Novel density meter for switchgear and calculation method of gas density
Technical Field
The disclosure relates to the field of pressure monitoring of SF6 gas in switchgear, and in particular relates to a novel density meter for switchgear and a calculation method for gas density.
Background
SF6 gas is used as an ultrahigh voltage insulating medium material, can effectively play an arc extinguishing role, and is widely applied to equipment such as circuit breakers of transformer substations, GIS and the like. However, the pressure of the SF6 gas seriously affects its arc extinguishing performance:
1. when the gas pressure is too low, the arc extinguishing capability of the circuit breaker is greatly reduced, and SF6 gas is more easily decomposed into toxic gases such as thionyl fluoride (SOF2) and Hydrogen Fluoride (HF), and meanwhile, the material is corroded;
2. when the gas pressure is too high, the mechanical life of the circuit breaker is shortened, and SF6 gas may be liquefied and lose the arc extinguishing capability.
Therefore, the pressure of the SF6 gas within the switchgear needs to be monitored. The traditional monitoring mode is mainly to monitor through a density meter installed on equipment.
The traditional monitoring mode has the following problems:
1. traditional densitometers monitor "the pressure (Mpa) of the gas in the switch when converted to 20 c" rather than the actual pressure in the gas chamber. When the circuit breaker and the GIS normally work, under the influence of load and loop resistance, the temperature of SF6 gas is inconsistent with the ambient temperature of a density meter, so that the density meter cannot correctly compensate the pressure change of SF6 gas caused by temperature, and the density of the SF6 gas in a gas chamber cannot be correctly monitored. This probably causes the circuit breaker not to block when should block, and the mistake is blocked when not should block, has the potential safety hazard.
2. The monitoring of the density meter on the pressure value is a mechanical conduction indication, the regulation of the standard fine rule of the national power grid company transformation detection general management regulation 39 th registration SF6 density meter (relay) calibration in 3.4.3 specifies that the indication value data of the SF6 density meter (relay) is estimated and read according to 1/5 of the division value, and simultaneously, the device error, the method error and the accidental error exist, the measurement error is larger, and the maximum error can reach 4%.
3. When gas leakage occurs, due to the action of temperature rise, more SF6 gas is leaked from the gas chamber than when the circuit breaker is out of operation, so that the electric shock of the density relay can be closed, and an alarm/locking signal is sent out. This may cause the pressure in the gas chamber not meeting the arc extinguishing condition when leakage is found, and at this time, fault tripping occurs, and the circuit breaker may have arc extinguishing failure and other phenomena, resulting in more serious accidents.
4. The manual work is needed to regularly tour, and a large amount of manpower and material resources are consumed.
Disclosure of Invention
The object of the present application is to solve the above problems by providing a new type of density meter for switchgear and a method for calculating the gas density.
In a first aspect, the present application provides a novel densitometer for a switchgear, including a central controller, a touch and display screen, a wireless transmission module, a temperature sensor, an air pressure sensor, a power module.
The central controller receives data of the temperature sensor and the air pressure sensor through the wireless transmission module, performs filtering operation on the received data, and then compensates the data through a Bridgman algorithm to obtain the actual density of the detected gas;
the temperature sensor is arranged on the air chamber shell closest to the contact of the switch device and used for measuring the actual working temperature of the switch device and sending the detected temperature data to the central controller;
the air pressure sensor is arranged on a three-way valve of the switch device and used for measuring the pressure of SF6 gas in the air chamber of the switch device and sending detected pressure data to the central controller.
According to the technical scheme provided by the embodiment of the application, the touch and display screen is used for displaying gas temperature data, pressure data and density data and providing a man-machine interaction interface.
According to the technical scheme provided by the embodiment of the application, the power supply module is used for providing direct current supply for the central controller, the touch and display screen and the wireless transmission module.
According to the technical scheme provided by the embodiment of the application, the power supply module is a three-port power supply structure formed by the storage battery and the external power supply.
In a second aspect, the present application provides a novel density meter for a switchgear comprising the steps of:
receiving temperature data of a temperature sensor and pressure data of an air pressure sensor;
filtering the temperature data and the pressure data;
and substituting the temperature data and the pressure data into a Bridgman algorithm to calculate the actual density of the gas.
According to the technical scheme provided by the embodiment of the application, the step of substituting the temperature data and the pressure data into the Bridgman algorithm to calculate the actual density of the gas specifically comprises the following steps:
the Bridgman algorithm formula:
P=(R×T×B-A)×C2+R×T×C (1)
in the above formula, A is 73.882 × 10-5+5.132105×10-7×C,B=2.50695×10-3-2.12238×10-6×C,R=56.9502×10-5(bar×m3K), P in bar, T in K, C in gas density in kg/m3;
Converting the temperature data into absolute temperature T1, substituting T in formula (1), substituting pressure data P1 in P in formula (1), and obtaining the value C1 of the theoretical density of the gas;
substituting the numerical value of C1 into C in formula (1), substituting the numerical value of T2 being 20+273 into T in formula (1), and obtaining the actual gas pressure P2;
the value of P2 is substituted into P in equation (1), and the value of T1 is substituted into T in equation (1), to obtain the value of C2 of the actual gas density.
The invention has the beneficial effects that: the application provides a novel density meter for switch equipment and a calculation method of gas density, the novel density meter can accurately measure the actual state of gas, and the potential safety hazard of circuit breaker damage caused by inconsistency between the meter reading and the actual gas pressure is avoided; through monitoring and analyzing data by the background, the state of each substation switching device can be predicted in advance, so that the suspected fault device is supervised mainly and overhauled and replaced in advance, and accidents such as equipment damage, cabinet ignition, large-scale power failure and the like caused by overheating of a breaker or leakage of an air chamber and the like are avoided; the gas state data are transmitted to the terminal in real time in a wireless transmission mode, online monitoring is facilitated, and potential safety hazards and inconvenience caused by live inspection are avoided; meanwhile, temperature data and gas pressure data are collected, and pressure data are compensated by using the temperature data through a Bridgman algorithm, so that errors caused by inconsistency of the environment temperature of a density meter and the actual temperature of gas are avoided; the digital display avoids errors caused by estimation and reading, and further improves the measurement accuracy.
Drawings
FIG. 1 is a schematic block diagram of a first embodiment of the present application;
FIG. 2 is a schematic diagram of the electrical connections between the central controller and other components in the first embodiment of the present application;
fig. 3 is a flowchart of a second embodiment of the present application.
Detailed Description
In order that those skilled in the art will better understand the technical solutions of the present invention, the following detailed description of the present invention is provided in conjunction with the accompanying drawings, and the description of the present section is only exemplary and explanatory, and should not be construed as limiting the scope of the present invention in any way.
Fig. 1 is a schematic diagram of a first embodiment of the present application, which includes a central controller, a touch and display screen, a wireless transmission module, a temperature sensor, an air pressure sensor, and a power supply module.
The central controller is used as the core of the density meter, receives data of the temperature sensor and the air pressure sensor through the wireless transmission module, performs filtering operation on the received data, and then compensates the data through a Bridgman algorithm to obtain the actual density of the detected gas.
The temperature sensor is arranged on the housing of the gas chamber closest to the contacts of the switchgear for measuring the actual operating temperature of the switchgear, and therefore it is necessary to respond quickly to temperature changes and convert the temperature into digital signals for transmission to the central controller.
The air pressure sensor is arranged on a three-way valve of the switch device and used for measuring the pressure of SF6 gas in the air chamber of the switch device and sending detected pressure data to the central controller.
The wireless transmission module is used for realizing the communication among the temperature sensor, the air pressure sensor and the central controller, and simultaneously, the electromagnetic spectrum characteristics in the transformer substation are considered, so that the wireless communication of the density meter is ensured not to interfere with other devices in the substation.
The power module is used for providing continuous and stable direct current power supply for the density meter, the reliability of the power module directly influences the service life of an internal chip and other elements, and therefore a three-port power supply mode formed by a storage battery and an external power supply is adopted, high-quality stable voltage is guaranteed to be output, and meanwhile the storage battery can replace the continuous power supply when the commercial power is interrupted.
In a preferred embodiment, the touch and display screen is used for displaying gas temperature data, pressure data and density data and providing a man-machine interaction interface.
Fig. 2 is a schematic diagram showing the signal connection between the central controller and other parts in the first embodiment of the present application.
Fig. 3 is a flow chart of a second embodiment of the present application, which is a method for calculating gas density by using the density table of the first embodiment, and includes the following steps:
and S1, receiving temperature data of the temperature sensor and pressure data of the air pressure sensor.
And S2, filtering the temperature data and the pressure data.
And S3, substituting the temperature data and the pressure data into a Bridgman algorithm, and calculating to obtain the actual density of the gas.
In this embodiment, the step S3 specifically includes:
the Bridgman algorithm formula:
P=(R×T×B-A)×C2+R×T×C (1)
in the above formula, A is 73.882 × 10-5+5.132105×10-7×C,B=2.50695×10-3-2.12238×10-6×C,R=56.9502×10-5(bar×m3K), P in bar, T in K, C in gas density in kg/m3;
Converting the temperature data into absolute temperature T1, substituting T in formula (1), substituting pressure data P1 in P in formula (1), and obtaining the value C1 of the theoretical density of the gas;
substituting the numerical value of C1 into C in formula (1), substituting the numerical value of T2 being 20+273 into T in formula (1), and obtaining the actual gas pressure P2;
the value of P2 is substituted into P in equation (1), and the value of T1 is substituted into T in equation (1), to obtain the value of C2 of the actual gas density.
The principles and embodiments of the present application are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts of the present application. The foregoing is only a preferred embodiment of the present application, and it should be noted that there are objectively infinite specific structures due to the limited character expressions, and it will be apparent to those skilled in the art that a plurality of modifications, decorations or changes may be made without departing from the principle of the present application, and the technical features described above may be combined in a suitable manner; such modifications, variations, combinations, or adaptations of the invention using its spirit and scope, as defined by the claims, may be directed to other uses and embodiments, or may be learned by practice of the invention.