VOLTAGE COLLAPSE CONSTRAINED LOADABILITY ANALYSIS OF BANGLADESH POWER SYSTEM NETWORK Md. Jan-E-Alam O&M Solutions Bangladesh Ltd. 121-C, Gulshan Avenue, Gulshan 2 Dhaka 1212, Bangladesh jan.eee.alam@gmail.com A. Hasib Chowdhury Department of Electrical and Electronic Engineering Bangladesh University of Engineering and Technology Dhaka 1000, Bangladesh hasib@eee.buet.ac.bd ABSTRACT Information on loading capability is highly important for secure operation of a power system, and also provide with a background for expansion planning. Loadability studies based on voltage collapse, considered as one of the severe limiting factors in system loading, can be used to obtain practical insights on the operational regime of an existing system. Findings of a preliminary level voltage collapse study on Bangladesh Power System Network (BPSN) have been presented in this paper. The complete network model of BPSN, represented in this work by a 166 bus system, has been used. Voltage collapse constrained maximum loading point at the base case – created with a recent peak-time operational data set, and with several selected contingencies have been determined and presented. Usefulness of additional information obtained from voltage collapse studies, such as identification of weak buses and their effectiveness in network performance improvement has also been discussed. KEY WORDS Bangladesh power system, saddle-node bifurcation, continuation power flow, tangent vector, and voltage collapse 1. Introduction Assessment of loading capability of a power system is essential not only for security of day-to-day operation, but also for catering the needs of adequate background information and data for system planning regime. Loading limits are governed by several factors including transmission line thermal limits, bus under-voltage limits, power system stability and so on. Administrative limitations, such as operational philosophy, specifications, local grid code, also can impose certain restrictions on loading. Voltage collapse, an event related to voltage instability in the system, seems to be one of the major governing factors in system loadability that have so far drawn most careful attention of the power system research community. Historically, several events of blackout have been directly associated with this event [1]. Moreover, evolution of deregulated market and eventual stressed operation of commercial power systems is increasing the threats for probable voltage collapse in the network. As a consequence, intensive research has been carried out in the industry to be able to better understand and control this phenomenon. Several papers, e.g., [2-9], have discussed the physical significance and mathematical equivalence of voltage collapse phenomenon. In [2-3], the authors described this event as a consequence of reactive power imbalance in the system. When a system is loaded higher than a reference base case operating point, amount of feasible load increase at any specific bus depends on availability of additional reactive power at that bus. If the network is loaded further, reactive reserve can no more support this loading and the system “collapses” with a rapid decline of voltage. In Bangladesh, application of advanced analytical techniques for planning and operation of power systems are not in wide practice, even in the recent days. Though this country is yet to go through deregulation of electricity market, high population growth rate, rapid industrialization in some cases – typical for an emerging economy, and lack of adequate and timely investment for transmission infrastructures have increased the possibility of operating the system in stressed condition. Moreover, inadequate reactive power support and poor voltage profile throughout the network might strengthen the risk of probable voltage collapse. Albeit there are other factors to limit the loading capability, considering the voltage and VAR related realities of BPSN, it is evident that study of voltage collapse constrained loadability holds an indispensable position in the assessment of loading capability of this system. This paper presents the findings of a voltage collapse based loading capability analysis performed on BPSN. Section 2 provides a brief description of the system model used. Analytical technique and the simulation tool used in this work have been described in Section 3. Appearance of voltage collapse in BPSN in several selective contingencies has been studied and results have been presented in Section 4. 684-021