Pre-insertion Resistor Research Articles

Assessment of Sudden Voltage Changes and Flickering for a Grid-Connected Photovoltaic Plant

In this paper, sudden voltage changes studies are carried out for a 20 MW grid-connected photovoltaic plant to assess the impact of energization of the step-up transformers, which may cause a voltage dip that could be a nuisance to the point of common coupling (PCC) of the transmission system. In addition, the flicking performance of the plant is checked. At the design stage, these studies are necessary to verify compliance of the photovoltaic plant and to design its connection with regulatory grid codes and international standards. The photovoltaic plant is compliant with the FICHTNER standard for long-term flicker severity and with the short-term flicker severity requirements of Engineering Standard P28. Based on the study results, the main breaker which is connected to the PCC should be ordered with 150 Ohm Pre-Insertion Resistor to make the Photovoltaic plant comply with grid code requirements of sudden voltage changes.

Relevant Parameters in a Statistical Analysis—Application to Transmission-Line Energization

This paper summarizes the important factors that affect statistical switching transients studies during transmission-line energization. These factors include the number of repetitions to ensure the statistical characteristic of the study, the variation range of the mean closing time of the circuit-breaker contacts, the model used for the representation of the transmission line, and the influence of transposition. In addition, a statistical analysis of mitigation methods to reduce overvoltages during transmission-line energization maneuver is presented, specifically the use of surge arresters, of controlled switching, and of a preinsertion resistor. The shunt compensation degree is considered as an independent parameter. Digital simulations were performed with PSCAD.

Capacitor Banks Switching Transients in Power Systems

This study provides an introduction to capacitor bank switching transients, illustrates the effects of the capacitor banks switching in the utility primary distribution system at different places of the power system, but specially at the customer’s plant. Study covers different operational cases to find the suitable method or techniques can be used to limit the effect of capacitor switching transients. Transient disturbances in power systems may damage key equipment, potentially having a great impact on system reliability. These transients may be introduced during normal switching operations, lightning strikes, or because the equipment failure. Therefore, time-domain computer simulations are developed to study dangers cases due to transient occurrences. The simulations are performed using the simulation software Electromagnetic Transient Program (EMTP). In this study, the Alternative Transients Program (ATP) version 5.7p2 was applied on a simple industry network. Key words : Capacitor banks; Transient overvoltage and current; Energization inrush; Back-to-back switching; Preinsertion resistor and inductor

Implementation and Performance Evaluation of a Reclosing Method for Shunt Reactor-Compensated Transmission Lines

This paper proposes a new control method to reduce overvoltages due to three-phase reclosing for shunt compensated transmission lines (TL). The method detects the first minimum voltage region of the beating across the circuit breakers after protection dead time and works independently of voltage zero crossing, reducing significantly the reclosure time. The controller was tested on a Real Time Digital Simulator (RTDS) and its performance was compared to the traditional preinsertion resistor approach and another existing control method.

Methods to Minimize Zero-Missing Phenomenon

With the increasing use of high-voltage ac cables at transmission levels, phenomena, such as current zero missing, start to appear more often in transmission systems. Zero-missing phenomenon can occur when energizing cable lines with shunt reactors. This could considerably delay the opening of the circuit breaker (CB), leaving the system unprotected and vulnerable to failures. Methods to prevent zero-missing phenomenon are still being studied and compared in order to identify effective countermeasures. This paper contributes to these efforts by presenting several countermeasures that can be applied to reduce the hazards of zero-missing phenomenon. The authors discovered that this phenomenon can be eliminated, merely by using an extra CB or a preinsertion resistor.

Switching overvoltage analysis and air clearance design on the KEPCO 765 kV double circuit transmission system

This paper presents the results of the air clearance design on the KEPCO 765 kV double circuit transmission system. At first the authors performed the switching overvoltage study. The switching overvoltage was analyzed by EMTP (Electro-Magnetic Transient Program) and TNA (Transient Network Analyzer). The full scale test for the air insulation strength of 765 kV double circuit transmission towers was performed by a 4 MV outdoor impulse generator. The simultaneous fault clearing case of a single line-to-ground fault at each circuit was considered because the probability of simultaneous single line-to-ground fault at each circuit is very high. However, the reclosing overvoltages with preinsertion resistor are lower than the simultaneous fault clearing overvoltages when the transmission line is short (about 170-180 km). The maximum phase to ground switching overvoltage in the simultaneous fault clearing case is 1.9 p.u. and the maximum switching overvoltage between phase to phase is 3.3 p.u. The required air clearance in a tower at the altitude of below 1000 m is 4950 mm to endure the maximum switching overvoltage of 1.9 p.u. The standard deviation of 5% in switching surge flashover voltage was verified from the full scale test.

Energization transients of shunt reactors

This paper investigates the impacts of energization transients of large shunt reactors on the operation of HVAC and HVDC/AC power systems. The Electromagnetic Transients Program for DC systems (EMTDC) is used for these simulation studies. The studies conclude that shunt reactor energization can result in undesirable response of power system apparatus and even interruption of power flow, e.g. commutation failure of HVDC power converters. The studies also indicate that the energization transients can be adequately alleviated based on the use of pre-insertion resistor and/or controlled energization strategies.