WO2016066478A1

WO2016066478A1 - System and method for ensuring a mixing ratio of an insulating gas mixture for a gas-insulated electric high-voltage device

Info

Publication number: WO2016066478A1
Application number: PCT/EP2015/074292
Authority: WO
Inventors: Michael Mann; Franz-Josef Körber
Original assignee: Abb Technology Ag
Priority date: 2014-10-29
Filing date: 2015-10-21
Publication date: 2016-05-06
Also published as: DE102014115718A1

Abstract

The invention relates to a system and a method for ensuring a desired mixing ratio in an insulating gas mixture (3) of a gas-insulated electric high-voltage device. The insulating gas mixture (3) is made of an insulating fluid and a carrier gas. In order to allow a refill of a high-voltage device which has been filled once, the system comprises a sensor (4) arranged in a gas chamber (1) of the high-voltage device for detecting the proportion of insulating fluid in the insulating gas mixture (3), a metering pump (6) for pumping liquid insulating fluid from a storage container in the direction of the gas chamber, and a controller (9) for actuating the metering pump until the insulating fluid proportion detected by the sensor lies within a specified value range. The pump rate of the metering pump (6) ranges less than one standard liter per hour, and the insulating gas mixture as such is not pumped into the gas chamber (1) but rather solely the insulating fluid.

Description

System and method for ensuring a mixing ratio of a

Isolierqasqemisches for a qasisoliertes electrical Hochspannunqsqerät

The invention relates to a system and a method for ensuring a

Mixing ratio of an insulating gas mixture for a gas-insulated electrical

High voltage equipment.

A gas-insulated electrical high-voltage device is understood in particular as meaning a gas-insulated switchgear (GIS) operating in the high-voltage range above 50 kV or a gas-insulated transformer (GIT). In these high-voltage equipment, an insulating gas is used instead of air in order to reduce the distances between the live parts and thus the required space can. In gas-insulated electrical high-voltage devices, sulfur hexafluoride (SF ₆ ) is generally used as an insulating gas today. However, due to its undesirable effect as a greenhouse gas, efforts are being made to replace SF ₆ with alternative insulating materials. So it has recently been possible to find a much more environmentally friendly gas mixture, which similar

Isolation features as the previously used SF ₆ .

JD Mantilla et al., Published at the 2014 Electrical Insulation Conference, Philadelphia, Pennsylvania, USA, June 8 to 1, 1, 2014, in the article "Investigation of the insulation performance of a new gas mixture with extremely low GWP" describes a gas mixture containing perfluorinated ketones and technical air or C0 ₂ as carrier gas The gas mixture has a dielectric strength comparable to SF ₆ , both at 50 Hz alternating voltage stress and lightning impulse voltage Understood composition, which contains substantially oxygen and nitrogen. A carrier gas is required because the perfluorinated ketones, hereinafter called fluoroketones, in

Room temperature in liquid form.

An alternative to the above gas mixture is described in the article "In search of SF6 replacement" published on www.think-grid.org The gas mixture there is based on a fluoronitrile.

In the following, therefore, it is assumed that an insulating gas mixture which contains a so-called insulating fluid and a carrier gas. The insulating fluid provides the for the The dielectric fluid is a fluoroketone or a fluoronitrile.

If one wants one of the gas mixtures described in gas-insulated electrical

High-voltage devices, especially switchgear to use, a way must be found, such as the high-voltage device at the production site or at the location of his

Commissioning can be filled as quickly and accurately as possible with the gas mixture. Since the gas mixture is not industrially prefabricated in large quantities and ready for storage

Is available and since it is advantageous to the requirements of the respective

Application should be adjusted directly on site by appropriate mixing of its individual components.

WO 2014/037031 A1 discloses a method and a system for filling a high-voltage device with insulating gas. The system includes a mixer for the controlled mixing of at least two fluids, wherein the mixing ratio is determined by sensors and the mixing process is controlled based on the specific mixing ratio so that the condensation temperature of the fluids to be mixed below the temperature when filling the system.

In this way, it is avoided that one or more of the at least two fluids condense out during the filling of the GIS, which leads to an undesired change of the GIS

Mixing ratio would lead. In principle, WO 2014/037031 A1 does not deal with the ongoing operation of the filled plant.

It is an object of the invention to provide a solution with which it can be ensured that the desired mixing ratio of the fluids can be maintained even during operation of the filled high-voltage device.

This object is achieved with a system and a method for ensuring the desired mixing ratio in the insulating gas mixture of the gas-insulated electric high-voltage device according to the independent claims.

The present invention is based on the finding that the gas mixture of insulating fluid and carrier gas has a property which differs substantially from SF ₆ , which is important as insulating gas when using the gas mixture: after ionization as a result of an arc occurring during a switching operation, the gas mixture does not recombine back to its original state. As a result, is in ongoing operation of a GIS depending on the switching powers, a gradual consumption of the insulating fluid contained in the gas mixture can be expected. However, with the installation for filling a GIS known from WO 2014/037031 A1, the used insulating fluid can not be refilled, since, on the one hand, no filling with pure

Insulating fluid is provided and on the other hand, the system is designed for significantly larger quantities.

Basically, the system presented here contains some elements, which are also known from WO 2014/037031 A1, namely a arranged in a gas space of the high voltage device sensor for detecting the proportion of insulating fluid in the insulating gas mixture, a pump for conveying liquid insulating fluid from a reservoir , as well as a control unit for controlling the pump.

However, the system according to the invention has the following differences: the pump is a metering pump whose delivery rate is in the range of less than a standard liter or standard liters per hour (<1 Nl / h); no evaporator is needed; in the system, not the insulating gas mixture as such but only the evaporated insulating fluid is conveyed through the gas line and supplied to the high-voltage apparatus; and the

The control unit activates the dosing pump until the proportion of insulating fluid detected by the sensor is within a preset value range.

The advantage of being able to dispense with an evaporator, is due to the fact that in the small flows generated by the metering pump, i. with slow filling of the

Isolierfluids in the gas space of the high voltage device, the low partial pressure of the insulating fluid present in the gas space causes the newly added insulating fluid evaporated without further aids.

Accordingly, the method presented here and practiced by the system according to the invention contains the following features: Detecting the proportion of insulating fluid in the

Insulating gas mixture in a gas space of the high voltage device; Transporting the liquid insulating fluid from a reservoir in the direction of gas space by means of a metering pump with a flow rate in the range of less than a standard liters per hour, wherein the

Metering pump is driven until the detected proportion of insulating fluid is within a preset value range, supplying the evaporated insulating fluid to the gas space of the high voltage device. With the invention, it becomes possible to refill the portion of insulating fluid consumed in the course of operation of the high-voltage device with high precision, starting from an arbitrary actual state and reaching any desired state preset in the control device. It requires no intervention by operating or

Service personnel, i. the highly accurate adjustment of the concentrations of the mixed gas components is carried out automatically, which is particularly in the series application of the

High voltage device is advantageous and also simplifies the service business.

By means of the sensor, therefore, a gas sample is taken from the gas space of the high-voltage device, analyzed and then automatically restored the desired target gas mixture, starting from the determined, any actual output state. In contrast to the known filling system, only a small-volume system is used, which realizes a small-volume cycle process which concentrates exclusively on the insulating fluid essential for the insulating properties of the gas mixture. In other words, therefore, the insulating fluid directly to the gas space of the

High-voltage device supplied without additional admixing of the carrier gas.

Accordingly, all the components required for mixing the insulating fluid with the carrier gas can be dispensed with. In addition, due to the only small moving volume overfilling the system is prevented.

The controller may be configured to vary the rate of delivery of the isolation fluid in response to the magnitude of a deviation between a desired and measured levels of insulating fluid in the headspace and from an initial rate of travel by reducing the rate of advance with decreasing offset. In this way, the desired target value is comparatively slow and thus approached in the temperature equilibrium.

The control unit may in particular be designed to determine a required amount of insulating fluid to be replenished, depending on the initial one

Set conveyor speed, while the required amount based on a

to determine the initial deviation of the measured proportion of the desired proportion of insulating fluid in the gas space and with the help of the volume of the gas space.

In one embodiment of the invention, the system additionally comprises a

Evaporation device with a gas mixing chamber. The evaporation device is arranged between the metering pump and the gas space. A gas line connects the gas mixing chamber of the evaporation device with the gas space such that a Gas exchange between the insulating gas mixture of the gas space and that of the

Metering of the gas mixing chamber supplied insulating takes place.

Furthermore, an additional heat supply device may be provided for heating the insulating fluid to be supplied to the gas space in order to avoid condensation formation and to increase the process reliability. As a result, superheated steam is generated in this way, it is subsequently possible to increase the delivery speed of the metering pump and still completely evaporate the insulating fluid - even if missing

Evaporating device - ensure.

The invention and a possible embodiment will be explained below with reference to the attached figure, wherein the figure shows:

Fig. 1 shows a system for ensuring a desired mixing ratio in one

Insulating gas mixture of a gas-insulated high-voltage electrical device;

In Fig. 1, a gas space 1 can be seen, leading to a gas-insulated electrical

High-voltage device, in particular a gas-insulated switchgear (GIS) or a gas-insulated transformer (GIT) belongs.

In the gas space 1 are live parts 2, and the gas space 1 has been filled via a connected for the purpose of filling line B with a Isoliergasgemisch 3, which is an insulating fluid, in particular fluoroketone or fluoronitrile, and a carrier gas, in particular C0 ₂ , 0 _second or air. The filling installation could be, for example, the installation known from WO 2014/037031 A1. After filling, it is separated from the gas space, which is why the line B is shown only by dashed lines.

Since it has been recognized that the insulating fluid consumed in the gas space 1 in the course of operation of the high voltage device, the system shown is for continuous

Refilling the insulating provided. The system comprises a sensor 4 arranged in the gas space 1 of the high-voltage device for detecting the proportion of insulating fluid in the insulating gas mixture 3, a gas line N for introducing the refill

Isolierfluids in the gas space 1 of the high voltage device, a metering pump 6 for

Carrying liquid insulating fluid 7 from a reservoir 8 to the gas line N and the gas line N on to the gas chamber 1, and a control unit 9 for driving the metering pump 6. The control unit 9 can represent a unit integrated into the metering pump 6, or it acts as stand-alone device. The sensor 4 is connected via a wireless or wired data connection D to the control unit 9, and the Control unit 9 transmits its control commands to the metering pump 6 via control line S. The metering pump 6 in turn is connected via a gas line to the reservoir 8, for example a tank or a bottle. Your job is next to the pure one

Transporting the insulating fluid from the reservoir 8 in the direction of the gas space 1 to bring the insulating fluid to the pressure prevailing in the gas chamber 1 working pressure. The working pressure can be in a range between 1 and 10 bar.

According to the invention, the pump is a metering pump whose delivery rate is in the range of less than one standard liter per hour. The delivery rate is preferably between 0.1 and 1 standard liters per hour. A value of 0.1 standard liters per hour corresponds approximately to a mass flow of 100 grams per hour. In the system shown in Figure 1, only the insulating fluid is conveyed through the gas line N in the direction of the gas space 1, i. no carrier gas is added, and the controller 9 controls the

Dosing pump 6 until the detected by the sensor 4 proportion of insulating fluid in the Isoliergasgemisch 3 within a pre-set in the control unit 9

Range of values lies.

The sensor 4 can, for example, the partial pressure of the insulating or the

Detecting the concentration of the insulating fluid in the insulating gas mixture 3. Based on the deviation of the measured from the required value and together with the knowledge of the volume of the gas space 1 could then be determined how large the required amount of

Isolierfluids is that must be refilled. Then the refilling process could be controlled, i. it would be the required amount measured and filled in the gas space 1, without the need for a review by means of the sensor 4. However, since the volume of the gas space is generally not known with sufficient accuracy, in the present case a regulated and thus sufficiently precise refilling is proposed, in which via the sensor 4 a feedback is made about how much insulating fluid has already been refilled. Only when a target value is reached or exceeded, the

Refilling process stopped. Accordingly, therefore, the controller 9 acts as a controller.

The conveying speed of the insulating fluid may vary depending on the size of the

Deviation between desired (setpoint) and measured (actual value) proportion

Insulating fluid can be varied in the Isoliergasgemisch 1, wherein preferably the initial conveying speed selected based on the above-described estimate of the required amount of insulating fluid and then the conveying speed is reduced with decreasing deviation of the setpoint from the actual value. In this way, the desired target value comparatively slowly and thus approached in the temperature equilibrium.

The system according to FIG. 1 can be permanently attached to the gas space 1. Alternatively, it can also be temporarily attached to the gas space 1 in a service case and subsequently separated again. Since it consists of only a few and especially small-volume parts, its ease of use is guaranteed by the service staff.

With the system according to FIG. 1, a method with subsequent steps can be carried out continuously or just in case of need:

1) detecting the proportion of insulating fluid in the insulating gas mixture 3 in the gas space 1;

2) transmitting this value to the control unit 9 via the data link D;

3) Check if the value is within the preset value range;

4) if yes, abort the procedure and report to a user;

5) if not, driving the metering pump 6, to convey a predetermined amount of the liquid insulating fluid 7 from the reservoir 8 either directly to the gas space 1 or first to the evaporator 5,

6) evaporation of the liquid insulating fluid 7, either in the evaporator 5 or - if no evaporation device is present - when passing through the heat supply due to the heating or when entering the gas space 1 due to the low partial pressure of the insulating in the

insulating gas,

7) supplying the gaseous insulating fluid to the gas space 1,

8) Continue with step 1).

Optionally, in the system of Figure 1, an additional evaporation device 5 may be provided which contains a gas mixing chamber. The evaporation device 5 is arranged between the metering pump and the gas space, so that the gas line N connects the gas mixing chamber of the evaporation device 5 with the gas space 1. By means of evaporation device 5 and adapted dimensioning of the gas line N it is achieved that a gas exchange takes place between the insulating gas mixture 3 of the gas space 1 and the insulating fluid supplied by the metering pump 6 to the gas mixing chamber. The gas exchange is based on the concentration gradient between the gas mixing chamber 5 and the gas space 1. As a dimensioning of the gas line N, a nominal width of 10 mm is proposed at a length of one meter. In a development, the evaporation device 5 via an additional

Heat supply be heated. Alternatively, a heat supply device without the evaporation device 5 may be provided. Meaning and purpose of the achieved

Heating the insulating gas supplied via the gas line N to the gas space 1 is to avoid undesired condensation. Superheated steam is thus generated by means of the heat supply device in order to increase process reliability in this way. This in turn allows to raise the conveying speed of the metering pump 6.

Claims

claims

System for ensuring a desired mixing ratio in one

Insulating gas mixture of a gas-insulated electrical high-voltage device, wherein the insulating gas mixture is formed from an insulating fluid and a carrier gas, comprising

A sensor arranged in a gas space of the high-voltage device for detecting the proportion of insulating fluid in the insulating gas mixture,

• a pump for conveying liquid insulating fluid from a

Reservoir, as well

• a control unit for controlling the pump,

characterized in that

The pump is a metering pump (6) whose delivery rate is less than one standard liter per hour,

• The metering pump (6) is arranged so that only the funded insulating fluid to the gas space (1) located Isoliergasgemisch (3) is supplied, and

• the control unit (9) is designed to the metering pump (6) while

to control until the detected by means of the sensor (4) proportion of insulating fluid is within a preset range of values.

The system of claim 1, wherein the controller (9) is adapted to

Conveying speed of the insulating fluid depending on the size of a

Deviation between a desired and the measured proportion of insulating fluid in the gas space and starting from an initial conveying speed to vary by reducing the conveying speed with decreasing deviation.

A system according to claim 2, wherein the controller (9) is adapted to determine a required amount of insulating fluid to be replenished, depending on the initial delivery rate, and thereby the required amount based on an initial deviation of the measured fraction from the desired fraction of insulating fluid in the Gas space and using the volume of the gas space (1) to determine.

A system according to any one of the preceding claims, wherein the system further comprises a

Evaporation device (5) comprising a gas mixing chamber, which is arranged between the metering pump (6) and the gas space (1), and wherein a gas line (N) the gas mixing chamber of the evaporation device (5) in such a way with the gas space (1) connects that gas exchange takes place between the insulating gas mixture (3) of the gas space (1) and the insulating fluid supplied by the metering pump (6) to the gas mixing chamber.

System according to one of the preceding claims, wherein additionally a

Heat supply device for heating the gas space (1) to be supplied insulating fluid is provided.

Method for ensuring a desired mixing ratio in one

Insulating gas mixture of a gas-insulated high-voltage electrical device, with the steps

• Detecting the proportion of insulating fluid in the insulating gas mixture in one

Gas space of the high-voltage device,

Conveying the liquid insulating fluid from a reservoir,

characterized by the steps

Conveying the liquid insulating fluid by means of a metering pump (6) at a delivery rate in the range of less than one normal liter per hour, the metering pump (6) being actuated until the detected proportion of insulating fluid is within a preset value range,

• Supply only the funded insulating fluid to the insulating gas mixture located in the gas space (1) of the high-voltage device.

The method of claim 6, wherein the conveying speed of the insulating fluid is dependent on the magnitude of a deviation between a desired and the measured amount of insulating fluid and starting from an initial one

Conveyor speed is varied by the conveying speed is reduced with decreasing deviation.

The method of claim 7, wherein a required amount of replenishment

Insulating fluid is determined, depending on the initial conveying speed is set, and thereby the required amount of an initial deviation of the measured portion of the desired proportion of insulating fluid and under

Addition of the volume of the gas space (1) is determined.

Method according to one of the preceding claims 6 to 8, wherein an evaporation of the insulating fluid on the way into the gas space (1) is achieved by means of a via a gas line (N) to the gas space (1) connected to a gas mixing chamber Evaporating device (5) causes a gas exchange between the insulating gas mixture (3) of the gas space (1) and the from the metering pump (6) of the gas mixing chamber supplied insulating fluid.

10. The method according to any one of the preceding claims 6 to 9, wherein the gas space (1) to be supplied insulating fluid is heated.