the invention] [Technical field of the invention] The invention relates to a current transformer, and more specifically, one end of a conductor constituting a disconnector section for a disconnector in a switchboard is used as a primary winding conductor. This paper relates to a combination structure of a winding current transformer for measurement and a feedthrough current transformer for protection.

[Technical background of the invention] Figure 1 shows a single line diagram of the switchboard circuit. The primary current is branched from the main circuit bus 1, and is passed through a power supply side disconnector 2, a bow disconnector 3, and a load side disconnector 4 provided for each power supply circuit to a through-type current transformer 5 and a winding current transformer. flows through the primary winding circuit of the device 6. Here, the electrical connection between the disconnector parts 2 and 4 located before and after the shield breaker 3 and the shield breaker 3 is not fixed, but can be connected and separated by moving the main body of the shield breaker 3. It shows a pull-out type that can be connected. Current transformers are used as secondary burdens, such as a protective current transformer connected to a relay for system protection, an ammeter for measuring the primary current,
It is broadly divided into instrument current transformers that are connected to meters such as wattmeters and watthour meters.

The current transformation ratio or rated primary current of a protective current transformer is often determined from the protection adjustment of the protective relay, and since the protection area is in the overcurrent area, it is generally higher than the load current. Specifications include a high current transformation ratio or rated primary current. Furthermore, for special protection such as busbar protection, low leakage reactance is often specified. In a current transformer with a general winding configuration, the leakage reactance increases in proportion to the number of turns, that is, approximately the square of the current transformation ratio, so it is not suitable for current transformers with a high current transformation ratio such as protection current transformers. In order to reduce leakage reactance, it is necessary to wind the secondary winding uniformly over the entire circumference of the magnetic core to create a structure that can suppress the occurrence of leakage flux, that is, leakage reactance. In order to realize the above structure, a feed-through current transformer using a toroidal iron core is often adopted because the structure and shape are simple and the winding work is easy using a toroidal winding machine or the like.

On the other hand, since the main purpose of an instrument current transformer is to accurately measure the load current, the current transformation ratio or rated primary current is specified to be slightly larger than the load current, and the current transformation ratio or rated primary current may vary depending on the load capacity. Become a type. In addition, in the secondary current circuit of the instrument current transformer,
In addition to general ammeters, load meters that require high accuracy, such as wattmeters for power trading, are connected, and the error accuracy generally improves in proportion to the square of the ampere-turns, so it is especially important for load current For instrument current transformers with low current transformation ratios or low rated primary currents for small circuits, or instrument current transformers that require ultra-high accuracy even at high current transformation ratios, a winding structure with several turns of the primary winding is used. Adopted.

In the circuit configuration example shown in FIG. 1, the protective feedthrough current transformer 5 protects a wide range of circuits on the load side of the shield breaker 3, including the winding type current transformer 6 for meters. Therefore, it is placed at a position closest to the shield breaker 3 in the load side circuit of the shield breaker 3, that is, generally closer to the power source than the winding type current transformer 6 for measuring instruments. Protection current transformers and instrument current transformers generally have different current transformation ratios, and the guaranteed characteristics range for the former is overcurrent range, while the latter is below the rated current range, so they cannot be used separately. is normal.

FIG. 2 is a side cross-sectional view showing a conventional example of a mounting structure for a protective feedthrough current transformer in a switchboard, a winding current transformer for an instrument, and a primary winding conductor for a disconnector/current transformer. Regarding the winding type current transformer 6 for meters, one end of the conductor constituting the disconnector section 4 is connected to the primary winding conductor around the outer periphery of the secondary coil 9 which is wound on the iron core 8 through an insulator (not shown). 7, rolled up several times, and molded the whole with resin 10 such as epoxy resin. Electrical connections are made to the disconnector section 4 by forcible contact with the electrode terminals of the disconnector (not shown) in a bare state, but due to the reduction of the phase-to-phase pitch dimension of the main circuit busbar and the corona voltage characteristics between the main circuit busbar and ground, etc. In order to improve
Therefore, the conductor of the disconnector section 4 and the wound current transformer 6
At the same time, it is integrally molded. Furthermore, the molded disconnector section 4 and wound current transformer 6 are firmly fixed to the mounting bracket 12 at ground potential by bolts (not shown).

On the other hand, a secondary coil 14 is evenly distributed over the entire circumference of the core magnetic path on a toroidal-shaped core 13 via an insulator (not shown), and then molded with a resin 15 such as epoxy resin. The feedthrough current transformer 5 is disposed on the outer periphery of the insulating cylindrical portion 11 and uses the conductor of the disconnector portion 4 as a primary winding conductor,
It is firmly fixed to the mounting bracket 12 at ground potential by bolts (not shown).

Historically, winding type current transformers for instruments were originally installed separately from the disconnector section and were installed separately using general current transformers molded with resin such as epoxy resin. The current transformer and disconnector section were electrically connected via a high-voltage insulated conductor, but as molding technology progressed and switchboards were required to be smaller, lighter, and easier to maintain and inspect, There is a history of how the disconnector part and the wound current transformer came to be integrally molded.
Protective feed-through current transformers were already used as structures placed on the outer periphery of the insulating cylindrical part of the disconnector even in the era when the disconnector part and the wound type current transformer were placed separately. . The main reason for this is that by placing the feed-through current transformer on the outer periphery of the insulating tube, most of the withstand voltage characteristics for the high-voltage primary winding circuit are borne by the insulating tube. This is because the device does not have to bear much burden on the withstand voltage characteristics of the primary winding circuit. In other words, it has the advantage that it can be handled with a simple through-type structure for low pressure, and can be made small, lightweight, and inexpensively. Moreover, there is an advantage that the installation work of the through-type current transformer is easy. In addition, the configuration in which the protective feedthrough current transformer is placed on the outer periphery of the insulating cylindrical part is designed to ensure that the protection range of the feedthrough current transformer is as wide as possible, in response to the desire to place it as close as possible to the electrode terminal of the shield breaker. Not only can this be handled satisfactorily, but it does not impede the draw-out operation of the disconnector on the disconnector unit side.

[Problems with Background Art] However, the structure of the conventional current transformer shown in FIG. 2 has the following problems.

(1) Since the primary winding conductor 7 of the wire-wound current transformer 6 rises vertically, the high potential part of the primary winding conductor 7 and
The electric field distribution between the ground potential portion of the mounting bracket 12 and the low potential portion of the surface of the resin 15 of the through-type current transformer 5 has been a problem. That is, the electric field distribution inside the resins 10 and 15, which have excellent withstand voltage characteristics, is relatively gentle, and can be adjusted by optimally selecting the mold shape, etc., if necessary. However, minute gaps are formed between the cut end of the mounting bracket 12, between the mounting bracket 12 and the surface of the resin 10, and between the surface of the resin 15 of the through-type current transformer 5 and the surface of the resin 10 for the wound type current transformer. Because the dielectric constant of air is lower than that of resin, the electric field concentrates due to electrostatic partial pressure, making it the weakest point. The withstand voltage characteristics, particularly the ground-to-ground corona voltage characteristics, can be adjusted by changing the shape, thickness, etc. of the resins 10 and 15, but this alone has a limit and no significant effect can be expected. As a countermeasure, applying conductive paint to minute voids has been carried out, but this requires additional work, and although these countermeasures have some effect, they are still insufficient.

(2) Dust and the like easily accumulate in the gap between the outer periphery of the insulating cylindrical portion 11 and the through window of the feed-through current transformer 5, and cleaning work during maintenance and inspection takes a long time.

(3) In order to simplify the work of fixing the wound current transformer 6 and the through-type current transformer 5, including the disconnector section 4, to the mounting bracket 12, bolts (not shown) are shared, reducing the number of parts. Although this will reduce the amount of damage, it will improve the accuracy of the dimensional pitch of holes for mounting or inserting bolts provided in a part of the resin of the wound type current transformer 6 including the disconnector part 4 and the through type current transformer 5. , high-precision molds and jigs were required, and the molding work and assembly and fixing work to the switchboard required careful and time-consuming work.

(4) The diameter of the through window of the through type current transformer 5 is
The outer circumferential dimension of the insulating cylindrical portion 11 itself, the electrode terminal dimension of the insulation breaker, and the voltage value of the high voltage circuit are standardized and determined. On the other hand, since the outer diameter of the feed-through current transformer 5 is determined by the phase-to-phase pitch of the main circuit busbar, if it is necessary to take a large overcurrent constant n for protection, the core 13 has a core thickness as described above. Therefore, it is necessary to deal with this by increasing the core width. However, if the core width is made too wide, the feed-through current transformer 5 will protrude beyond the length of the insulating tube 4, and the feed-through current transformer 5 may become impossible to install due to its low voltage structure, or the circuit may be damaged instead. A current transformer with a high-voltage structure suitable for the voltage was installed separately, and a new non-standard one was manufactured to extend the length of the insulating cylinder 11, all of which resulted in an expensive product. Put it away. Further, the length of the insulating cylindrical portion 11 is determined by the creepage distance from the disconnector portion 4 to the surface of the resin 15 of the feedthrough current transformer 5 in the low potential section, and the width dimension of the feedthrough current transformer 5 is There were problems such as the need to keep selecting for a relatively long time in anticipation of the large number of types.

[Purpose of the invention] The present invention solves the above-mentioned problems, eliminates imbalance in electric field distribution, and provides a current transformer with a combination structure of a feed-through current transformer and a wound current transformer with excellent insulation properties. The main purpose is to

[Summary of the invention] For this reason, the present invention provides a through-type current transformer to the side of the wound current transformer at an intermediate position between the straight part of the primary winding conductor from the wound current transformer to the disconnector section and the mounting bracket. It is characterized by arranging the vessels and molding the whole into one piece.

[Embodiments of the invention] Hereinafter, embodiments of the invention will be described based on the drawings.

Figure 3 shows a current transformer according to an embodiment of the present invention, including a protective feedthrough current transformer, a winding current transformer for meters, and a primary winding for a disconnector/current transformer in a switchboard. FIG. 3 is a side sectional view showing a wire conductor mounting structure. In the figure, the same reference numerals as in FIG. 2 indicate the same or equivalent parts, and the winding type current transformer 6 for measuring instruments has a secondary coil 9 wound around an iron core 8 via an insulator (not shown).
The conductor of the disconnector section 4 is used as the primary winding conductor 7 and wound several times around the outer periphery thereof. On the other hand, the feed-through current transformer 5 has an insulator (not shown) on a toroidal-shaped iron core 13 in a straight line portion of the conductor from the winding part of the primary winding conductor 7 of the wound type current transformer 6 to the disconnector part 4. The secondary coil 14 is formed by passing through the secondary coil 14 evenly distributed around the entire circumference on the magnetic path of the iron core. Furthermore, the entire structure including the wound current transformer 6, the through-type current transformer 5, and the disconnector section 4 is integrally molded with a resin 10 such as epoxy resin to form a so-called current transformer. In this case, the disconnector section 4 of the current transformer
In this case, the electrode terminals of the disconnector 3 (not shown) are electrically connected by forced connection while being bare, so the pitch between phases of the main circuit bus in this part is reduced and the corona voltage between the main circuit bus and ground is reduced. In order to improve the characteristics, an insulating cylinder part 1 is provided on the outer periphery of the disconnector part 4.
1 is integrally molded with a resin 10 such as epoxy resin at the same time as the current transformer. This molded current transformer is firmly fixed to the mounting bracket 12 at ground potential by bolts (not shown).

Here, the feedthrough current transformer 5 has the same core cross-sectional area as the conventional structure in order to maintain the required overcurrent constant n for protection, but the winding dimension of the secondary coil 14 is The stacking thickness and core width of the iron core 3 are selected so as to be approximately the same as the finished dimensions of the primary winding conductor of the winding current transformer 6, and the iron core 3 is placed on the side of the winding current transformer 6.

According to the current transformer configured in this way, the following effects can be obtained.

The iron core 13 and secondary coil of the through-type current transformer 5 are placed at intermediate positions between the primary winding conductor 7 of the wound type current transformer 6 and the conductor for the disconnector section 4 which are at high potential, and the mounting bracket 12 which is at ground potential. 14 and the entire body is integrally molded with resin or the like. The electric field is caused by the fact that the voltage between the terminals of the secondary coil 14 of the feedthrough current transformer 5 is several volts, for example, when the secondary load is 40VA and the secondary rated current is 5A, only about 8 volts is generated, or if one side of the secondary terminal is grounded. By being used as an electrostatic shield, the secondary coil 14 of the feedthrough current transformer 5, which is at a low potential, is evenly distributed over the entire circumference of the magnetic core of the iron core, and in combination with this, it acts as an electrostatic shield. , it is possible to prevent concentration of electric field and obtain uniform distribution. That is, most of the electric field is distributed between the high potential primary winding conductor 7 and the secondary coil 14,
The space between the high-potential primary winding conductor 7 and the secondary coil 14 is made of only the resin 10 with excellent withstand voltage characteristics. Stable characteristics can be obtained regardless of voltage.

(2) The microgap near the mounting bracket 12, which is at ground potential and is the weakest point in the electric field distribution in the conventional structure, is located behind the secondary coil 14 of the feedthrough current transformer 5 and is at a low potential. Secondary coil 14
Only the electric field associated with the potential difference between the two is applied. Therefore, since the electric field that generates corona does not reach the micro-gaps at all, it is possible to eliminate weak points in the withstand voltage, especially the corona-to-earth voltage characteristics. Incidental work such as coating can be eliminated.

(3) The distance between the mounting bracket 12 and the primary winding conductor 7 of the wire-wound current transformer 6 in order to reduce and alleviate the electric field applied to the microgap portion described in item (2) above in the conventional structure. , that is, compared to the case where the value was selected to be relatively larger than the value determined by the withstand voltage characteristics of the resin 10, in this example, as described in the above item (1), the electric field distribution is concentrated within the resin 10, and As mentioned in item (2) above, the thickness of resin 10 is reduced to 1
The minimum optimum value determined according to the circuit voltage can be selected from the withstand voltage characteristic of 0. Therefore, the amount of resin can be reduced, the size and weight can be reduced, and the price can be reduced.

Since the through-type current transformer 5 and the wound type current transformer 6 are integrally molded, (1) the through-hole of the through-type current transformer 5 and the outer periphery of the insulating cylinder part 11 of the disconnector part 4, as in the conventional structure; The shape of small-sized recesses such as gaps between the current transformer and the current transformer can be reduced, and the mold shape of the current transformer portion can be selected to be a simple shape such as a cylinder or a box shape. Therefore, cleaning work for dust accumulation is easy and maintenance and inspection can be simplified.

(2) One-time installation of integrally molded products,
Since the installation of the wound wire and through-type current transformers 6 and 5 is completed at the same time, the installation work can be simplified compared to conventional methods, and the precision of the dimensional pitch of the current transformer mounting holes is improved, and coordination is not required. Since there is no need to increase the dimensional accuracy of the mold, manufacturing becomes easy.

(3) The secondary terminals, which were conventionally provided separately for each winding and feedthrough current transformer 6, 5, can now be provided in one place at an optimal location.
Wiring supplies such as ducts in the switchboard and wiring work can be simplified.

(4) As mentioned in item (1) above, the mounting bracket 12, the wire-wound current transformer 6, and the conductor for the disconnector section 4, which were selected from a relatively wide range, were used to reduce the electric field to weak points. Since the through-type current transformer 5 is placed in the space between the resin 10 and the resin 10, it is effectively utilized. It will not be modified to a larger width or its dimensions will be increased.

Because the through-type current transformer 5 was arranged close to the outer periphery using a relatively small-sized conductor for the disconnector section as the primary winding conductor, (1) the iron core 13 used in the through-type current transformer 5 was used as the primary winding conductor; The inner diameter dimension of the magnet can be reduced, the average magnetic path length can be reduced, the iron core weight can be reduced, the excitation current consumed can also be reduced, and the error characteristics can also be improved. In some cases, compared to conventional structure through-type current transformers,
The core cross-sectional area can be reduced.

(2) Since the insulating cylindrical portion 11 of the disconnector section 4 does not have a through-type current transformer on its outer periphery, it is only necessary to provide a necessary creepage distance between the conductor of the disconnector section 4 and the mounting bracket 12. Therefore, the axial protrusion dimension can be reduced. Moreover, there is no need to modify or create a new mold according to the specifications of conventional through-type current transformers, so it is possible to unify the current transformers into one piece with standardized dimensions and shapes, resulting in inexpensive current transformers. .

(3) The core size can be easily increased for the through-type current transformer 5 with a large overcurrent constant n for protection, and the molding die etc. associated with the increase in the core size can also be used for the current transformer part. Since the shape of the mold can be simplified, it can be handled quickly and at low cost.

In the above embodiments, the current transformer placed on the load side of the disconnector was explained as an example. As shown, the present invention can also be applied when a current transformer is placed on the power source side.

[Effects of the invention] As described above, according to the invention, the wire-wound current transformer is penetrated to the side between the straight part of the primary winding conductor from the wire-wound current transformer to the disconnector section and the mounting bracket. As the shape current transformer is arranged and the entire body is molded, the electric field distribution is uniform, the insulation properties are excellent, and the product is small, lightweight,
A current transformer that is inexpensive and easy to manufacture, install, and maintain and inspect can be obtained.

[Brief explanation of the drawing]

Figure 1 is a single line diagram showing an example of a switchboard circuit.
Figure 2 is a side sectional view showing the mounting structure of a protective feedthrough current transformer, an instrument winding current transformer, and a primary winding conductor for a disconnector/current transformer in a conventional switchboard. FIG. 2 is a side cross-sectional view showing a mounting structure of a protective feedthrough current transformer, an instrument winding current transformer, and a primary winding conductor for a disconnector/current transformer in a switchboard according to an embodiment of the present invention. 1... Main circuit bus bar, 2... Power supply side disconnector section, 3
...Shipping disconnector, 4...Load side disconnector section, 5...Through current transformer, 6...Wound type current transformer, 7...Primary winding conductor, 8, 13...Iron core, 9 , 14...Secondary coil, 10, 15...Resin, 11...Insulating cylinder part,
12...Mounting bracket.

Claims (1)

[Scope of utility model registration request] A wound type current transformer that uses a conductor constituting a disconnector section in a switchboard as a primary winding conductor, and this primary winding conductor is wound around an iron core around which a secondary coil is wound; In a current transformer in which a through-type current transformer in which the primary winding conductor passes through an iron core around which a secondary coil is wound is combined, and the current transformer is attached to a mounting bracket at ground potential, a disconnector is connected to the wound current transformer. The through-type current transformer is arranged on the outer periphery of the linear portion of the primary winding conductor that reaches the part, and the entire body including the primary winding conductor, the through-type current transformer, and the wound type current transformer is integrally molded. , and the through-type current transformer is disposed at an intermediate position between the primary winding conductor and the mounting bracket.