Selective encryption method for remote control switch in power distribution area

Abstract

The invention discloses a power distribution area remote control switch selective encryption method, which overcomes the problem of large encryption and decryption calculation amount of a power distribution terminal and a power distribution remote control switch in the prior art, and comprises the following steps: adding encryption chips at the power distribution terminal at the head end and a switch at an important position at the tail end, inquiring the condition of the encryption chip at the tail end at the head end and establishing an information table, establishing an encryption channel with a tail end primary exchange encryption security certificate supporting encryption, and performing encryption selection of a first layer for switch equipment under different security levels; and the head end generates a management message and issues the management message, if the management message is a given remote control related message and a target node supports an encryption chip, the message is encrypted according to a data encryption strategy of the node and issued to the tail end, the tail end encrypts corresponding feedback information and then uploads the encrypted feedback information to the head end, and second-layer encryption selection work is completed. The encryption and decryption calculation amount in a single encryption switch is reduced under the condition that the security of an important area is guaranteed, and the data transmission efficiency is improved.

Description

Technical Field

[0001] The invention relates to the technical field of power distribution network information encryption transmission, and in particular to a selective encryption method for remote control switches in power distribution station areas. Background Art

[0002] Generally, the management of remote switches in distribution substations, including telemetry, telesignaling, and remote control, involves a large amount of data of various types. Remote switches have remote control operation, and remote control is different from telemetry and telesignaling. Since some areas involve the supply and disconnection of power in important areas, the impact is relatively large and requires higher security.

[0003] However, the existing power distribution network automation system does not take sufficient security measures, resulting in a variety of information security risks in the distribution network, which leads to information leakage, loss and theft during the communication transmission process when the master station sends remote control commands to the terminal or the master station obtains field data from the terminal. If the switches in all areas and all data items with different security levels are encrypted, the equipment will have a large amount of calculation, the workflow will increase, and it will be inconvenient for engineering debugging and troubleshooting. Summary of the invention

[0004] The purpose of the present invention is to solve the problems in the prior art that the encryption and decryption calculation amount of distribution terminals and distribution remote control switches is large and the data transmission efficiency is low. A selective encryption method for remote control switches in distribution stations is provided. The number of switches involved in encryption in the system is reduced while the safety of important areas is guaranteed, the encryption and decryption calculation amount in a single encryption switch is reduced, the equipment workflow is simplified, engineering debugging is simplified, the workload of troubleshooting is reduced, and data transmission efficiency is improved.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: A method for selective encryption of remote control switches in a distribution station area, characterized in that it comprises the following steps: Add encryption chips to the power distribution terminals at the head end and switches at important locations at the tail end. The head end queries the encryption chip status at the tail end and establishes an information table. It exchanges encryption security certificates with the tail end that supports encryption to establish an encryption channel, and performs the first layer of encryption selection for switch devices at different security levels. The head end generates a management message and sends it down. If the management message is a predetermined remote control-related message and the target node supports the encryption chip, the message is encrypted according to the data encryption policy of the node and sent down to the tail end. The tail end encrypts the corresponding feedback information and sends it uplink to the head end, completing the second-layer encryption selection work.

[0006] The method of the present invention implements a selective mechanism that only important switches are equipped with security chips according to the importance of applications, that is, in a single distribution area, some switches are equipped with encryption and some are not, thereby reducing the amount of calculation for encryption and decryption of the distribution terminal and the amount of interactive data related to system encryption. Only remote control related messages with high security are encrypted and decrypted, while other unimportant data such as telemetry are not encrypted, that is, in a single remote control switch, a selective mechanism is implemented, which reduces the amount of calculation for encryption and decryption of the distribution remote control switch, and a remote control switch equipped with an encryption chip.

[0007] Preferably, in the second-layer encryption selection, the tail end that supports encryption, after receiving the encrypted message, decrypts it according to the predetermined strategy to obtain the plain text and performs control operations. The tail end also encrypts the corresponding feedback information and sends it uplink to the head end. The head end performs the predetermined decryption and then sends it uplink to the upper layer of business for further processing.

[0008] Preferably, in the first layer of encryption selection, after the tail end is powered on and registered with the head end, the head end actively initiates queries in turn, and after the tail end receives the query message, it synchronizes the management information of whether encryption is supported or not to the head end.

[0009] Preferably, in the second layer encryption selection, if the target node does not support the encryption chip, the remote control related message is directly released.

[0010] Preferably, after encrypting the message according to the data encryption policy of the node, the encrypted message is filled into the payload area of ​​the encrypted message DI of the communication protocol extended for the encryption application, and sent downstream.

[0011] Preferably, the tail end encrypts the corresponding feedback information and then sends it uplink to the head end, including: determining whether the DI of the received message is an encrypted message DI of the extended communication protocol, and if so, decrypting the encrypted message of the load according to the encryption protocol; after the execution result is encrypted, it is filled into the load area of ​​the encrypted message DI of the communication protocol extended for this encryption application and then sent uplink.

[0012] Preferably, the security layer identifies the management message sent by the head end and performs predetermined decryption on the encrypted information fed back by the tail end, and the security layer is added to the software level of the original head end without encryption components.

[0013] Preferably, if the DI of the received message is not the encrypted message DI of the extended communication protocol, it indicates that it is ordinary plaintext data, and the message is directly parsed, and the execution result is sent back as plaintext.

[0014] Preferably, in the first encryption selection, for the tail end whose query fails, the head end keeps querying at a fixed frequency.

[0015] Preferably, the tail-end equipment includes a photovoltaic tail-end and a line monitoring unit. The tail-end equipment cooperates with the head-end to complete the first-layer encryption selection, and at the same time completes the second-layer single-node internal selection encryption mechanism to distinguish encrypted / unencrypted business operations.

[0016] Therefore, the present invention has the following beneficial effects: 1. For the remote control switches in the distribution station area, encryption chips are only installed for important switches according to the importance of the application. That is, in a single distribution station area, some switches are configured with encryption while others are not, thereby reducing the amount of calculation for encryption and decryption of the distribution terminal and the amount of system encryption-related interactive data.

[0017] 2. The remote control switch equipped with an encryption chip only encrypts and decrypts the remote control related messages with high security, and does not encrypt and decrypt other unimportant data such as telemetry. That is, a selective mechanism is adopted in a single remote control switch, in which part of the content is encrypted and part of the content is not encrypted, thereby reducing the calculation amount of encryption and decryption of the distribution remote control switch. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of the overall steps of the selective encryption method of the remote control switch in the distribution station area in the present invention.

[0019] Figure 2 This is a schematic diagram of the encryption preparation of the tail-end device in the second embodiment.

[0020] Figure 3 This is a flow chart of the tail end cooperating with the head end to complete the first layer encryption selection in the second embodiment.

[0021] Figure 4 This is a schematic diagram of the process of selecting the first layer of encryption performed by the head end to the tail end in the second embodiment.

[0022] Figure 5 This is a schematic diagram of the process of selecting the second layer encryption of a single node by the head end in Embodiment 2.

[0023] Figure 6 This is a schematic diagram of the process of completing the second layer encryption selection at the tail end in Embodiment 2. DETAILED DESCRIPTION

[0024] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: Embodiment 1: This embodiment provides a method for selective encryption of remote control switches in a distribution station area, such as Figure 1As shown, the operation process is as follows: Step 1, adding encryption chips to the power distribution terminal at the head end and the switches at important positions at the tail end, the head end queries the encryption chip status at the tail end and establishes an information table, exchanges encryption security certificates with the tail end that supports encryption once to establish an encryption channel, and performs the first layer of encryption selection for switch devices at different security levels; Step 2, the head end generates a management message and sends it down. If the management message is a predetermined remote control-related message and the target node supports the encryption chip, the message is encrypted according to the data encryption strategy of the node and sent to the tail end. The tail end encrypts the corresponding feedback information and sends it up to the head end, completing the second layer of encryption selection.

[0025] The selective encryption method for remote control switches in distribution areas provided in this embodiment implements a selective mechanism of adding security chips to important switches in distribution areas according to the importance of applications, that is, in a single distribution area, some switches are configured with encryption and some are not, thereby reducing the amount of calculation for encryption and decryption of distribution terminals and the amount of system encryption-related interactive data. The remote control switch equipped with an encryption chip only encrypts and decrypts high-security remote control-related messages, and does not encrypt and decrypt other unimportant data such as telemetry, that is, in a single remote control switch, a selective mechanism of encrypting some contents and not encrypting some contents reduces the amount of calculation for encryption and decryption of distribution remote control switches.

[0026] The following further illustrates the technical solution and technical effects of the present invention through specific examples and specific application scenarios. The following examples are explanations of the present invention and the present invention is not limited to the following examples.

[0027] Generally, the remote control switch of the distribution area, as the tail-end device of the area, is managed by the distribution terminal at the head end of the distribution area through the local communication network (485, power line carrier, etc.). This embodiment provides a method for selective encryption of the remote control switch of the distribution area, which is mainly divided into two mechanisms to achieve selective encryption of the remote control switch.

[0028] In this embodiment, some specific terms are represented as follows: Remote control switch: In the field of power distribution, some switches with remote control, such as circuit breakers, etc.

[0029] Local communication network: refers to a communication network in which the communication distance between nodes in the network is within a few hundred meters, such as 485 bus and broadband power line carrier.

[0030] Distribution terminal: A digital metering and monitoring device next to a distribution transformer in a distribution area in a distribution network, used to monitor the operation of the transformer and the entire distribution area.

[0031] The specific manifestations are: 1. First-tier mechanism: encryption selection for switchgear at different security levels.

[0032] Based on the original system without encryption components, encryption chips are added to the distribution terminal at the head end, and at the tail end, encryption chips are only added to switches in important positions to perform the first layer of encryption selection for switch devices at different security levels.

[0033] Specific working process: After each tail end is powered on and registered with the head end, the head end will actively initiate queries in turn and send query messages to determine whether each tail end supports encryption chips. After receiving the query message, each tail end will reply yes or no according to the actual situation to synchronize the management information of encryption support to the head end. For the tail end that fails the query, the head end continues to maintain a certain frequency of query. After collecting the encryption chip information of each tail end, the head end establishes an information table to reflect the encryption support status of the tail end in this area. At the same time, the head end and the tail end that supports encryption establish an encryption channel in turn by exchanging encryption security certificates and other methods to complete the first layer of encryption mechanism.

[0034] The information table includes the tail end location and whether the tail end device has an additional encryption chip.

[0035] The head end is the power distribution terminal; the tail end includes distributed equipment in the substation, such as photovoltaic micro-breakers and line monitoring units, which complete the encryption selection mechanism within the second-layer single-node device to distinguish between encrypted / unencrypted business operations.

[0036] Among them, the important position is determined according to the safety of the switch at that position in actual use.

[0037] 2. The second layer mechanism: encryption selection work for message data.

[0038] For this embodiment, among all types of data of the remote control switch, only the relevant messages of the actual remote control work are selectively encrypted, while the data items such as telemetry and telesignaling are not encrypted, thereby realizing the second layer of message level encryption selection.

[0039] The specific working process is as follows: add a security layer to the software layer of the original headend without encryption components. When the headend generates a management message and prepares to send it down, the security layer will identify the message when the management message passes through the security layer. If the security layer finds that the management message is a predetermined message related to the actual remote control work, and the target node supports the encryption chip, the management message will be encrypted according to the data encryption strategy of the node, and the encrypted management message will continue to be sent down. If the target node does not support the encryption chip, the management message will be released directly.

[0040] For the tail end that supports encryption chips, after receiving the encrypted message, it performs the decryption according to the predetermined strategy to obtain the plain text and perform the control operation. At the same time, the tail end encrypts the corresponding feedback information and sends it uplink to the head end. The security layer of the head end performs the predetermined decryption and then passes it to the upper layer for further processing. In this way, the encryption work selected by the second layer is completed.

[0041] The selective encryption method for remote control switches in distribution stations provided in this embodiment reduces the number of switches involved in encryption in the system while ensuring the safety of important areas, reduces the amount of encryption and decryption calculations in a single encryption switch, simplifies equipment workflow, simplifies engineering debugging, and reduces the workload of troubleshooting.

[0042] Embodiment 2: This embodiment provides a method for selectively encrypting a remote control switch in a distribution station area, which is used to further apply the method for selectively encrypting a remote control switch in a distribution station area provided in the first embodiment.

[0043] This working mechanism is mainly divided into two mechanisms to achieve selective encryption of the remote control switch.

[0044] The specific manifestations are: Mechanism 1: Encryption selection work for switchgear at different security levels.

[0045] Software and hardware preparation at the head end (distribution terminal): Based on the original system without encryption components, encryption chips are added to the hardware of the distribution terminal at the head end, and encryption communication functions are added to the software. At the tail end, encryption chips are added to the hardware of switches in important positions, and encryption communication functions are added to the software, so as to carry out the first layer of encryption selection for switch devices at different security levels.

[0046] The encryption process is: (1) Software and hardware preparation at the head end (distribution terminal).

[0047] The hardware of the power distribution terminal adds encryption chips, and the software of the power distribution terminal adds encryption communication functions, as well as software functions for encryption and decryption related interactions between the head end and the tail end. In this way, the power distribution terminal at the head end has the ability to establish a secure interactive channel through the encryption chip with the switch that supports decryption at the tail end, making software and hardware preparations for subsequent encryption and decryption communications.

[0048] (2) Preparation of tail-end equipment.

[0049] Preparation of tail-end equipment includes preparation of distributed equipment in the substation area, such as photovoltaic micro-breakers, line monitoring units and other equipment.

[0050] Importance assessment of tail-end switches: Users are required to assess the importance of all switches in the area. Switches with high security requirements (those in important locations in the substation area) are equipped with encryption chips that match the head-end power distribution terminal, while switches with low security requirements do not need to be equipped with encryption chips. In this way, it is ensured that switches with high security have confidentiality functions, and at the same time, the number of devices with encryption requirements is reduced because switches with low security requirements do not need to be equipped with encryption chips, thereby reducing the amount of encryption and decryption calculations and encryption and decryption-related communication interaction traffic at the head-end power distribution terminal, and also reducing the number of encryption switches involved in debugging and troubleshooting in subsequent projects.

[0051] At the same time, the software of the switch at the tail end adds encryption and decryption software functions related to the encryption chip, as well as software functions related to encryption and decryption interactions between the head end and the tail end. In this way, the switch at the tail end has the ability to establish a secure interaction channel with the power distribution terminal at the head end through the encryption chip, making software and hardware preparations for subsequent encryption and decryption communications.

[0052] The record adds the tail switch of the encryption chip and encryption / decryption software to generate a tail node record table.

[0053] like Figure 2 As shown, taking the PV micro-break as an example, first evaluate whether the PV micro-break to be tested is a PV micro-break in an important location in the substation. If so, add an encryption chip to the hardware of the PV micro-break, and add an encryption communication function to the software of the PV micro-break; if the PV micro-break to be tested is a PV micro-break in a non-important location, then other equipment such as line monitoring units will not add encryption chips.

[0054] (3) The tail end cooperates with the head end to complete the first layer of encryption selection.

[0055] Tail-end equipment: including photovoltaic micro-breakers, line monitoring units and other distributed equipment in the substation area, cooperating with the head-end to complete the first layer of encryption selection.

[0056] The specific process is: When the system environment is powered on, the software of each switch and line monitoring terminal at the tail end detects whether there is an encryption chip on the hardware circuit. If it exists, it will be recorded. When the head end inquires "whether encryption is supported", it will reply "yes"; if it does not exist, it will be recorded and replied "no" when it is queried "whether encryption is supported". Software workflow diagram of the tail end (photovoltaic switch and other equipment) side.

[0057] like Figure 3As shown, the tail end is powered on to detect whether there is an encryption chip on the tail end. If so, when the tail end receives the query message "whether encryption is supported" from the head end, the tail end replies yes, and then the tail end cooperates with the head end to establish an encrypted communication channel before secure communication. If there is no encryption chip on the tail end, when the tail end receives the query message "whether encryption is supported" from the head end, the tail end replies no.

[0058] (4) The headend selects the first layer of encryption.

[0059] Head end (distribution terminal): The first layer of encryption selection mechanism for the tail-end equipment in the substation (photovoltaic micro-breaker, line monitoring terminal).

[0060] After the system environment is initialized when it is powered on, each switch and line monitoring terminal at the tail end initiates network registration to the distribution terminal at the head end, and then the distribution head end initiates queries to each switch in turn to inquire whether encryption is supported. If so, the encryption chip-related process is followed to establish an encryption channel between the head end and the tail end. If not, no encryption-related transactions are processed. The head end saves the encryption support status of each tail end so that different encryption or non-encryption confidentiality strategies can be adopted for different nodes in the future. For switches that have not yet received a reply on whether encryption is supported, the head end continues to query at a certain frequency. Software workflow diagram of the head end (distribution terminal) side in this stage.

[0061] Specifically, Figure 4 As shown, the head end detects whether the tail end node has access to the network in this distribution substation area. If it is found, it will continue to detect until it detects that a tail end node has access to the network in this distribution substation area. After detecting that the tail end node has access to the network in this distribution substation area, the head end directly sends a query message "whether encryption is supported" to the tail end node. If the tail end node replies yes, the head end establishes an encrypted channel with the tail end according to the encryption protocol, and the software records that the tail end node is a device that supports encryption. The messages for the tail end node are subsequently encrypted. If the head end receives a no reply from the tail end, the software records that the node is a device that does not support encryption, and the messages for the node are not subsequently encrypted.

[0062] After the above steps, the encryption selection of mechanism one is completed.

[0063] Mechanism 2: Encryption selection work for message data.

[0064] Among all types of data of the remote control switch, only the relevant messages of the actual remote control work are selectively encrypted, while the data items such as telemetry and telesignaling are not encrypted, thus realizing the second-layer message level encryption selection.

[0065] The encryption process is: (1) Second layer encryption selection at the headend.

[0066] The headend (distribution terminal) selects the second layer of encryption for messages within a single node device.

[0067] When the headend generates a message and prepares to send it down, it will identify the message. If it is found to be a message related to the established actual remote control work and the target node supports the encryption chip, it will encrypt the message according to the data encryption policy of the node, and the encrypted message will continue to be sent down. If the target node does not support the encryption chip, it will be released directly.

[0068] The software workflow diagram for this stage is as follows Figure 5 As shown, it is determined whether there is a message involving remote control and needs to be encrypted. If so, the tail node record table is checked to see whether the tail node supports encryption. If so, the message is encrypted according to the encryption protocol recorded in the encryption and decryption software. If no message involves remote control, the message is sent downstream as plain text. If the node record table shows that the node does not support encryption, the message is sent downstream as plain text.

[0069] The encrypted message is filled into the payload area of ​​the encrypted message DI of the communication protocol extended for this encryption application and sent downstream. Similarly, the encrypted message in the upstream direction will also be filled into the payload area of ​​the DI.

[0070] In this embodiment, the communication protocol adopts the 645 protocol. The 645 protocol is a question-and-answer (master-slave) communication protocol. The Chinese power industry standard DL / T 645-2007, including DLT645-1997 and DLT645-2007, is a multifunctional electric energy meter communication protocol.

[0071] In this communication mode, there is usually a master station (head end) and one or more slave stations (tail end). The master station is responsible for initiating communication requests, and the slave station provides corresponding responses based on the master station's requests.

[0072] In this embodiment, the communication process of the question-answer protocol generally includes the following steps: 1) The head-end initiates a request: The head-end sends a request message to a specific tail-end. The request message contains the operations that need to be performed by the tail-end, such as reading electric energy and real-time parameters.

[0073] 2) The tail end receives the request: After the tail end receives the request from the head end, it processes it according to the content of the request.

[0074] 3) The tail end prepares the response: The tail end prepares the corresponding data according to the content of the request and constructs a response message.

[0075] 4) The tail end sends a response: The tail end sends the constructed response message back to the end.

[0076] 5) The head end receives the response: After the head end receives the response from the tail end, it performs corresponding processing based on the response content.

[0077] DI: Data identification in the 645 protocol. The data identification code uses four bytes to distinguish different data items. The four bytes are represented by DI3, DI2, DI1 and DI0 respectively, and each byte is encoded in hexadecimal. DI is an identification set up to ensure that communication system devices can recognize and distinguish each other. Communication DI mainly includes hardware DI and software DI. Hardware DI refers to the unique identification pre-set for hardware equipment when it leaves the factory, while software DI refers to the dynamic identification generated according to certain rules during the use of hardware equipment. Communication DI plays a vital role in modern communication technology. It can improve the security and stability of the overall system.

[0078] (2) The tail end completes the encryption selection mechanism within the single-node device of the second layer.

[0079] Tail end: including photovoltaic micro-breaks, line monitoring units and other distributed equipment in the substation area, completing the encryption selection mechanism within the second-layer single-node device to distinguish between encrypted / unencrypted business operations.

[0080] The tail end that supports encryption chips, after receiving the encrypted message, decrypts it according to the predetermined strategy to obtain the plain text and perform control operations. At the same time, the tail end encrypts the corresponding feedback information and sends it upstream to the head end, which decrypts it according to the predetermined strategy to convert it into plain text and then hands it over to the upper layer of business for further processing.

[0081] The software workflow at this stage is as follows Figure 6 As shown, it is determined whether the tail end has received the message sent from the head end to the tail end node. If received, it is determined whether the DI of the message is the encrypted message DI of the extended communication protocol (645 protocol in this embodiment). If so, the encrypted message in the message DI load area is decrypted according to the encryption protocol. If the tail end has not received the message sent from the head end to the tail end node, it indicates that it is ordinary plaintext data, and the message is directly parsed according to the normal operation, and the execution result is sent up and replied in plaintext. If the DI of the message is not the DI of the extended communication protocol, it indicates that it is ordinary plaintext data, and the message is directly parsed according to the normal operation, and the execution result is sent up and replied in plaintext.

[0082] The decrypted message is parsed and processed for normal business, and the execution result is encrypted and filled into the payload area of ​​the encrypted message DI of the 645 protocol extended for this encryption application before being sent upstream.

[0083] The selective encryption method for remote control switches in distribution stations provided in this embodiment can reduce the number of switches involved in encryption in the system while ensuring the safety of important areas, reduce the amount of encryption and decryption calculations in a single encryption switch, simplify equipment workflow, simplify engineering debugging, and reduce the workload of troubleshooting.

[0084] The above-described embodiment is only a preferred solution of the present invention and does not limit the present invention in any form. There are other variations and modifications without exceeding the technical solution described in the claims.

Claims

1. A method for selective encryption of remote control switches in a distribution station area, characterized in that: include: Add encryption chips to the power distribution terminals at the head end and switches at important locations at the tail end. The head end queries the encryption chip status at the tail end and establishes an information table. It exchanges encryption security certificates with the tail end that supports encryption to establish an encryption channel, and performs the first layer of encryption selection for switch devices at different security levels. The head end generates a management message and sends it down. If the management message is a predetermined remote control-related message and the target node supports the encryption chip, the message is encrypted according to the data encryption policy of the node and sent down to the tail end. The tail end encrypts the corresponding feedback information and sends it uplink to the head end, completing the second-layer encryption selection work.

2. A distribution station area remote control switch selective encryption method according to claim 1, characterized in that: In the second-layer encryption selection, the tail end that supports encryption, after receiving the encrypted message, decrypts it according to the predetermined strategy to obtain the plain text and performs control operations. The tail end also encrypts the corresponding feedback information and sends it uplink to the head end. The head end performs the predetermined decryption and then sends it uplink to the upper layer of business for further processing.

3. A distribution station area remote control switch selective encryption method according to claim 1 or 2, characterized in that: In the first layer of encryption selection, after the tail end is powered on and registered with the head end, the head end actively initiates queries in turn. After the tail end receives the query message, it synchronizes the management information of whether encryption is supported or not to the head end.

4. A method for selective encryption of remote control switches in a distribution station area according to claim 1 or 2, characterized in that: In the second layer encryption selection, if the target node does not support the encryption chip, the remote control related message is directly released.

5. A distribution station area remote control switch selective encryption method according to claim 1, characterized in that: After the message is encrypted according to the data encryption policy of the node, the encrypted message is filled into the load area of ​​the encrypted message DI of the communication protocol extended for this encryption application and sent downstream.

6. A distribution station area remote control switch selective encryption method according to claim 1 or 5, characterized in that: The tail end encrypts the corresponding feedback information and then sends it uplink to the head end, including: determining whether the DI of the received message is an encrypted message DI of the extended communication protocol, and if so, decrypting the encrypted message of the load according to the encryption protocol; after the execution result is encrypted, it is filled into the load area of ​​the encrypted message DI of the communication protocol extended for this encryption application and then sent uplink.

7. A distribution station area remote control switch selective encryption method according to claim 1, 2 or 5, characterized in that: The security layer identifies the management message sent by the head end and performs predetermined decryption on the encrypted information fed back by the tail end. The security layer is added to the software level of the original head end without encryption components.

8. A method for selective encryption of remote control switches in a distribution station area according to claim 6, characterized in that: If the DI of the received message is not the encrypted message DI of the extended communication protocol, it indicates that it is ordinary plaintext data, and the message is directly parsed, and the execution result is sent back as plaintext.

9. A method for selective encryption of remote control switches in distribution station areas according to claim 1, 2 or 5, characterized in that: In the first encryption selection, for the tail end whose query fails, the head end keeps querying at a fixed frequency.

10. A distribution station area remote control switch selective encryption method according to claim 1, 2 or 5, characterized in that: The tail-end equipment includes a photovoltaic tail-end and a line monitoring unit. The tail-end equipment cooperates with the head-end to complete the first-layer encryption selection, and at the same time completes the second-layer single-node internal selection encryption mechanism to distinguish between encrypted / unencrypted business operations.

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