10.5 PRACTICAL APPLICATION: A CASE STUDY 46710.5.1). This plant is part of the Ontario Hydro-Electric System on the Niagara River. Six lines
run into Ontario from the Beck plant, and the line controlled by the faulty relay was carrying 300
MW. Failure of the relay dumped this load onto the other five lines. Even though these lines were
not overloaded, all five tripped out.
Total power flow on these lines had been 1600 MW into Ontario, including 500 MW being
imported from the Power Authority of the State of New York. All this power was suddenly
dumped on the New York system. The resultant surge knocked out the Power Authority’s
main east–west transmission line and shut down seven units that had been feeding the north-
eastern grid. The resulting drain on systems to the south and east caused the whole system to
collapse.
New York City, for example, had been drawing about 300 MW from the network just before
the failure. Loss of the upstate plants caused a sudden reversal of flow and placed a heavy drain
on the City generators. The load was much greater than the plants still in service could supply,
and the result was a complete collapse. Automatic equipment shut down the units to protect them
from damage.
After the total failure the individual systems started up in sections, and most power was
restored by a little after midnight. However, Manhattan, with the greatest concentration of load,
was not fully restored unitl after six o’clock the following morning.
Only a rare combination of faults, however, will result in a cascading of tripouts and a
complete shutdown over an entire region. In order to avoid such large blackouts, stronger grids
have been planned and various techniques developed to operate large interconnected networks in
parallel with a high degree of operating stability, and with increasing dependence on automated
Figure 10.5.1Area affected by the blackout of 1965.