Powerware 9315s - Manual (Page 54)

7--2 Powerware 9315 Parallel Capacity/Redundant System with PHP SSBM
164201373 Rev. A 092402
During maintenance, the output of the system can be supplied power through the
bypass breakers in the SSBM or the optional System Maintenance Bypass (SMB).
The bypass input and breaker must be rated for the total system load since it must
supply all of the system load when on bypass. Manual transfers between the
bypass source and the paralleled UPMs are verified make before break.
Operations during transfers to bypass differ depending on the type of transfer:
Manual or Emergency. Manual and Emergency transfers function as follows:
Fully Rated Static Switch:
For Manual transfers to bypass, the static switch is not used. During the transfer,
CBP is closed and verified and then CBS is opened. For transfers of the load from
bypass to the UPMs, CBS is closed and verified and then CBP is opened. The
static switch is armed and ready during both types of transfers.
For Emergency transfers to bypass, the static switch is turned on. During the
transfer, CBP is closed and verified and then CBS is opened. The static switch
turns off after a set time delay which allows the CBP and CBS breakers to complete
their transfer.
Communications is required between the SSBM and UPMs in the system for full
system operation. System level communications and control are accomplished
using a dual redundant network known as PowerNet. PowerNet consists of two
independent networks that are connected to each component network node in the
parallel system.
Data is always transmitted on both networks simultaneously. Each network node
monitors both PowerNets. Failure of one of the two will only result in an alarm
condition. In addition, the applications at each node are designed such that
messages can be lost on the network without affecting the operation of the system.