JPH02107977A - Voltage detector circuit of gas insulation switching device - Google Patents

Abstract

PURPOSE:To enable detection of the impression of a high voltage on a high-voltage electrode by connecting low-voltage electrodes of two phases electrically and by grounding the part of this connection through a low-voltage side capacitance. CONSTITUTION:Low-voltage electrodes 5B and 5C of second and third phases are connected electrically and grounded through a low-voltage side capacitance 71, while a row-voltage electrode 5A of a first phase is connected to a low-voltage electrode connecting part of the capacitance 71 through an inter-phase connection capacitance 72 having the same value substantially as that of the capacitance 71, and a voltage of the electrode 5A is detected by a voltage detector. Since voltage to the ground of the electrode 5A is proportional to the sum of the double of a voltage of a high- voltage electrode 3A of a first phase and voltages of high-voltage electrodes 3B and 3C of other two phases, the voltage of the electrode 5A does not become zero in any case when the voltages of three high-voltage electrodes are balanced three-phase voltages, when the voltage of the high-voltage electrode of one phase is zero or when the voltage is impressed on the high-voltage electrode of only one phase, and it becomes zero only when no voltage is impressed on all the high-voltage electrodes.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is applicable to gas insulated switchgear, abbreviated as GIS, in which a high voltage electrode such as a high voltage lead is housed in a normally cylindrical sealed container, and a box. A gas for non-contact detection of the presence or absence of voltage application to a high voltage electrode housed in a sealed container, such as a cubicle-type gas insulated switchgear (abbreviated as CGIS) in which a high voltage section is housed in a sealed container. This invention relates to a voltage detection circuit for an insulated switchgear.

[Conventional technology]

In GIS and CGIS, an insulating gas made of sulfur hexafluoride, commonly known as SF&, is sealed in a sealed container at a predetermined pressure as an insulating medium, and high voltage leads and switches such as circuit breakers and disconnectors are installed in the container. It is used to construct a downsized switchgear by taking advantage of the high insulation properties of the insulating gas.

GIS and CGIS have a structure in which the high voltage part itself is not exposed to the outside, and the high voltage part drawn in from the outside is also connected to a cable, a gas insulated bus bar (abbreviated as GIB), a gas insulated transformer, or an oil-immersed transformer. By connecting the partition wall that separates the oil-filled part and the gas insulation part with a through-bushing that passes through this partition, a substation with no external high-voltage parts exposed is constructed, which significantly reduces the site area. place has been realized.

The standard stipulates that the current interrupting part of the circuit breaker included in gas-insulated switchgear must be inspected when a predetermined number of interruptions is reached, and if an internal abnormality occurs, it is necessary to investigate the abnormality location and cause. Therefore, it becomes necessary to conduct an internal inspection.

In this way, when inspecting the interior of a switchgear, the circuit breaker or disconnector is opened to ensure that no voltage is applied to the high-voltage electrode at the location to be inspected. If inspection work is performed with voltage being applied, there is a high risk of electric shock resulting in a disaster that could threaten human life.In order to prevent such a disaster from occurring, it is necessary to connect high-voltage electrodes from the outside. A method is used to accurately determine that no voltage is being applied to the

As mentioned above, in such substations, the high voltage parts are not exposed to the outside, so in order to detect that no voltage is applied to the high voltage electrodes, the high voltage electrodes are placed in a sealed container opposite the high voltage electrodes. A low-voltage electrode is provided that is insulated from a sealed container that is at ground potential, and the capacitance between the high-voltage electrode and the low-voltage electrode is defined as the high-voltage capacitance, and the low-voltage electrode has a large capacitance value. A method is adopted in which the presence or absence of voltage application to the high-voltage electrode is detected by detecting the voltage determined by the capacitance partial pressure by grounding it through a capacitor or the like.

As a low voltage electrode, in addition to the method of installing a dedicated electrode near the sealed container, the mounting method for attaching the support insulator of the disconnector installed in the sealed container to the sealed container is to install a metal fitting from the sealed container. It consists of an epoxy resin that serves as a support to keep the high voltage lead at a predetermined insulation distance from the sealed container and to withstand mechanical forces such as electromagnetic force applied to the high voltage lead. Insulating spacers can be installed by insulating the metal fittings from the sealed container in the same way as described above and using them as low-voltage electrodes.For GIS, a dedicated electrode is installed, and for CGIs, supporting insulators or insulating spacers are used. For installation, a method is often adopted in which the metal fittings also serve as low voltage electrodes.

Although it is possible to use a capacitor with a predetermined capacitance value as the low voltage side capacitance, the use of circuit elements such as capacitors may be avoided due to the reliability of gas-insulated switchgear. In some cases, a method is adopted in which the low voltage electrode is grounded via a shielded cable of several meters, and the capacitance between the lead of the shielded cable and the shielded conductor on the outer diameter side is set to the low voltage side capacitance.

The voltage of the high voltage electrode is extremely high, ranging from several tens of kilovolts to several hundreds of kilovolts, whereas the voltage generated at the low voltage electrode is set to about 100V. In setting the voltage of this low voltage electrode, as mentioned above, the value of the high voltage side capacitance can be freely selected only when a dedicated electrode is provided as the low voltage electrode, so we decided to adjust the low voltage side capacitance. However, when using a shielded cable, the value of the low voltage side capacitance can be easily set to the desired value by adjusting the length of the shielded cable.

The inside of the hermetically sealed container is filled with insulating gas, and its pressure is also increased to diffused pressure to ensure high insulation strength.This reduces the insulation distance and creates a compact gas insulated switchgear. Of course, it is necessary to keep the inside of the sealed container airtight, so the lead for drawing out the voltage of the low voltage electrode to the outside for voltage detection is designed to be drawn out in an airtight state.

FIG. 2 is a conventional circuit diagram for detecting the presence or absence of voltage application to a high voltage electrode. In this figure, a three-phase AC power supply 1 generates three-phase voltages V, , V, and V, and these voltages are applied to switches 2A, 2B, and 2G such as circuit breakers and disconnectors.
As mentioned above, the voltage is applied to the high voltage electrodes 3A, 3B, and 3C via the low voltage electrodes 5A, 5B, and 5C provided near the inner wall of the sealed container, respectively, and the high voltage electrode 3.
High voltage side capacitance 4A between A, 3B, 3C,
4B and 4C are formed. The capacitance values of these high voltage side capacitances 4A, 4B, and 4G are respectively C.
4A, C41C4C, these capacitance values are set to be the same value. however,
Even if the values are the same, it is not a measurement, so it does not need to be very strict.

Terminals drawn out by shielded cables from the low voltage electrodes 5A, 5B, and 5C are switches 6A, 6B.

6C, and low voltage side capacitances 7A, 7B, and 7C as capacitances between the shield cable lead and the shield are connected to the ground. The capacitance values of these low voltage side capacitances 7A, 7B, and 7C are respectively C'IA + C7m
+C'Ic, and these are also set to approximately the same value, which indicates that the lengths of the shielded cables of each phase are approximately the same.

As mentioned above, the switches 6A, 6B, and 6C actually mean the parts where the terminals pulled out to the outside of the shielded cable are electrically and mechanically connected to the sealed container with bolts. In this state, switches 6A and 6
B and 6C are in the "closed" state, and when the bolts are removed and the terminals are open, the switches 6A, 6B, and 6C are in the "open" state.
state.

Voltage detectors used to detect whether or not voltage is applied are of a type in which a voltage detector terminal is touched to an electrode, and when a voltage higher than a predetermined value is applied to this electrode, the discharge tube discharges. In order to prevent the user from getting an electric shock, the terminals of the voltage detector are short-circuited internally when the button attached to the voltage detector is not pressed, and there are devices on the market that detect electricity only after pressing this button. There is. In addition to the method of indicating the presence or absence of voltage application using the discharge light from the discharge tube, there is also a method of notifying the presence or absence of voltage using a buzzer.

High voltage electrodes 3A and 3B using this voltage detector.

The detection work to determine whether a high voltage is applied to 3C is performed in the following order.

■Loosen and remove the grounding bolt of the external terminal of the shielded cable connected to the low voltage electrode 5A and pulled out to the outside to open this terminal.

In this figure, this means changing the switch 6A from the "closed" state to the "open" state.

■Connect one end of the voltage detection terminal of the voltage detector to the shield cable terminal.

■Press the button on the voltage detector to detect the voltage.

■Remove the voltage detection terminal from the shield cable terminal.

■ Make a bolted connection to ground the shielded cable terminal.

Repeat the above for each phase and perform voltage detection three times. If it is determined that no voltage is applied to any phase, it means that there is no risk of electric shock even if you approach this high voltage electrode for the first time.

The voltage between the voltage detection terminals of the voltage detector, in other words, the voltage vk of the low voltage electrode is expressed by the following equation.

Vk= (C4A/C?A) V.

The only difference for the other phases is to change the second index, and since the capacitance on the high voltage side and the capacitance on the low voltage side are approximately the same value for each phase, the voltage between the voltage detection terminals is also approximately the same for each phase. The principle of detecting voltage with a voltage detector by connecting it to a piezo electrode is simple in principle, but the same voltage detection operation can be performed three times.
The problem is that it needs to be repeated several times. As mentioned above, this type of voltage detection work is necessary for internal inspections and is not a frequent occurrence, but it is because of the low voltage electrodes and shielded cables required for voltage detection while the switchgear is operating. In order to eliminate the possibility of an accident occurring, the external terminal of the shielded cable is connected to the sealed container using bolts, as described above, in order to ensure that it is grounded to the sealed container. For this reason, it is necessary to loosen and tighten the bolt for grounding the shield cable terminal every time the voltage detection work of phase 2 is performed, which is troublesome.

FIG. 3 is a circuit diagram showing a possible method for eliminating this trouble. In this figure, components common to those in FIG. 2 are given the same reference numerals and detailed explanations will be omitted. In this figure, the capacitance value of the low voltage side capacitance 4D, which is the ground capacitance of the shielded cable connected to the low voltage electrode 3A, is set to 0.
4°, and the other two high voltage side capacitances are 4B.

The capacitance value of 4C C4IIr I is twice that of C4C
I'll do it. That is, CM = C4m = C4C = CAD/2 Further, the capacitance value of the low voltage side capacitance 7 is assumed to be CL. The voltage vk generated between the terminals of the low voltage side capacitance 7 when the switch 6 is "open" is expressed by the following equation.

Vk”” (C++ /Ct) (2Vm +Vb
+Vc) As can be seen from this formula, when the voltage of the three-phase AC power supply l is a balanced three-phase voltage in a normal state, and when there is no zero-phase voltage, v, +Vb+VC
= 0, the value of the voltage in the parentheses is V, and in both cases, when the voltage of only one phase is zero or when the voltage is applied to only one phase. Voltage Vh
never becomes zero, and in the end, the low voltage electrodes 5 of the three phases
By connecting D, 5B, and 5C together and detecting the voltage between the terminals of the low voltage side capacitance 7 connected to this part, high voltage can be applied to the high voltage electrode with just one voltage detection operation. The configuration is capable of detecting the presence or absence of.

However, in this method, it is necessary to make the capacitance value CaO of the high voltage side capacitance 4D twice the capacitance value C, , C, of the high voltage side capacitances 4B and 4C of other phases, but as mentioned above, When installing supporting insulators and insulating spacers, it is impossible to double the low-voltage capacitance when the metal fittings are also used as low-voltage electrodes, so it is impossible to use this method, and special Even in the case where electrodes are provided, the shape and arrangement of the low voltage electrodes must be different from those of other phases, resulting in the problem of an increase in the number of types of parts that make up the gas insulated switchgear.

This invention provides a gas-insulated switchgear in which the low-voltage side capacitance of three phases is the same value, and which can detect the presence or absence of high voltage application to the high-voltage electrodes of three phases by performing voltage detection only once. The purpose is to provide a voltage detection circuit.

[Means for Solving the Problems] In order to solve the above problems, according to the present invention, a three-phase high voltage electrode consisting of three phases, first, second, and third, is housed in a sealed container. three low voltage electrodes provided opposite to the high voltage electrode for each phase of the gas insulated switchgear; a gas-insulated switchgear that detects the presence or absence of voltage application to the high-voltage electrode by detecting the ground voltage of the low-voltage electrode with a voltage detector; In the voltage detecting circuit, the low voltage electrodes of the second phase and the third phase are electrically connected and grounded via the low voltage side capacitance, and the low voltage electrode of the first phase is connected to the low voltage electrode of the first phase. The low voltage electrode connection of the low voltage side capacitance is connected to the low voltage electrode connection of the low voltage side capacitance through a correlated connection capacitance having a value substantially the same as the value of the voltage side passitance, and the voltage of the low voltage electrode of the first phase is detected by a voltage detector. It shall be.

[Effect]

In the configuration of this invention, the low voltage electrodes of the second phase and the third phase are electrically connected and grounded via the low voltage side capacitance, and the low voltage electrode of the first phase is connected to the low voltage side capacitance. is connected to the low voltage electrode connection of the low voltage side capacitance through an interphase connection capacitance having a value substantially the same as the value of Since the voltage to ground of the low voltage electrode of a phase is proportional to the sum of twice the voltage of the first high voltage electrode of that phase and the voltage of the high voltage electrode of the other two phases, the voltage of the three high voltage electrodes is Even if the voltage is a balanced three-phase voltage, the voltage at the high voltage electrode of one phase is zero, or the voltage is applied to the high voltage electrode of only one phase, the voltage is detected in any case. The voltage on the low voltage electrodes of the first phase never goes to zero, but only when no voltage is applied to all the high voltage electrodes.

〔Example〕

The present invention will be explained below based on examples. FIG. 1 is a circuit diagram showing an embodiment of the invention. In this diagram,
Components common to those in FIG. 2 are given the same reference numerals and detailed explanations will be omitted. High voltage side capacitance 4A, 4B.

4C capacitance 41ICaA, C4m,
The shape and arrangement of the low voltage electrodes 3A, 3B, and 3C are made common to each phase so that C4c has substantially the same value as in the prior art. The low voltage electrodes 5B and 5C are electrically connected and this connection is grounded via a low voltage side capacitance 71. The low voltage electrode 5A is connected to the connection portion of the aforementioned low voltage electrodes 5B and 5C via an interphase connection capacitance 72. Voltage detection using a voltage detector is performed on the low voltage electrode 5A.

The ground voltage vk of the low voltage electrode 5A is the same as that of the low voltage electrodes 5B and 5C.
It is the sum of the voltage v1 between the terminals of the interphase connection capacitance to the voltage v2 at the connection point of Considering that it is an order of magnitude larger, the voltage V is proportional to the sum of the voltages of the high voltage electrodes of each phase regardless of the presence or absence of the interphase connection capacitance 72, and the voltage v1 is proportional to the voltage of the high voltage electrode 3A. becomes the value. These proportionality constants are determined by the capacitance partial pressure and are the same for both, so in the end, the voltage of the low voltage electrode 5A is twice the voltage of the high voltage electrode 3A and the voltage of the high voltage electrodes of the other two phases. The value is proportional to the sum of These relationships can be expressed as the following equation.

Vz = (CM /CL) (Vll +Vb
+Vc)Wb=VZ+(Co/Ct)Va
=(C++/Ct) (2V, 10V+, +
Vc) Here, C,; Value of high voltage side capacitance (C4A=C4m=C4C=CH) ct i Value of low voltage side capacitance and interphase connection capacitance (C1=Cyt=Ct) In other words, the proportionality constant mentioned above is ( C1l/CL).

As mentioned above, the low voltage side capacitance 71 is the capacitance value between the lead of the shielded cable connected to the low voltage electrode and the shield conductor as in the conventional technology, but the interphase connection capacitance 72 is also the value when the same shielded cable is connected to the same length. This can be easily achieved by using However, since the shield conductor of the shield cable, which forms the interphase connection capacitance, is not at ground voltage, it must be insulated from the sealed container. Since the voltage of the low voltage electrode is approximately 100V at most as described above, this insulation is easy.

Instead of using the capacitance of the shield cable as the low voltage side capacitance 71 or the interphase connection capacitance 72, a capacitor having a predetermined capacitance value may of course be used. However, some users avoid using such circuit elements from the viewpoint of reliability of the switchgear, so it is necessary to make an appropriate selection.

〔Effect of the invention〕

As described above, this invention electrically connects the low voltage electrodes of two phases, grounds this connection via the low voltage side capacitance, and connects the low voltage electrode of the other phase to the low voltage side capacitance. is connected to said connection via an interphase connection capacitance of substantially the same value as
When the voltage of the low-voltage electrode of one phase is detected by a voltage detector, the voltage to ground of this low-voltage electrode is the sum of twice the voltage of the high-voltage electrode of this phase and the voltage of the high-voltage electrode of the other two phases. is proportional to. As a result, even if the voltages of the high-voltage electrodes of the three phases are balanced three-phase voltages, or even if the voltage of the high-voltage electrodes of any one phase is zero, the high-voltage electrodes of only one phase Even if a voltage is applied to the electrode, the voltage of the low voltage electrode to be detected does not become zero in any case, and becomes zero only when the voltage of all the high voltage electrodes is zero. on the other hand,
The low voltage side capacitance value can be the same for each phase, so
When installing support insulators and insulating spacers, use low voltage electrical
= It is possible to adopt a method that doubles as a pole, and if a dedicated electrode is provided as a low voltage electrode, the shape and arrangement of all three phases can be the same without changing the shape and arrangement of the low voltage electrode of one phase. Since low-voltage electrodes can be used, it becomes possible to economically realize a voltage detection circuit that can perform voltage detection on three phases of high-voltage electrodes in just one voltage detection operation. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram showing an example of the prior art, and FIG. 3 is a circuit diagram showing another example of the prior art. IA, 3B, 3C...High voltage electrode, 4A, 4B, 4C, 4D...High voltage side capacitance, 5A, 5B, 5C, 5D...Low voltage electrode, 71.7A
, 7B, 7C...low voltage side capacitance,

Claims (1)

[Claims] 1) A gas insulated switchgear in which three-phase high voltage electrodes consisting of three phases, first, second, and third, are housed in a sealed container. one low voltage electrode, and a low voltage side capacitance connected between the low voltage electrode and ground potential and sufficiently larger than the capacitance between the high voltage electrode and the low voltage electrode, In a voltage detection circuit of a gas-insulated switchgear that detects the presence or absence of voltage application to a high-voltage electrode by detecting the ground voltage of the electrode with a voltage detector, the low-voltage electrodes of the second phase and the third phase are connected to each other. electrically connected to ground through the low voltage side capacitance, and connecting the low voltage electrode of a first phase to the low voltage through an interphase connection capacitance having a value substantially the same as the value of the low voltage side capacitance. A voltage detection circuit for a gas insulated switchgear, characterized in that the voltage of the low voltage electrode of the first phase is detected by a voltage detector connected to a low voltage electrode connection portion of a side capacitance.