Method for evaluating switching events

Abstract

The invention relates to a method for evaluating a switching event in an electromechanical switching device connected to a load current path, comprising the following steps: acquiring a temperature-current intensity value pair (Tm, Im), the temperature-amperage value pair has a temperature measurement value (Tm) of the temperature measured at a temperature measurement point (X) of the switching device (10) and a amperage measurement value (Im) of the current (I) flowing through the load current path measured concurrently with the temperature measurement value (Tm); -recording said pairs of temperature-amperage values acquired at different points in time; comparing at least one temperature-amperage value pair at a point in time before the switching event with at least one temperature-amperage value pair at at least one point in time after the switching event; and evaluating the switching event based on the comparison.

Description

Technical Field

[0001] This invention relates to a method for evaluating switching events. Background Technology

[0002] Electromechanical switches and protective devices use movable contacts for switching. Due to these switching events and environmental influences, such as corrosion, the contact surface and thus the contact resistance change. The environmental influences cause this change more slowly, while the change occurs more suddenly during a switching event.

[0003] During each switching event, whether turning on or off, especially under higher current and voltage, the material on the contact surface rearranges, potentially causing a sudden increase or decrease in contact resistance. Increased contact resistance leads to increased power consumption and consequently, a rise in device temperature. Therefore, it cannot be ruled out that the switching device may enter a critical thermal state due to a switching event, even with sufficient contact material remaining. Consequently, switching events can cause the switching device to overheat, potentially leading to malfunction or fire. Summary of the Invention

[0004] To mitigate such risks, it may be useful to determine the current state of electromechanical switchgear after a switching event. Therefore, a method for evaluating switching events in electromechanical switchgear is needed.

[0005] This task is solved by the method according to claim 1. It relates to a method for evaluating switching events in an electromechanical switching device connected to a load current path. The term "electromechanical switching device" herein includes every electromechanical switch and protection device having movable switch contacts. Here, it is irrelevant whether the switching device is a multiple-disconnection or single-disconnection device. The manner in which the switch is triggered, such as an actuator, magnetic latching relay, or switch lock, is also irrelevant. This invention is applicable to all types of switching devices with movable switch contacts. The contact-based switching devices to which this invention is applicable follow different basic concepts. On the one hand, they are switching devices with single or multiple-disconnection contacts, whether linear or rotary. Furthermore, these switching devices are operated or driven in different ways. Switchable spring accumulators can be used, such as bistable switch locks in MCBs (Miniature Circuit Breakers) and MCCBs (Molded Base Circuit Breakers), or tensionable spring accumulators can be used, such as in ACBs (Air Circuit Breakers). Similarly, contactor contacts can be manipulated by means of magnetic actuators. Even direct engagement of knife contacts, such as in LBSs (Load Break Switches), is possible. The introduction of force or energy can be done manually, by a motor, or, in the case of a contactor, by applying voltage. However, all other possible implementations of switching devices with contacts are also included.

[0006] The switching device is connected to the load current path. Through the load current path, electrical energy is transferred from a power source, such as a power supply network providing network voltage, to the electrical load, also known as an electrical consumer, such as a motor. The load current path can, for example, be constructed as a three-phase current conductor. Here, the switching device can have input terminals (e.g., L1, L2, L3) and output terminals (e.g., T1, T2, T3), wherein the end of the current conductor connected to the power source (network voltage) is connected to the input terminals, and the end of the current conductor connected to the consumer is connected to the output terminals. An electromechanical switching device is provided inside the switching device, configured such that, in the first switching state (switching state "closed"), the connection between the input and output terminals is electrically conductive, i.e., an electromechanical switch with closed contacts, and in the second switching state (switching state "open"), the connection between the input and output terminals is electrically non-conductive, i.e., an electromechanical switch with open contacts. The switching from one of the two switching states to the other is called a switching event.

[0007] The method includes a step in which temperature-current intensity pairs are acquired. The temperature-current intensity pairs here include temperature measurements taken at the temperature measurement point of the switching device. The temperature-current intensity pairs also include current intensity measurements of the current flowing through the load current path, which are measured simultaneously with the temperature measurements.

[0008] Temperature measurements are the values ​​determined by temperature sensors. The temperature measurement point is located inside the switching equipment, either within the internal space of the equipment housing or on the outer surface of the housing, where the temperature sensor can be positioned to measure the temperature. Current intensity measurements are the values ​​of current intensity determined by current sensors.

[0009] The method includes a step in which the temperature-current intensity value pairs are recorded at different time points. Thus, a time series of temperature-current intensity value pairs is recorded, wherein a first subset of the time series is acquired before the switching event, and a second subset of the time series is acquired after the switching event. The time series of measurements is a sequence of measurements arranged in chronological order; here, the measurements can be acquired at arbitrary time intervals.

[0010] The method includes a step in which at least one pair of temperature-current intensity values ​​at a time point prior to a switching event is compared with at least one pair of temperature-current intensity values ​​at at least one time point after the switching event. This comparison includes a comparison of temperature measurements and a comparison of current intensity measurements.

[0011] The method includes a step in which the switching event is evaluated based on the comparison. In principle, the greater the current intensity (power) switched by the switching event, the greater the contact change caused by the switching event on average. This means that, on average, a switching event at rated current causes less contact wear than an overload switching event, and an overload switching event causes less contact wear than a short-circuit switching event. The greater the contact change (contact wear) caused by the switching event, the greater the probability that the contact resistance in the switching device after the switching event, and therefore the heat generated, is greater than before the switching event. The evaluation results can, for example, be used for contact wear indication.

[0012] This invention is based on the idea that, in order to evaluate a switching event in an electromagnetic switching device, the overall contact state (=contact state) before and after the switching event is observed. The contact state in an electromagnetic switching device is reflected in the temperature present within that device. Therefore, according to this invention, temperature is used as a measurement variable to evaluate a switching event because it best describes the quality of the overall contact state (=contact state) in an electromagnetic switching device. The essential difference from conventional methods for evaluating switching events lies in using temperature measurements for evaluation, and evaluating them as a function of time, thereby determining the time trend and the thermal life of the contacts, particularly the remaining thermal life. In this way, the condition of the switching device can be monitored based on its quality characteristic, i.e., temperature. Furthermore, a prediction of the contact thermal life can be derived. This predicted life can be shorter than the life predicted based on the current measured temperature, which does not consider previously collected temperature measurements.

[0013] The more measurements there are, the more reliably the trend of the contact state can be mapped; therefore, it is advantageous to average the temperature measurements to obtain sufficient smoothing of the measurements.

[0014] Advantageous configurations and improvements of the invention are given in the dependent claims. The method of the invention can also be modified according to the dependent device claims, and vice versa.

[0015] According to a preferred embodiment of the invention, a temperature sensor is arranged in the load current path of the switching device. This relates to a load current path that can be switched via the switching contacts of the switching device. Since in many cases the contact point, i.e., the point where the contacts touch each other, cannot be selected for temperature measurement, the nearest suitable point can be selected instead. In this way, the thermal critical point (=hot spot) in the switching device is detected. To evaluate the contact condition, the temperature at the hot spot before and after the switching event is evaluated.

[0016] According to a preferred embodiment of the invention, the comparison of temperature-current intensity values ​​before and after a switching event includes a comparison of absolute temperature values ​​Tabs. The change or temperature difference of absolute temperature Tabs ΔT = Tabs – Tamb, where Tamb is the ambient temperature of the switching device and can be used as a measure of the switching event, i.e., the change in contact state.

[0017] According to a preferred embodiment of the invention, temperature measurements are correlated with different temperature thresholds corresponding to the limit temperatures of the switching equipment. Since the limit temperatures are known for the switching equipment, they can be used for evaluation. Alternatively, the operator of the switching equipment may set known limit temperatures or warning thresholds themselves in this evaluation method.

[0018] The extreme temperature limit of a switchgear can be considered its permissible temperature. The permissible temperature of a switchgear is defined by an organization familiar with the materials used in the switchgear, such as the manufacturer or operator. The permissible temperature constitutes the upper limit of a first temperature range within which the switchgear will not thermally age faster. Within this first temperature range, thermal life decreases over time; for example, thermal life decreases by 24 hours over a 24-hour period.

[0019] The limiting temperature value of a switchgear can be considered its maximum permissible temperature. The maximum permissible temperature of a switchgear is defined by an organization familiar with the materials used in the switchgear, such as the manufacturer or operator of the switchgear. The maximum permissible temperature constitutes the upper limit of a second temperature range in which the switchgear ages faster due to increased temperature than in the first temperature range. Within this second temperature range, which includes all temperature values ​​greater than the permissible temperature and less than or equal to the maximum permissible temperature, the rate of decrease in thermal life is faster than the passage of time; for example, the thermal life decreases by more than 24 hours in 24 hours, such as 28 hours. Materials, such as plastics, have specific temperature-time characteristic curves for their material properties. These temperature-time characteristic curves take into account the assurance of important material properties such as strength or electrical insulation capabilities. The permissible temperature of a material can be determined from the temperature-time characteristic curve. As long as the permissible temperature is not exceeded, the material can withstand that permissible temperature without problems for a long period, such as 25 years, without damage. Furthermore, the maximum permissible temperature can also be determined from the temperature-time characteristic curve. For the maximum permissible temperature, the rated limit can be derived from the strength limit value.

[0020] For example, the area between the nominal temperature and the maximum permissible temperature can be divided into three or more evaluation zones. For instance, the first evaluation zone is "green," where the temperature rises or falls slightly, for example, <10%; the second evaluation zone is "yellow," where the temperature rises or falls significantly, for example, 10% to 30%; the third evaluation zone is "orange," where the temperature rises or falls, for example, 30% to 50%; and the fourth evaluation zone is "red," where the temperature rises or falls, for example, >50%. Alternatively, any other type of visualization can be used.

[0021] According to a preferred embodiment of the invention, a comparison of temperature-current intensity pairs before and after a switching event is performed based on calculated values ​​derived from temperature measurements. These calculated values ​​may also be referred to as characteristic values.

[0022] According to a preferred embodiment of the invention, the calculated value is a quotient Q, which is formed by dividing the temperature measurement value Tm by the associated current intensity measurement value Im: Q = Tm / Im, or by the squared associated current intensity measurement value Im: Q = Tm / Im². Here, the associated current intensity measurement value Im is the measurement value of the current flowing through the load current path, and these measurements are taken simultaneously with the temperature measurement value Tm at a current intensity measurement point Q of the switching device.

[0023] According to a preferred embodiment of the invention, the calculated value is equal to a dimensionless quotient Q, which is formed by dividing the temperature measurement value Tm by the temperature reference value Tref: Q = Tm / Tref. This quotient Q describes the ratio of the absolute measured temperature Tm to the reference temperature Tref, for example, in the case of a new switchgear at the rated current I_standard: Q = Tm / Tref(@I_standard). The reference temperature Tref can refer to a new circuit breaker. The reference temperature Tref can refer to a circuit breaker in the standard test setting DIN EN 60947-2:2020-11 Low-voltage switchgear - Part 2: Circuit breakers. The reference temperature Tref can also refer to the permissible temperature of the materials used in the switchgear that constitute the thermal weak points of the switchgear. However, any other temperature comparison variable can also be used as the reference temperature Tref.

[0024] According to a preferred embodiment of the invention, comparing at least one temperature-current intensity value pair at a time point before the switching event with at least one temperature-current intensity value pair at a time point after the switching event is achieved by dividing calculated values ​​from one or more measurement time points before the switching event by calculated values ​​from one or more measurement time points after the switching event. The switching event is then evaluated based on this comparison.

[0025] According to a preferred embodiment of the invention, the comparison of temperature-current intensity values ​​before and after a switching event includes dividing the temperature values ​​before and after the switching event. This generates dimensionless characteristic values. A value of 1 indicates that the switching event did not cause any change, a value < 1 indicates an improvement in the contact condition, and a value > 1 indicates a deterioration in the contact condition. Alternatively, dimensionless characteristic values ​​can be generated in different ways, such that other values ​​represent unchanged, improved, or deteriorated contact conditions.

[0026] According to a preferred embodiment of the invention, evaluating switching events includes classifying them into switching events under normal operating current, switching events under overload current, or switching events under short-circuit current. A switching event under normal operating current means that the current intensity is approximately equal to the rated current; at such current intensity, the contacts typically experience only small and slow changes. Under overload current, the contacts typically experience a larger change than under rated current. Under short-circuit current, the contacts typically experience the largest change; for example, according to the circuit breaker standard DINEN IEC 60947-2, such a switching device is designed to withstand three such maximum switching events.

[0027] According to a preferred embodiment of the invention, the method includes the step of dividing the current intensity range covered by the recorded current intensity measurements into two or more current levels. A current level is a current intensity range located between a lower limit boundary and an upper limit boundary. Here, current levels corresponding to a portion of the rated current range In of the switching device can be formed, such as (0.5 ± 0.05) x In, (0.6 ± 0.05) x In, (0.7 ± 0.05) x In, etc. Another alternative suggestion for current levels is, for example, 30-40% / 40-50% / 50-60% / 60-70% / 70-80% / 80-90% of the rated current In of the switching device. The recorded temperature-current intensity value pairs are respectively classified into the current level to which the current intensity measurement of that temperature-current intensity value pair belongs. For temperature-current intensity pairs within the same current level, at least one temperature-current intensity pair at a time point before the switching event is compared with at least one temperature-current intensity pair at a time point after the switching event.

[0028] For defined time intervals with a constant current intensity, the temperature at that time is measured. A constant current intensity exists as long as the current intensity is within a predefined current intensity range [I-; I+], i.e., between the lower limit boundary I- and the upper limit boundary I+. The corresponding temperature-current intensity pairs are stored. After a switching event, the temperature is again obtained for other time intervals with a constant current intensity. After comparing at least one temperature-current intensity pair at a time point after the switching event with at least one temperature-current intensity pair at a time point before the switching event, the contact state is evaluated if the compared pairs are in the same current level.

[0029] According to a preferred embodiment of the invention, temperature-current intensity value pairs are acquired only when the temperature measurement value is within a defined temperature tolerance band. The system checks whether temperature fluctuations are within the predefined tolerance band. As long as the temperature fluctuations are outside this tolerance band, the switching device is not yet in thermal equilibrium and cannot allocate temperature to the current value. Once the temperature fluctuations are within the tolerance band, the switching device is in thermal equilibrium and can allocate temperature to the current value. Only in thermal equilibrium can temperature-current intensity value pairs be formed and used for comparison.

[0030] According to a preferred embodiment of the invention, the temperature-current intensity pair is formed by averaging multiple individual measurements. To avoid measurement errors, measurements are collected over a time period in which both temperature and current intensity (load) are approximately constant, regardless of whether the measured value is temperature or current intensity. This ensures that no compensation process distorts the evaluation. To further improve the quality of the evaluation, it is advantageous to form an average over such a time period with constant temperature and current intensity measurements.

[0031] According to a preferred embodiment of the invention, it is estimated when a temperature measurement will reach a predefined limit. By comparing the temperature change caused by a switching event at a specific current intensity with the maximum permissible temperature in the switching device, it is possible to estimate how many more interruptions with comparable current intensities can occur before the switching device reaches its maximum permissible temperature and its lifespan ends. This allows for sending a message to the switching device operator, instructing them whether the switching device will be able to withstand the next switching event with a similar current intensity, or whether it will lead to the end of the switching device's lifespan. This estimation can be compared with the number of electrical switching operations given by the switching device manufacturer, or with an algorithm used to determine the remaining contact lifespan. It is possible to preferentially output the result that gives a shorter lifespan in different calculations.

[0032] According to a preferred embodiment of the invention, the method includes a step in which a temperature sensor for acquiring temperature measurements is positioned on the conductive path of the switching contacts of a switching device. Therefore, the temperature is measured on the conductive path of the switching device that carries the load current. In this case, the measurement point is located on the conductive path. If the current sensor is electrically insulated, the measurement point can be located directly on the surface of the conductive path; otherwise, a sufficiently large distance must be maintained from the current-carrying conductive path to ensure that electrical breakdown from the conductive path to the temperature sensor does not occur. Advantageously, the temperature can be measured on the main heat source of the switching device, i.e., the conductive path.

[0033] According to a preferred embodiment of the invention, the temperature is measured at a measurement point on the switching device, wherein the measurement point is a thermal weak point of the switching device. The thermal weak point is either a component near a hot spot or the hot spot itself, wherein the hot spot is the hottest point in the switching device. To determine the thermal weak point, in addition to considering the temperature conditions of the component, the temperature-time characteristic curve of the component's material must also be considered. The determination of the thermal weak point must be performed individually for each switching device. If a true hot spot or a true thermal weak point cannot be selected in the switching device, a suitable nearby measurement point can be selected as an alternative. Attached Figure Description

[0034] In the following description, the invention will be illustrated with reference to several embodiments and the accompanying drawings. The drawings are shown schematically and not to scale:

[0035] Figure 1 Switchgear;

[0036] Figure 2 The T / It graph plots the time curves of temperature and current measurements before and after a switching event.

[0037] Figure 3 :Tt graph, in which the graph is plotted by Figure 2 The time curve of the average temperature formed by the measured values;

[0038] Figure 4 The T / It graph plots the time curves of temperature and current measurements before and after three different switching events.

[0039] Figure 5 The Tt graph plots the time curves of temperature measurements.

[0040] Figure 6 : A Qt plot, which shows the time curve of the dimensionless calculated value Q = T_after / T_before; and

[0041] Figure 7 : EV-t plot, which plots the EV-t graph of the graph. Figure 6 The time curve of the evaluation variable EV formed by the quotient of the calculated values; and

[0042] Figure 8 :flow chart. Detailed Implementation

[0043] Figure 1A switching device 10 for switching load current is shown, the load current flowing through a load current conductor 16 from a voltage source such as a network transformer to an electrical load such as a motor. The switching device 10 has a housing 20 with load current connectors 15, 15', which are divided into input terminals 15 and output terminals 15'. The load current conductor 16 is electrically connected to the load current connectors 15, 15', such that the switching device 10 is connected between the two ends of the load current conductor 16. Inside the housing 20, the load current connectors 15 are electrically connected to the switch contacts 11 of a fixed switch contact pair 11 via conductive paths 14. The switch contacts 11 of the fixed switch contact pair 11 are electrically connected via a movable contact bridge 13 carrying the switch contacts 12 of a movable switch contact pair 12, provided that the contact bridge 13 is in a first closed position; in this position, there is a through electrical connection of the load current connector 15. In the second open position of the contact bridge 13, the two switch contacts 11 of the fixed switch contact pair 11 are electrically isolated; in this position, the load current connector 15 is electrically isolated. The actuator unit 17 is capable of moving the contact bridge 13 back and forth between the two positions; such a positional change of the contact bridge 13 constitutes a switching event. Such a switching event is triggered by manipulating the actuator unit 17 to make a positional change. The manipulation of the actuator unit 17 can be performed internally in the switching device 10, for example, in a line protection switch, by thermal or magnetic triggering. Such manipulation of the actuator unit 17 can also be performed by an external control signal, for example, in a contactor by a control command guided to the control current connector 18 of the actuator unit 17 via the control wire 19.

[0044] Inside the housing 20, a temperature sensor 23 is arranged at the first measurement point X, i.e., the temperature measurement point. The first measurement point X is located on the conductive path 14 of the switching device 10. This is the hottest spot of the switching device 10, the so-called "hot spot". The temperature measurement value collected by the temperature sensor 23 is transmitted to the evaluation unit 30 via the data cable 24.

[0045] Inside the housing 20, a current sensor 21 is arranged at the second measurement point Y, i.e., the current intensity measurement point. The second measurement point Y is located on the conductive path 14 of the switching device 10. The current measurement value collected by the current sensor 21 is transmitted to the evaluation unit 30 via the data cable 22.

[0046] The evaluation unit 30 has a calculation unit that can compare the received temperature measurements and, if necessary, determine the thermal life LD(T) of the switchgear 10. The comparison result determined by the evaluation unit 30 can be transmitted to the human-machine interface (HMI) 32 via the transmission medium 31 and communicated to the user of the switchgear 10 via the HMI 32.

[0047] Figure 2A T / It plot is shown, where temperature T and current intensity I are plotted on the y-axis, and time t is plotted on the x-axis. The plot shows the time curves for the temperature measurement Tm and the current intensity measurement Im. A switching event occurs at time point 35. Switching event 35 is switching event N at rated current, i.e., the current intensity present in the load current path at switching event N is <= IN (IN = rated current of the switching device).

[0048] Here, for a time interval Δt1 to Δt7 during which the current intensity Im is approximately constant in the load current path, temperature and current intensity measurements are collected, forming temperature-current value pairs [Tm_i, Im_i]. To this end, the current intensity range covered by the recorded current intensity measurements Im is divided into multiple current levels 46, each corresponding to a portion of the rated current range In of the switching device, such as (0.5 ± 0.05) x In, (0.6 ± 0.05) x In, (0.7 ± 0.05) x In, etc. The recorded temperature-current intensity value pairs are respectively categorized into the current level 46 to which the current intensity measurement of the temperature-current intensity value pair is located. For temperature-current intensity value pairs within the same current level 46, at least one temperature-current intensity value pair at a time point before switching event 35 is compared with at least one temperature-current intensity value pair at a time point after switching event 35.

[0049] Figure 3 As shown, after switching event 35, the average temperatures Tx, Ty, and Tz before switching event 35 are compared with the average temperatures Tx1, Ty1, and Tz1 after switching event 35. All average temperatures Tx, Ty, Tz, Tx1, Ty1, and Tz1 are formed from temperature measurements Tm within a time interval Δt in which there are approximately the same current intensity. That is, in this example, all average temperatures falling within the 0.5 In current level are therefore directly comparable to each other. Figure 3 The results show that switching event 35 did not cause a significant change in temperature; this is evident from the fact that all temperature averages are within the tolerance band [T-; T+].

[0050] Figure 4 The T / It plot is shown, where temperature T and current intensity I are plotted on the y-axis and time t on the x-axis. The plot shows the time curves for the temperature measurement Tm and the current intensity measurement Im. Here, for a time interval Δt1 to Δt6 where the current intensity Im is approximately constant in the load current path, temperature and current measurements are collected and a temperature-current pair [Tm_i, Im_i] is formed.

[0051] A switching event occurs at times 35, 36, and 37. Switching event 35 is switching event N under rated current, meaning the current intensity in the load current path at switching event N is <= IN (IN = rated current of the switching device). Switching event 36 is switching event O under overload current, meaning the current intensity in the load current path at switching event O is between IN and 6 IN. Switching event 37 is switching event S under short-circuit current, meaning the current intensity in the load current path at switching event S is > 6 IN.

[0052] Here, the range of current intensity covered by the recorded current intensity measurements is divided into multiple current levels 46. Temperature-current value pairs [Tm_i, Im_i] are assigned to these current levels 46, which correspond to portions of the rated current range In of the switching equipment, such as (0.5 ± 0.05) x In, (0.6 ± 0.05) x In, (0.7 ± 0.05) x In, etc.

[0053] The recorded temperature-current intensity pairs are categorized into the current class corresponding to the current intensity measurement of the temperature-current intensity pair. For temperature-current intensity pairs within the same current class, at least one temperature-current intensity pair at a time point before the switching event is compared with at least one temperature-current intensity pair at a time point after the switching event. Therefore, after a switching event (OFF / ON), the temperature measurement before the switching event is compared with the temperature measurement after the switching event, provided that the two temperature measurements were recorded at approximately the same current intensity.

[0054] Figure 5 The Tt graph is shown, plotting the time curve of the temperature measurement after switching event 35. Immediately after switching event 35, the temperature value is still outside the preset tolerance band [Tmax; Tmin]. As long as the temperature fluctuation is outside this tolerance band, the switching device has not yet reached thermal equilibrium, and comparing the temperature measurement values ​​before and after the switching event is meaningless. Once the temperature measurement value is within this tolerance band within the preset time interval Δt_in, thermal equilibrium is reached, and the temperature measurement value can be recorded within the time measurement interval Δt_mess, min = [t_start; t_end]. The temperature measurement values ​​recorded within this time measurement interval Δt_mess, min can be averaged and used for subsequent comparisons with the temperature measurement values ​​recorded before the switching event.

[0055] Figure 6 The comparison between the temperature measurement value before and after the switching event is shown to be based on the calculated value derived from the temperature measurement value. Figure 6 The calculated values ​​Q1, Q2, Q3, Q1N, Q2N, and Q3N are shown. These calculated values ​​are formed by dividing the temperature measurement value Tm or the average temperature formed by multiple temperature measurements by the temperature reference value Tref(@I_standard):

[0056] Q = Tm / Tref(@I_standard)

[0057] Here, the calculated values ​​Q1, Q2, and Q3 before the switch events 35, 36, and 37 to be evaluated are distinguished from the calculated values ​​Q1N, Q2N, and Q3N after the switch events 35, 36, and 37 to be evaluated.

[0058] Figure 7 Another step in the comparison is shown, in which the calculated value QiN after the switch events 35, 36, and 37 to be evaluated is divided by the calculated value Qi before the switch events 35, 36, and 37 to be evaluated, respectively, to obtain the evaluation variable EV:

[0059] EV = QiN / Qi

[0060] A value of 1 indicates that the switch event did not cause any change, a value < 1 indicates that the contact state improved, and a value > 1 indicates that the contact state deteriorated. Figure 7 The data shows that the first quotient Q1N / Q1, involving the first current level, is slightly greater than 1; the second quotient Q2N / Q2, involving the second current level, is approximately equal to 1; and the third quotient Q3N / Q3, involving the third current level, is slightly greater than 1. Therefore, based on this comparison, the switching event assessment might be that, although a switching event is likely to cause a temperature rise, the rise is very small. Thus, the switching event is likely a switching event N within the rated current range.

[0061] Figure 8 This is a flowchart of a method of the present invention for evaluating a switching event in an electromechanical switching device connected to a load current path. In a first step 601, temperature-current intensity value pairs are acquired, including a temperature measurement value taken at a temperature measurement point on the switching device and a current intensity measurement value taken simultaneously with the temperature measurement value of the current flowing through the load current path. In a second step 602, the temperature-current intensity value pairs acquired at different time points are recorded. In a third step 603, at least one temperature-current intensity value pair at a time point before the switching event is compared with at least one temperature-current intensity value pair at at least one time point after the switching event. And in a fourth step 604, the switching event is evaluated based on this comparison.

Claims

1. A method for evaluating switching events in an electromechanical switchgear connected to a load current path, the method comprising the steps of: - Collect temperature-current intensity value pairs (Tm, Im), the temperature-current intensity value pairs having a temperature measurement value (Tm) of the temperature measured at the temperature measurement point (X) of the switching device (10) and a current intensity measurement value (Im) of the current (I) flowing through the load current path, which is measured simultaneously with the temperature measurement value (Tm); - Record the temperature-current intensity pairs collected at different time points; - Compare at least one temperature-current intensity value pair at a time point before the switching event with at least one temperature-current intensity value pair at a time point after the switching event; as well as - The switching event is evaluated based on the comparison.

2. The method according to claim 1, wherein, The comparison of temperature-current intensity values ​​before and after the switching event includes a comparison of absolute temperature values.

3. The method according to any one of the preceding claims, wherein, The comparison of temperature-current intensity values ​​before and after the switching event is based on calculated values ​​derived from temperature measurements.

4. The method according to any one of the preceding claims, wherein, The evaluation of switching events includes classifying them into switching events during normal operation, switching events during overload, or switching events during short circuit.

5. The method according to any one of the preceding claims, wherein, The method includes the following steps: The range of current intensities covered by the recorded current intensity measurements is divided into two or more current levels; The recorded temperature-current intensity pairs are categorized into the current level corresponding to the measured current intensity value of the temperature-current intensity pair. For temperature-current intensity pairs within the same current level, at least one temperature-current intensity pair at a time point before the switching event is compared with at least one temperature-current intensity pair at a time point after the switching event.

6. The method according to any one of the preceding claims, wherein, Temperature-current intensity pairs (Tm, Im) are only collected when the temperature measurement (Tm) is within the defined temperature tolerance band.

7. The method according to any one of the preceding claims, wherein, The temperature-current intensity value is formed by averaging multiple individual measurements.

8. The method according to any one of the preceding claims, wherein, Establish a relationship between temperature measurements and different temperature thresholds corresponding to the extreme temperatures of switching equipment.

9. The method according to claim 8, wherein, Estimate when the temperature measurement will reach a predefined limit value.

10. The method according to any one of the preceding claims, the method comprising the following steps: The temperature sensor (23) used to collect the temperature measurement value (Tm) is positioned on the conductive path (14) of the switch contact of the switching device (10).

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