JP3325826B2 - Gas pressure measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas pressure measuring device used for a fault locating system of a gas insulated switchgear, for example.

[0002]

2. Description of the Related Art FIG.
FIG. 1 is a block diagram of a failure point locating system using a conventional gas pressure measuring device disclosed in Japanese Unexamined Patent Publication (Kokai) No. HEI 10-205, and is directed to a gas insulated switchgear. In the figure, reference numeral 1 denotes a plurality of gas pressure sensors for measuring a quasi-stationary pressure, which are provided in each circuit breaker (not shown). 2 is a relay board, 3 is a gas pressure measuring unit for obtaining gas pressure data based on a signal from the gas pressure sensor 1, 4 is an analog input unit provided corresponding to each gas pressure sensor 1, and 5 is an analog input unit 4
A / D (analog / digital) conversion of the signal from
A / D converter 6 is a CPU (central processing unit) for processing a signal from the A / D converter 5, and the analog input unit 4, A
The gas pressure measurement unit 3 is composed of the / D converter 5 and the CPU 6, and the gas pressure measurement device is composed of the gas pressure sensor 1 and the gas pressure measurement unit.

[0003] Reference numeral 8 denotes a plurality of current sensors for measuring the current at each location, and a current transformer is used. Reference numeral 9 denotes a breaking current measuring unit that measures a breaking current when the circuit breaker operates, 10 denotes an analog input unit provided corresponding to each current sensor 8, 11
Is an A / D converter for A / D converting a signal from the analog input unit 10.
D converter, 13 is an auxiliary contact of each circuit breaker, 14 is a contact input unit provided corresponding to each auxiliary contact 13, 15 is an interface for receiving a signal from the contact input unit 14, and 16 is A
A CPU that processes signals from the A / D converter 11 and the interface 15 to obtain interrupting current data, and the analog input unit 10, the A / D converter 11, the contact input unit 14, the interface 15, and the CPU 16 9.

A transmission processing unit 18 receives and sends signals from the CPUs 6 and 16, and includes a gas pressure measuring unit 3,
The relay panel 2 is constituted by the cutoff current measuring unit 9 and the transmission processing device 18. Reference numeral 19 denotes a fault location information processing board connected to the transmission processing device 18 of the relay board 2 by an optical cable 20 based on gas pressure data and cut-off current data sent from the relay board 2 and protection relay information. It is designed to issue alarms, display gas pressure, and output it to others.

Next, the operation will be described. A signal input from the gas pressure sensor 1 to the analog input unit 4 in the gas pressure measuring unit 3 is converted into a digital signal by the A / D converter 5 and then sampled by the CPU 6 in a cycle of several hundred ms, and the signal is increased. Minutes are calculated. The pressure increase ΔP is obtained by the difference between the gas pressure value Pk taken in this time and the gas pressure value Pk-1 taken in the last time. The measured pressure increase ΔP is transmitted to the transmission processing device 18. On the other hand, a signal input from the current sensor 8 to the analog input unit 10 in the breaking current measuring unit 9 is converted into a digital signal by the A / D converter 11 and then input to the CPU 16.
The CPU 16 constantly samples the waveform at regular intervals (for example, 1 ms) and stores waveform data for three cycles. That is, data from a certain point in time to three cycles before is always stored in the memory, and each time data is taken in, the past data is updated one by one. When the breaker performs the breaking operation, the CPU 16 stops sampling the breaking current data (main circuit current waveform data) by the contact signal of the auxiliary contact 13 and transmits the breaking current data at that time to the transmission processing device 18. The fault locating information processing board 19 calculates, based on the breaking current data transmitted from the transmission processing device 18 through the optical cable 20 and the calculation formula,
Calculate the gas pressure rise ΔP ', compare this with the rise ΔP measured by the gas pressure measuring unit 3, and further, based on the protection relay information, whether an accident has occurred inside the circuit breaker or outside. It can be determined whether or not this has occurred.

[0006]

A gas pressure measuring device used in a failure point standard system or the like needs to be able to accurately detect a change in gas pressure. The conventional gas pressure measuring device is configured as described above, and a gas pressure sensor having a resolution of about 0.01 kgf / cm ² is used. However, recently, the resolution of the gas pressure sensor has been improved, and an accuracy of 0.001 kgf / cm ² or less has been obtained. Therefore, it is desired that other devices used with such a pressure sensor have the same level of performance. It is. In steady-state 5 kgf / cm ² about the gas pressure, 0.001kgf /
To realize the detection capabilities of cm ² is a required resolution of about ^{0.0001kgf / cm 2, 0.0001 / 5} = 1/50000 ≒ 6553
6, that is, 16-bit resolution is required. Normally, in the case of a general-purpose 16-bit A / D converter, the lower two or three bits become an error, and the resolution is actually 13 to 14 bits.

As described above, there is a problem that a commercially available (general purpose) A / D converter cannot realize a resolution of 16 bits or more. Further, when an A / D converter having a resolution of 16 bits or more is used, there is a problem that the reliability is low such as being expensive and susceptible to noise. Further, there is a case where noise equivalent to about 0.001 kgf / cm ² is generated in the output of the gas pressure sensor, and there has been a problem that this noise is detected and it is erroneously recognized that a pressure change has occurred.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can detect a gas pressure change with high resolution even when a general-purpose A / D converter is used, and is affected by noise. It is intended to obtain a gas pressure measuring device which is difficult.

[0009]

A gas pressure measuring device according to the present invention uses a gas pressure value detected by a gas pressure sensor as A
A first A / D converter for performing A / D conversion, a computing device for integrating an output from the first A / D converter to calculate an average value, and a D / A for performing D / A conversion on an output from the computing device. a converter, a differential amplifier for amplifying a difference between an output from the output and the D / a converter from the pressure sensor, the second a / D converter for a / D converting the output of the differential amplifier, and Large change in gas pressure
Sometimes a differential is applied by applying a bias to the D / A converter.
Change the output of the amplifier to switch the range of the second A / D converter.
It has a range switching means for switching .

Further, when the range of the second A / D converter is switched, the output of the gas pressure sensor before switching is maintained as the output from the gas pressure sensor, and the maintained value is changed during the switching process by the differential amplifier. And a sample-and-hold circuit for outputting to the sampler. When switching of the range of the second A / D converter has occurred a predetermined number of times or more within a predetermined period, the switching is stopped, and the value calculated by the arithmetic unit from the output of the first A / D converter is calculated. This is to output.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing a gas pressure measuring device according to Embodiment 1 of the present invention, and FIG. 2 is a block diagram of a failure point locating system using the gas pressure measuring device of FIG. The following shows the case. In FIG. 1, 3
1 is a gas pressure sensor that measures quasi-stationary pressure, 0.00
One that can obtain an accuracy of 1 kgf / cm ² is used. 32 is an analog input unit provided corresponding to the gas pressure sensor,
Reference numeral 33 denotes an A / D (analog / analog) signal of the pressure value sent from the gas pressure sensor 31 via the analog input unit 32.
A general-purpose first A / D converter for performing digital (digital) conversion; a CPU (central processing unit) 3 as an arithmetic unit for integrating an output from the first A / D converter 33 to calculate an average value;
5 is a general-purpose D / A that performs D / A conversion of the output from the CPU 34.
An A converter 36 is a differential amplifier, which outputs an output sent from the gas pressure sensor 31 via the analog input unit 32,
The difference from the output from the D / A converter 35 is amplified, for example, 100 times. An A / D 37 outputs the output from the differential amplifier 36.
This is a general-purpose second A / D converter for conversion. The resolution of the first and second A / D converters 33 and 37 and the D / A converter 35 is 10 bits. Also, the CPU 34
It also serves as the range switching means in the present invention.
When the gas pressure change is large, the D / A converter
Change the output of the differential amplifier by adding
Switch the range of the A / D converter.

In FIG. 2, a gas pressure sensor 31 is provided in each circuit breaker (not shown). 32, 33 in FIG.
And a set of 35 to 37 are provided for each gas pressure sensor, and are indicated by A in FIG. 13 is an auxiliary contact of each circuit breaker, 14 is a contact input unit provided corresponding to each auxiliary contact 13, and 15 is an interface for receiving a signal from the contact input unit 14, and is connected to the CPU 34. 18
Is a transmission processing device for receiving and transmitting a signal from the CPU 34, and 39 is a relay panel installed near the installation site of the gas insulated square rooting device, and A, 14, 15, 34, and 18 constitute a relay panel 39. I have.

The transmission processing device 1 of the relay panel 39 is installed at a place distant from the relay panel 39 and is connected by an optical cable 20.
8 is a fault locating information processing board connected to the relay board 3
Based on the gas pressure data and auxiliary contact data sent from 9 and the protection relay information, an alarm is issued, the gas pressure is displayed, and output to others. Note that, in addition to the configuration of FIG. 2, similarly to FIG. 9, current data may be sent to the relay panel 39 for use.

Next, the operation will be described. A signal input from the gas pressure sensor 31 to the analog input unit 32 is A / D converted by the first A / D converter 33 and transferred to the CPU 34. The CPU 34 integrates (adds) this data, for example, 64 times to obtain an average value. Here, since the 10-bit data is integrated 64 (= 2 ⁶ ) times, the integrated value is 16
Bit. The CPU 34 always sets the upper 10 bits of the 16-bit data as the gas pressure value and outputs the same data to the D / A converter 35. By truncating the lower bits, the effect of noise can be reduced. The differential amplifier 36 amplifies the difference between the signal from the D / A converter 35 and the signal from the analog input unit 32 to amplify a small change in the pressure detected by the pressure sensor 31. The second A / D converter 37 performs A / D conversion of the amplified signal of the slight change in pressure, and outputs the converted signal to the CPU 34. CP
U34 integrates the data from the second A / D converter 37, for example, 64 times. Here, since the 10-bit data is integrated 64 times, the integrated value becomes 16 bits. The upper 10 bits of the 16-bit data are set as a minute pressure relative value.
By truncating the lower bits, the effect of noise can be reduced.

When the change in the signal from the analog input section 32 is large, the output of the differential amplifier 36 becomes large and does not fall within the range of the second A / D converter 37.
In such a case, the CPU 34 sets the first A / D converter 33
, The bias is applied to the output to the D / A converter 35 so that the second A / D converter 37 is not saturated. At this time, the minute pressure relative value is a value obtained by adding the bias equivalent value. As described above, the gas pressure is detected as a form in which the minute pressure relative value, which is a change, is added to the constant gas pressure value, which is a steady component of the gas pressure.

The above operation will be described using specific numerical values. FIG. 3 shows the relationship between the constant gas pressure value measurement range and the minute pressure relative value measurement range. In the figure, the code such as 3FFH is
The last H indicates that it is a hexadecimal number (hexadecimal), and the numerical value is displayed in other alphanumeric characters. For example,
3FFH represents the decimal number 1023. Here, since the amplification degree of the differential amplifier 36 is 100, the full range of the second A / D converter 37 is 1/100 of the range of the first A / D converter 33. 1 / of the first A / D converter 33
Since the second A / D converter 37 performs A / D conversion of 10 fluctuations with 10 bits, the second A / D converter 3
The precision of one digit of 7 is 1/100 × 1/1024 = 1/102400 <1
/ 65536, and the resolution of the minute pressure relative value is 16 bits or more, and the change in gas pressure can be measured with high accuracy.

The detected gas pressure change is transmitted from the CPU 34 to the failure point locating information processing board 19 via the transmission processing device 18 and the optical cable 20 together with the auxiliary contact information. In the fault point information processing board 19, the gas pressure change data based on the value detected by each gas pressure sensor 31, the information from each auxiliary contact 13, and the information from the protection relay,
Judgment of the presence or absence of failure, location of failure point, alarm, gas pressure display, etc.

Embodiment 2 FIG. FIG. 4 is a block diagram showing a gas pressure measuring device according to a second embodiment of the present invention. Reference numeral 41 denotes a second D / A converter for D / A converting a signal from a CPU 34, and reference numeral 35 denotes a D / A converter in FIG. A / D converter, but the second D / A converter 41
Hereinafter, it will be referred to as a first D / A converter. 42 is an operational amplifier, the first and second D / A converters 3
Signals from 5 and 41 are input, and the added operation result is output to the differential amplifier 36. The differential amplifier 36 is an operational amplifier 4
2 and the output of the analog input unit 32. CPU 34 is similar to that of FIG.
An output function to the / A converter 41 is added. Other configurations are the same as those in the first embodiment, and a description thereof will be omitted.

Next, the operation will be described. The basic operation is the same as in the first embodiment. That is, the signal from the analog input section 32 is A / D converted by the first A / D converter 33 and transferred to the CPU 34. C
The PU 34 performs an integration process on this, and a first D / A converter 35
After the D / A conversion, the differential amplifier 3
Send to 6. The differential amplifier 36 amplifies the difference between the signal from the operational amplifier 42 and the signal from the analog input unit 32,
A / D converter 37 performs A / D conversion, and CPU 34 integrates.

When the change in the signal from the analog input section 32 is large, the CPU 34 applies a bias to the output to the first D / A converter 35 so that the second A / D converter 37 is not saturated. I do. In this case, the first D / A converter 35
Before and after the bias is applied, the output value of the second A / D converter 37 is not continuous. CPU 3 detecting this discontinuity
4 finely adjusts the output of the operational amplifier 42, the output of the differential amplifier 36, and the output of the second A / D converter 37 by changing the output to the second D / A converter 41.

FIG. 5 shows the range switching of the second A / D converter 37. When the input of the second A / D converter 37 reaches the limit of the range, the range is switched by the above method. Adjustment is performed so that 3FFH before switching becomes a predetermined value near the center of the range after switching. Here, the value is set to 180H which is a value slightly below the center. By setting the value after the switching in the vicinity of the center of the range, there is an effect of preventing the need for the switching process finely and repeatedly. By considering the difference between 3FFH and 180H in addition to the output of the second A / D converter 37 after the switching, continuity of the minute pressure relative value is maintained. The above process is referred to as a measurement range switching process of the minute pressure relative value.

Embodiment 3 FIG. FIG. 6 is a block diagram showing a gas pressure measuring device according to Embodiment 3 of the present invention. In the drawing, reference numeral 44 denotes a sample-and-hold circuit provided between the analog input section 32 and the differential amplifier 36. Although the same signal as the signal from the input unit 32 is output, when the sample and hold signal from the CPU 34 is input, the output immediately before the input of the sample and hold signal is maintained. The CPU 34 sends a sample hold signal to the sample hold circuit 44 when the range of the second A / D converter 37 is switched. Other configurations are the same as those in the second embodiment, and a description thereof will be omitted.

Next, the operation will be described. First, CP
When U34 does not output the sample-and-hold signal to the sample-and-hold circuit 44, it operates in the same manner as in the second embodiment. Next, a case where the change of the signal from the analog input section 32 becomes large and the range switching processing of the second A / D converter 37 is performed will be described with reference to FIG. When the measurement range switching processing of the minute pressure relative value is performed, a sample hold signal is sent from the CPU 34 to the sample hold circuit 44 during the adjustment processing time B, and the sample hold circuit 4
4 retains its previous value C. This hold value C is
The range is adjusted so as to be the determined value 180H. Therefore, even if there is a fluctuation amount D that could not be measured during the adjustment time B for switching,
Starting from the value to which E is added. By considering the difference between 3FFH and 180H in addition to the value of E, continuity before and after the switching process can be maintained. If it starts from 180H after switching without the sample and hold circuit 44, it will be like F and an error will occur by D.

In FIG. 6, a portion surrounded by a chain line may be constituted by a one-chip microcomputer. In this example, the digital processing part is integrated into one chip.
External wiring between the / D converter, the D / A converter, and the CPU can be omitted, and the space can be reduced. FIG.
The same effect can be obtained by using a one-chip circuit having another circuit configuration.

Embodiment 4 The circuit configuration of the gas pressure measuring device in this embodiment is the same as that in FIG. 6, but the CPU 34 is within a certain period (called a switching number detection period) in which the measurement range switching processing of the minute pressure relative value is performed. When the number of times becomes, for example, three, the switching process is stopped. Other configurations are the same as those in the third embodiment, and a description thereof will be omitted.

Next, the operation will be described. FIG. 8 is an explanatory diagram of the number of range switching of the second A / D converter 37. Immediately after the measurement range switching processing of a certain minute pressure relative value is performed, counting of the number of times of execution of the switching processing is started. If three times are counted during the switching frequency detection period, the switching is stopped, and the detection of the minute pressure relative value is stopped. Then, the gas pressure value is constantly output to the outside. In such a case, since the change in the gas pressure is large, even the gas pressure value is always valid data for detecting the change in the gas pressure. When the change in gas pressure becomes small and falls within a certain range, the detection processing of the minute pressure relative value is restarted. As described above, when the change in the gas pressure is large, it is not necessary to take time for the frequent switching process.

[0027]

Since the gas pressure measuring device according to the present invention is constructed as described above, it can always measure the gas pressure value and the minute pressure relative value separately, and can measure the minute pressure relative value with high accuracy. And it can detect changes in gas pressure with high resolution, has the effect of being less susceptible to noise, and provides a D / A converter when the gas pressure change is large. Applying a bias to the second A / D
By switching the range of the converter, the measurement range of the minute pressure relative value can be increased. Further, by providing a sample-and-hold circuit for maintaining the value before the range switching, continuity before and after the range switching can be maintained. Furthermore, by stopping the switching when the switching of the range reaches a predetermined number of times within a predetermined period and constantly outputting the gas pressure value, the change of the gas pressure can be reduced without taking time for frequent range switching. Can be measured.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a pressure measuring device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram of a fault location system using the pressure measuring device of FIG.

FIG. 3 is an explanatory diagram showing a relationship between a constant gas pressure value measurement range and a minute pressure relative value measurement range in the pressure measurement device of FIG. 1;

FIG. 4 is a block diagram showing a pressure measuring device according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing range switching of a second A / D converter in the pressure measuring device of FIG.

FIG. 6 is a block diagram showing a pressure measuring device according to Embodiment 3 of the present invention.

FIG. 7 is an explanatory diagram showing range switching of a second A / D converter in the pressure measurement device of FIG. 6;

FIG. 8 shows a second A / A according to the fourth embodiment of the present invention.
It is explanatory drawing about the frequency | count of switching of a D converter.

FIG. 9 is a block diagram of a failure point locating system using a conventional pressure measuring device.

[Explanation of symbols]

31 gas pressure sensor, 33 first A / D converter, 3
4 CPU, 35 D / A converter, 36 differential amplifier,
37 second A / D converter, 44 sample and hold circuit.

Continuation of front page (58) Fields investigated (Int.Cl. ⁷ , DB name) G01L 9/00 G01R 31/08 H02B 13/025

Claims (3)

(57) [Claims] 1. A gas pressure sensor for detecting a gas pressure, a first A / D converter for A / D converting a gas pressure value detected by the gas pressure sensor, and a signal from the first A / D converter. An arithmetic unit for integrating the output to calculate an average value, a D / A converter for D / A converting the output from the arithmetic unit, and a D / A converter for converting the output from the gas pressure sensor to the output from the D / A converter. a differential amplifier for amplifying the difference, the output of this differential amplifier a
A / D converter for performing A / D conversion and gas pressure
When the change of the D / A converter is large, bias is applied to the D / A converter.
By changing the output of the differential amplifier,
Range switcher for switching the range of the A / D converter
Gas pressure measuring device with steps . 2. When the range of the second A / D converter is switched.
Output immediately before switching as the output from the gas pressure sensor
Maintain the force value, and change the value
Providing a sample-and-hold circuit to output to a dynamic amplifier
The gas pressure measuring device according to claim 1, wherein: 3. Switching of the range of the second A / D converter
Is switched to the specified number of times within the specified period
Is stopped and the output of the first A / D converter is
The calculated value is output.
The gas pressure measuring device according to claim 1 or 2 .