JP2019158750A - Water leakage detector - Google Patents

Abstract

To provide a water leakage detector with which it is possible to detect water leakage suddenly occurring in a short time.SOLUTION: The water leakage detector according to an embodiment detects leakage of the cooling water of a cooling system that cools an electric power conversion device. The water leakage detector comprises: a data recording circuit for successively detecting the water level of a surge tank for storing cooling water, and recording water level data each time detected; a change amount computing circuit for computing a change amount per unit time of the water level data recorded in the data recording circuit; and a change amount comparison circuit for comparing the computed change among with a previously set first determination value. When the change amount is greater than or equal to the first determination value, the change amount comparison circuit generates a first alarm signal to the effect that excess water leakage is detected.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a water leakage detection device that detects a leakage of cooling water in a water-cooled power conversion device.

  In power systems, electric railways, and industrial plants, many power electronics converters such as rectifiers, power compensators, grid interconnection devices, and motor drive devices are applied. Power electronics elements such as thyristors, IEGTs (Injection Enhanced Gate Transistors) and GCTs (Gate Commutated Turn-off thyristors) used in the main circuits of power electronics converters are increasing in capacity. It has reached a large capacity of several megawatts or hundreds of megawatts.

  Since these large-capacity power electronics converters generate a large amount of heat during operation in which the main circuit is energized, the cooling system is often water-cooled. As the cooling water used for main circuit cooling, pure water is used to enhance water insulation. The cooling water may be circulated and cooled via a heat exchanger.

  One of the problems of such a water-cooled converter is leakage of cooling water (water leakage) in a converter panel housing the converter. The cooling water is passed through a pipe using an insulating material such as Teflon (registered trademark), a metal conductor for element cooling, a collective pipe, and the like.

  There are various places where water leaks, but the pipes or the joints between the pipes and the metal conductors often deteriorate over time, causing cracks and leaking slowly. In such a case, the amount of water leakage per unit time is small, and the cooling water leaking into the converter panel evaporates due to the heat generated by the main circuit, which is not a problem.

  On the other hand, although the frequency of occurrence is low, the entire pipe may come off the joint due to an earthquake or the like, and a large amount of cooling water may be discharged into the converter panel in a short time. In this case, since the discharged cooling water does not have time to evaporate, there is a possibility that the discharged cooling water may scatter to the charging unit in the converter panel. If water enters the live parts, the insulation of the electric circuit in the converter panel will be lowered as a result, and in some cases, arcing or circuit short-circuiting may occur due to dielectric breakdown, causing serious damage such as damage to the converter. There is.

  As a method of detection and protection against cooling water leakage in the converter panel, the absolute amount of cooling water is monitored, and when it has dropped to a certain level, it is determined that leakage has occurred, or an alarm is issued, or In general, the converter performs a protection operation such as disconnecting the converter from the power supply (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-299219

  The above-described conventional water leakage detection protection circuit has the advantage that it can be implemented with a simple circuit, but has the following disadvantages.

  As mentioned above, when water leaks slowly due to deterioration of the packing of the water passage circuit, the amount of water leaked per unit time is small, so the leaked water evaporates in the converter and does not cause much problem. . Therefore, monitoring the cooling water level in the surge tank of the conventional water leakage detection protection circuit is sufficient for protection. In other words, the conventional water leakage detection and protection circuit is based on the idea of avoiding cooling water loss (cooling failure due to shortage) rather than detecting leakage of cooling water.

  On the other hand, in an extreme case where the cooling pipe falls off the flange due to vibration such as an earthquake, a large amount of cooling water is discharged into the converter panel in a short time. With the conventional leak detection protection circuit, the alarm will not be issued unless the surge tank water level falls below the set value. That is, the cooling water continues to be discharged into the converter panel until the set value is reached. The cooling water will not evaporate and will scatter to the main circuit conductor (charging part) in the panel. Normally, pure water used for cooling water has a lower electrical conductivity than tap water or industrial water, but when the live parts are wetted, insulation is lowered at the same time. As a result, in the worst case, an arc, a ground fault or a short circuit occurs between the charged parts in the converter panel or between the charged part and the ground. If a large amount of energy is supplied to the location from the power source, the converter panel will be damaged greatly, such as equipment breakage.

  An embodiment is made in order to solve the above-mentioned subject, and provides a water leak detection device which can detect a rapid water leak for a short time.

  The water leakage detection device according to the embodiment is a water leakage detection device that detects a leakage of cooling water of a cooling system that cools the power conversion device, and sequentially detects the water level of a surge tank that stores the cooling water. A data recording circuit for recording data every time it detects data, a change amount calculating circuit for calculating a change amount per unit time of the water level data recorded in the data recording circuit, the calculated change amount, And a change amount comparison circuit for comparing the set first determination value. When the change amount is equal to or greater than the first determination value, the change amount comparison circuit generates a first alarm signal indicating that excessive water leakage has been detected.

  In the present embodiment, the amount of change per unit time of the water level data is calculated and compared with a preset first determination value, and the first alarm signal is generated based on the comparison result. Can detect sudden water leaks over time.

It is a typical block diagram which illustrates the water leak detection apparatus concerning an embodiment. It is an example of the flowchart for demonstrating operation | movement of the water leak detection apparatus of embodiment. It is a typical block diagram which illustrates the water leak detection apparatus of a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The drawings are schematic or conceptual, and the relationship between the thickness and width of each part, the size ratio between the parts, and the like are not necessarily the same as actual ones. Further, even when the same part is represented, the dimensions and ratios may be represented differently depending on the drawings.
In the present specification and drawings, the same elements as those described above with reference to the previous drawings are denoted by the same reference numerals, and detailed description thereof is omitted as appropriate.

FIG. 1 is a schematic block diagram illustrating a water leakage detection device according to an embodiment.
As shown in FIG. 1, the water leakage detection device 6 of the embodiment includes a cooling water 3 in the surge tank 4 from a water level detection sensor 5 provided in the surge tank 4 of the cooling system that cools the main circuit 10 of the converter 1. Get water level data. The water leakage detection device 6 acquires the water level data of the cooling water 3 at regular intervals, for example, calculates the amount of change in the water level per unit time, and excessive water leakage occurs when the amount of change is greater than or equal to a predetermined value. An alarm signal for generating an alarm to the effect is generated.

  In the cooling system of the converter 1, the cooling pipe 3 is filled with the cooling water 3, and the cooling water 3 is circulated between the main circuit 10 and the cooling device 2 by the pump 23. The cooling device 2 includes a heat exchanger that absorbs heat generated in the main circuit 10 and cools the cooling water 3 that has been circulated again.

  The cooling water 3 is also connected to a pipe 22 connected to the pipe 21 and extending in the vertical direction, and is filled up to a predetermined water level in the surge tank 4 provided at the upper end of the pipe. Since the cooling water 3 circulates in such a closed fluid path, the amount of the cooling water 3 is constant. Therefore, in a normal state, the water level of the cooling water 3 in the surge tank 4 is substantially constant at a predetermined water level. The water level of the cooling water 3 in the surge tank 4 can be reduced according to the degree of leakage of the cooling water 3.

  The water level of the cooling water 3 in the surge tank 4 is detected by a water level detection sensor 5. The water level detection sensor 5 is, for example, an optical level sensor using a laser or the like. The water level detection sensor 5 transmits the detected water level data of the cooling water 3 to the water leakage detection device 6.

The configuration of the water leakage detection device 6 will be described in detail.
The water leakage detection device 6 of the embodiment includes a data recording circuit 6a, a change amount calculation circuit 6b, a change amount comparison circuit 6c, and a protection operation circuit 6d. The data recording circuit 6a inputs the water level data detected by the water level detection sensor 5 provided in the surge tank 4, and stores it in association with the acquisition time.

  The variation calculation circuit 6b sequentially reads out the water level data stored in time series from the data recording circuit 6a together with the data of the acquisition time associated therewith. The change amount calculation circuit 6b calculates the amount of change per unit time of the water level based on the two sets of read water level data and acquisition time data. That is, the amount of change ΔX per unit time of the water level is expressed by the following formula (1), where the water level X is assumed.

  ΔX = dX / dt (1)

  More specifically, the water level X is a function of time, and since the time is discrete in order to acquire a fixed period of data, it is expressed as X = X (ti). ti represents the i-th acquisition time in the time series, and indicates that as i (= natural number) increases, t1, t2,... When equation (1) is rewritten, the following equation (1 ') is obtained.

  ΔX = {X (ti + 1) −X (ti)} / {(ti + 1) − (ti)} (1 ′)

  The change amount comparison circuit 6c receives data of the change amount ΔX calculated by the change amount calculation circuit 6b. A change amount determination value ΔXs is preset in the change amount comparison circuit 6c. The change amount comparison circuit 6c compares the change amount ΔX data with the change amount determination value Xs. When the data of the change amount ΔX is greater than or equal to the change amount determination value ΔXs, an active determination result signal is generated and supplied to the protection operation circuit 6d. The change amount comparison circuit 6c deactivates the determination result signal when the data of the change amount ΔX is smaller than the change amount determination value ΔXs.

  The protection operation circuit 6d generates an alarm signal when receiving an active determination result from the change amount comparison circuit 6c. For example, the alarm signal causes the control device of the converter 1 to generate a gate block signal that stops the operation of the main circuit 10. The main circuit 10 is stopped by the gate block signal.

  The water leakage detection device 6 of the embodiment may not only determine the amount of change in the water level, but may also determine whether the surge tank water level X (ti) is equal to or higher than the minimum water level Xs.

FIG. 2 is an example of a flowchart for explaining the operation of the water leakage detection device of the embodiment.
The water leak detection device 6 of the embodiment executes two determination flows. The determination flow includes steps S11 to S13 for determining whether or not there is an abnormality in the water level change amount ΔX of the cooling water 3 in the surge tank 4, and steps S21 to S22 for determining an absolute level decrease in the water level X. . These flows are executed in parallel after the water leakage detection device 6 acquires the data of the water level X of the cooling water 3 of the surge tank 4 in step S01, for example.

First, a determination flow for the presence / absence of abnormality in the amount of change ΔX of the water level of the cooling water 3 in the surge tank 4 will be described.
As shown in FIG. 2, in step S01, after acquiring the water level X data, the data recording circuit 6a records the water level X data in association with the acquisition time.

  In step S11, the variation calculation circuit 6b reads the adjacent acquisition times ti + 1 and ti and the data of the water level X (X (ti + 1) and X (ti)) associated therewith from the data recording circuit 6a. The change amount calculation circuit 6b calculates the change amount ΔX of the water level from the read acquisition times ti + 1 and ti and the data of the water level X (X (ti + 1), X (ti)) (formula (1 ′)).

  In step S12, the change amount comparison circuit 6c compares the change amount ΔX calculated by the change amount calculation circuit 6b with a preset change amount determination value ΔXs. When the change amount ΔX is larger than the change amount determination value ΔXs, the change amount comparison circuit 6c shifts the process to the next step S13. If the change amount ΔX is less than or equal to the change amount determination value ΔXs, the process returns to step S11, and the next calculation related to the acquisition time is executed.

  In step S13, the protection operation circuit 6d determines that a large amount of water leakage has occurred in accordance with the change amount ΔX being greater than the change amount determination value ΔXs, and generates an alarm signal to be notified in the case of a large amount of water leakage. And output.

  The alarm signal is transmitted to the converter 1 or the control device, for example. In step S31, the converter 1 or the control device generates a gate block signal or an interlock signal that stops the converter 1, and stops the converter 1.

Next, a flow for determining an absolute level drop of the water level X will be described.
In step S21, the water leakage detection device 6 reads, for example, the latest acquisition time and water level X data associated with the acquisition time from the data recording circuit 6a. The water leak detection device 6 compares the read water level X data with a preset water level determination value Xs. When the water level X is smaller (lower) than the water level determination value Xs, the water leakage detection device 6 shifts the process to the next step S22. If the water level X is equal to or higher than the water level determination value Xs, the water leakage detection device 6 returns to step S21 and repeats the process of reading the next acquisition time and water level X data.

  In step S22, the water leakage detection device 6 determines that the cooling water 3 is insufficient, and generates and outputs an alarm signal indicating that the cooling water 3 is insufficient.

  The alarm signal in this case is transmitted to, for example, the HMI terminal that monitors the converter 1 and its cooling system, etc., and alerts the operator by displaying “cooling water level drop” or the like on the monitoring screen of the HMI terminal. .

  As described above, in the water leakage detection device 6 of the embodiment, when an abnormality in the amount of change ΔX of the cooling water 3 in the surge tank 4 is detected, an absolute level decrease in the water level X of the cooling water 3 in the surge tank 4 is detected. The degree of the protection operation can be changed depending on the case of detecting.

  In the above description, the detection of the change amount ΔX of the water level of the cooling water 3 in the surge tank 4 is not limited to setting one change amount determination value ΔXs, and a plurality of change amount determination values may be set. By setting a plurality of change amount determination values, different levels of protection operations can be executed.

  In the above description, the data of the water level X has been described as being acquired at a constant cycle. However, the data of the water level X is acquired at a non-constant cycle, and the change amount ΔX according to the equation (1) or the equation (1 ′). Of course, it does not matter if it is calculated.

  The water leakage detection device 6 according to the embodiment may include a CPU (Central Processing Unit) or the like that reads a program stored in a storage device (not shown) or the like and executes the program sequentially. The water leakage detection device 6 of the embodiment may be realized by a programmable controller (PLC). Part or all of each of the blocks (circuits) described above is realized by one or a plurality of steps constituting the program.

The effect of the water leakage detection device 6 of the embodiment will be described in comparison with the water leakage detection device of the comparative example.
FIG. 3 is a schematic block diagram illustrating a water leakage detection device of a comparative example.
As shown in FIG. 3, the water leakage detection device 106 has a protection operation circuit 106d. The protection operation circuit 106 d is connected to the water level detection sensor 5 provided in the surge tank 4.

  In the case of the comparative example, the water level detection sensor 5 is a water level sensor such as a level switch, for example, and when the cooling water 3 in the surge tank 4 drops to the water level determination value Xs set by the water level detection sensor 5, Outputs a low level signal.

  The protection operation circuit 106d performs a predetermined protection operation when the level lowering signal is supplied. The predetermined protection operation is, for example, a disconnection command for the converter 1, a signal generation or output for warning display to the HMI terminal, or the like.

  In the case of the comparative example, the water leakage determination is performed when the water level of the cooling water 3 in the surge tank 4 has reached one threshold value. Therefore, when a minute water leak occurs over a long period of time, it is suitable for performing inspections, repairs, and the like so as not to cause a decrease in cooling performance due to a decrease in the cooling water 3. For example, even if a minute water leak occurs around the converter 1, in a normal case, it does not evaporate and causes a problem such as dielectric breakdown. However, when a large amount of water leakage occurs in a short time due to a pipe rupture due to a natural disaster such as an earthquake, the leaked water does not have a period to evaporate. Insulation breakdown may occur, leading to an accident.

  In the water leakage detection device 6 of the embodiment, the data of the water level X of the cooling water 3 of the surge tank 4 is sequentially acquired and recorded in association with the acquisition time. Using the acquisition time and the data of the water level X associated therewith, the water level change amount ΔX is calculated, and if it is larger than the predetermined change amount determination value ΔXs, it is determined that there has been a large amount of water leakage due to pipe breakage or the like. Thus, the converter 1 can be stopped urgently. Even if cooling water enters the converter 1 due to a large amount of water leakage, the converter 1 is stopped, so that further damage can be prevented.

  Due to inadequate piping connection work, etc. during construction, it may not be as much as that due to pipe breakage, but it may cause significant water leakage, various water leakage factors, and water leakage levels. In the water leakage detection device 6 of the embodiment, since a plurality of change amount determination values ΔXs can be set, it is possible to cope with water leakage due to various disasters, accidents, construction failures, etc., and different alarms depending on the degree of water leakage Levels can be set easily.

  In the water leakage detection device 6 of the embodiment, since the data of the water level X is recorded together with the acquisition time, not only the change amount ΔX of the water level but also the absolute level decrease determination of the water level X can be performed at the same time, more reliably. A safe cooling system can be constructed.

  According to the embodiment described above, it is possible to realize a water leakage detection device that can detect a rapid water leakage in a short time.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and the equivalents thereof. Further, the above-described embodiments can be implemented in combination with each other.

1 converter, 2 cooling device, 3 cooling water, 4 surge tank, 5 water level detection sensor, 6 water leakage detection device, 6a data recording circuit, 6b change amount calculation circuit, 6c change amount comparison circuit, 6d protection operation circuit, 10 main Circuit, 21, 22 Piping, 23 Circulation pump

Claims (3)

A water leakage detection device for detecting leakage of cooling water in a cooling system for cooling a power converter,
A data recording circuit that sequentially detects the water level of a surge tank that stores cooling water and records the water level data each time it is detected;
A change amount calculation circuit for calculating a change amount per unit time of the water level data recorded in the data recording circuit;
A change amount comparison circuit that compares the calculated change amount with a preset first determination value;
With
When the change amount is equal to or greater than the first determination value, the change amount comparison circuit generates a first alarm signal indicating that excessive water leak has been detected. The change amount comparison circuit compares the change amount with a second determination value that is set in advance and smaller than the first determination value,
When the amount of change is equal to or greater than the second determination value, a second alarm signal indicating that water leakage has been detected is generated,
The first alarm signal is used to generate a signal for stopping the operation of the power converter,
The said 2nd alarm signal is used for producing | generating the command for displaying the warning which prompts inspection of the said cooling system with respect to the monitoring apparatus which monitors the operation | movement of the said power converter device and the said cooling system. Water leakage detection device. The water leak detection device according to claim 1 or 2, wherein the water level data recorded in the data recording circuit is compared with a preset third determination value.

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