31-07-2012, 04:44 PM
Blackout Prevention in the United States, Europe, and Russia
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INTRODUCTION
Recent cascading failures in several power systems
worldwide require urgent and thorough attention. Adequate
analysis, research, and development efforts are needed to
investigate the cascading processes, determine conditions
and triggering events that cause blackouts, evaluate the
consequences and identify potential blackouts, and develop
preventive transmission planning solutions, operating
procedures, and automatic protection systems. The North
American Electric Reliability Council (NERC) has established
four categories for events where the system impacts
must be limited or evaluated [1]. Category D addresses
extreme events resulting in removing two or more components
and/or cascading. NERC requires evaluating the
risk and consequences of these failures in terms of the load
and generation loss, achieving a new operating point, and
mitigating the extent of such events.
Summary of Observations and Recommendations
Here we summarize observations and recommendations
made by blackout investigators who analyzed the causes
of the U.S.–Canada, London, Sweden–Denmark, and Italy
blackouts.We also add come comments made by the authors
of this paper (indicated by square brackets) and indicate the
items already addressed in the Russian emergency control
and protection system (indicated by asterisks).
STRUCTURE OF CONTROL CENTERS AND PRINCIPLES OF REAL-TIME DISPATCH—FIRST LINE OF DEFENSE
A. Principles of Operation of the Grefid Control Centers
The main principles of the Russian hierarchical dispatch
system are as follows [11], [14]:
• separation and independence from the administrative
and economic management functions;
• hierarchical structure with the direct subordination
of the lower level dispatchers to the higher level dispatchers;
• independence of the dispatchers at each level when intervention
from the high-level dispatchers is not needed;
• clear definition of the dispatching personnel’s responsibilities
at each level at normal and emergency
conditions;
• strictest dispatch discipline.
Underfrequency and Undervoltage Load Shedding
This emergency automatic system is generally similar to
the one used in the United States. The difference is in the
stronger coordination of these important systems, absence
of geographical limits in selecting and prioritizing interruptible
loads, unified and strictly enforced principles of operation,
and a well-defined sequence of operations. As a result,
Russia’s grefid can withstand severe reductions of frequency
and voltages while preserving the all-system reliability and
the most important loads. The objective of the Russian underfrequency
relaying system is to eliminate any possibility
of frequency reductions below 45 Hz,13 limit frequency excursions
below 47.5 Hz by 20 s, and below 48.5 Hz by 60 s.