Patent Publication Number: US-11652846-B2

Title: Systems and methods for establishing a secure communication link in an electric power distribution system

Description:
RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §§ 120 and 121 as a divisional application of U.S. patent application Ser. No. 17/201,299 filed on 15 Mar. 2021 naming Ryan Bradetich, Colin Gordon, Arun Shrestha, Karen S J Wyszczelski, and Hidayatullah Ahsan as inventors and titled “Systems and Methods for Establishing a Secure Communication Link in an Electric Power Distribution System” which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     This disclosure relates to establishing a secure communication link between devices of an electric power distribution system based on operating data associated with the devices. 
     This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present techniques, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be noted that these statements are to be read in this light, and not as admissions of any kind. 
     Electric power distribution systems carry electricity from a transmission system to residential communities, factories, industrial areas, and other electricity consumers. An electric power distribution system may include various intelligent electronic devices (IEDs) that may communicate with other devices of the electric power distribution system during operation of the electric power distribution system. For example, the IED may receive and/or transmit a signal and/or data in order to perform a functionality, such as to control a circuit breaker in response to electrical measurements of the electric power distribution system. Unfortunately, it may be difficult to establish a secure communication link between the IED and other devices of the electric power distribution system to enable the devices to securely communicate with one another. 
     SUMMARY 
     Certain examples commensurate in scope with the originally claimed subject matter are discussed below. These examples are not intended to limit the scope of the disclosure. Indeed, the present disclosure may encompass a variety of forms that may be similar to or different from the examples set forth below. 
     In an embodiment, an intelligent electronic device (IED) of an electric power distribution system includes processing circuitry and a memory that includes a tangible, non-transitory, computer-readable comprising instructions. The instructions, when executed by the processing circuitry, are configured to cause the processing circuitry to receive operating data associated with the electric power distribution system, determine whether the operating data matches with expected operating data, generate a connectivity association key (CAK) based on the operating data in response to a determination that the operating data matches with the expected operating data, and establishing a connectivity association based on the CAK. 
     In an embodiment, a system includes a first intelligent electronic device (IED) configured to monitor first operating data of an electric power distribution system and a second IED The second IED is configured to receive the first operating data from the first IED, monitoring second operating data of the electric power distribution system, determine whether the first operating data matches with expected operating data, generate a connectivity association key (CAK) based on the first operating data and the second operating data in response to a determination that the first operating data matches with the expected operating data, and establish a connectivity association based on the CAK. 
     In an embodiment, a tangible, non-transitory, computer-readable medium includes instructions. The instructions, when executed by processing circuitry, are configured to cause the processing circuitry to monitor first operating data associated with a first section of an electric power distribution system, receive second operating data associated with a second section of the electric power distribution system, determine whether the first operating data substantially matches with the second operating data, generate a connectivity association key (CAK) based on the first operating data, the second operating data, or both, in response to a determination that the first operating data substantially matches with the second operating data, and establish a connectivity association based on the CAK. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic diagram of an embodiment of an electric power distribution system, in accordance with an aspect of the present disclosure; 
         FIG.  2    is a schematic diagram of an embodiment of a computing system that may be incorporated in a device of an electric power distribution system, in accordance with an aspect of the present disclosure; 
         FIG.  3    is a schematic diagram of an embodiment of a communication network in which intelligent electronic devices (IEDs) of an electric power distribution system are communicatively coupled to one another, in accordance with an aspect of the present disclosure; 
         FIG.  4    is a flowchart of an embodiment of a method for establishing secure communication links between devices of an electric power distribution system, in accordance with an aspect of the present disclosure; and 
         FIG.  5    is a schematic diagram of an embodiment of a communication network in which IEDs of an electric power distribution system are communicatively coupled to one another via a switch, in accordance with an aspect of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be noted that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be noted that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. Certain examples commensurate in scope with the originally claimed subject matter are discussed below. These examples are not intended to limit the scope of the disclosure. Indeed, the present disclosure may encompass a variety of forms that may be similar to or different from the examples set forth below. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be noted that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the phrase A “based on” B is intended to mean that A is at least partially based on B. Moreover, unless expressly stated otherwise, the term “or” is intended to be inclusive (e.g., logical OR) and not exclusive (e.g., logical XOR). In other words, the phrase “A or B” is intended to mean A, B, or both A and B. 
     The embodiments of the disclosure will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. The components of the disclosed embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the systems and methods of the disclosure is not intended to limit the scope of the disclosure, as claimed, but is merely representative of possible embodiments of the disclosure. In addition, the procedures of a method do not necessarily need to be executed in any specific order, or even sequentially, nor need the procedures be executed only once, unless otherwise specified. In some cases, well-known features, structures or operations are not shown or described in detail. Furthermore, the described features, structures, or operations may be combined in any suitable manner in one or more embodiments. The components of the embodiments as generally described and illustrated in the figures could be arranged and designed in a wide variety of different configurations. 
     Several aspects of the embodiments described may be implemented as software modules or components. As used herein, a software module or component may include any type of computer instruction or computer-executable code located within a memory device and/or transmitted as electronic signals over a system bus or wired or wireless network. A software module or component may, for instance, include physical or logical blocks of computer instructions, which may be organized as a routine, program, object, component, data structure, or the like, and which performs a task or implements a particular abstract data type. 
     In certain embodiments, a particular software module or component may include disparate instructions stored in different locations of a memory device, which together implement the described functionality of the module. Indeed, a module or component may include a single instruction or many instructions, and may be distributed over several different code segments, among different programs, and across several memory devices. Some embodiments may be practiced in a distributed computing environment where tasks are performed by a remote processing device linked through a communications network. In a distributed computing environment, software modules or components may be located in local and/or remote memory storage devices. In addition, data being tied or rendered together in a database record may be resident in the same memory device, or across several memory devices, and may be linked together in fields of a record in a database across a network. 
     Embodiments may be provided as a computer program product including a tangible, non-transitory, computer-readable and/or machine-readable medium having stored thereon instructions that may be used to program a computer (or other electronic device) to perform processes described herein. For example, a non-transitory computer-readable medium may store instructions that, when executed by a processor of a computer system, cause the processor to perform certain methods disclosed herein. The non-transitory computer-readable medium may include, but is not limited to, hard drives, floppy diskettes, optical disks, compact disc read-only memories (CD-ROMs), digital versatile disc read-only memories (DVD-ROMs), read-only memories (ROMs), random access memories (RAMs), erasable programmable read-only memories (EPROMs), electrically erasable programmable read-only memories (EEPROMs), magnetic or optical cards, solid-state memory devices, or other types of machine-readable media suitable for storing electronic and/or processor executable instructions. 
     Embodiments of the present disclosure are directed to establishing a secure communication link or channel between devices of an electric power distribution system. Intelligent electronic devices (IEDs) may be used to control certain devices and to perform certain operations of the electric power distribution system. For example, an IED may be a relay that enables or blocks electrical power flow between other devices of the electric power distribution system. The IED may, for instance, communicate with a computing device, and the IED may operate based on the communication with the computing device (e.g., based on a user input). Furthermore, multiple IEDs may transmit data, such as operating information or sensor data, to one another to control various functions of devices of the electric power distribution system. As such, the IEDs may facilitate operation of the electric power distribution system. 
     In some embodiments, certain devices, such as IEDs, of the electric power distribution system may be communicatively coupled to one another via a respective media access control security (MACsec) communication link or channel and/or a respective MACsec key agreement (MKA) connectivity association. To establish the MACsec communication link, an MKA protocol is used to enable communications between the devices. During the MKA protocol, a first device may generate a connectivity association key (CAK) and may identify whether a second device has generated a copy of the same CAK. Upon verification that the first device and the second device generated copies of the same CAK, an MKA connectivity association may be established between the first device and the second device. One of the devices may then generate a security association key (SAK) based on the CAK and may distribute a copy of the SAK to the other device. The first device and the second device may then use their respective copies of the SAK to establish a MACsec communication link for communicating with one another. For example, each of the devices may encrypt data using their copy of the SAK and/or may decrypt encrypted data using their copy of the SAK in order to transmit data securely between one another. 
     This disclosure provides for a secure and efficient establishment of a secure communication link. The techniques described herein may be in contrast to previous approaches to establish a communication link, as the previous approaches may be complex and may require a user to perform a series of procedures, such as entering passcodes, modifying device settings, verifying protocols, troubleshooting, or otherwise configuring a device of an electric power distribution system. To mitigate these concerns, embodiments of the present disclosure relate to a process for establishing a secure communication link between devices in a more simplified approach. 
     In particular, the process is associated with using operating data to perform the MKA protocol and establish an MKA connectivity association and/or a MACsec communication link. For example, a first device (e.g., a first TED) may monitor operating data associated with a first part of the electric power distribution system. A second device (e.g., a second IED) may monitor operating data associated with a second part of the electric power distribution system. The first and second devices may compare the respectively monitored operating data with one another. Based on a verification that the respective operating data match or substantially match (e.g., are within a threshold value of one another), the devices may generate copies of a CAK (e.g., based on the operating data). The devices may then compare the generated copies of the CAK with one another, and based on a determination that the generated copies of the CAK match, an MKA connectivity association may be established between the devices. SAKs may then be generated based on the CAK and the MKA connectivity association to establish a MACsec communication link. The disclosed process may simplify a manner in which secure communication links are established between devices by performing the MKA protocol without having to receive certain user inputs, such as user entered passcodes to generate the CAK and/or SAK. Further, the disclosed process may also improve data communication between devices by confirming that communicatively coupled devices are operating as desired via verification that the devices are detecting the same operating data. 
     With the preceding in mind,  FIG.  1    is a schematic diagram of an electric power distribution system  100  that may generate, transmit, and/or distribute electric energy to various loads (e.g., different structures). The electric power distribution system  100  may use various IEDs  104 ,  106 ,  108 ,  115  to control certain aspects of the electric power distribution system  100 . As used herein, an IED (e.g., the IEDs  104 ,  106 ,  108 ,  115 ) may refer to any processing-based device that monitors, controls, automates, and/or protects monitored equipment within the electric power distribution system  100 . Although the present disclosure primarily discusses the IEDs  104 ,  106 ,  108 ,  115  as relays, such as a remote terminal unit, a differential relay, a distance relay, a directional relay, a feeder relay, an overcurrent relay, a voltage regulator control, a voltage relay, a breaker failure relay, a generator relay, and/or a motor relay, additional IEDs  104 ,  106 ,  108 ,  115  may include an automation controller, a bay controller, a meter, a recloser control, a communications processor, a computing platform, a programmable logic controller (PLC), a programmable automation controller, an input and output module, and the like. Moreover, the term IED may be used to describe an individual IED or a system including multiple IEDs. 
     For example, the electric power distribution system  100  may be monitored, controlled, automated, and/or protected using the IEDs  104 ,  106 ,  108 ,  115 , and a central monitoring system  172  (e.g., an industrial control system). In general, the IEDs  104 ,  106 ,  108 ,  115  may be used for protection, control, automation, and/or monitoring of equipment in the electric power distribution system  100 . For example, the IEDs  104 ,  106 ,  108 ,  115  may be used to monitor equipment of many types, including electric power lines, electric power lines, current sensors, busses, switches, circuit breakers, reclosers, transformers, autotransformers, tap changers, voltage regulators, capacitor banks, generators, motors, pumps, compressors, valves, and a variety of other suitable types of monitored equipment. 
     A common time signal may be distributed throughout the electric power distribution system  100 . Utilizing a common time source may ensure that IEDs  104 ,  106 ,  108 ,  115  have a synchronized time signal that can be used to generate time synchronized data, such as synchrophasors. In various embodiments, the IEDs  104 ,  106 ,  108 ,  115  may receive a common time signal  168 . The time signal may be distributed in the electric power distribution system  100  using a communications network  162  and/or using a common time source, such as a Global Navigation Satellite System (“GNSS”), or the like. 
     The IEDs  104 ,  106 ,  108 ,  115  may be used for controlling various other equipment of the electrical power distribution system  100 . By way of example, the illustrated electric power distribution system  100  includes electric generators  110 ,  112 ,  114 ,  116  and power transformers  117 ,  120 ,  122 ,  130 ,  142 ,  144 ,  150 . The electric power distribution system  100  may also include electric power lines  124 ,  134 ,  136 ,  158  and/or busses  118 ,  126 ,  132 ,  148  to transmit and/or deliver power, circuit breakers  152 ,  160 ,  176  to control flow of power in the electric power distribution system  100 , and/or loads  138 ,  140  to receive the power in and/or from the electric power distribution system  100 . A variety of other types of equipment may also be included in electric power distribution system  100 , such as a voltage regulator, a capacitor (e.g., a capacitor  174 ), a potential transformer (e.g., a potential transformer  182 ), a current sensor (e.g., a wireless current sensor (WCS)  184 ), an antenna (e.g., an antenna  186 ), a capacitor banks (e.g., a capacitor bank (CB)  188 ), and other suitable types of equipment useful in power generation, transmission, and/or distribution. 
     A substation  119  may include the electric generator  114 , which may be a distributed generator and which may be connected to the bus  126  through the power transformer  117  (e.g., a step-up transformer). The bus  126  may be connected to the distribution bus  132  via the power transformer  130  (e.g., a step-down transformer). Various electric power lines  136 ,  134  may be connected to the distribution bus  132 . The electric power line  136  may lead to a substation  141  in which the electric power line  136  is monitored and/or controlled using the IED  106 , which may selectively open and close the circuit breaker  152 . The load  140  may be fed from the electric power line  136 , and the power transformer  144  (e.g., a step-down transformer) in communication with the distribution bus  132  via electric power line  136  may be used to step down a voltage for consumption by the load  140 . 
     The electric power line  134  may deliver electric power to the bus  148  of the substation  151 . The bus  148  may also receive electric power from the distributed electric generator  116  via the power transformer  150 . The electric power line  158  may deliver electric power from the bus  148  to the load  138  and may include the power transformer  142  (e.g., a step-down transformer). The circuit breaker  160  may be used to selectively connect the bus  148  to the electric power line  134 . The IED  108  may be used to monitor and/or control the circuit breaker  160  as well as the electric power line  158 . 
     According to various embodiments, the central monitoring system  172  may include one or more of a variety of types of systems. For example, the central monitoring system  172  may include a supervisory control and data acquisition (SCADA) system and/or a wide area control and situational awareness (WACSA) system. A switch  170  may be in communication with the IEDs  104 ,  106 ,  108 ,  115 . The IEDs  104 ,  106 ,  108 ,  115  may be remote from the switch  170  and may communicate over various media. For instance, the switch  170  may be directly in communication with the IEDs  104 ,  106  and may be in communication with the IEDs  108 ,  115  via the communications network  162 . 
     The switch  170  may enable or block data flow between any of the IEDs  104 ,  106 ,  108 ,  115 . For example, during operation of the electric power distribution system  100 , the IEDs  104 ,  106 ,  108 ,  115  may transmit data with one another to perform various functionalities for the electric power distribution system  100  by initially transmitting the data to the switch  170 . The switch  170  may receive the data and may subsequently transmit the data to an intended recipient of the data. The switch  170  may also control data flow between one of the IEDs  104 ,  106 ,  108 ,  115  and another device communicatively coupled to the switch  170 , such as a computing device  178 . For instance, the computing device  178  may be a laptop, a mobile phone, a desktop, a tablet, or another suitable device with which a user (e.g., a technician, an operator) may interact. As such, the user may utilize the computing device  178  to receive data, such as operating data, from the electric power distribution system  100  via the switch  170  and/or to send data, such as a user input, to the electric power distribution system  100  via the switch  170 . Thus, the switch  170  may enable or block operation of the electric power distribution system  100  via the computing device  178 . 
     A communications controller  180  may interface with equipment in the communications network  162  to create an SDN that facilitates communication between the switch  170 , the IEDs  104 ,  106 ,  108 ,  115 , and/or the central monitoring system  172 . In various embodiments, the communications controller  180  may interface with a control plane (not shown) in the communications network  162 . Using the control plane, the communications controller  180  may direct the flow of data within the communications network  162 . Indeed, the communications controller  180  may communicate with the switch  170  to instruct the switch  170  to transmit certain data (e.g., data associated with a certain set of characteristics or information) to a particular destination (e.g., an intended recipient) using flows, matches, and actions defined by the communications controller  180 . 
     In some embodiments, the IEDs  104 ,  106 ,  108 ,  115  may communicate with one another via MACsec communication links. The MACsec communication links may be established based on determined operating data. For example, the operating data may be used to generate CAKs for establishing an MKA connectivity association, and SAKs may be generated based on the CAKs for establishing a MACsec communication link. Although the present disclosure primarily discusses communication via MACsec communication links, the devices of the electric power distribution system  100  may communicate with one another via any suitable communication link in additional or alternative embodiments. 
       FIG.  2    is a schematic diagram of an embodiment of a computing system  200  that may be incorporated within a device of the electric power distribution system  100 , such as in any of the IEDs  104 ,  106 ,  108 ,  115 , the switch  170 , the computing device  178 , and/or the communications controller  180 . The computing system  200  may include a memory  201  and a processor or processing circuitry  202 . The memory  201  may include a non-transitory computer-readable medium that may store instructions that, when executed by the processor  202 , may cause the processor  202  to perform various methods described herein. To this end, the processor  202  may be any suitable type of computer processor or microprocessor capable of executing computer-executable code, including but not limited to one or more field programmable gate arrays (FPGA), application-specific integrated circuits (ASIC), programmable logic devices (PLD), programmable logic arrays (PLA), and the like. The processor  202  may, in some embodiments, include multiple processors. 
     The computing system  200  may also include a communication system  203 , which may include a wireless and/or wired communication component to establish a communication link with another device of the electric power distribution system  100 . That is, the communication system  203  enables the computing system  200  (e.g., of one of the IEDs  104 ,  106 ,  108 ,  115 ) to communication with another communication system  203  of another computing system  200  (e.g., of the switch  170 ), such as via MACsec. Indeed, the communication system  203  may include any suitable communication circuitry for communication via a personal area network (PAN), such as Bluetooth or ZigBee, a local area network (LAN) or wireless local area network (WLAN), such as an 802.11x Wi-Fi network, and/or a wide area network (WAN), (e.g., third-generation (3G) cellular, fourth-generation (4G) cellular, near-field communications technology, universal mobile telecommunication system (UMTS), long term evolution (LTE), long term evolution license assisted access (LTE-LAA), fifth-generation (5G) cellular, and/or 5G New Radio (5G NR) cellular). The communication system  203  may also include a network interface to enable communication via various protocols such as EtherNet/IP®, ControlNet®, DeviceNet®, or any other industrial communication network protocol. 
     Additionally, the computing system  200  may include input/output (I/O) ports  204  that may be used for communicatively coupling the computing system  200  to an external device. For example, the I/O ports  204  of the computing system  200  of the switch  170  may communicatively couple to corresponding I/O ports  204  of the computing system  200  of the computing device  178 . The computing system  200  may further include a display  205  that may present any suitable image data or visualization. Indeed, the display  205  may present image data that includes various information regarding the electric power distribution system  100 , thereby enabling the user to observe an operation, a status, a parameter, other suitable information, or any combination thereof, of the electric power distribution system  100 . Further still, the computing system  200  may include a user interface (UI)  206  with which the user may interact to control an operation of the computing system  200 . For instance, the UI  206  may include a touch screen (e.g., as a part of the display  205 ), an eye-tracking sensor, a gesture (e.g., hand) tracking sensor, a joystick or physical controller, a button, a knob, a switch, a dial, a trackpad, a mouse, another component, or any combination thereof. As an example, the user may utilize the UI  206  of the computing system  200  of the computing device  178  to transmit data to the switch  170 . 
       FIG.  3    is a schematic diagram of an embodiment of a communication network  230  of the electric power distribution system  100 . Each of the first IED  232  and the second IED  234  may monitor operating data associated with different sections or locations of the electric power distribution system  100 . By way of example, the operating data may include a set of voltage measurements and/or a set of current measurements. For example, the operating data may be indicative of normal load flow voltage and current, active power, reactive power, other suitable operating parameters, or any combination thereof. The IEDs  232 ,  234  may use the respective operating data to establish a secure communication link with one another. Although the illustrated communication network  230  includes a first IED  232  and a second IED  234 , an additional or alternative communication network  230  may include different devices, such as the switch  170  and/or the computing device  178 , that establish a secure communication link with one another. 
     At a first block  236 , the first IED  232  and the second IED  234  may exchange operating data with one another. That is, the first IED  232 , which may monitor first operating data  238 , may transmit the first operating data  238  to the second IED  234 . Further, the second IED  234 , which may monitor second operating data  240 , may transmit the second operating data  240  to the first IED  232 . 
     Each of the IEDs  232 ,  234  may then compare the received operating data with expected operating data, such as the monitored operating data. That is, the first IED  232  may compare the second operating data  240  received from the second IED  234  with the first operating data  238  that was monitored by the first IED  232 . Additionally, the second IED  234  may compare the first operating data  238  received from the first IED  232  with the second operating data  240  that was monitored by the second IED  234 . In response to a determination that the first operating data  238  and the second operating data  240  match one another, the IEDs  232 ,  234  may proceed with initiating the MKA protocol. For example, in some embodiments, the first operating data  238  and the second operating data  240  should have operating values that match exactly with one another (e.g., based on the operating values being measured at common time stamps or a common time interval). In additional or alternative embodiments, the first operating data  238  and the second operating data  240  may have operating values that do not match exactly with one another (e.g., based on the operating values being measured at different time stamps or different time intervals, based on the operating values being measured at different sections of the electric power distribution system  100 ). In such embodiments, the IEDs  232 ,  234  may determine whether the operating data  238 ,  240  are within a threshold of one another, such as within a threshold value (e.g., 0.1 volts, 0.2 volts, 0.5 volts, 1 volt, 0.1 amperes, 0.2 amperes, 0.5 amperes, 1 ampere) and/or within a threshold percentage (e.g., 1 percent, 2.5 percent, 5 percent, 10 percent) of one another. 
     Based on the operating data  238 ,  240  matching one another, each of the IEDs  232 ,  234  may store the operating data  238 ,  240  for establishing the secure communication link. At a second block  242 , each of the IEDs  232 ,  234  may generate a respective copy of a CAK  244  derived from the stored operating data  238 ,  240 . In certain embodiments, such as embodiments in which the operating data  238 ,  240  do not match exactly with one another, each of the IEDs  232 ,  234  may store both of the operating data  238 ,  240  for generating the CAK  244 . In additional or alternative embodiments, mismatching operating data  238 ,  240  may be rounded or approximated to equal one another. Each of the IEDs  232 ,  234  may then perform the same protocol that uses the operating values associated with the operating data  238 ,  240  to generate a respective copy of a CAK  244 . Performing the same protocol may enable each of the IEDs  232 ,  234  to generate a copy of the same CAK  244 , because each of the IEDs  232 ,  234  are using the same stored operating data  238 ,  240 . In additional or alternative embodiments, such as embodiments in which the operating data  238 ,  240  match exactly with one another, the IEDs  232 ,  234  may only store one of the operating data  238 ,  240 . As such, each of the IEDs  232 ,  234  may perform the same protocol using operating values associated with one of the operating data  238 ,  240  to generate a respective copy of the same CAK  244 . 
     At a third block  246 , the IEDs  232 ,  234  may verify whether the same CAK  244  has been generated. Based on a verification that each of the IEDs  232 ,  234  have generated the same CAK  244 , a connectivity association  248  may be generated based on the CAK  244 . In addition, one of the IEDs  232 ,  234  may generate a SAK  250  based on the CAK  244  and distribute a copy of the SAK  250  to the other of the IEDs  232 ,  234  via the connectivity association  248  for communicating data. For instance, after the SAK  250  has been generated and distributed, a MACsec communication link may be established between the IEDs  232 ,  234 . The IEDs  232 ,  234  may then use their respective copies of the SAK  250  to communicate data via the MACsec communication link. That is, the first IED  232  may use its copy of the SAK  250  to encrypt data to be transmitted to the second IED  234 , and/or the first IED  232  may use its copy of the SAK  250  to decrypt encrypted data received from the second IED  234 . Additionally or alternatively, the second IED  234  may use its copy of the SAK  250  to encrypt data to be transmitted to the first IED  232 , and/or the second IED  234  may use its copy of the SAK  250  to decrypt encrypted data received from the first IED  232 . In this manner, the IEDs  232 ,  234  may establish a secure communication link and communicate via the secure communication link without having to receive certain user input, such as for generating the CAK  244  and/or the SAK  250 . 
       FIG.  4    is a flowchart of an embodiment of a method  270  for establishing a secure communication link between devices of the electric power distribution system  100 . The illustrated method  270  depicts the secure communication link being established between the first IED  232  and the second IED  234 , but a method similar to the method  270  may be used to establish a secure communication link between different devices of the electric power distribution system  100 , such as between the switch  170  and one of the IEDs  232 ,  234 . In some embodiments, the method may be performed by the respective computing systems  200  (e.g., the respective processors  202 ) of the IEDs  232 ,  234 . It should be noted that additional procedures may be performed with respect to the described method  270 . Moreover, certain procedures of the depicted method  270  may be removed, modified, and/or performed in a different order. 
     At block  272 , the first IED  232  may monitor the first operating data  238  associated with a first section of the electric power distribution system  100 . As an example, the first operating data  238  may include a first set of operating values (e.g., a set of voltage values, a set of current values) measured at specific time stamps and/or time intervals. At block  274 , the second IED  234  may monitor the second operating data  240  associated with a second section of the electric power distribution system  100  in parallel with respect to the first IED  232  monitoring the first operating data  238 . In some embodiments, the second operating data  240  may include a second set of operating values measured at the same time stamps and/or the same time intervals as that of the first set of operating values. In additional or alternative embodiments, the second set of operating values of the second operating data  240  may be measured at different time stamps and/or different time intervals as that of the first set of operating values. 
     At block  276 , the first IED  232  may transmit the first operating data  238  to the second IED  234 . Further, at block  278 , the second IED  234  may transmit the second operating data  240  to the first IED  232 . In certain embodiments, the IEDs  232 ,  234  may be communicatively coupled to one another with a physical cable, such as an Ethernet link, and may transmit the operating data  238 ,  240  between one another via the physical link. In additional or alternative embodiments, the IEDs  232 ,  234  may be communicatively coupled to one another via another communication link (e.g., over any suitable network, such as a local area network, a personal area network, a wide area network) and may transmit the operating data  238 ,  240  between one another via the virtual link. At block  280 , as a result of the second IED  234  transmitting the second operating data  240 , the first IED  232  may receive the second operating data  240 . Moreover, at block  282 , as a result of the first IED  232  transmitting the first operating data  238 , the second IED  234  may receive the first operating data  238 . 
     At block  284 , the first IED  232  may determine whether the second operating data  240  received from the second IED  234  is within a threshold of expected operating data. In some embodiments, the expected operating data may include the first operating data  238  monitored by the first IED  232 . In additional or alternative embodiments, the expected operating data may include calculated operating data, such as an adjustment of the first operating data  238  based on the time stamps and/or time intervals associated with the second operating data  240  relative to the time stamps and/or time intervals associated with the first operating data  238  or based on operation of other devices of the electric power distribution system  100  (e.g., at the different sections of the electric power distribution system  100 ). At block  286 , the second IED  234  also determines whether the first operating data  238  received from the first IED  232  is within a threshold of additional expected operating data, such as the second operating data  240  monitored by the second IED  234  and/or calculated operating data. In certain embodiments, operating data may be constantly transmitted between the IEDs  232 ,  234 , such as at a particular frequency and/or at particular times, to constantly verify that the IEDs  232 ,  234  are monitoring expected operating data  238 ,  240 . Indeed, the IEDs  232 ,  234  may repeat performance of the procedures described with respect to blocks  272 - 286  to verify the monitored operating data  238 ,  240  without having to establish the secure communication link between the IEDs  232 ,  234 . 
     At block  288 , a notification is flagged in response to either of the operating data  238 ,  240  being outside of the threshold of expected operating data, and a secure communication link is blocked from being established between the IEDs  232 ,  234 . That is, the first IED  232  may flag a notification in response to a determination that the second operating data  240  is outside of the threshold of expected operating data, and the second IED  234  may flag a notification in response to a determination that the first operating data  238  is outside of the threshold of the additional expected operating data. As an example, a mismatch between the operating data  238 ,  240  and expected operating data may indicate that the electric power distribution  100  is not operating as desired, such as to deliver, supply, or transmit a desirable amount of power to different sections of the electric power distribution system  100 , and/or that one of the IEDs  232 ,  234  is not operating as desired to monitor the operating data  238 ,  240 . As another example, a mismatch between the operating data  238 ,  240  may indicate that an unauthorized or unexpected device is attempting to establish a secure communication link with one of the IEDs  232 ,  234 . Indeed, the unauthorized or unexpected device may not be able to monitor or generate operating data that is within the threshold of the expected operating data, and the procedure described with respect to block  288  may be performed to block establishment of a secure communication link with the unauthorized or unexpected device. 
     For these reasons, the notification may inform a user (e.g., an operator, a technician) of the mismatch between the operating data  238 ,  240  and the expected operating data to cause the user to take corresponding action, such as to inspect the operation and/or certain devices of the electric power distribution system  100 . In some embodiments, the notification may be transmitted to a device (e.g., the computing device  178 ) associated with the user. In additional or alternative embodiments, the notification may include a visual output and/or an audio output directly presented by the first IED  232 , the second IED  234 , or another suitable device of the electric power distribution system  100 . 
     However, at block  290 , in response to a determination that the second operating data  240  is within the threshold of the expected operating data, the first IED  232  may generate a first CAK based on the first operating data  238  and/or the second operating data  240 . Additionally, at block  292 , in response to a determination that the first operating data  238  is within the threshold of the expected operating data, the second IED  234  may generate a second CAK based on the first operating data  238  and/or the second operating data  240 . In certain embodiments, each of the IEDs  232 ,  234  may perform the same protocol that generates the copies of the CAK, and the IEDs  232 ,  234  may therefore generate copies of the same CAK based on the operating data  238 ,  240  that are within the respective expected thresholds. By way of example, the protocol may include generating a respective passcode or password based on the operating data  238 ,  240  (e.g., respective passcodes or passwords that match one another), and then generating a respective CAK based on the generated passcode or password. Thus, the IEDs  232 ,  234  may generate a respective copy of the CAK via the monitored operating data  238 ,  240  without having to receive a user input that manually enters matching passcodes, passwords, or other data to the IEDs  232 ,  234  for generating the CAKs. 
     At block  294 , a connectivity association may be established between the IEDs  232 ,  234  based on a verification that the first CAK matches with the second CAK. The connectivity association may then be used to further establish a MACsec communication link between the IEDs  232 ,  234  for communicating data. For example, after the connectivity association has been established, one of the IEDs  232 ,  234  may generate a SAK based on the matching CAKs for distribution via the connectivity association to establish the MACsec communication link between the IEDs  232 ,  234 . The IEDs  232 ,  234  may then use their respective copies of the SAK to encrypt data for transmission via the MACsec communication link and/or to decrypt encrypted data received via the MACsec communication link. In additional or alternative embodiments, an additional connectivity association may be established between the IEDs  232 ,  234  before the MACsec communication link is established between the IEDs  232 ,  234 . For example, after the initial connectivity association is established between the IEDs  232 ,  234  based on a verification that the first CAK matches with the second CAK, one of the IEDs  232 ,  234  may generate a new CAK (e.g., based on random or entropy data instead of based on the operating data  238 ,  240 ) for distribution to the other of the IEDs  232 ,  234  via the initial connectivity association. Upon verification that each of the IEDs  232 ,  234  possesses a copy of the new CAK, a new connectivity association may be established between the IEDs  232 ,  234  to replace the initial connectivity association. The IEDs  232 ,  234  may then use an SAK generated based on the new CAK for establishment of the MACsec communication link. 
     In some embodiments, based on an identification that the first CAK does not match with the second CAK, the MACsec communication link may not be established. Instead, for example, another notification may be flagged to inform a user that the CAKs do not match. For instance, one of the IEDs  232 ,  234  may have used unexpected operating data and/or may have used an unexpected protocol to generate their copy of the CAK. Therefore, the notification may cause a user to examine the IEDs  232 ,  234  and address the mismatch between the generated CAKs. 
     In certain embodiments, the method  270  may be performed while there is no current connectivity association and/or current MACsec communication link established between the IEDs  232 ,  234 . In additional or alternative embodiments, there may be an existing connectivity association and/or existing MACsec communication link currently established between the IEDs  232 ,  234 . Thus, the method  270  may be performed to update the existing connectivity association and/or the existing MACsec communication link. As an example, the method  270  may be performed at a predetermined frequency, at a predetermined time, in response to receipt of a user input, in response to other received data, based on another parameter, or any combination thereof, to update the connectivity association and/or the MACsec communication link established between the IEDs  232 ,  234 . 
       FIG.  5    is a schematic diagram of an embodiment of a communication network  320  for establishing a secure communication link between devices of the electric power distribution system  100 . The illustrated communication network  320  includes the switch  170 , the first IED  232 , the second IED  234 , and a third IED  322 . Each of the IEDs  232 ,  234 ,  322  may monitor respective operating data associated with different sections of the electric power distribution system  100  and to transmit the monitored operating data to one another via the switch  170  to establish secure communication links between the IEDs  232 ,  234 ,  322 . For example, the first IED  232  may monitor the first operating data  238  and transmit the first operating data  238  to the switch  170 , and the switch  170  may transmit the first operating data  238  to the second IED  234  and/or to the third IED  322 . The second IED  234  may monitor the second operating data  240  and transmit the second operating data  240  to the switch  170 , and the switch  170  may transmit the second operating data  240  to the first IED  232  and/or to the third IED  322 . The third IED  322  may monitor third operating data  324  and transmit the third operating data  324  to the switch  170 , and the switch  170  may transmit the third operating data  324  to the first IED  232  and/or to the second IED  234 . 
     Each of the IEDs  232 ,  234 ,  322  may establish a respective MKA connectivity association and/or MACsec communication link with the switch  170  to communicate data with one another. For example, the switch  170  may establish a first connectivity association with the first IED  232 , a second connectivity association with the second IED  234 , and/or a third connectivity association with the third IED  322 . The switch  170  may also establish a first MACsec communication link with the first IED  232  based on the first connectivity association, a second MACsec communication link with the second IED  234  based on the second connectivity association, and/or a third MACsec communication link with the third IED  322  based on the third connectivity association. The first IED  232  may then transmit data to the switch  170  (e.g., for subsequent transmission to the second IED  234  and/or to the third IED  322 ) and/or receive data from the switch  170  (e.g., initially transmitted by the second IED  234  and/or by the third IED  322 ) via the first MACsec communication link. The second IED  234  may transmit data to the switch  170  (e.g., for subsequent transmission to the first IED  232  and/or to the third IED  322 ) and/or receive data from the switch  170  (e.g., initially transmitted by the first IED  232  and/or by the third IED  322 ) via the second MACsec communication link. The third IED  322  may transmit data to the switch  170  (e.g., for subsequent transmission to the first IED  232  and/or to the second IED  234 ) and/or receive data from the switch  170  (e.g., initially transmitted by the first IED  232  and/or by the second IED  234 ) via the third MACsec communication link. 
     In some embodiments, each of the connectivity associations between the IEDs  232 ,  234 ,  322  may be established based on the same CAK. For example, each of the IEDs  232 ,  234 ,  322  may receive the operating data  238 ,  240 ,  324  from one another. Upon verification that each of the operating data  238 ,  240 ,  324  are within a threshold of expected operating data, each of the IEDs  232 ,  234 ,  322  may generate a copy of the same first CAK  326  by performing the same protocol using each of the operating data  238 ,  240 ,  324 . Each of the IEDs  232 ,  234 ,  322  may then establish an MKA connectivity association and a MACsec communication link based on the same first CAK  326  upon verification that each of the IEDs  232 ,  234 ,  322  generated the same first CAK  326 . Accordingly, the IEDs  232 ,  234 ,  322  may communicate with one another via secure communication links established based on the same operating data  238 ,  240 ,  324 . 
     In additional or alternative embodiments, different CAKs may be used to establish the respective connectivity associations between different pairs of the IEDs  232 ,  234 ,  322 . For example, the connectivity association established between two of the IEDs  232 ,  234 ,  322  may be based on the particular operating data  238 ,  240 ,  324  shared between the two IEDs  232 ,  234 ,  322 . In this way, a second CAK  328  that is derived from the first operating data  238  monitored by the first IED  232  and the second operating data  240  monitored by the second IED  234  may be used to establish the connectivity association(s) enabling secure communication between the first IED  232  and the second IED  234  (e.g., the respective connectivity associations established between the switch  170  and the first IED  232  and between the switch  170  and the second IED  234 ). A third CAK  330  that is derived from the first operating data  238  monitored by the first IED  232  and the third operating data  324  monitored by the third IED  322  may be used to establish the connectivity association(s) enabling secure communication between the first IED  232  and the third IED  322  (e.g., the respective connectivity associations established between the switch  170  and the first IED  232  and between the switch  170  and the third IED  322 ). A fourth CAK  332  that is generated based on the second operating data  240  monitored by the second IED  234  and the third operating data  324  monitored by the third IED  322  may be used to establish the connectivity association(s) enabling secure communication between the second IED  234  and the third IED  322  (e.g., the respective connectivity associations established between the switch  170  and the second IED  234  and between the switch  170  and the third IED  322 ). Thus, each pair of IEDs  232 ,  234 ,  322  may communicate with one another via secure communication links established based on a different set of operating data  238 ,  240 ,  324 . 
     As described above, the IEDs  232 ,  234 ,  322  may block establishment of a secure communication link upon determination that received operating data is outside of a threshold of expected operating data. Indeed, one of the IEDs  232 ,  234 ,  322  may be blocked from communicating with any of the other IEDs  232 ,  234 ,  322 . For instance, based on a determination that the first operating data  238  is outside of a threshold of expected operating data, the second IED  234  may block a secure communication link from being established (e.g., between the first IED  232  and the switch  170 ) to block the first IED  232  from communicating with the second IED  234  and also to block the first IED  232  from communicating with the third IED  322 . In an example, the second IED  234  may communicate with the third IED  322  to cause the third IED  322  to block communication with the first IED  232  (e.g., to block establishment of a connectivity association that would otherwise enable the third IED  322  to communicate with the first IED  232 ). In this manner, the first IED  232  may be blocked from communicating with the third IED  322  without the third IED  322  having to perform additional procedures (e.g., described with respect to the method  270 ) to block communication with the first IED  232 , such as based on a determination that the first operating data  238  does not match with expected operating data. 
     Although the illustrated communication network  320  includes three IEDs  232 ,  234 ,  322 , an additional or alternative communication network  320  may include any suitable number of IEDs (e.g., two IEDs, more than three IEDs) that may communicate data with one another via the switch  170 . Further still, although the illustrated communication network  320  includes the switch  170 , an additional or alternative embodiment of the communication network  210  may not include the switch  170 , and the IEDs  232 ,  234 ,  322  may be directly communicatively coupled to one another (e.g., in a point-to-point manner). As such, the IEDs  232 ,  234 ,  322  may directly transmit the operating data  238 ,  240 ,  324  between one another and may establish respective MKA connectivity associations and/or MACsec communication links directly between one another. 
     While specific embodiments and applications of the disclosure have been illustrated and described, it is to be noted that the disclosure is not limited to the precise configurations and devices disclosed herein. For example, the systems and methods described herein may be applied to an industrial electric power distribution system or an electric power distribution system implemented in a boat or oil platform that may or may not include long-distance transmission of high-voltage power. Accordingly, many changes may be made to the details of the above-described embodiments without departing from the underlying principles of this disclosure. The scope of the present disclosure should, therefore, be determined only by the following claims. 
     Indeed, the embodiments set forth in the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it may be noted that the disclosure is not intended to be limited to the particular forms disclosed. The disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. In addition, the techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). For any claims containing elements designated in any other manner, however, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).