02-02-2012, 04:47 PM
IMPROVING RELIABILITY AND PERFORMANCE OF TRANSMISSION LINE USING FACTS TECHNOLOGY
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INTRODUCTION :-
As generation and consumption of electricity has grown, investment in the transmission infrastructure has declined. The grid is aging and few new lines are being built, given high cost and permitting delays. The inability to control power flow on the grid results in poor asset utilization and impedes the growth of the energy market. Uncertainties in transmission investment recovery and the high cost of existing power flow control solutions further exacerbate the problem. It is generally agreed that the transmission grid is under stress, and that steps need to be taken quickly to eliminate the transmission constraints and bottlenecks and to improve the utilization of existing Transmission & Distribution assets, to ensure the flow of reliable and affordable electricity
ACTIVE POWER FLOW CONTROL :-
One of the most pressing challenges facing the utility community is controlling power flow on the grid. The underlying assumption for a vibrant energy market is that the T&D infrastructure could optimally transport energy from where it was generated to where it was needed.
The distribution of current in a meshed network (important for high reliability) is governed by line impedances. In such a network, the first line that becomes ‘congested’, i.e. Becomes overloaded, limits the capacity of the network. Trying to push more power through the network can cause lines to trip and can initiate a cascading failure, even though most of the lines may be operating below their rated capacity. The situation is rendered even more complex due to a requirement for continued operation under a (N-1) contingency condition.
FACTS Technology :-
A new technology that holds the promise of realizing a smart grid and achieving power flow control is “Flexible AC Transmission Systems” or “FACTS”. FACTS devices, such as STATCOM, SVC, SSSC and UPFC can be inserted in series with a line, connected in parallel, or a combination of the two, to achieve a myriad of control functions, including voltage regulation, system damping and power f l ow control. Typical FACTS devices can operate at up to 345 kV and can be rated as high as 200 MVA.Even though FACTS technology is technically proven, it has not seen widespread commercial acceptance due to a number of reasons –
High total cost of ownership.
Difficulty in computing ROI for investments that decrease congestion, or increase system capacity or reliability.
High fault currents (60,000 Amps) and insulation requirements (1000 kV) stress the power electronics system, making implementation of FACTS systems, in particular series connected devices, very difficult and expensive.
