Relay protection sampling automatic checking method based on regulation cloud and big data analysis

Abstract

The application discloses a kind of based on regulation and control cloud and big data analysis's relay protection sampling automatic checking system, it is related to electric power relay protection technical field;The system includes SCADA system, protection signal system and protection sampling checking system;SCADA system is connected to each protection terminal by station control layer network, utilizes first sampling value of each protection terminal to be obtained by power flow calculation, and this first sampling value is output to protection sampling checking system;Protection signal system is connected to each protection terminal by station control layer network, for collecting the second sampling value of each protection terminal, and this second sampling value is output to protection sampling checking system;Protection sampling checking system integrates and utilizes first sampling value to check second sampling value received first sampling value and second sampling value.It is obtained by the amplitude and phase of secondary voltage, current from power flow distribution in SCADA system, cross-platform verifies the accuracy of protection sampling value in protection signal system, to find the situation of alternating current sampling exception in the process of relay protection operation.

Description

Technical Field

[0001] This invention relates to the field of power relay protection technology, and in particular to an automatic inspection method for relay protection sampling based on control cloud and big data analysis. Background Technology

[0002] In high-voltage power systems, accurate sampling of secondary voltages and currents in transmission lines is crucial to the reliability of protection operations. Abnormal sampling by relay protection can trigger a chain reaction during system faults, leading to the escalation of accidents. For protection devices already in operation, sampling inspections are mainly carried out during annual peak-load winter (summer) inspections. However, this method is challenging due to the large number of devices and the heavy workload. Furthermore, problematic branches may not be detected during inspections when the load is low.

[0003] The protection information substation system is mainly used for collecting, forwarding, and monitoring information from protection devices, viewing and managing settings, enabling and disabling protection functions, managing protection action information, and monitoring the status of protection devices. Currently, the data from the protection information substation system is only at the source-end maintenance stage and lacks effective application. Although there are relatively mature state estimation algorithms in automated SCADA systems that can identify malfunctioning data and calculate the phase of voltage and current based on power flow to verify the correctness of protection sampling, it still cannot automatically sample and verify the data of each protection device at regular intervals according to load conditions. This results in a still large workload for inspections, and the verification effect needs to be improved. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a patent name and to solve the technical problem.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] An automatic inspection system for relay protection sampling based on control cloud and big data analysis, including SCADA system, protection information system and protection sampling inspection system;

[0007] The SCADA system is connected to each protection terminal through the station control layer network, uses power flow calculation to obtain the first sample value of each protection terminal, and outputs the first sample value to the protection sampling inspection system.

[0008] The protection system is connected to each protection terminal through the station control layer network, and is used to collect the second sample value of each protection terminal and output the second sample value to the protection sampling inspection system.

[0009] The protection sampling inspection system integrates the received first and second sampling values ​​and uses the first sampling value to verify the second sampling value.

[0010] A further technical solution is that the protection sampling inspection system includes:

[0011] The SCADA system verification unit includes bus protection sampling checks, line protection sampling checks, main transformer protection sampling checks, and the setting of sampling abnormality alarm threshold values.

[0012] The differential current anomaly detection unit is used to issue a differential current anomaly alarm signal when the differential current of the bus differential protection exceeds the starting value of the differential current and remains so for a certain period of time; it records the maximum differential current Imax that has occurred during the operation of the protection device, and issues a corresponding differential current anomaly alarm signal when Imax > 0.25 times the rated current; and

[0013] The sampling value verification unit at both ends of the line is used to determine an abnormality when the current amplitudes on both sides of the line differ significantly, and to issue an abnormal line current alarm signal.

[0014] A further technical solution is that the bus protection sampling check specifically includes the SCADA system calculating the amplitude and phase of the secondary current of each branch and verifying the sampled values ​​in the bus protection.

[0015] The line protection sampling check includes calculating the secondary voltage value, phase angle, secondary current value, and phase angle of the I-side line and II-side line protection, and comparing them with the corresponding actual sampling values ​​in the line protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0016] The main transformer protection sampling check includes calculating the secondary voltage values, phase angles, secondary current values, and phase angles of the high-voltage, medium-voltage, and low-voltage sides of the main transformer protection, and comparing them with the corresponding actual sampling values ​​in the line protection of the protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0017] The threshold value for the sampling anomaly alarm is specifically calculated using the following formula:

[0018]

[0019] In the formula, ΔI d For sampling abnormal alarm values, ΔI d-Base For a fixed threshold, set manually, the measurement error of the device and the sampling synchronization should be considered; ΔI d-Load The floating threshold is determined by the load change rate, and K is the ratio coefficient.

[0020] A further technical solution is as follows: the SCADA system includes a master station front-end server, a PAS advanced application server, and a monitoring server. The master station front-end server collects the first sampled value of the measurement and control device through the remote control device and the real-time subnet of the scheduling data network. The monitoring server is electrically connected to the protection sampling and inspection system.

[0021] A further technical solution is as follows: the information protection system includes a communication server, an information protection master station, and information protection substations. The information protection substations are connected to the station control layer. The communication server is connected to the information protection substations through the non-real-time subnet of the scheduling data network. The information protection master station is electrically connected to the communication server and the protection sampling and inspection system.

[0022] A further technical solution is that a real-time switch and a first vertical encryption device are connected between the remote control device and the real-time subnet of the scheduling data network.

[0023] A further technical solution is that the remote control device, the real-time switch, and the first vertical encryption device are provided in two sets to form a dual-channel transmission line.

[0024] A further technical solution involves setting up a firewall between the information security substation and the station control layer network.

[0025] A further technical solution is that a second vertical encryption device is also connected between the security substation and the communication server.

[0026] A further technical solution is provided in which a forward lateral isolation device is provided between the SCADA system, the information protection system and the protection sampling and inspection system. The forward lateral isolation device is used to receive the first sample value and the second sample value output by the SCADA system and the information protection system, and output the first sample value and the second sample value to the protection sampling and inspection system.

[0027] The beneficial effects of adopting the above technical solution are as follows:

[0028] In the circuit system, for the protection devices that have been put into operation, the amplitude and phase of the secondary voltage and current are obtained by utilizing the power flow distribution in the SCADA system. The accuracy of the protection sampling values ​​in the protection information system is verified across platforms. At the same time, sampling self-test rules are set in the protection information substation system, and the control cloud and big data correlation analysis technology are applied to automatically detect abnormal AC sampling during the operation of relay protection. Attached Figure Description

[0029] Figure 1a This is a block diagram illustrating the sampling and inspection principle of a protection device already in operation, provided in an embodiment of the present invention.

[0030] Figure 1b This is a block diagram of a protective sampling inspection system provided in an embodiment of the present invention;

[0031] Figure 2a This is a power flow diagram of a bus in a SCADA system provided by an embodiment of the present invention;

[0032] Figure 2b This is a method provided by an embodiment of the present invention for... Figure 2a Sampling value diagram of the middle busbar;

[0033] Figure 3a This is a power flow diagram of a line in a SCADA system provided by an embodiment of the present invention;

[0034] Figure 3b This is a method provided by an embodiment of the present invention for... Figure 3a Sampling value diagram of the middle line;

[0035] Figure 4a This is a power flow diagram for main transformer protection in a SCADA system provided by an embodiment of the present invention;

[0036] Figure 4b This is a method provided by an embodiment of the present invention for... Figure 4a Sampling value diagram of the main transformer;

[0037] Figure 5a This is a comparison chart of the theoretically calculated SCADA values ​​and the actual sampling current amplitude provided in this embodiment of the invention;

[0038] Figure 5b This is a comparison chart of the phase change of the SCADA theoretical calculation value and the actual sampling current provided in this embodiment of the invention;

[0039] Figure 6a This is a comparison chart of the theoretical SCADA calculation value and the actual sampling current amplitude of the protection when the polarity of the line protection current loop is reversed, provided in this embodiment of the invention.

[0040] Figure 6b This is a comparison chart of the phase change of the SCADA theoretical calculation value and the actual sampling current when the polarity of the line protection current loop is reversed, as provided in the embodiments of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0042] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0043] This invention discloses an automatic inspection system for relay protection sampling based on control cloud and big data analysis, which is applied to high-voltage distribution lines at all levels. The system includes a SCADA system, a protection information system, and a protection sampling inspection system.

[0044] The SCADA system connects to each protection terminal via the station control layer network, uses power flow calculation to obtain the first sampled value of each protection terminal, and outputs this first sampled value to the protection sampling check system. The protection information system connects to each protection terminal via the station control layer network, collects the second sampled value of each protection terminal, and outputs this second sampled value to the protection sampling check system. The protection sampling check system integrates the received first and second sampled values ​​and uses the first sampled value to verify the second sampled value.

[0045] Please refer to Figure 1a This embodiment uses a 220kV single busbar connection outgoing line bay as an example for illustration. The voltage of the line voltage transformer and the current of the line current transformer at the substation end are connected to the line measurement and control and line protection terminals, while the voltage of the busbar voltage transformer is connected to the line protection. Therefore, the acquisition of AC quantities at the substation end has strong redundancy.

[0046] The SCADA system includes a main station front-end server, a PAS advanced application server, and a monitoring server. The main station front-end server collects the live data from the telemetry and control device through the real-time subnet of the dispatch data network via the remote control device. After processing by the state estimation algorithm in the PAS advanced application server and removing bad data, the data becomes the first sample value for use by the monitoring server. The monitoring server is electrically connected to the protection sampling and inspection system.

[0047] Among them, the dispatch data network is a dedicated wide area data network for power dispatch production services. It is the infrastructure for real-time and near-real-time data communication between power dispatch production departments and between power dispatch production departments and power plants and substations, such as computer monitoring systems.

[0048] A real-time switch and a first vertical encryption device connect the remote control unit and the real-time subnet of the dispatch data network. Two sets of remote control units, real-time switches, and the first vertical encryption device are provided, forming a dual-channel transmission line with one plane and two planes. All data transmission equipment between the two channels remains independent, ensuring that a failure in either transmission channel does not affect the uploading of data at the station end, thus guaranteeing the reliability of data transmission.

[0049] State estimation algorithms can utilize power grid models and parameters, as well as real-time telemetry and information dissemination data, to solve for the real-time operating state of the power grid and detect and identify abnormal data in measurements. The mathematical model for state estimation is based on measurement equations that reflect the interrelationships between network structure, line parameters, state variables, and real-time measurements.

[0050] z = h(x) + v

[0051] In the formula, z is the measurement; h(x) is the state variable, generally the node voltage amplitude and phase angle; v is the measurement error. They are all random variables.

[0052] The protection and information system includes a communication server, a protection and information master station, and protection and information substations. The protection and information substations are connected to the station control layer. The communication server is connected to the protection and information substations through the non-real-time subnet of the scheduling data network. The raw data collected by the protection device is sent to the master station communication server through the protection and information substation and the non-real-time subnet of the scheduling data network. The communication server processes the raw data to form a second sample value, which is available for the protection and information master station system to access and use. The protection and information master station is electrically connected to the communication server and the protection sampling and inspection system.

[0053] A firewall is installed between the information security substation and the station control layer network. The firewall scans network communications flowing through it, filtering out attacks to prevent execution on target computers. It can also close unused ports and block outgoing communications on specific ports, preventing Trojan horses. Furthermore, the firewall can block access from specific sites, thus preventing all communication from unknown intruders. Two sets of non-real-time switches and two sets of second-level vertical encryption devices are also connected between the information security substation and the communication server. The first and second vertical encryption devices are directly connected to the dispatch data network, employing authentication, encryption, and access control technologies to achieve secure data transmission and vertical boundary security protection for the power secondary system.

[0054] It is important to note that Figure 1a The transmission of data should meet the requirements of secondary security. The SCADA system is located in Security Zone I, the security information system is located in Security Zone II, and for ease of use, the protection sampling and inspection system is located in Security Zone III. The protection sampling and inspection system is also known as the protection sampling and inspection server. Data from the SCADA system and the security information system is transmitted to the protection sampling and inspection server via Web publishing.

[0055] The definitions of Safety Zone I, Safety Zone II, and Safety Zone III of the power system are explained below:

[0056] Based on the characteristics of the power secondary system, it is divided into a production control area and a management information area. The production control area is further divided into a control area (safety area I) and a non-control area (safety area II).

[0057] The information management area is divided into the production management area (safety zone III) and the management information area (safety zone IV). Different safety protection requirements are set for different safety zones, with safety zone I having the highest safety level, followed by safety zone II, and so on.

[0058] Typical systems in Safety Zone I include: dispatch automation systems, substation automation systems, relay protection systems, and automatic safety control systems.

[0059] Typical systems in Safety Zone II include: reservoir dispatch automation system, power metering system, relay protection and fault recording information management system, etc.

[0060] Typical systems in Safety Zone III include: Dispatch and Production Management System (DMIS), Lightning Monitoring System, and Statistical Reporting System.

[0061] Typical systems in Security Zone IV include: Management Information System (MIS), Office Automation System (OA), and Customer Service System.

[0062] A forward lateral isolation device is also provided between the SCADA system, the protection information system and the protection sampling and inspection system. The forward lateral isolation device is used to receive the first sample value and the second sample value output by the SCADA system and the protection information system, and output the first sample value and the second sample value to the protection sampling and inspection system.

[0063] Among them, the forward lateral isolation device is used only for transmission between security zones 1, 2 and 3. The lateral isolation device is equivalent to a security gate, and data can only be transmitted in one direction, not in two directions.

[0064] For example, if services in Security Zone 1 and Security Zone 2 need to access the external network of Security Zone 3, then a forward isolation device should be added. Conversely, if services in the external network of Security Zone 3 need to access services in the internal network of Security Zone 1 or Security Zone 2, then a reverse isolation device should be used. In this way, even if a hacker intrudes, there will be no data returned, so they cannot steal data, thus protecting the network security of the power grid to a certain extent.

[0065] Please refer to Figure 1b The protection sampling inspection system includes: SCADA system verification unit, differential current anomaly detection unit, and sampling value verification unit at both ends of the line.

[0066] The SCADA system verification unit includes sampling checks for bus protection, line protection, and main transformer protection, as well as the setting of alarm thresholds for sampling anomalies. Specifically, the bus protection sampling check involves the SCADA system calculating the amplitude and phase of the secondary current in each branch and verifying the sampled values ​​in the bus protection.

[0067] like Figure 2a and Figure 2bAs shown, taking a double busbar substation as an example, the sampling and inspection of busbar protection is explained: In the SCADA system, the power of each branch is set to be positive when flowing out of the busbar and negative when flowing into the busbar. The polarity of the bus tie is the same as that of each branch of busbar I. The power is negative when flowing into busbar I and positive when flowing out of busbar I. The sampling value of each branch can be obtained according to the power.

[0068] Figure 2a In the middle, P i Q i These represent the active power and reactive power of the i-th branch (i is the branch number, i = 1, 2, 3...), and U1 and U2 are the voltages of bus I and bus II, respectively. Buses I and II are usually operated in parallel to improve power supply reliability. The A-phase voltages of bus I and II are U... a1 U a2 The phases are the same. Only in a few substations located at the boundary of the power supply area or in substations operating under special modes, are the two busbars operated separately. In this case, there is a deviation in the phase angle of the I and II bus voltages, but since the electrical distance between the two busbars is small, the phase difference can be ignored, and U can be approximated as U. a1 U a2 The phase angles are the same.

[0069] Because busbar protection is also based on U a1 As a phase reference, the A-phase current of each branch is reduced to U. a1 The sampled values ​​are shown in the figure below. Figure 2b As shown, I ai Let θ be the primary value of phase A current in the i-th branch. i 'I is calculated based on the power of branch i' ai Take U a1 The phase angle is used as a reference. The phase θ of the current in each branch is... i The calculation method is shown in equation (1):

[0070]

[0071] After obtaining the phase angle of the A-phase current from equation (1), and considering that the three-phase currents are in a positive sequence during normal operation, the phase angles of the B and C-phase currents can be obtained as θ. i -120° and θ i -240°. In equation (1), θ i All are represented by positive numbers. When checking with busbar protection, if the phase angle of a certain branch is equal to (θ) i The -120° value was also considered to be correct.

[0072] The primary current value in the SCADA system is converted to the secondary current value based on the CT reference ratio in the bus protection, as shown in equation (2):

[0073] i i =I i / n B (2)

[0074] In equation (2), i i For the converted secondary value of branch i current, n B The reference ratio for the bus protection CT.

[0075] n B From the parameters of the bus protection system, it can be deduced that the typical bus protection RCS915 uses the maximum CT ratio of each branch as n. B The BP-2B uses the most frequently used CT ratio in each branch as n. B The protective device after the six unifications, n B It becomes a configurable parameter. The amplitude and phase of the secondary current of each branch are obtained from the SCADA system according to equations (1) and (2), and the sampled values ​​in the bus protection are checked. The current phase of the branch without current in the bus protection will fluctuate greatly. The sampling check only checks the branch with current. The branch with too small current to determine the phase is not checked.

[0076] The line protection sampling check includes calculating the secondary voltage values, phase angles, secondary current values, and phase angles of the I-side and II-side line protection, and comparing them with the corresponding actual sampling values ​​in the line protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0077] In line protection systems, the current transformer (CT) polarity is specified to point towards the line, while in SCADA systems, power is defined with the outflow bus as positive; both specify the positive direction. The principle of using the power flow distribution of the SCADA system to check the sampled values ​​of line protection is as follows: Figure 3a and Figure 3b As shown.

[0078] Figure 3a In the diagram, optical differential protection is configured on the line between stations A and B. Station A (side I) is the power supply side, with P1 and Q1 both greater than 0. Station B (side II) is the power receiving side, with P2 and Q2 both less than 0. I1 and I2 are the currents on sides I and II of the line, respectively, and U1 and U2 are the bus voltages on sides I and II of the line, respectively. Figure 3b The diagram shows the line sampling values ​​derived from the power flow in the SCADA system. The optical differential protection on line I side uses the A-phase voltage Ua1 of U1 as the reference, while the optical differential protection on line II side uses the A-phase voltage Ua2 of U2 as the reference. Ia1 and Ia2 are the A-phase currents of I1 and I2, respectively. a1 Ahead of U a1 The phase angle of Ia2 is θ1, and the phase angle of Ia2 leading Ua2 is θ2. The calculation methods of θ1 and θ2 are the same as those in equation (1).

[0079] The voltage drop generated during power transmission on the line includes the d-axis component ΔU2 and the q-axis component δU2, resulting in a phase difference θ between Ua1 and Ua2. μ The phase of the voltage at one end of the line can be calculated based on the bus voltage at one end. The calculation method is shown in equation (3):

[0080]

[0081] In equation (3), the phase difference θ between the voltages on both sides is calculated based on the bus voltage U2 on side II. μ .

[0082] The sampled values ​​of the line protection on both sides calculated by the SCADA system are shown in Table 1:

[0083] Table 1

[0084] Bus voltage on this side <![CDATA[u a1 ∠0°]]> <![CDATA[u a2 ∠0°]]> opposite bus voltage <![CDATA[u a2 ∠θ u ]]> <![CDATA[u a1 ∠-θ u ]]> Current on this side <![CDATA[i a1 ∠θ1]]> <![CDATA[i a2 ∠θ2]]> opposite current <![CDATA[i a2-1 ∠(θ2+θ u )]]> <![CDATA[i a1-2 ∠(θ1-θ u )]]>

[0085] In Table 1, μ a1 μ a2 These are the secondary values ​​of the bus voltages on side I and side II, calculated as shown in equation (4):

[0086]

[0087] In equation (4), n TV The PT ratios for the I and II busbars should be the same on both sides.

[0088] In Table 1, i a1 i a2 These are the secondary values ​​of the local current in the line protection of sides I and II, respectively. a2-1 i represents the value of the II-side current displayed in the I-side line protection. a1-2 The value of the current on side I displayed in the line protection on side II is calculated as shown in equation (5):

[0089]

[0090] In equation (4), nTA1 and nTA2 are the CT ratios of sides I and II, respectively.

[0091] Table 1 lists only the voltage and current sampling values ​​of phase A. Under normal conditions, the three-phase voltage and current are in a positive phase sequence, from which the phases of phases B and C can be obtained. The amplitude calculation of the voltage and current of phases B and C is the same as that of phase A, as shown in equations (4) and (5). Table 1 includes the voltage of the opposite bus because some line protections (such as PSL603U) obtain the voltage of the opposite bus through the optical differential channel for capacitor current compensation and double-end distance measurement. RSCS compares the values ​​in Table 1 with the actual sampling values ​​of the line protection in the protection system. When the amplitude or deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0092] The main transformer protection sampling check includes calculating the secondary voltage values, phase angles, and secondary current values ​​of the high-voltage, medium-voltage, and low-voltage sides of the main transformer protection, and comparing them with the corresponding actual sampling values ​​in the line protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0093] Taking a 220kV three-winding transformer with a YNynd11 connection as an example, the principle of checking the main transformer protection sampling value using the power flow distribution of the SCADA system is as follows: Figure 4a and Figure 4b As shown, the protection of the main transformer specifies that the polarity of each CT points to the main transformer, while the SCADA system specifies that the power is positive when it flows out of the bus. The two specify the same positive direction.

[0094] Figure 4a In the diagram, P1, Q1, I1, and U1 represent the active power, reactive power, current, and voltage on the high-voltage side (I side), respectively; P2, Q2, I2, and U2 represent the active power, reactive power, current, and voltage on the medium-voltage side (II side), respectively; and P3, Q3, I3, and U3 represent the active power, reactive power, current, and voltage on the low-voltage side (III side), respectively. Figure 4a It can be seen that the power on the high-voltage side flows from the bus to the main transformer, P1>0, Q1>0; the power on the medium-voltage side flows from the main transformer to the bus, P2<0, Q2<0; and the power on the low-voltage side flows from the main transformer to the bus, P3<0, Q3<0.

[0095] Figure 4b Taking phase A as an example, the phase relationship of the voltage and current on the high, medium, and low voltage sides is shown. The medium voltage and current are marked in blue, and the low voltage and current are marked in red. Due to the phase difference between the high and medium voltages caused by power transmission, the calculation method is shown in equation (6):

[0096]

[0097] In equation (6), θ u1-2 For the middle side voltage U a2 Leading high-voltage side voltage U a1 phase, X T1 and X T2 These are the per-unit values ​​of the equivalent reactance on the high-voltage and medium-voltage sides of the transformer (both attributed to the high-voltage side). The transformer resistance is ignored in the calculation; only the reactance is considered. From equation (6), it can be seen that when the main transformer transmits power from the high-voltage side to the medium-voltage side, θ u1-2 <0; Conversely, when the main transformer sends power back from the medium-voltage side to the high-voltage side, θ u1-2 >0.

[0098] The calculation method for the phase difference between the high-voltage and low-voltage sides is shown in equation (7):

[0099]

[0100] In equation (7), θ u1-3 For the low-side voltage U a3 Leading high-voltage side voltage U a1 phase, X T3 The per-unit value of the equivalent reactance on the low-voltage side of the transformer (all are referred to the high-voltage side). The transformer resistance is ignored in the calculation; only the reactance is considered. From equation (7), we know that θ u1-3 The occurrence of this is partly due to the θ generated by power transmission on the high and low voltage sides. u ' 1-3 On the other hand, it is due to the 30° rotation angle caused by the 11-point connection method of the transformer.

[0101] The primary current and voltage of each side of the main transformer in the SCADA system are converted to the secondary side according to the CT and PT ratios, as shown in equation (8):

[0102]

[0103] In equation (8), n TA1 n TA2 n TA3 These represent the CT ratios of the main transformer's high, medium, and low sides, respectively, n TV1 n TV2 n TV3 These are the PT ratios on the high, medium, and low sides of the main transformer.

[0104] The voltage and current sampling values ​​of each side of the main transformer protection calculated by the SCADA system are shown in Table 2:

[0105] Table 2

[0106]

[0107]

[0108] In Table 2, θ1, θ2, θ 3 These represent the phases by which the current of phase A on the high, medium, and low sides leads the voltage of the corresponding phase A bus, respectively, and are calculated using the same method as formula (1). Table 1 only lists the values ​​of phase A voltage and current. The voltage and current of phases B and C are in positive phase sequence with phase A, and the amplitude is calculated using formula (8). The RSCS compares the values ​​in Table 2 with the actual sampled values ​​of the main transformer protection in the protection system. When the amplitude or deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued.

[0109] The threshold value for sampling anomaly alarms is calculated using the following formula:

[0110]

[0111] In equation (9), ΔI d For sampling abnormal alarm values, ΔI d-Base For a fixed threshold, set manually, the measurement error of the device and the sampling synchronization should be considered; ΔI d-Load This is a floating threshold, determined by the load change rate, where K is the ratio coefficient. Setting a floating threshold automatically adjusts it based on daily load changes; when the load changes rapidly, the threshold value is automatically increased.

[0112] Factors affecting the judgment of sampling anomalies: 1) Load change rate and load size. The more stable the load, the smaller the error caused by the calculation and transmission links; the larger the load, the larger the relative allowable error of the measurement. 2) Adjusting the cloud computing speed. The faster the cloud computing speed, the smaller the error between the theoretical value and the measured value due to data asynchrony. When a sampling anomaly is determined for a certain protection, an alarm signal can be pushed to the monitoring system to promptly notify maintenance personnel for inspection and handling. In addition, for protection devices such as bus differential protection and malfunction protection, which would cause a large-scale power outage if they were to malfunction, their function can be immediately deactivated by remotely modifying the setting value to prevent malfunction.

[0113] The differential current anomaly detection unit is explained using bus differential protection as an example. When the polarity of a branch is reversed, the differential current in the bus differential protection is twice the current of that branch. When the phase sequence of a branch is incorrectly connected (BCA), the differential current in the bus differential protection is a multiple of the current of that branch. Bus differential protection is equipped with a differential current anomaly detection function. When the differential current exceeds the differential current over-limit alarm setting, after a delay, it will report "Protection has been carrying a differential current for a long time" and "CT is disconnected", and block the differential protection.

[0114] However, considering the worst-case scenario, if the phase sequence of a branch is incorrectly connected, and the differential current generated by the load current of that branch under normal conditions does not exceed the differential current over-limit alarm setting, the protection will not be blocked due to prolonged differential current. If a fault occurs in that branch at this time, the differential current in the bus differential protection will be a multiple of the fault current of that branch, and the overvoltage condition will be met. The sensitivity and speed of the bus differential protection are both higher than the branch line protection (the main protection is distance protection), and the bus differential protection will malfunction. Therefore, a differential current anomaly detection function should be set in the RSCS:

[0115] 1) When Id > Iset and this value remains above Iset for a certain period of time, a differential current abnormality alarm signal is issued to alert protection personnel. Iset is lower than the differential current over-limit alarm setting of the protection device, exhibiting high sensitivity. Generally, Iset can be taken as 0.025 times In. Wherein, Id is the differential current of the bus differential protection, and Iset is the starting setting of the differential current.

[0116] 2) Record the maximum differential current Imax that occurs during the operation of the protection device. When Imax > 0.25 times the rated current, issue a differential current abnormality alarm signal for the corresponding protection device.

[0117] The sampling value verification unit at both ends of the line is used to determine an abnormality when the current amplitudes on both sides of the line differ significantly, and to issue an abnormal line current alarm signal.

[0118] A test platform was built, consisting of a SCADA system comprised of a CSC200E measurement and control device and a CSC1321 remote control device; and a protection and information system comprised of a CSC161A line protection device and a CSC1326 protection and information system substation. A relay protection experimental instrument simultaneously outputs voltage and current to replace PTs and CTs, connecting the voltage loops of the line protection and measurement and control devices in parallel and the current loops in series to ensure consistency of the input voltage and current for protection and measurement and control. A PC was used as a simulated master station, with SCADA monitoring software (CS2000) and protection and information system master station software (CSGC3000) installed. C++ programming was used to periodically compare the data collected by the monitoring system and the protection and information system master station. The results are as follows: Figure 5a and Figure 5b As shown.

[0119] Figure 5a The system compares one point every 5 minutes, for a total of 24 points. The relay protection tester outputs a constant voltage of 57.7V, and the output current lags the voltage phase by 30°. The amplitude simulates the changing trend of the daily load curve. The CT and PT ratios are set to 600 / 5 and 110kV / 100V, respectively. Figure 5b Under normal circumstances, the deviation between the theoretically calculated SCADA value and the actual sampled current amplitude and phase variation curve of the protection is less than the alarm threshold.

[0120] Figure 6a , Figure 6b To simulate the situation where the polarity of the line protection current loop is reversed, the deviation in current amplitude is not significant, such as... Figure 6a As shown; however, the actual sampled value of the current phase differs from the theoretical calculated value by 180°, as shown. Figure 6b As shown, this demonstrates that the system can reliably detect sampling anomalies.

[0121] Experiments have demonstrated that the automatic sampling and inspection strategy for relay protection based on scheduling cloud and big data analysis technology, through horizontal comparison of data from the SCADA system and the protection information system, can automatically perform sampling and inspection at multiple time points throughout the day according to load conditions. This improves the utilization rate of protection information system data, enhances the automation level of professional relay protection maintenance, saves manpower and resources compared to traditional manual inspection, and improves inspection results. At the same time, it meets the requirements of the "Outline for the Development of Relay Protection" to build a relay protection status monitoring platform and strengthen the sampling and inspection of relay protection. It is also an advanced development and utilization of the control cloud platform beyond the display level, and has good prospects for promotion.

Claims

1. An automatic inspection system for relay protection sampling based on control cloud and big data analysis, characterized in that: This includes SCADA systems, information security systems, and protection sampling and inspection systems; The SCADA system is connected to each protection terminal through the station control layer network, uses power flow calculation to obtain the first sample value of each protection terminal, and outputs the first sample value to the protection sampling inspection system. The protection system is connected to each protection terminal through the station control layer network, and is used to collect the second sample value of each protection terminal and output the second sample value to the protection sampling inspection system. The protection sampling inspection system integrates the received first and second sampling values ​​and uses the first sampling value to verify the second sampling value. The protective sampling inspection system includes: The SCADA system verification unit includes bus protection sampling checks, line protection sampling checks, main transformer protection sampling checks, and the setting of sampling abnormality alarm threshold values. The differential current anomaly detection unit is used to issue a differential current anomaly alarm signal when the differential current of the bus differential protection exceeds the differential current start value and remains so for a certain period of time; it also records the maximum differential current I that has occurred during the operation of the protection device. max , when I max When the current exceeds 0.25 times the rated current, a differential current abnormality alarm signal is issued by the corresponding protection device; and The sampling value verification unit at both ends of the line is used to determine an abnormality when the current amplitudes on both sides of the line differ significantly, and to issue an abnormal line current alarm signal. The bus protection sampling check specifically includes the SCADA system calculating the amplitude and phase of the secondary current of each branch and verifying the sampled values ​​in the bus protection. The line protection sampling check includes calculating the secondary voltage value, phase angle, secondary current value, and phase angle of the I-side line and II-side line protection, and comparing them with the corresponding actual sampling values ​​in the line protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued. The main transformer protection sampling check includes calculating the secondary voltage values, phase angles, secondary current values, and phase angles of the high-voltage, medium-voltage, and low-voltage sides of the main transformer protection, and comparing them with the corresponding actual sampling values ​​in the line protection of the protection system. When the amplitude or phase deviation is greater than the set value, a corresponding protection sampling abnormality alarm is issued. The threshold value for the sampling anomaly alarm is specifically calculated using the following formula: In the formula, To sample abnormal alarm values, For a fixed threshold, which is set manually, the measurement error of the device and the sampling synchronization should be taken into account; The floating threshold is determined by the load change rate, and K is the ratio coefficient.

2. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 1, characterized in that: The SCADA system includes a master station front-end server, a PAS advanced application server, and a monitoring server. The master station front-end server collects the first sampled value of the measurement and control device through the real-time subnet of the scheduling data network via a remote control device. The monitoring server is electrically connected to the protection sampling and inspection system.

3. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 2, characterized in that: The remote control device and the real-time subnet of the scheduling data network are connected by a real-time switch and a first vertical encryption device.

4. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 3, characterized in that: The remote control device, real-time switch, and first longitudinal encryption device are provided in two sets, forming a dual-channel transmission line.

5. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 1, characterized in that: The information protection system includes a communication server, an information protection master station, and information protection substations. The information protection substations are connected to the station control layer. The communication server is connected to the information protection substations through the non-real-time subnet of the scheduling data network. The information protection master station is electrically connected to the communication server and the protection sampling and inspection system.

6. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 5, characterized in that: A firewall is installed between the information security substation and the station control layer network.

7. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 6, characterized in that: A second vertical encryption device is also connected between the security substation and the communication server.

8. The automatic inspection system for relay protection sampling based on control cloud and big data analysis according to claim 1, characterized in that: A forward lateral isolation device is also provided between the SCADA system, the information protection system, and the protection sampling and inspection system. The forward lateral isolation device is used to receive the first sample value and the second sample value output by the SCADA system and the information protection system, and output the first sample value and the second sample value to the protection sampling and inspection system.

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