WO2023031449A1

WO2023031449A1 - Measuring and monitoring method for an insulation device, and a vehicle

Info

Publication number: WO2023031449A1
Application number: PCT/EP2022/074563
Authority: WO
Inventors: Julian NOWROTH
Original assignee: Webasto SE
Priority date: 2021-09-03
Filing date: 2022-09-05
Publication date: 2023-03-09
Also published as: DE102021122817A1

Abstract

A measuring and monitoring method for checking an insulation resistance of an insulation device in an unearthed supply network comprising a battery, wherein the battery is in particular a high-voltage battery (HV battery), by ascertaining a measurement voltage (V_M) across at least one defined resistance for a measurement duration (ΔT) in one of the following measurement branches, specifically measuring it between - the H(+) pole of the battery and the main frame (chassis), - the H(-) pole of the battery and the main frame and/or - the two poles of the battery, and wherein the supply network has a reference voltage (V_R), wherein the reference voltage (V_R) - constitutes the stable, drop-free voltage level in a given target state of the supply network and/or - is reached and/or is defined as reached after a reference duration (⌕T_R). The insulation resistance of the supply network is determined here on the basis of a defined limit voltage gradient (G_VG), wherein the limit voltage gradient (G_VG) is defined as the voltage change (ΔV) per measurement step (Δt_M), and wherein the limit voltage gradient (G_VG) is ascertained in the three measurement branches. The invention furthermore comprises a battery system for a vehicle that comprises a measuring device by way of which the measuring and monitoring method is able to be performed.

Description

Measuring and monitoring method for an isolation device and a vehicle

The present invention relates to a measuring and monitoring method according to the preamble of claim 1 and a battery system according to the preamble of claim 14.

The invention relates to a method for detecting an insulation fault in an electrical supply network, in particular a defect in the insulation of an unearthed power supply unit of a vehicle. Insulation faults can be, for example, an excessive drop in resistance or an electrical short to a ground potential and/or ground potential.

In the present case, an electrical supply network means in particular a circuit with at least one power source, such as an alternator or a battery in a car, and at least one electrical consumer as a current sink, the current sink also being another electrical load (capacitive, inductive and/or ohmic load). can. The at least one current source and the at least one current sink are interconnected via at least one electrical line element, e.g. via at least one cable. If one of the line elements and/or a current sink is damaged mechanically or due to aging, this can lead to an insulation fault or defect.

In a known passive insulation measurement using the 3VM method (three voltmeter method/measuring method), the battery voltage, the H(+) and H(-) pole voltages against the main frame are measured during operation of a vehicle with a fixed cycle , according to the SAE J 1766 standards and, for example, in compliance with manufacturer specifications such as the LV123. Here, the voltage profile over time is measured using a measuring resistor until a stable voltage is reached, so that symmetrical and asymmetrical insulation faults can be measured in DC voltage IT systems.

This fundamentally very accurate and safe, passive insulation measurement is primarily designed to record and monitor the insulation resistance of a specific, known high-voltage system (HV system). In such a case, the basic parameters such as the capacity and the current flow are known with sufficient accuracy. A disadvantage of the 3VM method when used for complex supply networks in operation is that the voltage measurement and the charging and discharging behavior of the capacitive network components until a fixed, saturated voltage due to competing, parallel processes requires a relatively long time, which can be, for example, 20 to 30 seconds. In other words, due to the parasitic capacitances or mains leakage capacitances, the saturated voltage must be measured over a time delay. In order to achieve maximum accuracy, this time delay should be chosen to be as large as possible, which is very disadvantageous. In addition to the operating conditions, environmental influences such as humidity, temperature and aging are also important parameters that affect the voltage measurement.

The object of the present invention is to provide an improved measuring and monitoring method and a battery system that enable reliable monitoring and recording of the insulation parameters, in particular the insulation resistance, even in complex supply networks and in the case of operating and environmental influences that change at short notice.

According to this, the object is achieved by a measuring and monitoring method according to the characterizing features of claim 1, and a battery system according to the characterizing features of claim 14. Exemplary embodiments are described in the associated dependent subclaims.

The measuring and monitoring method for testing an insulation resistance of an insulation device in an unearthed supply network that includes a battery, such as a high-voltage battery (HV battery), for example, provides that a measurement voltage is determined via at least one defined resistance for a measurement period in one of the following measurement branches will, namely between

- the H(+) pole of the battery and the main frame (chassis),

- the H(-) pole of the battery and the main frame and/or

- is measured at the two poles of the battery, and the supply network has a reference voltage, the reference voltage representing the stable, drop-free voltage level for a given TARGET state of the supply network and/or being reached after a reference period and/or being defined as being reached.

Here, the insulation resistance of the supply network is determined on the basis of a defined limit voltage gradient. This limit voltage gradient is defined as the change in voltage per time or measurement step, with the limit voltage gradient being determined in the three measurement branches. The insulation resistance is therefore derived from the three measured voltages and voltage curves. If necessary, the respective measurement voltages at the respective point in time when the limit voltage gradient is recognized as having been reached.

Ideally, the insulation resistance is calculated directly from the three most recently tapped voltages, although a voltage measurement can also be provided immediately downstream in the three measuring branches, on the basis of which the insulation resistance is calculated.

The particular advantage is that maximum accuracy is not striven for at all, but sufficient accuracy is chosen as the decisive factor. This achieves a significant time reduction per measurement Z duration.

With this method, the measurement duration can be selected dynamically and variably. The time at which a measurement is complete or is defined as complete is the identification of a voltage saturation, i.e. the limiting voltage gradient, which is at DV less than or equal to 0.5V / 100ms or > V less than or equal to 0.2V / 100ms. In an ideal variant of the method, the limit voltage gradient is in the range from 0.1 V/100 ms to 0.05 V/100 ms.

In a variant of the method, the insulation resistance of the supply network is determined on the basis of a limit voltage determined by a limit voltage gradient. In this case, the absolute limit voltage is measured or calculated when the limit voltage gradient is reached, because it can be advantageous in terms of the process if the approach to the limit voltage gradient is not iterative, step-by-step, but only or additionally an absolute measured voltage value and thus a limit voltage is determined.

In one embodiment of the method, the reference voltage is defined at the time of delivery of the supply network, i.e. under laboratory conditions, and/or the final voltage reached is determined after a reference period of more than 20 s, in particular after more than 30 s, with the reference period being a maximum of 60 s.

In a further improved variant of the method, a limit measurement duration is determined when the limit voltage gradient is reached. This limit measurement time is defined as the measurement time until the limit voltage gradient and/or the limit voltage is reached. The insulation resistance can thus be determined for a specific number of measurement periods (measurements) and/or for a specific period of time for insulation measurement by a specified limit voltage and/or limit measurement period.

Insulation is to be qualified as faulty in particular if the limit voltage gradient or the limit voltage is reached in a measurement period that is shorter than the limit measurement period and/or the measured voltage value is absolutely below the limit voltage. Conversely, insulation can be classified as intact and error-free if the measurement time until the limit voltage and/or the limit voltage gradient is reached is less than or equal to the limit time. The measurement can thus be terminated at this earliest possible point in time without reaching the reference voltage or a voltage gradient of zero.

In one variant of the method, an insulation or an insulation resistance is defined as faulty if the measurement time until the limit voltage gradient and/or the limit voltage is reached falls short of a defined limit time.

The limit voltage is advantageously 80% to 98%, primarily 90% to 97% and ideally 93% to 96% of the reference voltage.

In order to describe the invention, absolute values of the reference voltage and also ranges of the reference voltage are described as the difference between the output measured value or starting voltage and the lowest voltage level. Since these can be converted into one another or can be derived directly analogously, an absolute value also means the span or the delta in an analogous manner. This also applies in an analogous manner to the other values, such as the limiting voltage gradient or the limiting voltage or the measurement duration, unless expressly stated otherwise or an analog reading is absolutely impossible.

Overall, the reference duration is a maximum of 60s and a theoretical reference gradient would be a horizontal line, i.e. a stable voltage level over time. In an analogous manner, the limit duration is defined from the reference voltage and limit voltage/limit voltage gradient, which describes the period of time until the limit voltage gradient or the limit voltage is reached. Ideally, the limit duration is also determined under the legal and/or standardized test conditions before or during the final inspection after or during the manufacturing process of the supply network and/or a vehicle with this supply network.

In an improved variant of the method, the voltage is determined periodically. The measurement steps are in the range of 0.01s to 1s, primarily 0.01s to 0.05s.

Advantageously, at least when the limit measurement duration is reached and/or when the limit measurement duration is reached until the limit voltage gradient and/or the limit voltage is reached, information is sent as a (warning) notice about the isolation device being inoperative and/or not safe on a display unit that can be seen by a user of the supply network directed. Such a display unit can be any conventional optical, sensory and/or acoustic device that is suitable for this purpose. Alternatively or additionally, the supply network at an isolation device identified as faulty is at least partially switched off. Of course, an immediate or staged switch-off process can also be initiated after the limit measurement duration has been reached or fallen below.

One embodiment consists in providing a qualitative and/or quantitative indication of the status of the isolation device of the supply network in the display unit periodically or based on an active request by the user to the supply network and/or a component thereof.

In a preferred variant of the method, the measurement is carried out with a maximum current flow of 1 mA and/or a maximum Y capacitance of 2 pF.

The supply network according to the invention is advantageously provided in a vehicle, with the measuring and testing method being carried out periodically during operation of the vehicle. These total measurement periods up to the determination of the limit voltage are carried out in particular in total periods of less than 30 s, in particular less than 20 s. As a rule, the insulation measurements are carried out immediately, i.e. without a measurement break.

An improved embodiment of the method provides that at least one processor unit and at least one storage medium are provided, depending on the service life and/or operating states of the supply network or a vehicle

- Insulation valuesZ-resistances are stored and/or

- Measurement durations until reaching the limit voltage gradient and/or the limit voltages and/or their time profiles, such as measurement durations or measurement steps, are stored and evaluated by the at least one processor unit.

All in all, the processor unit, the storage media and the voltage network as well as their components are connected to one another in a necessary or known manner to conduct electricity and/or data, which is not explained in detail here.

For this purpose, the other measured values, such as temperatures, humidity, vibration, etc., which are usually recorded in particular in the vehicle, are advantageously also taken into account and correlated.

It is particularly advantageous if, in this way, insulation values, measurement durations or their chronological sequences which are dependent on the service life or the operating states are stored and evaluated by the processor unit. This makes it possible to make a prognosis or a probability for faults in the insulation unit that are to be expected in the future. This could for example Correlations with the engine temperature, outside temperature, humidity and/or vibration and/or their progressions, which can be evaluated together with the resistance values.

The method according to the invention is particularly suitable for detecting an insulation fault in a battery or a battery system of a vehicle, so that the invention also includes a battery for a vehicle with an electrical supply network. This primarily means land-based vehicles, but the method according to the invention or the battery system also includes use in aircraft and/or water vehicles.

The battery system according to the invention can be used in particular for vehicles for transporting people and/or loads and includes a supply network or can be connected to it. In addition, at least one processor unit is included or connected, such as an on-board computer and/or one or more microprocessors. The control and system information can be routed from these to a display unit. The associated battery is designed in particular as a high-voltage battery (HV battery). In the case of an HV battery, for example, the nominal voltage of the electrical supply network is in a range of over 60 V.

In this case, a measuring unit is provided for determining the measuring voltage, by means of which the measuring and monitoring method can be carried out according to one of the variants mentioned above.

In an improved embodiment, the processor unit is connected in a data-conducting manner to at least one storage element, the storage medium being stored on the delivery side and/or during operation

- of the vehicle and/or

- Voltage values and/or measurement durations determined for the supply network are stored. In particular, these are at least one reference voltage and/or one end voltage of the supply network and/or a maximum permissible limit or reference duration.

It is particularly advantageous if insulation values that depend on the service life and/or the operating states of the battery, the vehicle or the supply network, measurement times until the limit voltages are reached and/or their time profiles are stored in the storage medium and can therefore be evaluated by the processor unit. In this way, a prognosis or a probability for a future scenario and an associated, expected error or failure of the insulation unit can be determined and displayed. This can for example, correlations with the engine or outside temperature, humidity, vibration and/or their progression, which can be evaluated together with the resistance values.

Further details and advantages of the invention will now be explained in more detail using an exemplary embodiment illustrated in the drawings.

Show it:

Fig. 1 shows a graphical progression of a voltage measurement for a branch up to

reaching the reference voltage,

Fig. 2 shows a section of the graph of Figure 1 until reaching

limit voltage (VG),

Fig. 3 shows another voltage measurement for a faulty branch of a

supply network and

Fig. 4 is a curve representation dV / dt of the voltage change until reaching the

limit voltage.

FIG. 1 shows the graphical progression of a voltage measurement as a voltage (V, Y axis) over time (s, X axis) for a branch of the supply network until the reference voltage VR is reached. At the start time at 45 seconds, the measurement voltage VM is 445V and falls to the reference voltage V of 355V up to the 66th second, i.e. within 21s, the reference duration D DR. The voltage gradients Gvi to GVG that result per measurement step AtM of 2 ms are symbolized as gradient triangles above the voltage curve. The battery system or the associated vehicle is not shown below.

Subsequently, there is no or almost no further reduction in the voltage over time. This theoretically achievable horizontal line as the final voltage level defines the reference voltage VR.

In the present exemplary embodiment, the limit voltage gradient GVG is defined by a voltage change AV of 0.1 V per 100 ms, which in the present case is reached after the measurement period AT, which in the present case is identical to the limit measurement period ATG.

The limiting voltage gradient GG is determined by the manufacturer or by the user and can be adjusted over the period of use, for example of a vehicle. Analogously, a limit measurement period ATG can also be determined from the reference period ATR or can be derived from the limit voltage gradient GVG. Isolation is all the more valuable the greater the limit measurement duration ATG. In the prior art, the point in time at second 66 would also be the end of the measurement, which could only then be evaluated by the processor.

As shown in the detail view of FIG. 2, the limit voltage gradient GVG is reached after a measurement duration AT of 17s, with the limit voltage VG of 359.5 V being 95% of the reference voltage VR of 355V.

In the present case, the measurement can therefore already be successfully completed 4s (ÜTG-R=4s) before the limit voltage gradient or reference voltage V is reached, because a sufficient degree of certainty that the insulation state was not defective was determined.

In the course of the voltage according to Figure 3, there is a defective insulation of the supply network or the measured section, so that the limit voltage gradient GVG and thus the limit voltage VG is already reached after 53.5 s, i.e. in a measurement time spanZ duration DTM less than the limit duration DTG , which was stored as the minimum value in the system, whereby the limit stress gradient G G can also be measured directly.

The particular advantage of the invention is clearly evident here, namely that despite the use of this relatively easy-to-implement measuring and monitoring method, faulty insulation is detected earlier the larger the defect and thus the loss of voltage or fault currents. In the example shown, the time advantage DT M-G compared to completely passing through the limit duration DTG is almost 8s and the time advantage ÜTG-R compared to completely reaching the reference voltage is almost 13s.

Finally, FIG. 4 shows the step-by-step course of a voltage measurement period (measurement duration ΔT) as a course according to the previous illustrations. Each measuring step AtM is 0.25s and the last four measuring steps i-iv until reaching the limit voltage gradient GVG approx. 0.15 V per 250 ms or the limit voltage VG of ~359V at ~53.2 seconds leads to the end of the measurement or the total period without the actual reference voltage V or the stable voltage level being reached. .

Claims

9

Measuring and monitoring method for testing an insulation resistance of an insulation device in an unearthed supply network comprising a battery, the battery being in particular a high-voltage battery (HV battery) in that a measurement voltage (VM) is applied across at least one defined resistance for a measurement period (AT ) is determined in one of the following measuring branches, namely between

- the H(+) pole of the battery and the main frame (chassis),

- the H(-) pole of the battery and the main frame and/or

- the two poles of the battery, and the supply network having a reference voltage (VR), the reference voltage (V )

- represents the stable, drop-free voltage level for a given TARGET state of the supply network and/or

- is reached after a reference period (ÜTR) and/or is defined as being reached, characterized in that the insulation resistance of the supply network is determined on the basis of at least one defined limit voltage gradient (GVG), the limit voltage gradient (GVG) being defined as a voltage change (AV) per Measuring step ( IM), and where the limiting stress gradient (GVG) is determined in the three measuring branches. Method according to Claim 1, characterized in that the limiting voltage gradient (G G) is less than 0.5V/100ms, advantageously less than 0.3V/100ms and ideally in the range from 0.25V/100ms to 0.05V/100ms. Method according to one of Claims 1 or 2, characterized in that the insulation resistance of the supply network is determined on the basis of a limit voltage (VG) determined by a limit voltage gradient (GVG). Method according to one of the preceding claims, characterized in that - the reference voltage (VR) is defined at the time of delivery of the supply network and/or

- the final voltage reached after a reference period (□ DR) of more than 20s, in particular after more than 30s, with the reference period (D DR) being a maximum of 60s. Method according to one of the preceding claims, characterized in that a limit measurement time (□ DG) is determined by the limit voltage gradient (GVG), the limit measurement time (□ DG) being defined by the measurement time (AT) until the limit voltage gradient (GVG ) and/or the limit voltage (VG) is required. Method according to one of the preceding claims, characterized in that the insulation resistance for a specific number of measurement periods (AT) and/or for a specific period of time for insulation measurement by means of a limit voltage gradient (GVG) determined and fixed limit voltage (VG) and/or limit measurement period ( D DG) is determined. Method according to one of the preceding claims, characterized in that the measuring voltage (VM) is measured periodically, in particular in measuring steps (IM) of 0.01s to 1s, primarily 0.01s to 0.05s. Method according to one of the preceding claims, characterized in that an insulation resistance is defined as faulty if the measurement duration (AT) falls below a defined limit duration (ATG) until the limit voltage gradient (GVG) and/or the limit voltage (VG) is reached. Method according to one of the preceding claims, characterized in that at least when reaching and/or falling below the limit measurement duration (D DG) until the limit voltage gradient (GG) and/or the limit voltage (VG) is reached, information about the isolation device indicates that it is not functional a display unit that can be seen by a user of the supply network is managed and/or the supply network is switched off at least partially, in particular completely. Method according to one of the preceding claims, characterized in that a qualitative and/or quantitative indication of the state of the isolation device is given in the display unit periodically and/or based on a user request to the supply network and/or a component of the supply network. Method according to one of the preceding claims, characterized in that the maximum current flow in the voltage measurement is 1 mA and/or the maximum Y capacitance is 2 pF. Method according to one of the preceding claims, characterized in that the supply network is provided in a vehicle and the method is carried out periodically during operation of the vehicle, in particular in a total period of less than 30s, in particular less than 20s. Method according to one of the preceding claims, characterized in that at least one processor unit and at least one storage medium are provided, the lifetime and/or operating states being dependent 11

- Insulation values are stored and/or

- Measurement duration (ATM until reaching the limiting voltage gradient (GVG) and/or the limiting voltages (VR) and/or

- The time curves of the measurement durations (ATM) and/or the measurement steps (AtM) until the limit voltage gradient (GVG) and/or the limit voltages (V) is reached are stored and evaluated by the at least one processor unit. Battery system, comprising in particular a high-voltage battery (HV battery) for a vehicle, in particular a vehicle for passenger and/or freight transport, comprising or connectable to at least one processor unit, and comprising or connectable to at least one display unit, characterized in that the one measuring unit for determining the measurement voltage according to a measurement and monitoring method according to one of claims 1 to 13. Battery system according to Claim 14, characterized in that the processor unit is connected in a data-conducting manner to at least one storage element, at least one reference voltage (VR), a limit duration (Dtc) and/or an end voltage (Vmin) of the supply network being stored on the storage medium, in particular the Reference voltage (VR), limit duration (Dtc) and/or final voltage (Vmin) determined at a given TARGET condition. Battery system according to Claim 15, characterized in that in the storage medium depend on the service life and/or on the operating states of the vehicle and/or the supply network

- Insulation values are stored and/or

- Measurement duration (AtM) until reaching the limit voltages (VG) and/or

- The time curves of the measurement duration (AtM) until the limit voltages (VG) are reached can be stored, and which can be evaluated by the at least one processor unit.