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Related Concept Videos

Differential Relays01:20

Differential Relays

113
Differential relays are used to protect generators, buses, and transformers by comparing electrical quantities at different points. When a fault occurs, the difference in current between the two points triggers the relay to operate, opening the circuit breaker. Under normal conditions, the current entering (i1) and leaving (i2) a generator are equal. When a fault occurs, however, these currents become unequal, and the difference current flows in the relay operating coil, causing the relay to...
113
Directional Relays01:25

Directional Relays

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Directional relays, essential for managing unidirectional fault currents, enhance the safety and efficiency of power systems. On power lines equipped with directional relays, faults downstream (to the right) of the current transformer typically cause the fault current to lag the bus voltage by approximately 90 degrees, known as the forward direction. In contrast, upstream (left-side) faults may result in the fault current leading the bus voltage by nearly 90 degrees, termed the reverse...
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Pilot and Numeric Relaying01:21

Pilot and Numeric Relaying

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Pilot relaying is a type of differential protection used in power systems. It compares electrical quantities at the terminals of equipment via a communication channel instead of direct relay interconnection. This method is essential for transmission lines where the terminals are far apart, typically up to 80 km for lines with 69 to 115 kV ratings. Four types of communication channels are used for pilot relaying:
82
Line Protection with Impedance Relays01:27

Line Protection with Impedance Relays

67
Coordinating time-delay overcurrent relays in complex radial systems and directional overcurrent relays in multi-source transmission loops can be challenging. Impedance relays address these issues by responding to the voltage-to-current ratio, specifically measuring the apparent impedance of a line. These relays become more sensitive during faults as current increases and voltage decreases, thereby reducing the apparent impedance.
Under normal conditions, low load currents keep the measured...
67
Overcurrent Relays01:26

Overcurrent Relays

70
Overcurrent relays, crucial for circuit protection, are connected to the secondary current of a current transformer. There are two primary types of overcurrent relays: instantaneous and time-delay.
Instantaneous overcurrent relays activate immediately when the input current exceeds a predetermined value, known as the pickup current, instantly energizing the circuit breaker trip coil. This rapid response is vital for addressing severe faults quickly.
Time-delay overcurrent relays, on the other...
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Reclosers and Fuses01:26

Reclosers and Fuses

87
Automatic circuit reclosers enhance the protection of distribution circuits by interrupting and auto-reclosing an AC circuit according to a preset sequence. They effectively manage temporary faults on overhead distribution lines, often caused by tree limbs or wildlife, by briefly disrupting service to improve overall reliability. However, contact with reclosers or energized broken conductors on the ground can pose serious hazards.
A comprehensive protection scheme for radial distribution...
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Covert Communications in a Hybrid DF/AF Relay System.

Jihwan Moon1

  • 1Department of Mobile Convergence Engineering, Hanbat National University, Daejeon 34158, Republic of Korea.

Sensors (Basel, Switzerland)
|October 26, 2024
PubMed
Summary
This summary is machine-generated.

This study introduces optimal and low-complexity criteria for selecting decode-and-forward (DF) or amplify-and-forward (AF) relay modes to enhance covert communication rates and reduce detection risk.

Keywords:
amplify-and-forwardcovert communicationsdecode-and-forwardlow probability of detectionphysical layer security

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Area of Science:

  • Wireless communication systems
  • Information security
  • Signal processing

Background:

  • Covert communication is essential for transmitting sensitive information undetected.
  • Hybrid relay systems offer flexibility but require optimal mode selection.
  • Existing methods may lack efficiency in balancing covert rate and complexity.

Purpose of the Study:

  • To develop optimal and low-complexity criteria for mode selection in hybrid DF/AF relay systems.
  • To maximize the covert communication rate while minimizing detection probability.
  • To analyze the trade-offs between delay, covert rate, and computational complexity.

Main Methods:

  • Analysis of delay-aware achievable covert rates for individual DF and AF modes.
  • Derivation of an optimal DF/AF mode selection criterion.
  • Proposal of a simplified, low-complexity selection criterion for practical applications.
  • Numerical simulations to evaluate performance.

Main Results:

  • The optimal criterion maximizes covert rate by considering delay-aware achievable rates.
  • The low-complexity criterion significantly reduces computational time.
  • Achieved covert rate gains up to 50% and running time gains up to 20% for specific system parameters.
  • Demonstrated effectiveness of proposed criteria in enhancing covert communication performance.

Conclusions:

  • The proposed DF/AF mode selection criteria effectively enhance covert communication rates.
  • The low-complexity criterion offers practical advantages for real-world implementations.
  • This research contributes to more secure and efficient wireless communication systems.