A variable range dynamic gain acquisition method for microampere-level ground current

Abstract

The present invention discloses a variable range dynamic gain acquisition method for micro-ampere ground current, which relates to the technical field of relay protection and online monitoring thereof. It includes system initialization and data acquisition; programmable gain control and voltage amplification operation; the acquired current signal is processed by a CPU algorithm, and the effective value of the AC signal is calculated using an RMS algorithm; the current current value is judged in real time according to the calculation result, and the amplification factor is automatically switched. The present invention can realize high-precision monitoring of the tiny current generated by the secondary AC circuit so that accurate early warning of faults can be given.

Description

Technical Field

[0001] The invention relates to the technical field of relay protection and online monitoring thereof, in particular to a variable range dynamic gain acquisition method for microampere-level grounding current. Background Art

[0002] With the rapid development of power technology, the power grid system has gradually become larger and more complex. Many regulations and measures require that the secondary side of the transformer has a reliable grounding point. If there is multi-point grounding in the secondary circuit, a voltage that does not exist will appear in the primary circuit. When the protection device collects the wrong component, it will cause the relay protection device to malfunction. Therefore, it is necessary to monitor the change of the loop current of each grounding wire. The existing technologies include: resistance method - by changing the resistance value to calculate and compare the current passing through to determine whether there is multi-point grounding. However, when the potential difference generated by multi-point grounding is too small, it is difficult for the resistance method to accurately measure the current that is too small;

[0003] Signal injection method - input signal current into the grounding wire, and judge whether there are multiple grounding points by comparing the current on the grounding wire. However, the State Grid stipulates that the grounding current cannot exceed 50mA, so the signal current input by the signal injection method cannot exceed 50mA. The low mA level signal current is passed into the grounding wire, combined with various errors, resulting in very small changes, which makes it difficult to manually judge multiple grounding points.

[0004] Manual live zero-sequence current detection - use a clamp-on current transformer to measure the current of the N600 grounding wire. If it exceeds 50mA, it indicates that there may be multiple grounding points.

[0005] Unbalanced load current method - existing monitoring devices collect unbalanced load current, amplify and filter the load current through the current transformer, convert it into analog-to-digital form through the CPU, and then compare it with existing parameters to decide whether to issue an alarm.

[0006] The core of the current field application of multi-point grounding fault monitoring in secondary AC circuits is to study the current on the grounding wire. However, the existing methods have many defects, including:

[0007] High precision: The current detection on the grounding wire is always at the mA level. Whether it is the introduction of resistance, the collection of amplified load current or the external current signal source, there will be a certain error, which is unavoidable. However, this will have a considerable impact on the already weak mA-level current, making the result difficult to judge and uncontrollable, and increasing the misjudgment of multi-point grounding;

[0008] Real-time performance: The troubleshooting of multi-point grounding faults in the secondary circuit requires high real-time performance, which is similar to the manual live zero-sequence current detection method, but has poor timeliness.

[0009] Fault point location determination: Existing methods such as the signal injection method have many N lines connected to N600, with lengths ranging from tens of meters to thousands of meters. The signal injection method is difficult to detect and determine the multi-point grounding conditions outside the N600 and the current signal injection point. Summary of the invention

[0010] In view of the problems existing in the above background technology, the present invention is proposed.

[0011] Therefore, the problem to be solved by the present invention is how to achieve ultra-high precision sampling of micro-current in the secondary AC circuit.

[0012] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0013] In the first aspect, an embodiment of the present invention provides a variable range dynamic gain acquisition method for microampere-level ground current, which includes system initialization and data acquisition; programmable gain control and voltage amplification operation; the current signal after programmable gain is processed by a CPU algorithm, and the effective value of the AC signal is calculated using an RMS algorithm; the current current value is determined in real time according to the calculation result, and the amplification factor is automatically switched.

[0014] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level ground current described in the present invention, STM32F407 is used as the main control chip, AD7606 is used as the sampling chip; the AD7606 chip is set to a full scale of plus or minus 10V.

[0015] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level ground current described in the present invention, the voltage amplification operation includes: adjusting the gain through a programmable operational amplifier according to the collected current size to perform a multiple amplification; the multiple is based on 70% of the total range of the sampling chip.

[0016] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level ground current described in the present invention, the programmable gain operational amplifier sampling circuit includes: segmented processing of different input voltages through the programmable gain operational amplifier so that input currents in different ranges pass through different amplification resistors to reach 70% of the total range of the sampling chip.

[0017] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level ground current described in the present invention, the process of the programmable gain operational amplifier includes: the initial state defaults to amplification by n times; judgment is made based on the calculated current value result and the pin level state: if it is less than n1mA and the amplification factor is n times, the amplification factor is switched to 10n times; if it is greater than n1mA and the amplification factor is 10n times, the gain is switched to 10 times; if it is other cases, the corresponding matched current and gain are directly output.

[0018] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level ground current described in the present invention, wherein: the use of the RMS algorithm to calculate the effective value of the AC signal includes the following steps: calculating the DC component of the input voltage value; using the result of subtracting the DC component from the input value to calculate the square of each value and sum them; finding the average value to obtain the variance, and taking the square root of it to obtain the effective value; returning the calculated effective value;

[0019] The effective value is expressed by the calculation formula:

[0020]

[0021] In the formula, Expressed as the DC component, It is expressed as the square of the input value minus the DC component. Expressed as variance, V rms Represents a valid value.

[0022] As a preferred solution of the variable range dynamic gain acquisition method for microampere-level grounding current described in the present invention, wherein: the real-time judgment of the current current value based on the calculation result and the automatic switching of the amplification factor include the following steps: multiplying the result processed by the RMS algorithm by the resolution of the sampling chip; dividing by the corresponding amplification factor to obtain the initial voltage converted after the sampling resistor; dividing by the value of the sampling resistor to obtain the current value entering the device; amplifying the current value by m times to obtain the actual current value on the grounding wire loaded with the current transformer.

[0023] In the second aspect, an embodiment of the present invention provides a variable-range dynamic gain high-precision current acquisition system for microampere-level ground current sampling, which includes a data acquisition module for initialization and data acquisition; a programmable gain control module for performing programmable gain control and voltage amplification operations; an RMS calculation module for processing the current signal after programmable gain through a CPU algorithm and using an RMS algorithm to calculate the effective value of the AC signal; and a dynamic gain adjustment module for determining the current current value in real time based on the calculation results and automatically switching the amplification factor.

[0024] In a third aspect, an embodiment of the present invention provides a computer device, comprising a memory and a processor, wherein the memory stores a computer program, wherein: when the computer program instructions are executed by the processor, the steps of the variable-range dynamic gain acquisition method for microampere-level ground current as described in the first aspect of the present invention are implemented.

[0025] In a fourth aspect, an embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon, wherein: when the computer program instructions are executed by a processor, the steps of the variable-range dynamic gain acquisition method for microampere-level ground current as described in the first aspect of the present invention are implemented.

[0026] The beneficial effects of the present invention are as follows: the present invention amplifies the collected current signals of 0-20mA and 20-1000mA with different gains according to actual conditions, and amplifies them to the range of the highest accuracy of the AD chip, which is about 70% of the total range of 10V, to achieve high-precision sampling, so that the micro-current (i.e., below 20mA) that we are concerned about can also be collected with high precision, avoiding the situation where the micro-current error is large due to the excessive measurement range. The method can achieve high-precision acquisition of multiple ranges, so that each small range current that wants to be accurately measured can obtain a higher resolution, achieving a multi-range "rail-to-rail" operational amplifier in another sense to utilize the range of the sampling chip, and the accuracy index reaches: the measurement error is <2mA when 0-20mA; the measurement error is <3mA when 20-1000mA; the present invention can realize high-precision monitoring of the tiny current generated by the secondary AC circuit so that accurate warning of faults can be given. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 Flowchart for sampling operation of distributed acquisition terminals and multi-range operational amplifiers.

[0029] Figure 2 This is the programmable gain op amp sampling circuit diagram.

[0030] Figure 3 This is the program flow chart of the programmable gain op amp.

[0031] Figure 4 This is the schematic diagram of the programmable gain op amp module. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

[0033] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0034] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0035] Example 1

[0036] Reference Figure 1 to Figure 3 , which is the first embodiment of the present invention, provides a variable range dynamic gain acquisition method for microampere-level ground current, including:

[0037] S1: System initialization and data collection.

[0038] Use STM32F407 main control chip and AD7606 sampling chip, and communicate through carrier module and RS485 interface.

[0039] To collect the ground current signal, the AD7606 chip is set to a full scale of plus or minus 10V, and the actual collected voltage is the effective value (RMS).

[0040] The initial current signal is converted by a current transformer and further sampled and processed.

[0041] Specifically, the full scale of the AD7606 sampling chip is plus or minus 10V or plus or minus 5V. The present invention selects a scale of plus or minus 10V (peak voltage). The voltages actually collected and converted are all effective values ​​(root mean square value). For a sine wave, the effective value of the voltage is equal to 1 / root 2 of the peak voltage.

[0042] The more the range of the sampling chip is utilized, the higher the measurement accuracy. Therefore, since the full range of the present invention is 10V (peak voltage), its effective value can be utilized up to 10 / root 2, which is about 70% of the total range of the sampling chip. The closer the amplified voltage is to this value, the more accurate the measurement result is.

[0043] S2: Perform programmable gain control and voltage amplification operation.

[0044] According to the current size collected, the gain is adjusted through the programmable operational amplifier to select the appropriate magnification. For 0-20mA current, the amplification is 500 times; for 20-1000mA current, the amplification is 10 times. By amplifying the voltage to close to 70% of the full scale of the sampling chip, the measurement accuracy is improved to ensure that the voltage after the signal is amplified is closest to the optimal sampling range.

[0045] Specifically, the present invention uses a programmable operational amplifier to obtain different gains to amplify the initially converted voltage to approximately 70% of the total range of the sampling chip.

[0046] After judging the current, if the current is small, that is, between (0-20mA), it will be amplified by a larger multiple; if the current is large, it will be amplified by a slightly smaller multiple. The selection of this multiple is calculated in advance according to the maximum value of the range to be measured, and then the corresponding programmable gain amplifier is selected. For example, when the current measurement result is between (0-20mA), the multiple is calculated based on its maximum current value. The actual voltage value of 20mA is reduced by 1000 times to 20UA current through the current transformer, and then converted into a voltage of 14mA through a 700 ohm sampling resistor. 14mA needs to be amplified to about 70% of the total range of the sampling chip, that is, (about 7V). The amplification factor is about 7000mA / 14mA, and the result is about 500 times.

[0047] Similarly, when the current measurement result is between (20-1000mA), the maximum current value is used for calculation. The actual voltage value of 1000mA is reduced by 1000 times to 1mA current through the current transformer, and then converted into a voltage of 700mA through a 700-ohm sampling resistor. 700mA needs to be amplified to about 70% of the total range of the sampling chip, that is, (about 7V). The amplification factor is about 7000mA / 700mA, and the result is about 10 times.

[0048] Further, such as Figure 2 As shown in the figure, it is a programmable gain op amp sampling circuit. It can be seen that the programmable gain op amp performs segmented processing on the judgment of different input voltages so that input currents in different ranges pass through different amplification resistors, so that they can finally reach 70% of the total range of the sampling chip, making the measurement accuracy of small currents higher. The module can theoretically realize segmented processing of four ranges, and process the two ranges of 0-20mA and 20mA-1000mA in combination with application scenarios and actual conditions.

[0049] Figure 3This is the program flow chart of the programmable gain op amp. It can be seen that the initial state defaults to amplification n times, that is, 50 times, and then judges based on the calculated current value and the pin level state. If it is less than n1mA, which is 20mA here and the amplification factor is 50 times, the amplification factor is switched to 500 times. If it is greater than 20mA and the amplification factor is 500 times, the gain is switched to 10 times. The remaining cases are corresponding matching currents and gains, and the results can be directly output.

[0050] S3: The current signal after programmable gain is processed by the CPU algorithm, and the effective value of the AC signal is calculated using the RMS algorithm.

[0051] The calculation steps include removing the DC component, squaring and averaging, and finally taking the square root to get the effective value. According to the resolution and magnification of the sampling chip, the current value is calculated, and finally the actual ground current is obtained.

[0052] The sampling values ​​obtained by the sampling chip are processed by the CPU algorithm program, mainly to calculate the implementation of the effective value (RMS) function of the AC signal, and to process the final result according to the transformation ratio and amplification factor.

[0053] Among them, the AC signal effective value (RMS) function includes:

[0054] Calculate the DC component of the input voltage value;

[0055] The result of subtracting the DC component from the input value is used to calculate the square of each value and sum them;

[0056] Find the mean to get the variance and take the square root to get the effective mean value (RMS);

[0057] Returns the calculated effective value;

[0058] The effective value is expressed by the calculation formula:

[0059]

[0060] In the formula, Expressed as the DC component, It is expressed as the square of the input value minus the DC component. Expressed as variance, V rms Represents a valid value.

[0061] S4: Determine the current value in real time based on the calculation results and automatically switch the magnification.

[0062] The result after RMS algorithm processing is multiplied by the resolution of the sampling chip (the resolution of a 16-bit sampling chip is 1 / 65536, that is, -10V to 10V is quantized with a number between 0 and 65536 to obtain the digital quantity corresponding to the sampled voltage value), and then divided by the corresponding magnification factor (500 or 10) to obtain the initial voltage converted after the sampling resistor, and then this result is divided by the value of the sampling resistor (700 ohms) to obtain the current value entering the device (Ohm's law - voltage = resistance * current), and finally this value is amplified by m times, where m = 1000, (previously, the actual current has been reduced by 1000 times through the transformer) to obtain the actual current value on the grounding wire loaded by the current transformer, that is, the desired result.

[0063] Furthermore, this embodiment also provides a variable range dynamic gain high-precision current acquisition system for microampere-level ground current sampling, including:

[0064] Data acquisition module, used for initialization and data acquisition;

[0065] A programmable gain control module, used for performing programmable gain control and voltage amplification operations;

[0066] RMS calculation module, used for current signal after programmable gain is processed by CPU algorithm, and uses RMS algorithm to calculate the effective value of AC signal;

[0067] The dynamic gain adjustment module is used to determine the current current value in real time according to the calculation results and automatically switch the amplification factor.

[0068] This embodiment also provides a computer device, which is suitable for the case of a variable-range dynamic gain acquisition method for microampere-level ground current, including a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute computer-executable instructions to implement the variable-range dynamic gain acquisition method for microampere-level ground current as proposed in the above embodiment.

[0069] The computer device may be a terminal, and the computer device includes a processor, a memory, a communication interface, a display screen and an input device connected via a system bus. The processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The communication interface of the computer device is used to communicate with an external terminal in a wired or wireless manner, and the wireless manner can be achieved through WIFI, an operator network, NFC (near field communication) or other technologies. The display screen of the computer device may be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device may be a touch layer covering the display screen, or a key, trackball or touchpad provided on the housing of the computer device, or an external keyboard, touchpad or mouse, etc.

[0070] This embodiment also provides a storage medium on which a computer program is stored. When the program is executed by a processor, the variable range dynamic gain acquisition method for microampere-level ground current proposed in the above embodiment is implemented.

[0071] In summary, the present invention amplifies the collected current signals of 0-20mA and 20-1000mA with different gains according to actual conditions, and amplifies them to the range with the highest accuracy of the AD chip, which is about 70% of the total range of 10V, to achieve high-precision sampling, so that the micro-current (i.e., below 20mA) that we are concerned about can also be collected with high precision, avoiding the situation where the micro-current error is large due to the large measurement range. This method can achieve high-precision acquisition of multiple ranges, so that each small range current that wants to be accurately measured can obtain a higher resolution, achieving a multi-range "rail-to-rail" operational amplifier in another sense to utilize the range of the sampling chip, and the accuracy index reaches: measurement error <2mA at 0-20mA; measurement error <3mA at 20-1000mA; the present invention can realize high-precision monitoring of the tiny current generated by the secondary AC circuit so that accurate warning of faults can be given.

[0072] Example 2

[0073] The second embodiment of the present invention provides a schematic diagram of a programmable gain amplifier module, which is as follows:

[0074] like Figure 4As shown, CH7+ is an external input small signal current connected to the VIN pin. Before entering the programmable operational amplifier, the CH7+ current signal needs to be converted into an initial voltage signal through resistor R1, and connected to the CPU through PB10 and PB11. Different gains are selected by changing the logic level of the CPU. For example, if PB10 is low level 0 and PB11 is low level 0, the amplification factor is 10 times, and the voltage signal entering from the VIN pin will be amplified 10 times and output from the Vo pin.

[0075] Similarly, if PB10 is low level 0 and PB11 is high level 1, the amplification factor is 50 times; if PB10 is high level 1 and PB11 is low level 0, the amplification factor is 100 times; if PB10 and PB11 are both high level 1, the amplification factor is 500. 10 times and 500 times are the gains we need. This gain is used to convert the voltage signal converted by resistor R1 to about 70% of the full scale of the sampling chip, and then transmit it to the sampling chip for further processing.

[0076] The programmable operational amplifier device requires positive and negative 12V power supply, among which C1 and C2 capacitors are grounded (OP_GND is the ground of the analog signal) mainly to filter the power supply. C3 capacitor is grounded to filter the output voltage analog signal to reduce noise and make the signal smoother. Resistor R2 can help stabilize the output signal to ensure that it does not fluctuate greatly when the load changes or is disturbed.

[0077] Example 3

[0078] The third embodiment of the present invention provides a variable range dynamic gain acquisition method for microampere-level ground current. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through real experiments.

[0079] Take the distributed acquisition terminal of this product as an example:

[0080] First, determine the reduction multiple of the front current transformer and calculate the current output range of the transformer end. For example, if the transformer selected in the application scenario of the present invention is 1000:1 and the current range to be collected is 0-1000mA, the output current range of the transformer end is 0-1mA.

[0081] Determine the current range to be measured. For example, the current range to be collected by the distributed acquisition terminal of this product is 0-1000mA. According to actual needs, for example, the error within 0-20mA needs to be less than 2mA, and the error within 20-1000mA needs to be less than 3mA, so two-stage gain is required for amplification;

[0082] Select the corresponding programmable gain operational amplifier according to the needs. The following points should be noted in the selection: 1. How many different gain options are there for the operational amplifier? Do they meet the requirements? 2. Whether the positive and negative driving voltages of the operational amplifier are greater than the range of the sampling chip. If they are less than the range, clipping will occur.

[0083] Select a suitable sampling resistor, for example, 700 ohms is selected in this product. The current passing through the sampling resistor will be converted into 0-14MV and 14-140MV respectively. Then, according to their different voltage ranges, they will be enlarged by 500 times and 50 times, and both different ranges will be enlarged to 7V, which is the most accurate measurement interval of the sampling chip.

[0084] Two gain selection signal lines are connected to the CPU. Taking this product as an example, if the two CPU signals are "00", they are amplified 10 times, "01" is amplified 50 times, "10" is amplified 100 times, and "11" is amplified 500 times. This product only needs two gain selections, that is, the two signals can be switched between "00" and "11" outputs in the CPU logic algorithm.

[0085] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A variable range dynamic gain acquisition method for microampere-level ground current, characterized by: include, System initialization and data collection; Perform programmable gain control and voltage amplification operations; The current signal after programmable gain is processed by the CPU algorithm, and the effective value of the AC signal is calculated using the RMS algorithm; Determine the current value in real time based on the calculation results and automatically switch the magnification; The method of calculating the effective value of the AC signal using the RMS algorithm includes the following steps: Calculate the DC component of the input voltage value; The result of subtracting the DC component from the input value is used to calculate the square of each value and sum them; Find the mean to get the variance, and take the square root to get the effective value; Returns the calculated effective value; The effective value is expressed by the calculation formula: In the formula, Expressed as the DC component, It is expressed as the square of the input value minus the DC component. Expressed as variance, V rms Represented as a valid value; The method of determining the current current value in real time according to the calculation result and automatically switching the magnification factor comprises the following steps: Multiply the result processed by the RMS algorithm by the resolution of the sampling chip; Divide by the corresponding magnification factor to obtain the initial voltage converted after passing through the sampling resistor; Divide by the value of the sampling resistor to get the current value entering the device; The current value is magnified m times to obtain the actual current value on the grounding wire loaded with the current transformer.

2. The variable range dynamic gain acquisition method for microampere-level ground current according to claim 1, characterized in that: STM32F407 is used as the main control chip, and AD7606 is used as the sampling chip; The AD7606 chip is set to a full scale of plus or minus 10V.

3. The variable range dynamic gain acquisition method for microampere-level ground current according to claim 2, characterized in that: The voltage amplification operation comprises: According to the size of the collected current, the gain is adjusted through the programmable operational amplifier to amplify the current by multiples; The multiple is based on 70% of the total range of the sampling chip.

4. The variable range dynamic gain acquisition method for microampere-level ground current according to claim 3, characterized in that: The programmable gain op amp sampling circuit includes: The programmable gain amplifier is used to perform segmented processing on the judgment of different input voltages so that input currents in different ranges pass through different amplification resistors, reaching 70% of the total range of the sampling chip.

5. The variable range dynamic gain acquisition method for microampere-level ground current according to claim 4, characterized in that: The process of the programmable gain operational amplifier includes: The initial state is enlarged by n times by default; Judge based on the calculated current value and pin level status: If it is less than n1mA and the amplification factor is n, the amplification factor is switched to 10n; If it is greater than n1mA and the amplification factor is 10n times, the gain is switched to 10 times; If it is other cases, the current and gain are matched accordingly and the result is output directly.

6. A variable range dynamic gain acquisition system for microampere-level ground current, based on the variable range dynamic gain acquisition method for microampere-level ground current according to any one of claims 1 to 5, characterized in that: Also includes, Data acquisition module, used for initialization and data acquisition; A programmable gain control module, used for performing programmable gain control and voltage amplification operations; RMS calculation module, used for current signal after programmable gain is processed by CPU algorithm, using The RMS algorithm calculates the effective value of an AC signal; The dynamic gain adjustment module is used to determine the current current value in real time according to the calculation results and automatically switch the amplification factor.

7. A computer device comprising a memory and a processor, wherein the memory stores a computer program, wherein: When the processor executes the computer program, the steps of the variable range dynamic gain acquisition method for microampere-level ground current described in any one of claims 1 to 5 are implemented.

8. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the variable range dynamic gain acquisition method for microampere-level ground current described in any one of claims 1 to 5 are implemented.

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