Verification method for transient waveform of relay protection tester

Abstract

The invention relates to the technical field of relay protection testers, in particular to a verification method for a transient waveform of a relay protection tester. A microcomputer platform inputs a simulation current waveform I1 to a protection device through a switch and a protection tester, the microcomputer platform also inputs the simulation current waveform I1 to a verification alarm system, and the protection device receives a waveform output by the protection tester and then outputs a recovery current waveform I2 to the verification alarm system. The simulation current waveform I1 and the protection device recovery current waveform I2 are sequentially subjected to time axis alignment and preprocessing, then the waveform distortion coefficient mu, the attenuation rate difference upsilon and the higher harmonic content difference wj are calculated, and finally the mu, the upsilon and the wj are comprehensively evaluated to obtain an evaluation matrix R. According to the invention, the real-time simulation current waveform collected by the tester and the current waveform collected by the protection device are compared and corrected to form a closed-loop detection system, and the comprehensive evaluation matrix R is adopted in the waveform calibration method, so that misleading of a single evaluation standard to waveform correction is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of relay protection testers, and in particular to a method for verifying transient waveforms of relay protection testers. Background Art

[0002] Relay protection is one of the important components of power system protection. When a short circuit, fault or abnormal operation occurs somewhere inside the power system, the voltage and current will fluctuate abnormally. In this state, relay protection can respond at the fastest speed. After the relay protection equipment is applied to the power system, the protection device will conduct a comprehensive and detailed detection of the voltage, current, etc., and can also feed back the test results to the designated place, so as to provide due convenience for relevant workers to be familiar with the actual operation of the power system. Generally, when a problem occurs in the power system, the relay protection device will act in the shortest time, and detect and separate the parts with fault problems to ensure that other parts can operate in an orderly manner. In addition, the facility will also feed back to the relevant workers as soon as possible, so that they can have a comprehensive understanding of the actual operation of the power system and provide due convenience for immediately solving the fault problem.

[0003] The effective use of relay protection technology is usually the process of fully realizing the value of relay protection. The protector is mainly composed of the following parts: one is the switch; the other is the power supply No. 2 current transformer, etc. After sensing the abnormal voltage and current, the transformer will generally cut off the main circuit as soon as possible to ensure that the equipment will not be affected. In general, relay protection usually covers overcurrent, distance, differential and other protection functions. Therefore, the operation and characteristics of relays and protection devices should be tested regularly. For functional testing of relay protection equipment, it should be placed in various actual operation scenarios of the power grid to simulate the response of the relay protection equipment under different system conditions.

[0004] With the application of computer technology in power systems, microcomputer-based relay protection test devices, relay protection testers, have been put into use. Relay protection testers are based on microcomputers and use the computer's computing function to generate power frequency signal waveforms and other frequency signal waveforms, such as harmonics and DC signal waveforms; based on advanced electronic technology, digital waveforms are converted into analog signals through digital-to-analog conversion chips; the power amplifier amplifies the analog signal with a small amplitude into a larger voltage and current signal that can simulate the output of the secondary side of the power system transformer; the computer's memory function is used to record the action of the device under test; the computer's processing function is used to analyze the relay protection action performance under certain input signals and determine the accuracy and reliability of the relay protection. A typical relay protection tester consists of the following parts: a signal generation unit, a digital-to-analog conversion unit, a power amplifier unit, a switch quantity detection unit, and a communication unit.

[0005] The signal generation unit generates voltage and current to simulate the normal operation and fault conditions of the power system. In the early fault tester, the simulated signal was only the power frequency sine. With the development of technology, the generated signal can be a power frequency sine superimposed with harmonic components and DC components. The digital-to-analog conversion unit converts the digital signal generated by the signal generation unit into a small signal analog quantity. The power amplifier unit amplifies the small signal analog quantity output by the digital-to-analog conversion unit into a 0-100V, 0-50A high voltage and high current signal to simulate the secondary output of the power system transformer; the switch quantity detection unit detects the state of the external switch quantity and records the action of the tested device; the communication unit is the communication between the tester body and the external computer to exchange test content and test results. In addition, through the communication unit, the relay protection tester can also complete the function of replaying the field recorded data. On the one hand, the existing fault tester is developed for the test requirements of relay protection based on power frequency electrical quantities, and on the other hand, due to the performance limitations of the power amplifier unit, the frequency of the output current and voltage is within 1kHz, so it cannot provide large current, high voltage, and wide-band fault signals.

[0006] Most of the current relay protection is constructed by detecting the fault characteristics of steady-state power frequency electrical quantities. These technologies have played an important role in ensuring the safe operation of power systems. However, due to the inherent defects of steady-state power frequency electrical quantities as fault information, such as the difficulty in distinguishing between faults and heavy loads, the influence of the saturation characteristics of current transformers, the influence of transition resistance, and the influence of long-line distributed capacitance, the reliability and sensitivity of fault detection are greatly reduced. Strictly speaking, the transmission lines, distribution lines, busbars, transformers and generator windings in the power system are all distributed parameter circuits. The transient transition process after a distributed parameter circuit fails is actually the propagation process of electromagnetic waves. Fault traveling waves are electrical quantities unique to the fault transition process, reflecting the occurrence, development and change value of the fault. According to the characteristics of the power system under study, the entire network is divided into core area, peripheral area and peripheral area. The core area has a great influence on the electromagnetic transients of the research object, which requires precise modeling and emphasis on calculation accuracy; the peripheral area has little influence on the electromagnetic transients of the research object, and an appropriately simplified model can be established, taking into account the calculation accuracy and calculation time; the peripheral area has a small influence on the electromagnetic transients of the research object, and a simplified equivalent circuit can be established.

[0007] At present, there are three commonly used testing methods: power system dynamic simulation, real-time digital simulator RTDS (Real Time Digital Simulator) and traditional microcomputer-based relay protection tester. The dynamic simulation system can more realistically reflect the fault characteristics of the power system, and the relay protection test based on the dynamic model system is intuitive and reliable. The dynamic model system is based on the principle of similarity. According to the reduced size of the real power system, a model system that does not change the physical characteristics of the real power system is designed. The dynamic model system can simulate the following equipment in the real power system: synchronous generators, transformers, transmission lines, loads, etc. The simulated generator uses a special generator with an additional intermediate tap on the neutral point side of the three-phase winding of the generator stator or an additional intermediate tap on the machine end of the three-phase winding of the generator stator; the prime mover driving the simulated generator uses a DC motor. The transmission line is simulated using a concentrated parameter П-type circuit. The middle branch is an air-core reactor to simulate the impedance of the line, and the parallel branches on both sides are capacitors to simulate the line admittance. According to the length of the line, different numbers of transmission line units are connected in series. Conventional step-up transformers and step-down transformers are used to simulate large-capacity actual transformers; incandescent bulbs are used to simulate static loads, and asynchronous motors-DC generators are used to simulate dynamic loads. However, the dynamic model system is not a special system designed for relay protection testing, and its structure is complex and inconvenient to use. It can only be carried out in a special dynamic model laboratory, which cannot meet the needs of on-site pre-production testing. In addition, the transmission line in the dynamic model system uses a centralized parameter circuit, so there is no traveling wave component in the fault electrical quantity simulated by the dynamic model system, which cannot fully and truly reflect the power system fault. At the same time, the action result recording of relay protection requires additional equipment to complete, which increases the workload of the test. The relay protection tester developed by this institute has the advantages of small size, light weight, and a total weight of less than 10 kilograms, which is suitable for portable testing needs. It can realize dynamic waveform and transient waveform output with the simulation system, and has eight pairs of open inputs, which can read the relay action signal to form an action report, further forming a closed-loop test system.

[0008] RTDS can perform a more comprehensive real-time simulation of complex power systems. RTDS uses a combination of digital simulation and analog signal power amplification to simulate the fault process of the power system, and has the basic conditions for testing relay protection devices based on transient traveling wave fault information. However, the power amplification system in RTDS cannot generate broadband, high-current transient traveling wave signals with frequencies of hundreds of kilohertz and amplitudes of tens of amperes. In addition, RTDS is expensive, the entire device is large and not portable, and it is difficult to upgrade, making it inconvenient for widespread use. Therefore, it cannot meet the test requirements of relay protection devices based on transient fault information. The relay protection tester developed by this institute has great advantages in price and cost, and the output current amplitude can reach 35A, and the single-phase voltage can reach 350V. It can also perform a more comprehensive online real-time simulation of the relay protection device.

[0009] Traditional microcomputer-based relay protection testers need to prepare fault recording data in advance. If you want to test different faults or change the fault system parameters, you need to prepare the fault data again, which will bring inconvenience. This study integrates the simulation system with the relay protection tester, and establishes real-time communication with the relay protection tester to make the preparation and modification of fault data faster, forming a closed-loop test system that can be used on site.

[0010] In summary, the existing power system dynamic simulation system lacks a verification method for the transient waveform after the above-mentioned distributed parameter circuit fails. The fault electrical quantities simulated by the dynamic simulation system do not have traveling wave components and cannot fully and truly reflect the power system fault. Therefore, there is an urgent need for a testing method for relay protection devices that can meet the requirements based on transient fault information. Summary of the invention

[0011] The problem to be solved by the present invention is to provide a test method for a relay protection device that can meet the requirements based on transient fault information.

[0012] In view of the deficiencies of the prior art, the technical solution adopted by the present invention to solve the technical problems is: a method for verifying the transient waveform of a relay protection tester, a microcomputer platform running simulation software is connected to a switch, the switch is connected to a protection device through a protection tester, the microcomputer platform inputs a simulated current waveform I1 to the protection device through the switch and the protection tester, the microcomputer platform also inputs the simulated current waveform I1 to the verification alarm system, the protection device receives the waveform output by the protection tester and then outputs a recovery current waveform I2 to the verification alarm system, the simulated current waveform I1 is a voltage and current signal with significant transient characteristics, the simulated current waveform I1 is compared and corrected with the protection device recovery current waveform I2, specifically comprising the following steps,

[0013] Step 1: Align the time axis of the real-time simulation current waveform I1 collected in the tester with the protection device recovery current waveform I2;

[0014] Step 2: pre-process the simulation current waveform I1 and the protection device recovery current waveform I2;

[0015] Step 3: Calculate the waveform distortion coefficient μ between the real-time simulation current waveform I1 and the recovery current waveform I2;

[0016] Step 4: Calculate the difference in waveform attenuation rate υ between the simulated current waveform I1 and the recovered current waveform I2 at the transient moment;

[0017] Step 5: Calculate the difference w between the high-order harmonic content of the simulated current waveform I1 and the recovered current waveform I2 in the transient current j ;

[0018] Step 6: Distortion coefficient μ, attenuation rate difference υ and high-order harmonic content difference w j A reasonable weight distribution is performed for comprehensive evaluation to obtain the evaluation matrix R; when the result of the evaluation matrix R>R0, the waveform calibration signal alarm is issued.

[0019] Preferably, the simulation current waveform I1 described in step 1 is aligned with the protection device recovery current waveform I2 in time axis by using a waveform calibration procedure, and the specific method of the waveform calibration procedure is as follows:

[0020]

[0021] Among them, I1 is the real-time simulation waveform collected by the tester, I2 is the actual waveform collected by the protection device backflow, t X is the time difference between the recovered current waveform I2 and the simulated current waveform I1.

[0022] Preferably, the method of preprocessing the waveform in step 2 is: taking 200 sampling points per cycle; during the verification process, selecting the first quarter of the cycle with significant transient characteristics:

[0023]

[0024] Among them, x(k) and y(k) are the simulation waveform and the sampling value of the recovered waveform in the waveform verification method respectively, T is the sampling time of one cycle, T = 0.02s; N is the number of sampling points of one cycle, N = 200; k is the number of sampling points of the first quarter of the cycle.

[0025] Preferably, the calculation of the waveform distortion coefficient μ described in step 3 is to normalize the difference between the simulation current waveform I1 and the recovery current waveform I2, and obtain the waveform distortion coefficient μ as an indicator to measure the degree of waveform transmission distortion:

[0026]

[0027] Among them, x(k) and y(k) are the simulation waveform and the sampling value of the recovered waveform in the waveform verification method respectively, and k is the number of sampling points in the first quarter of the cycle, k=50.

[0028] Preferably, the waveform attenuation rate difference υ described in step 4 is obtained by normalizing the difference between the attenuation rates of the simulated current waveform I1 and the recovered current waveform I2, as an indicator of the difference in attenuation degree in waveform transmission:

[0029]

[0030] Preferably, the high-order harmonic content difference w in step 5 is jThe difference between the high-order harmonic content in the simulated current waveform I1 and the recovered current waveform I2 is normalized and used as an indicator of the degree of high-order harmonic loss in waveform transmission to obtain the high-order harmonic content difference w j :

[0031] w j =w 1j -w 2j

[0032] Among them, w j is the loss degree of the jth harmonic, w 1j is the loss degree of the jth harmonic in the simulated current waveform I1, w 2j It is the loss degree of the jth harmonic in the recovered current waveform I2.

[0033] Preferably, the calculation method of the evaluation matrix R is as follows:

[0034]

[0035] Among them, a j is the evaluation coefficient, a1 = 0.5; a2 = 0.2;

[0036] Preferably, R0 ranges from 0.3 to 0.4.

[0037] The beneficial effects of the present invention are as follows:

[0038] 1. The present invention is based on a portable microcomputer platform, which can solve the drawback of inaccurate transient component output of existing protection testers, can accurately simulate the transient characteristics of the waveform when a fault occurs, and improve the reliability of the protection tester in detecting relay protection devices.

[0039] 2. The present invention compares and corrects the real-time simulated current waveform collected in the tester and the current waveform collected by the protection device, forming a closed-loop detection system.

[0040] 3. The present invention adopts a comprehensive evaluation matrix in the waveform calibration method, thereby avoiding the misleading of waveform correction by a single evaluation criterion.

[0041] 4. The present invention has great advantages in price cost, and has the advantages of small size and light weight, which are suitable for portable testing needs; and it can realize dynamic waveform and transient waveform output with the simulation system, and has eight pairs of input quantities, which can read the relay action signal, form an action report, and further form a closed-loop test system. The output current amplitude of the system of the present invention can reach 35A, and the single-phase voltage can reach 350V, which can perform a relatively comprehensive online real-time simulation of the relay protection device. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1It is a hardware schematic diagram involved in the present invention;

[0043] Figure 2 The present invention is a flow chart of the method. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0045] Figure 1 This is a hardware schematic diagram involved in the present invention. The simulation software is run in a portable microcomputer platform, and the voltage and current signals with significant transient characteristics are processed by the filter conditioning circuit in the microcomputer platform and output to the switch. Multiple protection testers are connected through the switch to form a distributed test network. The protection tester inputs the fault signal into the relay protection device to be detected to obtain an output switch signal. The present invention compares and corrects the simulation current waveform I1 output by the simulation software and the recovery current waveform I2 of the protection device to form a closed-loop detection system. The simulation current waveform I1 output by the simulation software in the microcomputer platform is given to the verification alarm system, and the recovery current waveform I2 output by the relay protection device is given to the verification alarm system. The verification alarm system evaluates the simulation current waveform I1 and the recovery current waveform I2 through a verification algorithm. Once the degree of deviation between the simulation current waveform I1 and the recovery current waveform I2 of the protection device exceeds the evaluation standard, the verification alarm system will alarm through a signal.

[0046] Figure 2 This is a flow chart of the verification method of the transient waveform of the relay protection tester of the present invention, and the specific implementation steps are as follows:

[0047] Step 1: Align the time axis of the real-time simulation current waveform I1 output by the simulation software with the protection device recovery current waveform I2 to calibrate the error between the two. At this time, start the waveform calibration signal, and the time axis alignment starts the waveform calibration procedure as follows:

[0048]

[0049] Among them, I1 is the simulation current waveform I1, I2 is the protection device recovery current waveform, t X is the time difference between the recovered current waveform I2 and the simulated current waveform I1.

[0050] Step 2: Preprocess the simulated current waveform I1 and the recovered current waveform I2. To ensure the sensitive action of the protection device, the output waveform accuracy of the tester is relatively high, and 200 sampling points are taken per cycle. Since the influence of transient components in the protection device detection is much higher than that of steady-state components, the first quarter of the cycle with significant transient characteristics is selected during the verification process:

[0051]

[0052] Among them, x(k) and y(k) are the sampling values ​​of the simulated current waveform I1 and the recovered current waveform I2 in the waveform verification method, respectively; T is the sampling time of one cycle, T=0.02s; N is the number of sampling points of one cycle, N=200; k is the number of sampling points of the first quarter of the cycle.

[0053] Step 3: Calculate the waveform distortion coefficient μ between the simulated current waveform I1 and the recovered current waveform I2, normalize the difference between the simulated current waveform I1 and the recovered current waveform I2, and obtain the index μ of the waveform transmission distortion degree:

[0054]

[0055] Among them, x(k) and y(k) are the sampling values ​​of the simulated current waveform I1 and the recovered current waveform I2 in the waveform verification method, respectively, and k is the number of sampling points in the first quarter of the cycle, k=50.

[0056] Step 4: Calculate the attenuation rates of the simulated current waveform I1 and the recovered current waveform I2 at the transient moment and calculate the attenuation rate difference υ between the two. Normalize the attenuation rate difference υ between the two waveforms as an indicator of the attenuation degree difference in waveform transmission:

[0057]

[0058] Step 5: Calculate the high-order harmonic content of the transient current of the simulated current waveform I1 and the recovered current waveform I2 respectively, and calculate the difference between the high-order harmonic content of the two w j Normalization is performed as an indicator of the degree of high-order harmonic loss in waveform transmission.

[0059] w j =w 1j -w 2j

[0060] Among them, w j is the loss degree of the jth harmonic, w 1j is the loss degree of the jth harmonic in the simulated current waveform I1, w 2j It is the loss degree of the jth harmonic in the recovered current waveform I2.

[0061] Step 6: For the distortion coefficient μ, attenuation rate difference υ and high-order harmonic content difference w in steps 3, 4 and 5 j The evaluation matrix R is obtained by performing a comprehensive evaluation through reasonable weight distribution. The calculation method of the evaluation matrix R is as follows:

[0062]

[0063] Among them, a j is the evaluation coefficient, a1 = 0.5; a2 = 0.2;

[0064] Step 7: The evaluation matrix in step 6 uses the waveform distortion coefficient as the main judgment standard, and its evaluation coefficient is the largest. The larger the distortion coefficient μ, the larger the gap between the actual collected waveform and the simulated output waveform. The larger the corresponding a1*μ, the greater the impact on the evaluation matrix result. When the difference between the actual and simulated waveforms is not significant, it is considered that the error between the currents is small. At this time, the evaluation matrix compares the attenuation rate difference υ and the high-order harmonic content difference w j To assist in judging the error between currents. Therefore, when the evaluation matrix is ​​close to 0, the simulated current waveform I1 and the recovered current waveform I2 are completely consistent. The larger the result of the evaluation matrix, the higher the degree of error. Taking into account the error of electronic components during the verification process, R0 is generally taken as 0.3 to 0.4. When the result of the evaluation matrix R>R0, the waveform calibration signal alarms. At this time, there is a large error between the output waveform of the protection tester and the input waveform. The output waveform of the protection tester needs to be recalibrated so that the protection tester can obtain an output waveform with a smaller error.

[0065] The relay protection tester developed by the present invention has the advantages of small size, light weight, and the weight of the whole machine is less than 10 kilograms, which is suitable for portable testing needs, and realizes dynamic waveform and transient waveform output with the simulation system, and has eight pairs of input quantities, which can read the relay action signal to form an action report, and further constitute a closed-loop test system. Moreover, the relay protection tester involved in the present invention has great advantages in price cost, the output current amplitude can reach 35A, and the voltage single-phase can reach 350V, and a relatively comprehensive online real-time simulation of the relay protection device can be performed. This study integrates the simulation system with the relay protection tester, and establishes a real-time communication connection with the relay protection tester. The difference between the verification method of the present invention and the RTDS model is the verification comparison of the real-time simulation current waveform I1 and the protection device recovery current waveform I2. The real-time simulation current waveform I1 collected in the tester is compared with the protection device recovery current waveform I2, so that the preparation and modification of fault data become fast, forming a closed-loop test system that can be applied on site.

Claims

1. A method for verifying transient waveforms of a relay protection tester, wherein a microcomputer platform running simulation software is connected to a switch, and the switch is connected to a protection device through a protection tester. The microcomputer platform inputs a simulated current waveform I1 to the protection device through the switch and the protection tester, and the microcomputer platform also inputs the simulated current waveform I1 to a verification alarm system. After the protection device receives the waveform output by the protection tester, it outputs a recovery current waveform I2 to the verification alarm system. The simulated current waveform I1 is a voltage and current signal with significant transient characteristics, and is characterized in that: The simulation current waveform I1 is compared and corrected with the protection device recovery current waveform I2, which specifically includes the following steps: Step 1: Align the time axis of the real-time simulation current waveform I1 collected in the tester with the protection device recovery current waveform I2; Step 2: pre-process the simulation current waveform I1 and the protection device recovery current waveform I2; Step 3: Calculate the waveform distortion coefficient μ between the real-time simulation current waveform I1 and the recovery current waveform I2; Step 4: Calculate the difference in waveform attenuation rate υ between the simulated current waveform I1 and the recovered current waveform I2 at the transient moment; Step 5: Calculate the difference w between the high-order harmonic content of the simulated current waveform I1 and the recovered current waveform I2 in the transient current j ; Step 6: Distortion coefficient μ, attenuation rate difference υ and high-order harmonic content difference w j A reasonable weight distribution is performed for comprehensive evaluation to obtain the evaluation matrix R; when the result of the evaluation matrix R>R0, the waveform calibration signal alarm is issued.

2. The method for verifying transient waveform of a relay protection tester according to claim 1, characterized in that: The waveform calibration procedure is used to align the time axis of the simulated current waveform I1 described in step 1 with the protection device recovery current waveform I2. The specific method of the waveform calibration procedure is as follows: Among them, I1 is the real-time simulation waveform collected by the tester, I2 is the actual waveform collected by the protection device backflow, t X is the time difference between the recovered current waveform I2 and the simulated current waveform I1.

3. The method for verifying transient waveform of a relay protection tester according to claim 2, characterized in that: The method of preprocessing the waveform described in step 2 is: take 200 sampling points per cycle; during the verification process, select the first quarter of the cycle with significant transient characteristics: Among them, x(k) and y(k) are the simulation waveform and the sampling value of the recovered waveform in the waveform verification method respectively, T is the sampling time of one cycle, T = 0.02s; N is the number of sampling points of one cycle, N = 200; k is the number of sampling points of the first quarter of the cycle.

4. The method for verifying transient waveform of a relay protection tester according to claim 3, characterized in that: The calculation of the waveform distortion coefficient μ described in step 3 is to normalize the difference between the simulated current waveform I1 and the recovered current waveform I2, and obtain the waveform distortion coefficient μ as an indicator to measure the degree of waveform transmission distortion: Among them, x(k) and y(k) are the simulation waveform and the sampling value of the recovered waveform in the waveform verification method respectively, and k is the number of sampling points in the first quarter of the cycle, k=50.

5. The method for verifying transient waveform of a relay protection tester according to claim 4, characterized in that: The waveform attenuation rate difference υ described in step 4 is the normalized difference between the attenuation rates of the simulated current waveform I1 and the recovered current waveform I2, which is used as an indicator of the difference in attenuation degree in waveform transmission:

6. The method for verifying transient waveform of a relay protection tester according to claim 5, characterized in that: The high-order harmonic content difference w described in step 5 j The difference between the high-order harmonic content in the simulated current waveform I1 and the recovered current waveform I2 is normalized and used as an indicator of the degree of high-order harmonic loss in waveform transmission to obtain the high-order harmonic content difference w j : In j =in 1j -In 2j Among them, w j is the loss degree of the jth harmonic, w 1j is the loss degree of the jth harmonic in the simulated current waveform I1, w 2j It is the loss degree of the jth harmonic in the recovered current waveform I2.

7. The method for verifying transient waveform of a relay protection tester according to claim 6, characterized in that: The calculation method of the evaluation matrix R is as follows: Among them, a j is the evaluation coefficient, 8. The method for verifying transient waveform of a relay protection tester according to claim 1, characterized in that: The range of R0 is 0.3 to 0.4.

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