Method and apparatus for determining current on basis of optical current transformer

Abstract

A method and apparatus for determining a current on the basis of an optical current transformer. The method comprises: according to a preset sampling period, acquiring first emergent light intensity sampling values generated by a first optical current transformer; according to the preset sampling period, acquiring second emergent light intensity sampling values generated by a second optical current transformer; identifying whether each first emergent light intensity sampling value exceeds a first light intensity measurement range; when a first emergent light intensity sampling value is located within the first light intensity measurement range, determining a first final real-time current value of a target device at the same sampling moment on the basis of the first emergent light intensity sampling value and a second emergent light intensity sampling value at the same sampling moment; and generating a current waveform of the target device on the basis of the first final real-time current value, and executing a relay protection operation on the basis of the current waveform.

Description

Method and device for determining current based on optical current transformer Technical Field

[0001] The present invention relates to the field of power systems, and in particular to a method and device for determining current based on an optical current transformer. Background Art

[0002] The operating principle of an optical current transformer (OCT) is to calculate the current of the device being measured by utilizing the Faraday magneto-optical effect. Specifically, in magneto-optical materials, an applied magnetic field causes a corresponding deflection of the plane of linear polarization propagating along the magnetic field. The angle of deflection of the incident light is related to the strength of the magnetic field (the magnitude of the current passing through it), the length of the interaction between the light and the magnetic field in the transparent material, and the properties of the material. Therefore, by measuring this deflection angle, the corresponding primary current can be calculated.

[0003] Therefore, how to accurately determine the primary side current becomes an urgent problem to be solved.

[0004] Summary of the Invention

[0005] In view of this, the present invention proposes a method for determining current based on an optical current transformer, wherein a target device corresponds to both a first optical current transformer and a second optical current transformer, the target device uses alternating current, and the first optical current transformer and the second optical current transformer are both used to determine the real-time current value of the target device. The real-time current of the target device is proportional to the intensity of the output light of the first optical current transformer, and the real-time current of the target device is proportional to the intensity of the output light of the second optical current transformer. The first optical current transformer corresponds to a first light intensity measurement range, and the second optical current transformer corresponds to a second light intensity measurement range, and the second light intensity measurement range is larger than the first light intensity measurement range.

[0006] The method comprises:

[0007] Acquire each first outgoing light intensity sampling value generated by the first optical current transformer according to a preset sampling period;

[0008] Acquire each second outgoing light intensity sampling value generated by the second optical current transformer according to the preset sampling period;

[0009] Identifying whether each of the first emergent light intensity sampling values ​​exceeds the first light intensity measurement range;

[0010] When the first emergent light intensity sampling value is within the first light intensity measurement range, determining a first final real-time current value of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment;

[0011] A current waveform of the target device is generated according to the first final real-time current value, and a relay protection operation is performed according to the current waveform.

[0012] According to the method described above, optionally, the method further includes:

[0013] If the identification result is that the second output light intensity sampling value exceeds the second light intensity measurement range, the last second output light intensity sampling value that does not exceed the second light intensity measurement range is used as the first final light intensity of the target device in a first time period, and the second final real-time current value of the target device in the first time period is determined based on the first final light intensity, and the second output light intensity sampling values ​​all exceed the second light intensity measurement range in the first time period;

[0014] A current waveform of the target device is generated according to the second final real-time current value.

[0015] According to the method described above, optionally, the method further includes:

[0016] If it is identified that the first output light intensity sampling value exceeds the first light intensity measurement range, then when it is determined that the second output light intensity sampling value is within the second light intensity measurement range, the fourth final real-time current value of the target device is determined according to the second output light intensity sampling value.

[0017] According to the method described above, optionally, determining the first final real-time current of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment includes:

[0018] Determine the first current value according to the first output light intensity sampling value at the same sampling moment;

[0019] Determine the second current value according to the second output light intensity sampling value at the same sampling moment;

[0020] The first final real-time current of the target device at the same sampling moment is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

[0021] According to the method described above, optionally, the preset weight value q is 0.7≤q≤0.9.

[0022] According to the method described above, optionally, the first optical current transformer corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, the second optical current transformer corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value;

[0023] in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

[0024] A device for determining current based on an optical current transformer, wherein a target device corresponds to both a first optical current transformer and a second optical current transformer, the target device uses alternating current, the first optical current transformer and the second optical current transformer are both used to determine the real-time current value of the target device, the real-time current of the target device is proportional to the intensity of the output light of the first optical current transformer, and the real-time current of the target device is proportional to the intensity of the output light of the second optical current transformer, the first optical current transformer corresponds to a first light intensity measurement range, the second optical current transformer corresponds to a second light intensity measurement range, and the second light intensity measurement range is larger than the first light intensity measurement range;

[0025] The device comprises:

[0026] a sampling unit, configured to obtain, according to a preset sampling period, each first outgoing light intensity sampling value generated by the first optical current transformer, and to obtain, according to the preset sampling period, each second outgoing light intensity sampling value generated by the second optical current transformer;

[0027] an identification unit, configured to identify whether each of the first emergent light intensity sampling values ​​exceeds the first light intensity measurement range, and trigger a first determination unit if the identification result is no;

[0028] The first determining unit is configured to determine a first final real-time current value of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment;

[0029] a generating unit, configured to generate a current waveform of the target device according to the first final real-time current value;

[0030] An operating unit is used to perform a relay protection operation according to the current waveform.

[0031] According to the device as described above, optionally, it further includes:

[0032] a setting unit, configured to, if a recognition result shows that the second output light intensity sample value exceeds the second light intensity measurement range, use the last second output light intensity sample value that does not exceed the second light intensity measurement range as the first final light intensity of the target device within a first time period;

[0033] a second determining unit, configured to determine a second final real-time current value of the target device within the first time period according to the first final light intensity, wherein the second output light intensity sampling values ​​all exceed a second light intensity measurement range within the first time period;

[0034] The generating unit is configured to generate a current waveform of the target device according to the second final real-time current value.

[0035] According to the device as described above, optionally, it further includes:

[0036] A third determining unit is configured to determine a fourth final real-time current value of the target device based on the second exit light intensity sampling value if it is identified that the first exit light intensity sampling value exceeds the first light intensity measurement range and if it is determined that the second exit light intensity sampling value is within the second light intensity measurement range.

[0037] According to the above device, optionally, the first determining unit is specifically configured to:

[0038] Determine the first current value according to the first output light intensity sampling value at the same sampling moment;

[0039] Determine the second current value according to the second output light intensity sampling value at the same sampling moment;

[0040] The first final real-time current of the target device at the same sampling moment is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

[0041] According to the device as described above, optionally, the first optical current transformer corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, the second optical current transformer corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value;

[0042] in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

[0043] The present invention also provides a device for determining current based on an optical current transformer, comprising:

[0044] at least one memory for storing instructions;

[0045] At least one processor is configured to execute the method for determining current based on an optical current transformer according to any one of the above items according to instructions stored in the memory.

[0046] The present invention further provides a readable storage medium, wherein the readable storage medium stores machine-readable instructions. When the machine-readable instructions are executed by a machine, the machine executes the method for determining current based on an optical current transformer as described in any one of the above items.

[0047] It can be seen from the above scheme that the present invention determines the real-time current of the target device by using two optical current transformers, which not only expands the measurement range of the optical current transformer but also improves the measurement accuracy when the current is small. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, so that those skilled in the art will understand the above and other features and advantages of the present invention more clearly. In the accompanying drawings:

[0049] FIG1 is a schematic diagram of a current waveform determined based on an optical current transformer in the prior art.

[0050] FIG2 is a flow chart of a method for determining current based on an optical current transformer according to an embodiment of the present invention.

[0051] FIG3A is a schematic diagram of a current waveform corresponding to a method for determining current based on an optical current transformer according to an embodiment of the present invention.

[0052] FIG3B is a schematic diagram of current waveforms corresponding to a method for determining current based on an optical current transformer according to another embodiment of the present invention.

[0053] FIG4A is a schematic diagram of current waveforms in various states corresponding to a method for determining current based on an optical current transformer according to an embodiment of the present invention.

[0054] FIG. 4B is a schematic diagram of a current waveform corresponding to an optical current transformer according to an embodiment of the present invention.

[0055] FIG5 is a schematic structural diagram of a device for determining current based on an optical current transformer according to an embodiment of the present invention.

[0056] FIG6A is a schematic structural diagram of a device for determining current based on an optical current transformer according to another embodiment of the present invention.

[0057] FIG6B is a schematic structural diagram of a device for determining current based on an optical current transformer according to yet another embodiment of the present invention. DETAILED DESCRIPTION

[0058] To make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail with reference to the following embodiments. Nouns and pronouns related to people in this patent application are not limited to specific genders.

[0059] The inventors have discovered that when the deflection angle of the incident light of the optical current transformer exceeds a certain angle, the current value measured by the optical current transformer will deviate.

[0060] Specifically, the formula that can be obtained according to Malus' law is: I = I0·cos 2 α, where I is the intensity of the outgoing light, I0 is the intensity of the incident light, and α is the deflection angle of the incident light. Generally, the deflection angle of the incident light of the optical current transformer is within 45°.

[0061] According to the Faraday effect, α(t) = B(t)·V·d;

[0062] According to Ampere's circuit theorem,

[0063] According to the above two formulas, we can get

[0064] Then we get the following formula:

[0065] Where i(t) represents the current of the device at time t, α(t) represents the deflection angle of the incident light at time t, and μ r represents the relative permeability of the optical current transformer, μ0 represents the vacuum permeability of the optical current transformer, V represents the Verdet constant of the optical current transformer, r represents the radius of the closed magnetic field loop, and d represents the length of the medium through which light travels.

[0066] As can be seen from the above formula, the larger the deflection angle α(t), the greater the real-time current of the device. However, due to the monotonicity of the cosine function, if the deflection angle of the incident light increases from 45° to a negative angle and then from a negative angle to 45°, the real-time current of the device obtained by the optical current transformer is shown in Figure 1, with the horizontal axis representing time in milliseconds (ms) and the vertical axis representing current in kA. As can be seen from Figure 1, the real-time current waveform in segment E is distorted. The real-time current waveform obtained by the optical current transformer will be transmitted to the relay protection device, and the relay protection device is likely to malfunction due to this distorted waveform.

[0067] Based on the above reasons, the present invention provides a method for determining current based on an optical current transformer. The method is used to determine the real-time current of a target device. The target device can be any device that requires current measurement, such as a switchgear. The measured current is the primary-side current. The target device of the present invention corresponds to both a first optical current transformer and a second optical current transformer. The first optical current transformer and the second optical current transformer are both used to determine the real-time current value of the target device. The real-time current of the target device is proportional to the output light intensity of the first optical current transformer. The real-time current of the target device is proportional to the output light intensity of the second optical current transformer. The first optical current transformer corresponds to a first light intensity measurement range, and the second optical current transformer corresponds to a second light intensity measurement range. The second light intensity measurement range is greater than the first light intensity measurement range. Here, the second light intensity measurement range being greater than the first light intensity measurement range means that the wavelength of the incident wave of the first optical current transformer is smaller than the wavelength of the incident wave of the second optical current transformer. Here, the first light intensity measurement range indicates a range less than or equal to the first maximum light intensity measurement value and greater than or equal to the first minimum light intensity measurement value. The second light intensity measurement range indicates a range less than or equal to the second maximum light intensity measurement value and greater than or equal to the second minimum light intensity measurement value. The second optical current transformer has lower accuracy than the first optical current transformer. Especially when the target device's real-time current is low, the error in the real-time current value obtained based on the second optical current transformer can be significant. Therefore, it is necessary to combine the first optical current transformer to determine the real-time current value.

[0068] The present invention uses two optical current transformers as an example to process the measured real-time current of the target device, thereby avoiding erroneous triggering of the relay protection device. It should be noted that in actual applications, more than two optical current transformers may be used, for example, three, four, or even more current transformers.

[0069] Example 1

[0070] This embodiment provides a method for determining current using an optical current transformer. This method is performed by a device for determining current using an optical current transformer. This device can be integrated into a relay protection device or provided separately, and is not described in detail here. The wavelengths of the light sources of the first and second optical current transformers can differ significantly. This combination facilitates the measurement of real-time current over a wider range while maintaining accuracy.

[0071] As shown in FIG2 , it is a flow chart of a method for determining current based on an optical current transformer according to this embodiment. The method includes:

[0072] Step 101: acquiring each first outgoing light intensity sampling value generated by a first optical current transformer according to a preset sampling period, and acquiring each second outgoing light intensity sampling value generated by a second optical current transformer according to a preset sampling period.

[0073] The wavelength of the light source corresponding to the first optical current transformer is shorter than the wavelength of the light source corresponding to the second optical current transformer. The first optical current transformer senses the real-time current of the target device and generates output light. The device for determining the current samples the output light according to a preset sampling period. The intensity of the output light obtained is the first output light intensity sampling value. In other words, the output light intensity of the first optical current transformer needs to be monitored in real time.

[0074] The second optical current transformer senses the real-time current of the target device and generates output light. The current determining device samples the second optical current transformer according to a preset sampling period. The intensity of the output light obtained is the second output light intensity sampling value. In other words, the output light intensity of the second optical current transformer needs to be monitored in real time.

[0075] In this embodiment, the device for determining current based on an optical current transformer samples the first optical current transformer and the second optical current transformer simultaneously according to the same preset sampling period.

[0076] Step 102 , identifying whether each of the first emergent light intensity sampling values ​​exceeds the first light intensity measurement range. If the identification results are all yes, executing step 103 .

[0077] As an exemplary illustration, it is necessary to monitor the first outgoing light intensity sampling value and the second outgoing light intensity sampling value at the same moment in real time. It is possible to determine whether the first outgoing light intensity sampling value is within the first light intensity measurement range based on the first outgoing light intensity sampling value. If not, it means that it exceeds the first light intensity measurement range. It is also possible to determine whether the second outgoing light intensity sampling value is within the second light intensity measurement range based on the second outgoing light intensity sampling value. Since each outgoing light intensity sampling value is continuously collected, it is necessary to continuously monitor whether each first outgoing light intensity sampling value is within the first light intensity measurement range, and continuously monitor whether each second outgoing light intensity sampling value is within the second light intensity measurement range. Of course, in the case where the second light intensity measurement range is greater than the first light intensity measurement range, it is also possible to determine whether the second outgoing light intensity sampling value is within the second light intensity measurement range when it is identified that the first outgoing light intensity sampling value exceeds the first light intensity measurement range. The specific selection can be made based on actual needs and will not be repeated here.

[0078] In this embodiment, the first light intensity measurement range can be determined based on the characteristics of the first optical current transformer, and the second light intensity measurement range can also be determined based on the characteristics of the second optical current transformer. It should be noted that the first light intensity measurement range is not the maximum or minimum light intensity that the first optical current transformer can measure, and the inflection point at which the real-time current obtained based on the output light intensity of the first optical current transformer begins to differ from the actual current, such as inflection point F in Figure 1. That is, the real-time current obtained based on the output light intensity within the first light intensity measurement range is consistent with the actual current, while the real-time current obtained based on the output light intensity outside the first light intensity measurement range is inconsistent with the actual current. Similarly, the second light intensity measurement range is not the maximum or minimum light intensity that the second optical current transformer can measure, and the inflection point at which the real-time current obtained based on the output light intensity of the second optical current transformer is inconsistent with the actual current. That is, the real-time current obtained based on the output light intensity within the second light intensity measurement range is consistent with the actual current, while the real-time current obtained based on the output light intensity outside the second light intensity measurement range is inconsistent with the actual current.

[0079] The measurement range of the second optical current transformer here is greater than that of the first optical current transformer, but the accuracy of the first optical current transformer is higher than that of the second optical current transformer.

[0080] Step 103 : when the first emergent light intensity sampling value is within the first light intensity measurement range, determine the first final real-time current of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment.

[0081] Specifically, the first current value can be determined according to the first output light intensity sampling value, and the second current value can be determined according to the second output light intensity sampling value at the same moment, and the first final real-time current at the target sampling moment can be determined according to the weight of the first current value and the weight of the second current value.

[0082] Of course, other methods can also be used to determine the first final real-time current at the target sampling moment based on the first outgoing light intensity sampling value and the second outgoing light intensity sampling value. For example, the first outgoing light intensity sampling value and the second outgoing light intensity sampling value are weighted to obtain a new outgoing light intensity sampling value, and the two incident light intensity sampling values ​​are also weighted to obtain a new incident light intensity sampling value. The first final real-time current at the target sampling moment is obtained based on the new incident light intensity sampling value and the new outgoing light intensity sampling value.

[0083] Because the first optical current transformer has higher precision than the second optical current transformer, the weight of the first outgoing light intensity sampling value can be set higher when the sensor is far from point F, and lower when the sensor is close to point F. This can avoid jumps at point F, which can cause waveform irregularities, and thus prevent erroneous operations caused by waveform jumps.

[0084] As a specific example, the steps include:

[0085] Determine a first current value according to a first output light intensity sampling value at a same sampling moment;

[0086] Determine a second current value according to a second output light intensity sampling value at the same sampling moment;

[0087] The first final real-time current of the target device at the same sampling time is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

[0088] The specific method for determining the current value of the target device based on the output light intensity sampling value is a matter of prior art and will not be further described here. The preset weight value here can be set according to actual needs, for example, the preset weight value q is 0.7≤q≤0.9. Adjusting the weight of the first current value to a higher value can increase the accuracy of the first final real-time current.

[0089] In addition, the same sampling moment here means that the sampling moments of the output light intensity sampling values ​​corresponding to the first current value and the second current value used when determining the first final real-time current are the same, and the situation where the first output light intensity sampling value is within the first light intensity measurement range will last for a period of time. During this period of time, there are multiple first final real-time current values, and the corresponding current waveform can be formed.

[0090] Step 104 : Generate a current waveform of the target device according to the first final real-time current, and perform a relay protection operation according to the current waveform.

[0091] Specifically, a corresponding waveform can be generated based on all first final real-time current values. That is, when the output light intensity is within the first light intensity measurement range, the method of this embodiment is used to obtain the first final real-time current value in this case and generate a corresponding current waveform, as specifically shown in current waveform S2 in Figure 3A. The relay protection device then performs the corresponding relay protection operation based on this current waveform. The specific method for performing the corresponding protection operation based on the current waveform is well known in the art and will not be further elaborated here.

[0092] Optionally, the target device may also correspond to a third optical current transformer, a fourth optical current transformer, and so on, and the corresponding light intensity measurement ranges are all different. The method of this embodiment can be used between two optical current transformers with adjacent light intensity measurement ranges to obtain the final real-time current in the corresponding situation. For example, if there is a third optical current transformer and the third light intensity measurement range corresponding to the third optical current transformer is greater than the second light intensity measurement range, when it is identified that the first outgoing light intensity sampling value exceeds the first light intensity measurement range and the second outgoing light intensity sampling value is within the second light intensity measurement range, the real-time current value within the time period is determined based on the second outgoing light intensity sampling value and the third outgoing light intensity sampling value of the third optical current transformer at the same time, and a waveform is generated accordingly. This can avoid jumps at the inflection point and improve the accuracy of the third optical current transformer. The specific details are analogous and will not be repeated here.

[0093] According to this embodiment, the real-time current of the target device is determined by using two optical current transformers, which not only expands the measurement range of the optical current transformers but also improves the measurement accuracy when the current is small.

[0094] Example 2

[0095] This embodiment further supplements the method for determining current using an optical current transformer in Example 1. This embodiment primarily describes how, after exceeding the first and second optical measurement ranges, the real-time current waveforms obtained using the first and second optical current transformers are processed to avoid malfunctions caused by distortion.

[0096] In this embodiment, if the identification result is that the second output light intensity sampling value exceeds the second light intensity measurement range, the last second output light intensity sampling value that does not exceed the second light intensity measurement range is used as the first final light intensity of the target device in the first time period, and the second final real-time current of the target device in the first time period is determined based on the first final light intensity. The second output light intensity sampling values ​​all exceed the second light intensity measurement range in the first time period.

[0097] A current waveform of the target device is generated according to the second final real-time current.

[0098] For example, as shown in Figures 3A and 3B, the horizontal axis is time, in seconds (s), and the vertical axis is current. Specifically, a column of numbers close to the vertical axis indicates that the current unit is kA. S2 in Figure 3A refers to the current waveform when the second outgoing light intensity sampling value finally exceeds the second light intensity measurement range. S4 in Figure 3B refers to the current waveform when the first outgoing light intensity sampling value exceeds the first light intensity measurement range and the second outgoing light intensity sampling value has not exceeded the second light intensity measurement range. As shown in Figure 3A, the part between moment A and moment B represents the first time period when the second outgoing light intensity sampling value exceeds the second light intensity measurement range, wherein the second light intensity sampling value at the sampling moment before moment A is the last second outgoing light intensity sampling value that does not exceed the second light intensity measurement range, and the real-time current of the target device determined based on the second outgoing light intensity sampling value is the second final real-time current value. During the first time period between time A and time B, a current waveform is generated using the second final real-time current value. That is, after processing, the current waveform during the first time period is shown as segment AB in S2 in FIG3A , where time A is the starting point of the first time period and time B is the end point of the first time period. Thus, the current waveform generated based on the second real-time current does not cause malfunction of the relay protection device.

[0099] Similarly, if the identification result is that the first output light intensity sampling value exceeds the first light intensity measurement range, the last first output light intensity sampling value that does not exceed the first light intensity measurement range is used as the second final light intensity of the target device in the second time period, and the third final real-time current of the target device in the second time period is determined based on the second final light intensity;

[0100] A current waveform of the target device is generated according to the third final real-time current.

[0101] S1 in FIG3 , S3 in FIG3B , and FIG4B are real-time current waveforms obtained based on the first optical current transformer, wherein the current waveforms in the second time period between time C and time D all use the third final real-time current. In this way, the relay protection device will not malfunction due to this current waveform. The real-time current waveforms obtained based on the first optical current transformer referred to by S1 in FIG3 and S5 in FIG4B are current waveforms obtained by correcting the real-time current corresponding to the exceeding portion when the first output light intensity sampling value exceeds the first light intensity measurement range. This correction refers to using the last first output light intensity sampling value that does not exceed the first light intensity measurement range as the second final light intensity of the target device in the second time period, and determining the third final real-time current of the target device in the second time period based on this second final light intensity.

[0102] Optionally, if it is identified that the first emergent light intensity sampling value is within the first light intensity measurement range, a current waveform of the target device is generated according to the first emergent light intensity sampling value and the second emergent light intensity sampling value, and a relay protection operation is performed according to the current waveform.

[0103] That is, the current waveform S2 in Figure 3A is composed of three parts. The case where the output light intensity of the first optical current transformer is within the first light intensity measurement range is regarded as state 0, the case where the output light intensity of the first current transformer is greater than or equal to the first maximum light intensity measurement value and the output light intensity of the second current transformer is less than or equal to the second maximum light intensity measurement value is regarded as state 1, the case where the output light intensity of the first current transformer is less than or equal to the first minimum light intensity measurement value and the output light intensity of the second current transformer is greater than or equal to the second minimum light intensity measurement value is regarded as state -1, the case where the output light intensity of the second current transformer is greater than the second maximum light intensity measurement value is regarded as state 2, and the case where the output light intensity of the second current transformer is less than the second minimum light intensity measurement value is regarded as state -2, as represented by the left column of numbers on the vertical axis of Figure 3A. Among them, when the first emergent light intensity sampling value is within the first light intensity measurement range, the part corresponding to the current waveform S2 is determined based on the first emergent light intensity sampling value and the second emergent light intensity sampling value; when the first emergent light intensity sampling value exceeds the first light intensity measurement range and the second emergent light intensity sampling value is within the second light intensity measurement range, the part corresponding to the current waveform S2 is obtained based on the second emergent light intensity sampling value, for example, the fourth final real-time current value of the target device during this period of time is determined according to the second emergent light intensity sampling value, and the waveform is determined accordingly; when the second emergent light intensity sampling value exceeds the second light intensity measurement range, the part corresponding to the current waveform S2 is obtained based on the second final real-time current value, and the final current waveform is S2 in Figure 3A, and the current protection device performs the relay protection operation according to the current waveform.

[0104] The current waveform S4 in FIG3B consists of two parts, and FIG3B does not include the state 2 or state -2. For the current waveform S4 in FIG3B , when the first outgoing light intensity sampling value is within the first light intensity measurement range, the portion corresponding to the current waveform S4 is determined based on the first outgoing light intensity sampling value and the second outgoing light intensity sampling value. When the first outgoing light intensity sampling value exceeds the first light intensity measurement range and the second outgoing light intensity sampling value is within the second light intensity measurement range, the portion corresponding to the current waveform S4 is obtained from the second outgoing light intensity sampling value. For example, the fourth final real-time current value of the target device during this period is determined based on the second outgoing light intensity sampling value, and the waveform is determined accordingly. The situation where the output light intensity of the first optical current transformer is within the first light intensity measurement range is regarded as state 0, the situation where the output light intensity of the first current transformer is greater than or equal to the first maximum light intensity measurement value and the output light intensity of the second current transformer is less than or equal to the second maximum light intensity measurement value is regarded as state 1, and the situation where the output light intensity of the first current transformer is less than or equal to the first minimum light intensity measurement value and the output light intensity of the second current transformer is greater than or equal to the second minimum light intensity measurement value is regarded as state -1, as shown in the column of numbers away from the vertical axis in Figure 3B.

[0105] In this way, when further operation needs to be performed based solely on the real-time current waveform of the first optical current transformer or the real-time current waveform of the second optical current transformer, erroneous operation due to the original distorted waveform can be avoided.

[0106] Example 3

[0107] This embodiment further supplements the method for determining current based on an optical current transformer in the previous embodiment.

[0108] In this embodiment, the first light intensity measurement range corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, and the second light intensity measurement range corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, wherein the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value.

[0109] In this embodiment,

[0110] in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

[0111] The preset factor here can be set according to actual conditions, for example, according to the characteristics of the optical current transformer. The preset factor is 0<preset factor<1, for example, 0.9. Of course, it can also be other values, which will not be described here.

[0112] As an example, a first optical current transformer and a second optical current transformer are simultaneously used to measure the primary current of a target device. The real-time output light intensity of the first and second optical current transformers is input into a relay protection device, which also knows the incident light intensity of the first and second optical current transformers in advance. More specifically, the relay protection device includes two circuit boards, the first of which is used to perform protection analysis on the input current waveform to trigger the corresponding protection action, and the second circuit board is used to collect the light intensity information transmitted by the first and second optical current transformers and generate a corresponding current waveform for input into the first circuit board. The current waveform generated by the second circuit board can also be obtained during other periods.

[0113] In this embodiment, the situation where the output light intensity of the first optical current transformer is within the first light intensity measurement range is regarded as state 0, the situation where the output light intensity of the first current transformer is greater than or equal to the first maximum light intensity measurement value and the output light intensity of the second current transformer is less than or equal to the second maximum light intensity measurement value is regarded as state 1, the situation where the output light intensity of the first current transformer is less than or equal to the first minimum light intensity measurement value and the output light intensity of the second current transformer is greater than or equal to the second minimum light intensity measurement value is regarded as state -1, the situation where the output light intensity of the second current transformer is greater than the second maximum light intensity measurement value is regarded as state 2, and the situation where the output light intensity of the second current transformer is less than the second minimum light intensity measurement value is regarded as state -2, as shown in Figures 3A and 3B. Figure 4A is a flow diagram of each state according to this embodiment. That is, from state 0 to state 1, then from state 1 to state 2, then restore from state 2 to state 1, and then restore from state 1 to state 0. Similarly, from state 0 to state -1, then from state -1 to state -2, then restore from state -2 to state -1, and then restore from state -1 to state 0.

[0114] The relay protection device continues to sample the outgoing light intensity of the first optical current transformer and the outgoing light intensity of the second optical current transformer at the same sampling period to obtain the first outgoing light intensity sampling value and the second outgoing light intensity sampling value at the same moment.

[0115] FIG4B is a schematic diagram of the current waveform when the first outgoing light intensity sampling value exceeds the first light intensity measurement range, wherein S5 is a schematic diagram of the current waveform obtained solely based on the first optical current transformer. Specifically, based on the first outgoing light intensity sampling value, it is determined that the current state is 0, then the current waveform S5 obtained based on the first outgoing light intensity sampling value is as shown in the M1 to N1 segment in FIG4B . If it is identified that the first outgoing light intensity sampling value exceeds the first light intensity measurement range, then based on the last first outgoing light intensity sampling value that does not exceed the first light intensity measurement range, the first final real-time current value of the target device at the target sampling moment is determined to be as shown in the N1 to P1 segment of the current waveform S5 in FIG4B . If it is identified that the first outgoing light intensity sampling value returns to the first light intensity measurement range, that is, returns to state 0, then the current waveform S5 obtained based on the first outgoing light intensity sampling value is as shown in the P1 to Q1 segment in FIG4B . And so on.

[0116] If the second output light intensity sample value exceeds the second light intensity measurement range, the current waveform obtained solely based on the second optical current transformer has a shape similar to that of Figure 4B . Furthermore, current waveform S2 in Figure 3A is a schematic diagram of the current waveform output by the second circuit board to the first circuit board, illustrating the current waveforms between states 0, 1, and 2. This current waveform S2 is used by the first circuit board to perform subsequent relay protection operations based on this current waveform.

[0117] Example 4

[0118] This embodiment provides a device for determining current based on an optical current transformer. This device can be integrated into a relay protection device, provided separately, or considered the relay protection device itself. The details are omitted here. The wavelengths of the light sources of the first and second optical current transformers can differ significantly. This combination facilitates the measurement of real-time currents over a wider range while maintaining accuracy.

[0119] As shown in Figure 5, a schematic diagram of the structure of the device for determining current based on an optical current transformer according to this embodiment is shown. The device for determining current based on an optical current transformer includes a sampling unit 501, an identification unit 502, a first determination unit 503, a generation unit 504, and an operation unit 505.

[0120] Among them, the sampling unit 501 is used to obtain each first outgoing light intensity sampling value generated by the first optical current transformer according to a preset sampling period, and obtain each second outgoing light intensity sampling value generated by the second optical current transformer according to the preset sampling period; the identification unit 502 is used to identify whether each first outgoing light intensity sampling value exceeds the first light intensity measurement range, and if the identification result is no, triggering a first determination unit 503; the first determination unit 503 is used to determine the first final real-time current value of the target device at the same sampling moment based on the first outgoing light intensity sampling value and the second outgoing light intensity sampling value at the same sampling moment; the generation unit 504 is used to generate a current waveform of the target device according to the first final real-time current value; the operation unit 505 is used to perform a relay protection operation according to the current waveform.

[0121] Optionally, the first determining unit 503 is specifically configured to:

[0122] Determine a first current value according to a first output light intensity sampling value at a same sampling moment;

[0123] Determine a second current value according to a second output light intensity sampling value at the same sampling moment;

[0124] The first final real-time current of the target device at the same sampling time is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

[0125] Optionally, the preset weight value q is 0.7≤q≤0.9.

[0126] Optionally, the first optical current transformer corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, the second optical current transformer corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value;

[0127] in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

[0128] The working methods of the various units in this embodiment are the same as those in the previous embodiment and will not be described again here.

[0129] According to this embodiment, two optical current transformers are used to determine that the output light intensity caused by the real-time current of the target device exceeds the first light intensity measurement range of the first optical current transformer and is within the second light intensity measurement range of the second optical current transformer. The first output light intensity sampling value and the second output light intensity sampling value are combined to obtain the real-time current of the target device in the above situation. The real-time current is closer to the true current of the target device. Relay protection operation is performed according to the current waveform generated by the real-time current, which can avoid false operation.

[0130] Example 5

[0131] This embodiment further supplements the device for determining current based on an optical current transformer in the fourth embodiment.

[0132] FIG6A is a schematic diagram of the structure of an apparatus for determining current based on an optical current transformer according to this embodiment. In addition to the sampling unit 501, identification unit 502, first determination unit 503, generation unit 504, and operation unit 505 included in the aforementioned embodiments, the apparatus for determining current based on an optical current transformer according to this embodiment further includes a setting unit 601 and a second determination unit 602.

[0133] Among them, the setting unit 601 is used to use the last second output light intensity sampling value that does not exceed the second light intensity measurement range as the first final light intensity of the target device in a first time period if the recognition result is that the second output light intensity sampling value exceeds the second light intensity measurement range; the second determination unit 602 is used to determine the second final real-time current value of the target device in the first time period based on the first final light intensity, and the second output light intensity sampling values ​​all exceed the second light intensity measurement range in the first time period; accordingly, the generation unit 504 is used to generate a current waveform of the target device based on the second final real-time current value.

[0134] Optionally, as shown in Figure 6B, the optical current transformer-based current determination apparatus further includes a third determination unit 603. This third determination unit 603 is configured to, if the first outgoing light intensity sample value is identified as exceeding the first light intensity measurement range, then determine a fourth final real-time current value of the target device based on the second outgoing light intensity sample value, if the second outgoing light intensity sample value is determined to be within the second light intensity measurement range. The operation of identifying that the first outgoing light intensity sample value exceeds the first light intensity measurement range can be specifically performed by the identification unit 502 and notified to the third determination unit 603, or the third determination unit 603 can actively obtain the information from the identification unit 502. Accordingly, the generation unit is configured to generate a current waveform for the target device based on the fourth final real-time current value.

[0135] The working methods of the various units in this embodiment are the same as those in the previous embodiment and will not be described again here.

[0136] In this way, the current waveform obtained according to the second final real-time current will not cause malfunction of the relay protection device.

[0137] This invention also provides a device for determining current based on an optical current transformer, comprising at least one memory and at least one processor. The memory is configured to store instructions. The processor is configured to execute the method for determining current based on an optical current transformer described in any of the aforementioned embodiments according to the instructions stored in the memory. The device for determining current based on an optical current transformer may be a relay protection device itself.

[0138] An embodiment of the present invention further provides a readable storage medium having machine-readable instructions stored therein, wherein when the machine-readable instructions are executed by a machine, the machine executes the method for determining current based on an optical current transformer as described in any of the aforementioned embodiments.

[0139] The readable medium stores machine-readable instructions that, when executed by a processor, cause the processor to perform any of the aforementioned methods. Specifically, a system or device equipped with a readable storage medium may be provided, wherein the readable storage medium stores software program code that implements the functions of any of the aforementioned embodiments, and causes a computer or processor of the system or device to read and execute the machine-readable instructions stored in the readable storage medium.

[0140] In this case, the program code itself read from the machine-readable medium can realize the function of any one of the above embodiments, and thus the machine-readable code and the machine-readable storage medium storing the machine-readable code constitute part of the present invention.

[0141] Examples of readable storage media include floppy disks, hard disks, magneto-optical disks, optical disks (e.g., CD-ROMs, CD-Rs, CD-RWs, DVD-ROMs, DVD-RAMs, DVD-RWs, DVD+RWs), magnetic tapes, non-volatile memory cards, and ROMs. Alternatively, the program code may be downloaded from a server computer or a cloud via a communication network.

[0142] Those skilled in the art will appreciate that the various embodiments disclosed above may be modified and altered in various ways without departing from the essence of the invention. Therefore, the scope of protection of the present invention shall be defined by the appended claims.

[0143] It should be noted that not all steps and units in the above processes and system structure diagrams are required, and certain steps or units can be omitted according to actual needs. The execution order of each step is not fixed and can be adjusted as needed. The device structure described in the above embodiments can be a physical structure or a logical structure, that is, some units may be implemented by the same physical entity, or some units may be implemented by multiple physical entities, or may be implemented by certain components in multiple independent devices.

[0144] In the above embodiments, the hardware unit can be realized by mechanical means or electrical means. For example, a hardware unit or a processor can include a permanent dedicated circuit or logic (such as a special processor, FPGA or ASIC) to complete the corresponding operation. The hardware unit or the processor can also include programmable logic or circuit (such as a general-purpose processor or other programmable processors), which can be temporarily set up by software to complete the corresponding operation. Concrete implementation (mechanical means or dedicated permanent circuit or temporarily set circuit) can be determined based on the consideration in cost and time.

[0145] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for determining current based on an optical current transformer, wherein a target device corresponds to both a first optical current transformer and a second optical current transformer, the target device uses alternating current, and both the first optical current transformer and the second optical current transformer are used to determine the real-time current value of the target device. The real-time current of the target device is proportional to the intensity of the output light of the first optical current transformer, and the real-time current of the target device is proportional to the intensity of the output light of the second optical current transformer. The first optical current transformer corresponds to a first light intensity measurement range, and the second optical current transformer corresponds to a second light intensity measurement range, and the second light intensity measurement range is greater than the first light intensity measurement range. The method comprises: Acquire each first outgoing light intensity sampling value generated by the first optical current transformer according to a preset sampling period; Acquire each second outgoing light intensity sampling value generated by the second optical current transformer according to the preset sampling period; Identifying whether each of the first emergent light intensity sampling values exceeds the first light intensity measurement range; When the first emergent light intensity sampling value is within the first light intensity measurement range, determining a first final real-time current value of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment; A current waveform of the target device is generated according to the first final real-time current value, and a relay protection operation is performed according to the current waveform.

2. The method according to claim 1, characterized in that Also includes: If the identification result is that the second output light intensity sampling value exceeds the second light intensity measurement range, the last second output light intensity sampling value that does not exceed the second light intensity measurement range is used as the first final light intensity of the target device in a first time period, and the second final real-time current value of the target device in the first time period is determined based on the first final light intensity, and the second output light intensity sampling values all exceed the second light intensity measurement range in the first time period; A current waveform of the target device is generated according to the second final real-time current value.

3. The method according to claim 1, characterized in that Also includes: If it is identified that the first output light intensity sampling value exceeds the first light intensity measurement range, then when it is determined that the second output light intensity sampling value is within the second light intensity measurement range, the fourth final real-time current value of the target device is determined according to the second output light intensity sampling value.

4. The method according to claim 1, wherein Determining the first final real-time current of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment includes: Determine the first current value according to the first output light intensity sampling value at the same sampling moment; Determine the second current value according to the second output light intensity sampling value at the same sampling moment; The first final real-time current of the target device at the same sampling moment is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

5. The method according to claim 4, characterized in that The preset weight value q is 0.7≤q≤0.

9.

6. The method according to any one of claims 1 to 5, characterized in that The first optical current transformer corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, the second optical current transformer corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value; in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

7. An apparatus for determining current based on optical current transformers, wherein a target device corresponds to both a first optical current transformer and a second optical current transformer, the target device uses alternating current, and both the first optical current transformer and the second optical current transformer are used to determine the real-time current value of the target device. The real-time current of the target device is proportional to the intensity of the light emitted by the first optical current transformer, and the real-time current of the target device is proportional to the intensity of the light emitted by the second optical current transformer. The first optical current transformer corresponds to a first light intensity measurement range, and the second optical current transformer corresponds to a second light intensity measurement range, wherein the second light intensity measurement range is greater than the first light intensity measurement range. The device comprises: a sampling unit, configured to obtain, according to a preset sampling period, each first outgoing light intensity sampling value generated by the first optical current transformer, and to obtain, according to the preset sampling period, each second outgoing light intensity sampling value generated by the second optical current transformer; an identification unit, configured to identify whether each of the first emergent light intensity sampling values exceeds the first light intensity measurement range, and trigger a first determination unit if the identification result is no; The first determining unit is configured to determine a first final real-time current value of the target device at the same sampling moment according to the first emergent light intensity sampling value and the second emergent light intensity sampling value at the same sampling moment; a generating unit, configured to generate a current waveform of the target device according to the first final real-time current value; An operating unit is used to perform a relay protection operation according to the current waveform.

8. The device according to claim 7, characterized in that Also includes: a setting unit, configured to, if a recognition result shows that the second output light intensity sample value exceeds the second light intensity measurement range, use the last second output light intensity sample value that does not exceed the second light intensity measurement range as the first final light intensity of the target device within a first time period; a second determining unit, configured to determine a second final real-time current value of the target device within the first time period according to the first final light intensity, wherein the second output light intensity sampling values all exceed a second light intensity measurement range within the first time period; The generating unit is configured to generate a current waveform of the target device according to the second final real-time current value.

9. The device according to claim 7, characterized in that Also includes: A third determining unit is configured to determine a fourth final real-time current value of the target device based on the second exit light intensity sampling value if it is identified that the first exit light intensity sampling value exceeds the first light intensity measurement range and if it is determined that the second exit light intensity sampling value is within the second light intensity measurement range.

10. The device according to claim 7, characterized in that The first determining unit is specifically configured to: Determine the first current value according to the first output light intensity sampling value at the same sampling moment; Determine the second current value according to the second output light intensity sampling value at the same sampling moment; The first final real-time current of the target device at the same sampling moment is determined according to the following formula: first final real-time current=first current value*preset weight value+second current value*(1-preset weight value).

11. The device according to any one of claims 7 to 10, characterized in that The first optical current transformer corresponds to a first maximum light intensity measurement value and a first minimum light intensity measurement value, the second optical current transformer corresponds to a second maximum light intensity measurement value and a second minimum light intensity measurement value, the second maximum measurement value is greater than the first maximum measurement value, and the second minimum measurement value is less than the first minimum measurement value; in, is 45°, I1 is the intensity of the incident light of the first optical current transformer, I2 is the intensity of the incident light of the second optical current transformer, γ1 is the deflection angle of the incident light of the first optical current transformer, and γ2 is the deflection angle of the incident light of the first optical current transformer.

12. Device for determining current based on an optical current transformer, characterized in that include: at least one memory for storing instructions; At least one processor is configured to execute the method for determining current based on an optical current transformer according to any one of claims 1 to 6 according to instructions stored in the memory.

13. A readable storage medium, characterized in that The readable storage medium stores machine-readable instructions. When the machine-readable instructions are executed by a machine, the machine executes the method for determining current based on an optical current transformer according to any one of claims 1 to 6.

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