IEEE 277:2007 pdf free download

IEEE 277:2007 pdf free download.IEEE Recommended Practice for Cement Plant Power Distribution.
3.1.13 Limiting voltage drop
Design the power system to limit voltage drop during starting large motors (at the distribution voltage) to a maximum of 10% of system nominal voltage at the motor terminals. The possibility of equipment malfunction increases when the voltage drop exceeds 10%. Special precautions to maintain control voltage may be required where a greater than 10% drop in system oltage is anticipated.
During normal running, voltage at the large motors at the distribution voltage should not vary more than 5% of rated motor voltage.
A motor starting study, short-circuit study. and a coordination study are required to properly design the power system.
When purchasing new transformers, it may be economical to incorporate automatic tap changers on the new transformers to enable voltage level changes.
3.1.14 Isolating synchronous machines
Isolate synchronous machines from the utility system prior to any reclosing action subsequent to a plant power interruption due to the utility system. A power interruption allows the synchronous machines to shift iii phase position in respect to the utility system. Subsequent application of power to the machines, when out of synchronism. may result in inrushes and torque well above drive equipment mechanical limits. High- speed underfrcquency relays without any intentional time delay can usually act to isolate loaded synchronous motors prior to a reclosing action. Note that lightly loaded motors or motors connected to high inertia loads or both may not decelerate in time to allow underfrequency relay action prior to utility reclosing.
Coordination with the utility to block or delay reclosing is suggested,
3.1.15 Choosing and setting protective relays
Choose and set protective relays to selectively initiate the isolation of faults on the primary distribution system. Periodically, check relays to ensure proper operation. A short-circuit and relay coordination study should be made to enable selective isolation of both phase and ground overcurrents for the load on each feeder back to the utility system.