Handbook of Energy Storage for Transmission or ... - W2agz.com
Handbook of Energy Storage for Transmission or ... - W2agz.com
Handbook of Energy Storage for Transmission or ... - W2agz.com
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EPRI Proprietary Licensed Material<br />
Figure 9<br />
Negatively damped oscillations observed on August 8, 1974, on the BPA Pacific HVAC Intertie.<br />
Power Quality<br />
A variety <strong>of</strong> loads--ranging from modest industrial installations to substations <strong>of</strong> significant<br />
capacity--require energy to provide power quality and backup power. This energy is used <strong>f<strong>or</strong></strong> a<br />
variety <strong>of</strong> conditions such as when momentary disturbances require real power injection to avoid<br />
power interruptions. In the case <strong>of</strong> industrial customers, a local source <strong>of</strong> power may be required<br />
when there is an interruption <strong>of</strong> power from the utility. This power source may function until the<br />
power feed from the utility is rest<strong>or</strong>ed, until a reserve generat<strong>or</strong> is started, <strong>or</strong> until critical loads<br />
are shut down in a safe manner. In the case <strong>of</strong> a substation, a variety <strong>of</strong> momentary disturbances<br />
such as lightning strikes <strong>or</strong> transmission flashovers cause power trips <strong>or</strong> low voltages. The total<br />
energy st<strong>or</strong>age requirement is greater and there may be a need power flow separation to insure<br />
continuous power to imp<strong>or</strong>tant customers.<br />
Load leveling<br />
Demands <strong>f<strong>or</strong></strong> electric power vary both randomly and with predictable variations. Perhaps the<br />
most significant variation <strong>of</strong> power demand is the diurnal change associated with the functioning<br />
<strong>of</strong> an industrial society. Both <strong>com</strong>mercial and residential demands are greater during the day<br />
than at night. On the other hand, many power plants operate most efficiently and have longer<br />
lives if they operate continuously near their maximum power output. One method <strong>of</strong><br />
ac<strong>com</strong>modating users’ power demands and the characteristics <strong>of</strong> these plants is to install an<br />
energy st<strong>or</strong>age system that can accept energy at night and can deliver it back to the grid during<br />
periods <strong>of</strong> high demand. The value <strong>of</strong> this type <strong>of</strong> st<strong>or</strong>age is based on the difference in marginal<br />
cost <strong>of</strong> <strong>of</strong>f-peak power and the price paid <strong>f<strong>or</strong></strong> power during the peak. An additional impact <strong>of</strong><br />
diurnal st<strong>or</strong>age is that it can replace <strong>or</strong> defer the installation <strong>of</strong> extra generation capacity to<br />
ac<strong>com</strong>modate.<br />
SMES Page 15
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