On-site accurate calibration method of electrochemical oxygen sensor in sulfur hexafluoride distribution room

Abstract

The present invention discloses an on-site accurate calibration method for an electrochemical oxygen sensor in a sulfur hexafluoride distribution device room, which comprises the following steps: starting a ventilation device, circulating ventilation for a period of time T, and ensuring that fresh natural air flows evenly to an oxygen meter; collecting the ambient temperature t during calibration; Rel 、Ambient humidity H Rel , sensor output C s , atmospheric pressure BP Rel ; Using the ambient temperature t during calibration Rel Calculate the saturated water vapor pressure WVP max ; Using ambient humidity H Rel , saturated water vapor pressure WVP max Calculate the corrected water vapor pressure WVP Rel ; Using water vapor pressure WVP Rel and atmospheric pressure BP Rel Calculate the oxygen partial pressure ppO2; use the oxygen partial pressure ppO2 to calculate the oxygen concentration V S The oxygen concentration Vs and the output Cs of the sensor during calibration are used as calibration high points to calibrate the oxygen sensor. The present invention can improve the accuracy of detection, avoid missed reports or false reports, and improve the safety of the sulfur hexafluoride distribution device indoors.

Description

Technical Field

[0001] The invention relates to the technical field of power distribution equipment, in particular to an on-site precise calibration method for an electrochemical oxygen sensor in a sulfur hexafluoride power distribution device room. Background Art

[0002] According to the requirements of the power safety work regulations, the current sulfur hexafluoride distribution device room is generally equipped with an oxygen meter with an alarm function, and the oxygen meter requires an oxygen sensor. Electrochemical oxygen sensors have been widely used in oxygen meters for monitoring sulfur hexafluoride distribution device rooms across the country because of their stable performance, reasonable price, and not easily interfered by other gases.

[0003] The electrolyte inside the electrochemical oxygen sensor will be consumed over time, resulting in a time-dependent output decrease drift. In a typical time-dependent change, the signal output decays by 0.4mV after 2000 hours, which is converted to 0.65% O2 under standard measurement conditions, exceeding the technical requirement of the oxygen meter range drift of less than 0.5% O2. Therefore, in order to make accurate measurements, the sensor needs to be calibrated regularly, and the calibration of the electrochemical oxygen sensor is required at least once a month.

[0004] Because there are many oxygen meters installed on site, the calibration cycle is short, and most of the sulfur hexafluoride distribution device rooms are restricted, so it is impossible to take them back to the test room for accurate calibration every time. The commonly used method now is to use ventilation equipment to circulate the air around the oxygen sensor to natural air without sulfur hexafluoride, and then perform on-site automatic calibration.

[0005] In the prior art, the calculation of oxygen value in the sulfur hexafluoride distribution device room generally adopts a two-point calibration method, and the oxygen content V Rel The calculation formula is:

[0006] ;

[0007] Among them, C Rel Represents the output value of the oxygen sensor during calibration (mV); C H Represents the sensor output value at the calibration high point (mV); C L Represents the sensor output value at the calibration low point (mV); V H Represents the oxygen content at the calibration high point (%); V L Represents the oxygen content at the calibration low point (%).

[0008] Calibration low point V L Generally, zero oxygen 0% is selected, and there is no drifting. The corresponding V when natural air is selected for on-site calibration H , C HSave it as the calibration high point, and calculate the oxygen content according to the formula before recalibration. In natural air, the volume ratio of oxygen accounts for 20.95% of the air, so in the current actual calibration process, it is generally directly considered that the oxygen content of natural air is V H The oxygen concentration is 20.95%O2. However, this method ignores the influence of temperature, humidity, altitude and other factors on oxygen measurement. The water vapor pressure will change at different temperatures and humidities, and the oxygen partial pressure will also change accordingly. Therefore, the oxygen content will not remain constant at 20.95%. Direct substitution of 20.95% will result in deviation. For example, when the ambient temperature is 22°C, the ambient humidity is 32%RH, and the atmospheric pressure is 986mbar, the calculated oxygen concentration is 20.77%. If it is corrected according to 20.95%, the measurement result will be inaccurate, and oxygen misreporting or omission will easily occur in the application, which will affect the safety of the staff. Summary of the invention

[0009] The purpose of the present invention is to solve the problem of the calibration high point V of oxygen content when calibrating the electrochemical oxygen sensor in the prior art described in the background technology. H It will change with the changes in natural environment such as ambient temperature, humidity, atmospheric pressure, etc., which makes the existing calibration method easily cause the measurement results of the oxygen sensor to be inaccurate, and oxygen false alarm or missed alarm may occur in the application. This paper provides an on-site accurate calibration method for the electrochemical oxygen sensor in the sulfur hexafluoride distribution device room.

[0010] To achieve the above objectives, the present invention is implemented by the following technical solutions: a method for accurate on-site calibration of an electrochemical oxygen sensor in a sulfur hexafluoride distribution device room, which comprises the following steps:

[0011] S1. Start the ventilation device and circulate the ventilation time period T to ensure that fresh natural air flows evenly to the oxygen meter;

[0012] S2, the ambient temperature during the acquisition and calibration Rel 、Ambient humidity H Rel , sensor output C s , atmospheric pressure BP Rel ;

[0013] S3, using the ambient temperature t during calibration Rel Calculate the saturated water vapor pressure WVP max ;

[0014] S4. Using ambient humidity H Rel , saturated water vapor pressure WVP max Calculate the corrected water vapor pressure WVP Rel ;

[0015] S5. Using water vapor pressure WVP Rel and atmospheric pressure BPRel Calculate the oxygen partial pressure ppO2;

[0016] S6. Calculate oxygen concentration V using oxygen partial pressure ppO2 S ;

[0017] S7. Use the oxygen concentration Vs and the sensor output Cs during calibration as the calibration high point to calibrate the oxygen sensor.

[0018] As a further improvement of the above scheme, in step S3, the ambient temperature t Rel Calculate the saturated water vapor pressure WVP max , the calculation formula is:

[0019] (1);

[0020] Wherein, WVP0 is the saturated water vapor pressure at 0°C.

[0021] As a further improvement of the above scheme, in step S4, the ambient humidity H Rel , saturated water vapor pressure WVP max Calculate the corrected water vapor pressure WVP Rel , the calculation formula is:

[0022] (2).

[0023] As a further improvement of the above scheme, in step S5, the water vapor pressure WVP is used Rel and atmospheric pressure BP Rel Calculate the oxygen partial pressure ppO2 using the formula:

[0024] (3).

[0025] As a further improvement of the above scheme, in step S6, the oxygen concentration V is calculated using the oxygen partial pressure ppO2 S , the calculation formula is:

[0026] (4).

[0027] As a further improvement of the above scheme, in step S7, the oxygen concentration Vs and the output Cs of the sensor during calibration are used as calibration high points to calibrate the oxygen sensor. The calculation formula of the oxygen concentration detected by the oxygen sensor after calibration is:

[0028] (5).

[0029] The present invention has positive effects: the on-site accurate calibration method of the electrochemical oxygen sensor in the sulfur hexafluoride distribution device room of the present invention first uses fresh air to ventilate the environment of the oxygen sensor, and then uses the ambient temperature, air pressure and humidity during calibration to calculate the accurate value V of the oxygen concentration during calibration. S , and then use this value and the output value C of the oxygen sensor during detection S The oxygen sensor is calibrated as the calibration high point. After the oxygen sensor is calibrated, the detected oxygen concentration value is more accurate. Therefore, the calibration error caused by the existing calibration method can be overcome and the false alarm or missed alarm of the oxygen sensor can be avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic diagram of the present invention. DETAILED DESCRIPTION

[0031] The technical scheme of the present invention is clearly and completely described below through embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] like Figure 1 A method for accurate on-site calibration of an electrochemical oxygen sensor in a sulfur hexafluoride distribution device room is shown, comprising the following steps:

[0033] S1. Start the ventilation device and circulate the ventilation time period T to ensure that fresh natural air flows evenly to the oxygen meter. The ventilation time T is not less than 15 minutes. Through sufficient ventilation, the air near the oxygen sensor can be fully circulated, making the detected air closer to the fresh air outside the sulfur hexafluoride distribution device room, making the test results more accurate and reliable.

[0034] S2, the ambient temperature during the acquisition and calibration Rel 、Ambient humidity H Rel , sensor output C s , atmospheric pressure BP Rel .

[0035] S3, using the ambient temperature t during calibration Rel Calculate the saturated water vapor pressure WVP max , the calculation formula is:

[0036] (1); where WVP0 is the saturated water vapor pressure at 0°C.

[0037] S4. Using ambient humidity H Rel , saturated water vapor pressure WVPmax Calculate the corrected water vapor pressure WVP Rel , the calculation formula is:

[0038] (2).

[0039] S5. Using water vapor pressure WVP Rel and atmospheric pressure BP Rel Calculate the oxygen partial pressure ppO2 using the formula:

[0040] (3).

[0041] S6. Calculate oxygen concentration V using oxygen partial pressure ppO2 S , the calculation formula is:

[0042] (4).

[0043] S7, using the oxygen concentration Vs and the output Cs of the sensor during calibration as the calibration high point, calibrate the oxygen sensor, and the calculation formula of the oxygen concentration detected by the calibrated oxygen sensor is:

[0044] (5).

[0045] Application Example 1

[0046] Using the method of the above embodiment, the indoor ambient temperature of a power distribution room is 22°C, the ambient humidity is 32%RH, the atmospheric pressure is 986mbar, and the low point oxygen concentration V of a certain oxygen sensor is L The oxygen sensor output is 0% at the low point. L If the calibration method of the present invention is used, after air circulation, the oxygen sensor high point output C S is 11.35mV. Substituting these parameters into formulas (1)-(4), the high point oxygen concentration V is calculated. s In subsequent tests, the oxygen sensor output C rel is 9.87mV, substituting into formula 5,

[0047] .

[0048] The oxygen concentration V can be calculated Rel is 17.99%; if the existing calibration method is used, the high point oxygen concentration V S Directly use 20.95%, then the calculated oxygen concentration V relIt is 18.14%. According to the electric power safety work regulations, alarm ventilation should be performed when the oxygen concentration is lower than 18%. Therefore, the result obtained by the correction method of the present invention should be alarm ventilation, but the existing correction method will not cause alarm ventilation. In this case, there may be leakage of sulfur hexafluoride in the sulfur hexafluoride distribution device room. This underreporting may threaten the personal safety of the staff. Therefore, the correction method of the present invention can improve the accuracy of detection, avoid underreporting or false reporting, and improve the safety of the sulfur hexafluoride distribution device room.

[0049] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for accurate on-site calibration of electrochemical oxygen sensors in a sulfur hexafluoride distribution device room, characterized in that: It includes the following steps: S1. Start the ventilation device and circulate the ventilation time period T to ensure that fresh natural air flows evenly to the oxygen meter; S2, the ambient temperature during the acquisition and calibration Rel 、Ambient humidity H Rel , sensor output C s , atmospheric pressure BP Rel ; S3, using the ambient temperature t during calibration Rel Calculate the saturated water vapor pressure WVP max ; S4. Using ambient humidity H Rel , saturated water vapor pressure WVP max Calculate the corrected water vapor pressure WVP Rel ; S5. Using water vapor pressure WVP Rel and atmospheric pressure BP Rel Calculate the oxygen partial pressure ppO2; S6. Calculate oxygen concentration V using oxygen partial pressure ppO2 S ; S7, using the oxygen concentration Vs and the sensor output Cs during calibration as the calibration high point to calibrate the oxygen sensor; In step S3, the ambient temperature t Rel Calculate the saturated water vapor pressure WVP max , the calculation formula is: Where WVP0 is the saturated water vapor pressure at 0°C; In step S4, the ambient humidity H Rel , saturated water vapor pressure WVP max Calculate the corrected water vapor pressure WVP Rel , the calculation formula is: In step S5, the water vapor pressure WVP is used Rel and atmospheric pressure BP Rel Calculate the oxygen partial pressure ppO2 using the formula: In step S6, the oxygen concentration V is calculated using the oxygen partial pressure ppO2. S , the calculation formula is: In the step S7, the oxygen concentration Vs and the output Cs of the sensor during calibration are used as the calibration high point to calibrate the oxygen sensor. The calculation formula of the oxygen concentration detected by the oxygen sensor after calibration is:

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