PPC380AE02 HIEE300885R0102 controller card

Dead Bus Closing When a dead bus is detected and dead bus closing mode is enabled in a multiple unit system, the synchronizer will attempt to get an exclusive lock on permission to issue a breaker closure command. This security is required to prevent two or more units from closing their breakers at the same time. To provide this security, a network message requesting the lock is made to all other EGCP-2 controls currently active on the network.The GENERATOR AUX CONTACT open requirement backs up the dead bus condition in the event of a bus PT failure. If a dead bus condition is indicated by lack of bus voltage, but the generator breaker is closed, a reply will not be sent.

When an EGCP-2 control receives a lock request

 it does the following actions: 

1. If a dead bus permission request is not also currently being made, a dead bus condition is indicated, and the GENERATOR AUX CONTACT discrete input is inactive (the EGCP-2 control returns a reply message to the requesting unit).

2. If a dead bus permission request is also being made and that request sequentially precedes the received request, the received request is retained, otherwise the reply is sent. (In the event of a sequential tie, the unit with the lower assigned network address wins.) When all other units have replied verifying that they also indicate a dead bus (bus input less than 40 Vac) and do not hold a lock, the requesting unit then holds lock permission and may attempt to close its circuit breaker. The lock is released automatically after issuing the circuit breaker closure command. This will allow any other unit to get permission to lock if the breaker fails to close. The dead bus closing function may be enabled or disabled by the user with the Dead Bus Closure set point in the Synchroscope tuning menu.

Voltage Matching

 The voltages of the generators in a parallel system must be matched within a small percentage to minimize the reactive power flow in the system. If two synchronous generators of unequal voltage are paralleled, the combined voltage will have a value different from the voltage generated by either of the generators. The difference in voltages results in reactive currents flowing in the system with subsequent lowered system efficiency.