A method for detecting the state of a frame switch based on lateral differential power loss

Abstract

The present invention discloses a method for detecting the state of a frame switch based on lateral differential of power loss. By collecting the three-phase voltages U a1 、U b1 、U c1 of the bus connected to the frame switch, the three-phase voltages U a2 、U b2 、U c2 at the outlet point of the frame switch, and the currents Ia, Ib, and Ic flowing through each phase of the frame switch, the absolute value of the longitudinal power difference between the active power flowing into and out of the frame switch in each phase at the same moment is calculated, and the longitudinal power differences are pairwise subtracted laterally, and further the minimum value ΔP min and the maximum value ΔP max of the lateral differences are obtained, and the differential ratio K between the minimum value and the maximum value of the lateral difference of the power loss is calculated. The alarm delay and even the trip outlet are determined by the magnitude of the K value. The present invention can identify in real time the impedance change in any link inside the frame switch, and give different alarm messages according to the degree of change, so as to achieve the purpose of detecting the state of the frame switch.

Description

Technical Field

[0001] The present invention belongs to the technical field of frame switch element state detection, and particularly relates to a frame switch state detection method based on power loss transverse differential. Background Art

[0002] The contacts and opening / closing structures in the three compartments of the main circuit frame switch, especially the moving and static contacts, knife contacts of the frame switch, and the joint parts of the cable inlets and outlets, after long-term oxidation and wear, and sometimes mechanical looseness, are very likely to increase the contact resistance at the connection; at the same time, these components of the main circuit frame switch operate under full load of large current and high voltage for a long time. When current flows through, the temperature at the contact will rise and generate heat. If the heat is not dissipated in time, over time, the equipment will be in a high-temperature environment for a long time, which is likely to cause the aging of the insulating materials inside the frame switch cabinet, resulting in oxidation at the contacts, further increasing the contact resistance, causing a vicious cycle. If this hidden danger is not discovered early, when a short-circuit hidden danger occurs, the current flowing through the main frame switch equipment will be dozens of times higher than the normal load, and the generated heat will increase sharply, leading to local welding and causing serious accidents. In order to discover the hidden danger early, currently, temperature sensors are generally selected to be installed at key points such as moving contacts and cable joints, and the occurrence of abnormalities is judged by monitoring the temperature change. However, this method of measuring temperature has the following problems when used:

[0003] Since the main frame switches are all high-voltage equipment with complex structures and many links, on the one hand, it is difficult to fully cover the installation of temperature sensors, and for the temperature of the contacts inside the frame switch, indirect methods are generally used for measurement; at the same time, since the temperature sensors need to be in direct contact with high-voltage equipment, the transmission of temperature signals is relatively complex and the technical difficulty is high. Currently, various commercial temperature measurement methods have their limitations.

[0004] The temperature measurement method through temperature sensors is easily affected by environmental ventilation and heat dissipation conditions. At the same time, due to factors such as high temperature and mechanical vibration, the temperature measurement sensors may become loose or fall off, and thus it cannot be guaranteed that the temperature measured by the temperature measurement system can truly reflect the operating state of the equipment, and it will also cause additional failure risks.

[0005] The temperature measurement method through temperature sensors requires adding equipment to high-voltage equipment, and this method is costly; at the same time, since the temperature measurement system itself is in direct contact with high-voltage equipment, the later operation and maintenance are not convenient, thus increasing the failure risk of the power supply system. Summary of the Invention

[0006] In order to solve the above problems, the present invention provides a frame switch state detection method based on power loss transverse differential.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method for detecting the state of a frame switch based on power loss transverse differential includes the following steps:

[0009] Step 1: Synchronously collect the three-phase bus voltages U a1 、U b1 、U c1 connected to the frame switch, the three-phase voltages U a2 、U b2 、U c2 at the outlet point of the frame switch, and the currents Ia, Ib, Ic flowing through each phase of the frame switch, and calculate the absolute value of the longitudinal power difference of the active power flowing into and out of the frame switch for each phase at the same moment;

[0010] Step 2: Perform pairwise subtraction of the three power differences transversely to obtain three power loss transverse differences, and find the minimum and maximum values of the three power loss transverse differences;

[0011] Step 3: Calculate the current power loss over-limit threshold ΔP set ;

[0012] Step 4: Determine whether ΔP max <ΔP set holds.

[0013] Further, in Step 2: Obtain three power loss transverse differences ΔP AB 、ΔP BC 、ΔP CA , and find the minimum value ΔP min and the maximum value ΔP max of the three power loss transverse differences;

[0014] ΔP max =max{|ΔP AB |、|ΔP BC |、|ΔP CA |}

[0015] ΔP min =min{|ΔP AB |、|ΔP BC |、|ΔP CA |}

[0016] Further, in Step 3, according to the comprehensive contact resistance Rset of the frame switch and the current flowing through the frame switch, calculate the current power loss over-limit threshold ΔP set :

[0017] ΔPset = (max{Ia, Ib, Ic}) 2 *Rset*0.25

[0018] Further, in step 4: Determine ΔP max < ΔP set Whether it holds. If it holds, it is determined as an abnormal state and the power loss transverse differential ratio K is calculated. Otherwise, it is determined that the frame switch state is normal, where:

[0019] K = ΔP min / ΔP max

[0020] If ΔP max > ΔP set , then corresponding alarms or trips are given according to the value range of the power loss transverse differential ratio K:

[0021] If K > 0.5, an alarm for aging of the detection link is given;

[0022] If K < 0.5, an alarm for abnormality of the detection link is given.

[0023] Further, in step 1, the synchronous sampling rate is not less than 4000 Hz.

[0024] Compared with the prior art, the technical progress achieved by the present invention lies in:

[0025] By synchronously and real-time collecting the voltages at the inlet and outlet of the frame switch and the current flowing through the frame switch, calculating the longitudinal active power loss of each phase of the frame switch at the same moment, and further obtaining the difference in the three-phase transverse active power loss of the frame switch. The method of using an adaptively dynamically obtained power loss difference threshold and the reverse characteristic of the ratio of the power loss difference to judge the state of the frame switch has high reliability and safety, can identify the impedance change of any link inside the frame switch in real time, and give different alarm information according to the degree of change, so as to achieve the purpose of detecting the state of the frame switch. This method can directly detect the electrical power loss, is not affected by the operating environment, the system is simple, does not require additional detection sensors, avoids the situation of installing temperature sensors on the terminal posts of the frame switch, overcomes the problem that the measurement accuracy of the temperature sensor is affected by environmental factors, and there is no insulation problem of the temperature sensor, improving the accuracy, economy and convenience of the state detection of the power frame switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and are used together with the embodiments of the present invention to explain the present invention, and do not constitute a limitation to the present invention.

[0027] In the drawings:

[0028] Figure 1 This is the flowchart for detecting the status of the frame switch in the present invention.

[0029] Figure 2 This is the system diagram for detecting the status of the frame switch in the present invention. Specific Embodiments

[0030] The following specific embodiments can be combined with each other. For the same or similar concepts or processes, they may not be repeated in some embodiments. The embodiments of the present invention will be described below with reference to the accompanying drawings.

[0031] Combined with Figure 1 and Figure 2 As shown, the present invention discloses a method for detecting the status of a frame switch based on lateral differential of power loss, including the following steps:

[0032] (1) Synchronously collect the three-phase bus voltages U a1 , U b1 , U c1 connected to the frame switch, the three-phase voltages U a2 , U b2 , U c2 at the outlet point of the frame switch, and the currents Ia, Ib, Ic flowing through each phase of the frame switch, and then calculate the absolute value of the longitudinal power difference (i.e., power loss) flowing in and out of each phase of the frame switch at the same moment;

[0033] (2) Horizontally subtract the three power differences pairwise to obtain three lateral power loss differences ΔP xx (for AB, BC, and CA phases), and find the minimum value ΔP min and the maximum value ΔP max of the three lateral power loss differences. The calculation method is as follows:

[0034] ΔP max = max{|ΔP AB |, |ΔP BC |, |ΔP CA |}

[0035] ΔP min = min{|ΔP AB |, |ΔP BC |, |ΔP CA |};

[0036] (3) Calculate the current power loss overlimit threshold ΔP set according to the comprehensive contact resistance Rset under normal conditions of the frame switch and the current flowing through the frame switch:

[0037] ΔP set= (max{Ia, Ib, Ic}) 2 *Rset*0.25

[0038] where Rset is the comprehensive resistance of each link between two voltage acquisition points under normal conditions of the frame switch.

[0039] (4) If ΔP max < ΔP set , the detection link is in normal state, return to (1) for continuous detection. If ΔP max < ΔP set holds, it is determined that the state is abnormal and the lateral differential ratio K of power loss is calculated. Otherwise, it is determined that the frame switch is in normal state, where:

[0040] K = ΔP min / ΔP max

[0041] (5) If ΔP max > ΔP set , corresponding alarms or trips are given according to the value range of the lateral differential ratio K of power loss: if K > 0.5, an alarm of aging of the detection link is given; if K < 0.5, an alarm of abnormality of the detection link is given.

[0042] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A method for detecting the state of a frame switch based on transverse differential of power loss, characterized in that, Step 1: Synchronously collect the three-phase voltages U a1 , U b1 , U c1 of the bus connected to the frame switch, and the three-phase voltages U a2 , U b2 , U c2 at the outlet point of the frame switch, as well as the currents Ia, Ib, and Ic flowing through each phase of the frame switch, and calculate the absolute value of the longitudinal power difference of the active power flowing into and out of the frame switch for each phase at the same moment; Step 2: Horizontally calculate the differences between every two of the three power differences to obtain three horizontal differences in power losses, and find the minimum and maximum values of the three horizontal differences in power losses; the maximum value of the three horizontal differences in power losses is ΔP max； Step 3: Calculate the current power loss threshold ΔP based on the comprehensive contact resistance Rset of the frame switch and the current flowing through the frame switch set ; Step 4: Determine whether ΔP max <ΔP set holds.

2. The method for detecting the state of a frame switch based on transverse differential of power loss according to claim 1, characterized in that: In step 2: Obtain three lateral power loss differences ΔP AB , ΔP BC , ΔP CA , and find the minimum value ΔP min of the three lateral power loss differences and the maximum value ΔP max ; ΔP max = max{|ΔP AB |, |ΔP BC |, |ΔP CA |} ΔP min = min{|ΔP AB |, |ΔP BC |, |ΔP CA |}.

3. The method for detecting the state of a frame switch based on transverse differential of power loss according to claim 1, characterized in that: In step 3, according to the comprehensive contact resistance Rset of the frame switch and the current flowing through the frame switch, calculate the current power loss overlimit threshold ΔP set : ΔP set = (max{Ia, Ib, Ic}) 2 * Rset * 0.25 4. The method for detecting the state of a frame switch based on transverse differential of power loss according to claim 1, characterized in that: In step 4: Determine ΔP max <ΔP set whether it holds. If it holds, it is determined that the state is abnormal and the power loss transverse differential ratio K is calculated; otherwise, it is determined that the frame switch state is normal, where: K = ΔP min / ΔP max If ΔP max > ΔP set , corresponding alarms or trips are given according to the magnitude range of the power loss transverse differential ratio K value: If K > 0.5, give an aging warning for the detection link; If K < 0.5, give an abnormal warning for the detection link.

5. The method for detecting the state of a frame switch based on transverse differential of power loss according to claim 1, characterized in that: In step 1, the synchronous sampling rate is not less than 4000Hz.

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