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  • What is the TA disconnection criterion for line protection?

    * Question

    What is the TA disconnection criterion for line protection?

    * Answer

    The TA (Transverse Admittance) disconnection criterion for line protection is a technique used in power systems to detect faults and disconnect the affected section to prevent damage and maintain system stability. Here’s an overview of the TA disconnection criterion for line protection:


    The TA disconnection criterion is based on the measurement of the transverse admittance of a transmission line. Transverse admittance is a parameter that describes the relationship between the line’s voltage and the current flowing through it, considering the effects of shunt capacitance and leakage conductance. This criterion leverages the fact that faults on a transmission line significantly alter the transverse admittance values.


    Normal Conditions:

    Under normal operating conditions, the transverse admittance of the line remains within a predictable range. This range is determined by the line’s physical properties and the load it carries.

    2.Fault Conditions:

    When a fault occurs (such as a short circuit, ground fault, or line-to-line fault), the electrical characteristics of the line change abruptly. This change is reflected in the transverse admittance, which will deviate significantly from its normal range.


    Protection devices continuously monitor the transverse admittance. When the admittance values exceed predefined thresholds, indicative of a fault, the protection system recognizes the anomaly.


    Upon detecting a significant change in transverse admittance, the protection system triggers the circuit breakers to isolate the affected section of the transmission line. This prevents further damage to the equipment and ensures the stability of the power system.

    Implementation Steps

    • Measurement: Install sensors or measurement devices that can accurately measure the voltage and current at different points along the transmission line.
    • Calculation: Calculate the transverse admittance using the measured voltage and current values.
    • Threshold Setting: Define thresholds for normal and fault conditions based on historical data, simulations, and engineering judgment.
    • Monitoring: Continuously monitor the admittance values in real-time.
    • Action: Configure the protection system to trip the circuit breakers when the admittance exceeds the set thresholds.


    • Speed: The TA disconnection criterion allows for rapid detection and disconnection of faulted sections, minimizing the duration of fault conditions.
    • Sensitivity: It is sensitive to various types of faults, making it a versatile protection mechanism.
    • Reliability: Helps in maintaining the stability and reliability of the power system by ensuring timely fault isolation.

    Example Scenario

    Consider a transmission line with a nominal transverse admittance range determined during normal operating conditions. If a ground fault occurs, the admittance suddenly increases due to the additional path created by the fault. The protection system detects this change and disconnects the faulted section to prevent further damage and to maintain system integrity.

    By employing the TA disconnection criterion, power systems can effectively manage and isolate faults, ensuring a stable and reliable supply of electricity.



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