JP2000277363A - Capacitance divider voltage transformer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To construct a capacitance divider voltage transformer without increasing space. SOLUTION: A voltage transformer comprises a power cable or an insulated bus, having an internal semiconductor layer 3, a main insulating layer 4, and an external semiconductor layer 5 arranged outside a conductor 2, and a capacitance divider voltage metal layer 6, an auxiliary insulating layer 7, a ground metal layer 8, are as necessary, a protection layer 9 arranged outside the power cable or the insulating bus. A divided voltage extracting tap T is provided by connecting an insulated line 10 to the layer 6, and a ground tap E is provided by connecting a ground line 11 to the layer 8. In this case, the thickness and the like of the layer 7 are selected such that a capacitance C1 provided by the layer 4 is sufficiently larger than a capacitance C2 provided by the layer 7, so as to obtain a low voltage between the taps T and E.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitance-divided voltage transformer using a power cable or an insulated bus.

[0002]

2. Description of the Related Art There are two types of voltage transformers (VT): an inductive type VT having a transformer configuration and an electrostatic capacity dividing type VT having a series capacitor configuration (FIG. 7). The usage type of the induction type VT and the capacitance division type VT is roughly classified as follows according to the line voltage (system voltage) used.

[0003] In the case of open substations and power plants, 36k
Up to V, an inductive VT is used, and above 72.5 kV, a capacitance-divided VT is used. In the case of GIS type substations and power plants, induction type VTs up to 245 kV
Is used, and when the voltage is 300 kV or more, a capacitance-divided VT is used.

[0004] The boundary between the use of the induction type VT and the use of the capacitance division type VT is not strictly determined by the voltage, but is mainly due to the economic reason of which one is the same specification and which is cheaper. In general, the higher the voltage, the more economically the capacitance-divided VT is advantageous.

[0005]

SUMMARY OF THE INVENTION An induction type VT (FIG. 7)
When the frequency is set to 0 when a DC voltage is applied as in the DC withstand voltage test or the DC insulation test in (a)), the inductive VT generates impedance (ωL _O ) by reactance (L _O ), so that the impedance is reduced. It will be 0.
Unless this inductive VT is separated from the line and tested, a true insulation check cannot be performed. Therefore, a disconnecting device or a drawing device is required.

In addition, when a test is performed with the inductive VT connected to the line by mistake, a short-circuit current may flow due to impedance 0 and the inductive VT may be destroyed. In many cases, a power fuse is attached to the primary side of the VT.

On the other hand, a capacitive voltage dividing type VT (FIG. 7B)
In the case of the above, since there is no such a problem, an economical comparison of the capacitance-divided VT alone and its attached devices shows that the range of use of the capacitance-divided VT can be expanded. Be expected.

Further, with the recent spread of digital relays / meters, the secondary load of the VT has been extremely reduced. Voltage 36
The VT below kV is now 200VA and the load is now 3
0 VA. In addition, a voltage of 72.5 kV or more V
T has been reduced from 500 VA in the past to 50 VA. In the future, it may decrease even further.

In addition, an inductive type VT is often used in a gas insulated switchgear (GIS). However, if voltage detection can be performed without increasing space, or voltage detection can be performed without using SF6 gas. If so, there is a great possibility that they will be capacitance divided VTs, which may further expand the manufacturing limit of the capacitance divided VT.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a capacitance-divided voltage detector using a power cable or an insulated bus that does not require an installation space. Is to do.

[0011]

According to the present invention, there is provided a capacitance-divided voltage detector according to the present invention, comprising: an internal semiconductor layer, a main insulating layer,
A metal layer for capacitance division is provided on the external semiconductor layer of the power cable or the insulating bus bar on which the external semiconductor layer is provided, and a ground metal layer is provided thereon via an auxiliary insulation layer, and the metal for capacitance division is provided. A capacitance divided voltage is drawn from between the layer and the ground metal layer.

This capacitance-divided voltage detector can be used with one end sealed and the other end connected to a circuit conductor inside the gas insulated switchgear via a connector.

Alternatively, a capacitance-divided voltage detector is provided on at least one of a power cable and an insulated bus, and its conductor is connected to a circuit conductor in a gas insulation device for use.

Alternatively, a cylindrical internal conductor serving as a connection bus and one or more cylindrical external conductors having the same potential as the internal conductor are concentrically arranged, and the space between the internal conductor and the external external conductor or inside the internal external conductor is provided. A cylindrical grounding metal layer is concentrically arranged between the conductor and the outer outer conductor and each outer conductor, and a cylindrical grounding metal layer is concentrically arranged outside the outermost outer conductor. Between the outer conductor and the ground metal layer, a metal layer for electrostatic capacity division is arranged, and the inner conductor and the outer conductor are connected by a lead wire,
Each of the capacitance dividing metal layers and each of the grounding metal layers are connected by a lead wire.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows a cross-sectional structure of a capacitance-divided voltage transformer (hereinafter referred to as CVT) using a power cable or an insulated bus.

The CVT 1 uses a power cable or an insulating bus having an internal semiconductor layer 3 for alleviating an electric field and potential on the conductor 2, a main insulating layer 4, an external semiconductor layer 5 for reducing the electric field and potential on the conductor 2. On the external semiconductor layer 5, a metal layer 6 for capacitive voltage division, an auxiliary insulating layer 7, a ground metal layer 8, and a protective layer 9 as an outermost layer if necessary, are provided. The configuration is such that the voltage dividing tap T is drawn out, and the grounding tap E is drawn out from the grounding metal layer 8 by the conducting wire 11. The protective layer 9 is provided in consideration of mechanical stress removal, weather resistance, improvement of heat dissipation, and the like.

The material and the thickness of the auxiliary insulating layer 7 are adjusted so that the AC voltage applied to the auxiliary insulating layer 7 is at a low voltage level and the capacitance C _{2 in} consideration of the ratio with the capacitance C ₁ of the main insulating layer 4 is obtained. select.

In consideration of allowing a certain amount of current to flow, the capacitance dividing metal layer 6 is connected to one of the cable connection points by an insulating wire 10 from the capacitance dividing metal layer 6.
To pull out the divided voltage tap T, and the grounding tap E is drawn out from the grounding metal layer 8 by the conducting wire 11 as in the conventional case.

The capacitance division capacitance C ₁ ,
C ₂ varies with the length of the cable or the insulated bus, but since the ratio of C ₁ / C ₂ is constant, C _{1 is} different for each voltage.
The minimum required capacitance is determined in advance. Once the cable size is determined, calculate the shortest length of the cable and apply it freely if it is longer than that length.

As shown in FIG.
Stand (1_R, 1_Y, 1_B) Star connection as a three-phase device and grounding
The tap E is grounded as a neutral point. In addition, three phase
T _R, T_Y, T_BTake out and tap T_R, T_Y, T_BThan
Three-phase with low-voltage insulation cable (or low-voltage shielded wire) 21
It is pulled into the low pressure VT box 22 and the five cores 24 in the box.
To the primary winding 26 of the three-phase low-voltage VT 25 using
It is connected via the yoke coil 23. Primary winding of VT25
The connection of the wire 26 / secondary winding 27 / tertiary winding 28 is star /
Star / open delta with star neutral point grounded
It is.

The low-pressure VT box 22 does not need to be directly mounted on the CVT, but is mounted at a place slightly away from the CVT 1, for example, in a low-pressure board or outside a GIS tank. Secondary winding 27 and tertiary winding 28 of VT 25 output from terminal box 29
Is input to a digital relay / meter.

An embodiment of the CVT (FIG. 1) will be described.

Embodiment 1 Referring to FIG. 3, a CVT having a sectional structure similar to that of FIG.
1 of 1 end cover Fujikiri to surround the end of the conductor 2 (2 ₂₎ in each layer member 3 to 8, the CVT1 in a state in which the conductor 2 ₂ is projected from the other end with a protective layer 9. On the other hand, a bushing 32 having the conductor 21 for connection of the CVT ₁ is provided on a device container 31 such as a gas insulated switchgear, and a connector 34 for connecting the CVT ₁ is provided on an internal conductor 33 of the device container 31. ₁ is connected to the connector 34 and placed. Moreover, the bushing-side conductor 2 ₁ CVT1 side conductor 2 ₁ provided connector 2 ₃ to be connectable.

[0024] Thus, by fitting the CVT1 bushing 32, the CVT side conductor 2 ₂ bushing side conductor 2 ₁
Can be connected to an internal conductor 33 such as a gas insulated switch. Note that the voltage dividing tap T and the ground tap E
Is pulled out of GIS from CVT1. Further, between the bushing 32 and the equipment container 31 and between the bushing 32 and C
The space between the VT1 and the VT1 is made airtight, and the CVT1 is prevented from falling out of the bushing 32.

[0025] For Example 2 Figure 4, the power cable 1 ₁ to be connected to the device 41
Or insulated bus 1 ₂ connected between devices 41, 41 formed in the CVT similar to that shown in FIG. 1, the cable connector 4
2 is attached, and the tap T and the ground E (not shown) are pulled out from the connector 42 on one side. Power cable 1 ₁ work cable, insulated bus 1 ₂ functions as CVT while working busbar. The tap T and the ground tap E of the CVT 1 are always considered as a pair, and are pulled out from one of the connectors on both sides.

If the insulating material of the main insulating layer 4 and the auxiliary insulating layer 7 is made of a thermoplastic material in the structure shown in FIG. 1, the CVT becomes easy to bend like a power cable, and if it is made of a thermosetting material, A CVT that is hard to bend and has high mechanical strength, such as an epoxy molded product, can be obtained. We will use this separately.

Second Embodiment FIGS. 5 and 6 show a configuration of a CVT according to a second embodiment. This CVT 1 is placed on a cylindrical inner conductor 2 which is a bus for GIS connection through which a large current can flow, as in FIG.
An internal semiconductor layer 3, a main insulating layer 4, an external semiconductor layer 5, a metal layer 6 for capacitance division, an auxiliary insulating layer 7, and a cylindrical grounding metal layer 8 are sequentially provided. An auxiliary insulating layer 61, a metal layer 62 for capacitance division, a semiconductor layer 63, an external main insulating layer 6
4. A semiconductor layer 65 and an external conductor 66 made of a cylindrical foil are sequentially provided. Further thereon, a semiconductor layer 67, an external main insulating layer 68, a semiconductor layer 69, a metal layer for capacitance division 70, an auxiliary insulating layer 71, a ground metal layer 72, and a protective layer 73 are sequentially provided.

The inner conductor 2 and the outer conductor 66 are connected to an insulated wire 74
To make the outer conductor 66 the same potential as the inner conductor 2.
The metal layers 6, 62, and 70 for dividing the capacitance are connected by an insulated wire 75 to form a tap T.
Are connected by an insulated wire 76 to form a ground terminal E.

The capacitance between the internal conductor 2 and the capacitance dividing metal layer 6 is C ₁ , the capacitance between this metal layer 6 and the ground metal layer is C ₂ , and the capacitance between the metal layer and the capacitance dividing metal layer is C ₂ . The capacitance between the layers 62 is C ₂ ′, the capacitance between the metal layer 62 and the external conductor 66 is C ₁ ′, and the capacitance between the conductor 66 and the capacitance dividing metal layer 70 is C _1. Assuming that the capacitance between the metal layer 70 and the ground metal layer 72 is C _{2, the} capacitance between the internal conductor 2 and the tap T is C ₁ + C ₁ ′.
+ C ₁ ″, and the capacitance between tap T and ground tap E is C ₂ +
C ₂ ′ + C ₂ ″. Therefore, CVT having a large capacitance
Is configured.

The capacitance dividing metal layers 6, 62 and 70 share the same voltage, that is, C ₁ = C ₁ '=
The thickness and dielectric constant of the insulating layer are designed so that C ₁ ″ and C ₂ = C ₂ ′ = C ₂ ″.

The bushing 32 has a bushing-side conductor 2 ₁ as in the case of FIG. 3, is attached to the equipment container 31. Connector 2 ₃ This bushing side conductor 2 ₁ of the lower end
Is provided. The tip of the CVT side conductor 2 ₂ is a connectable bushing side conductor 2 ₁ via the connector 2 _3, CVT-side conductor 2 ₂ When inserting the CVT1 into bushing 32 is connected to the bushing side conductor 2 _1, CVT1 A large current can be supplied to a load or the like by the internal conductor 2 and a divided voltage is output from the tap T.

According to the second embodiment, a CVT in which the GIS connection bus has a relatively large capacitance can be obtained. And
If a low-voltage through-type current transformer or a low-voltage split-type current transformer is arranged outside this bus, it becomes a bus that also serves as an integrated instrument-use voltage transformer.

The second embodiment is an example in which one external conductor is provided. However, a plurality of external conductors are provided concentrically, a ground metal layer is provided between each external conductor, and a semiconductor layer is provided between each external conductor and the ground metal layer. Layers, a main insulating layer, a semiconductor layer, a metal layer for capacitance division, and an auxiliary insulation layer. The internal conductor and a plurality of external conductors are connected by the electric wire 74, and each metal layer for capacitance division and each ground metal are provided. By connecting the layers with electric wires 75 and 76, respectively, a CV having a larger capacitance can be obtained.
T can be obtained.

[0034]

Since the capacitance-divided transformer of the present invention is constructed as described above, the following effects can be obtained. (1) It can be configured using a power cable or an insulated bus. (2) Since the outside is grounded, there is no exposure of the charged portion, and the device is safe and does not require an interphase insulation distance. (3) Since the connection is made with a cable connector, it can be detached and attached and can also serve as a disconnector. (4) The present invention can be applied to a common bus of a gas insulated switchgear. In this case, since the SF6 gas is not used or is externally mounted, the environment-resistant type in which the SF6 gas amount is reduced is provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a main structure of a capacitance-divided voltage transformer according to a first embodiment.

FIG. 2 is a connection circuit diagram of the capacitance-divided voltage transformer and the low-voltage transformer.

FIG. 3 is a longitudinal sectional view showing the structure of the capacitance-divided voltage transformer according to the first embodiment.

FIG. 4 is a side view showing a device connection example according to the second embodiment;

FIG. 5 is a cross-sectional view showing the main structure of the capacitance-divided voltage transformer according to the second embodiment;

FIG. 6 is a longitudinal sectional view showing the structure of the capacitance voltage dividing type transformer.

FIG. 7 is a configuration explanatory diagram of a conventional induction type voltage transformer and a capacitance-divided type voltage transformer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Capacitance division type voltage transformer (CVT) using a power cable or an insulating bus bar 2 ... Conductor 3 ... Inner semiconductive layer 4 ... Main insulating layer 5 ... External semiconductive layer 6 ... Capacitance dividing metal Layer 7 ... Auxiliary insulating layer 8 ... Ground metal layer 9 ... Protective layer 10 ... Tap lead-out insulated wire (lead wire) 11 ... Ground tap lead-out wire 22 ... Low voltage transformer box 23 ... Choke coil 31 ... Gas insulated switchgear Equipment container 34 ... Connector 41 ... Gas insulated switchgear etc. equipment 42 ... Cable connector 61 ... Auxiliary insulation layer 62 ... Capacitance voltage division metal layer 63 ... Semiconductor layer 64 ... External main insulation layer 65 ... Semiconductor layer 66 ... External conductor 67 ... Semiconductor layer 68 ... External main insulation layer 69 ... Semiconductor layer 70 ... Capacitance voltage dividing metal layer 71 ... Auxiliary insulation layer 72 ... Ground metal layer 73 ... Protective layer 74 ... Insulated wire 75,76 ... Touch C ₁ : Capacitance between conductor and metal layer for capacitance division C ₂ : Capacitance between metal layer for capacitance division and ground metal layer T: Capacitance division tap.

 ──────────────────────────────────────────────────続 き Continued on front page (72) Inventor Takashi Sakurai 2-1-1-17 Osaki, Shinagawa-ku, Tokyo F-term in Meidensha Co., Ltd. 5E081 AA03 BB04 CC22 DD15 EE11 GG05 5G017 BB19

Claims (5)

[Claims] 1. A metal layer for electrostatic capacity division is provided on an external semiconductor layer of a power cable or an insulating bus in which an internal semiconductor layer, a main insulating layer, and an external semiconductor layer are provided on a conductor, and an auxiliary layer is provided thereon. A capacitance-divided voltage transformer characterized in that a grounded metal layer is provided via an insulating layer, and a capacitance-divided voltage is drawn from between the capacitance-divided metal layer and the grounded metal layer. 2. The capacitance dividing voltage transformer according to claim 1, wherein one end of the voltage dividing type voltage transformer is sealed off, and the other end is connected to a circuit conductor inside the gas insulated switchgear. Voltage type voltage transformer. 3. A voltage dividing type voltage transformer according to claim 1, provided on at least one of a power cable and an insulating bus, and a conductor thereof is connected to a circuit conductor in a gas insulated switchgear. Capacitive voltage divider. 4. A cylindrical internal conductor which is a connection bus,
A cylindrical outer conductor having the same potential as the inner conductor is concentrically arranged. A cylindrical grounding metal layer is concentrically arranged between the inner conductor and the outer conductor and outside the outer conductor. Between the conductor and the ground metal layer,
A metal layer for capacitance division should be placed, and the inner conductor and the outer conductor should be connected by lead wires, and each metal layer for capacitance division and each ground metal layer should be connected by leads. A capacitance-divided voltage transformer characterized by the following: 5. A cylindrical inner conductor which is a connection bus,
A plurality of cylindrical outer conductors having the same potential as the inner conductor are concentrically arranged, and a cylindrical grounding metal layer is concentrically arranged between the inner conductor and the outer outer conductor and between each outer conductor,
A cylindrical grounding metal layer is arranged concentrically outside the outermost outer conductor, and between the inner conductor, the outer conductor and the grounding metal layer,
A metal layer for capacitance division should be placed, and the inner conductor and the outer conductor should be connected by lead wires, and each metal layer for capacitance division and each ground metal layer should be connected by leads. A capacitance-divided voltage transformer characterized by the following: