Power-system protection

About: Power-system protection is a research topic. Over the lifetime, 6353 publications have been published within this topic receiving 117961 citations.

Closure on "A new protection scheme for fault detection, direction discrimination, classification, and location in transmission lines"

Abstract: This paper presents a new adaptive fault protection scheme for transmission lines using synchronized phasor measurements. The work includes fault detection, direction discrimination, classification and location. Both fault detection and fault location indices are derived by using two-terminal synchronized measurements incorporated with distributed line model and modal transformation theory. The fault detection index is composed of two complex phasors and the angle difference between the two phasors determines whether the fault is intemal or external to the protected zone. The fault types can be classified by the modal fault detection index. The proposed scheme also combines on-line parameter estimation to assure protection scheme performance and to achieve adaptive protection. Extensive simulation studies show that the proposed scheme provides a fast relay response and high accuracy in fault location under various system and fault conditions. The proposed method responds very well with regard to dependability, security and sensitivity (high-resistance fault coverage).

Model Predictive Control-Based Real-Time Power System Protection Schemes

Abstract: The objective of power system controls is to keep the electrical flow as well as voltage magnitudes within acceptable limits in spite of the load and network topology changes. The control of voltage level is accomplished by controlling the production, absorption as well as flow of reactive power at various locations in the system. This paper presents an approach to determine a real-time system protection scheme to prevent voltage instability and maintain a desired amount of post-transient voltage stability margin (an index of system security) following the occurrence of a contingency by means of reactive power control. This approach is based on the model predictive control (MPC) theory. According to an economic criterion and control effectiveness, a control switching strategy consisting of a sequence of amounts of the shunt capacitors to switch is identified for voltage restoration. The effect of the capacitive control on voltage recovery is measured via trajectory sensitivity. The sensitivity of voltage stability margin with respect to the capacitive control is used to construct a security constraint for post-fault operation in the MPC formulation. The efficacy of the proposed approach is illustrated through applications to the WECC system for enhancing the voltage performance and to the 39-bus New England system for preventing voltage collapse.

Investigation of anti-islanding protection of power converter based distributed generators using frequency domain analysis

Abstract: The anti-islanding algorithm proposed by the Sandia national laboratories is analyzed in this study because this scheme, also known as the Sandia scheme, is considered to be effective in detecting islanding of distributed generation systems. Previously, other than heuristic approaches, there has not been any quantitative analysis for tuning the control gains of the algorithm based on the power rating and bandwidth of the distributed generation (DG) power converter. The paper interprets the components of the algorithm that affect the voltage magnitude and frequency into block diagrams that can be linearized and studied using continuous time approximations. This paper uses a frequency domain approach to analyze the range for the gains required by anti-islanding algorithm to effectively determine the disconnection of the mains grid within an acceptable time duration. The analysis provides guidelines for using Sandia's national laboratory schemes under different application conditions. The results are validated using detailed time domain DG and power system simulations.

Wide area protection and emergency control

Abstract: This paper discusses wide area protection and emergency control in power system. System-wide disturbances in power systems are a challenging problem for the utility industry because of the large scale and the complexity of the power system. Addition of nonutility generators and independent power producers, an interchange increase, an increasingly competitive environment, and introduction of FACTS devices make the power system more complex to operate and control, and, thus, more vulnerable to a disturbance. The advanced measurement and communication technology in wide area monitoring and control, FACTS devices and new paradigms (fuzzy logic and neural networks) may provide better ways to detect and control an emergency. The proposed panel presentation will include an overview of causes and risks of wide area disturbances, currently used protective relaying schemes to mitigate them.

A new microprocessor based islanding protection algorithm for dispersed storage and generation units

Abstract: The ability to detect when dispersed storage and generation (DSG) units become islanded from the main source of generation enables the DSG to be quickly disconnected from the utility network and for that network to be rebuilt in a safe and orderly manner. The new islanding protection algorithm described in the paper has been developed to be part of an integrated protection package to cover all the protection requirements of a DSG. A selection of the results obtained from extensive laboratory and field tests are presented and show that the algorithm reliably trips for islanding conditions within 120 milliseconds, trips for load fluctuations should the DSG be operating independent of the main source of supply and restrains for single phase faults close to the DSG. >