GE D25 User Manual

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GE D25 User Manual Manual pdf 108 page image

D25User's Manual GE Grid Solutions108 994-0081-3.00-21 GE InformationUsing Current-Monitored Digital OutputsCurrent-MonitoredDigital OutputsD25s equipped with a high-current control card are provided with 8 digitaloutputs that have current monitoring. The last 8 of the 32 points on the card(i.e. 25 – 32) are designated as the current-monitored points.By default, current monitoring and seal-in is enabled in the D25configuration. A point enabled for monitoring and seal-in operates accordingto the following rules:Rules Current-MonitoredDigital Outputs• Only pulse type commands are accepted.• If the current across the relay contacts exceeds the relay breaking current duringthe pulse operation, and clears before the pulse duration expires, the relay willopen normally when the pulse duration expires and no alarm will be raised.• If current in excess of the relay breaking current is detected across the contactsof the point when the pulse duration has expired, the contact will remain closedand a current seal-in digital input alarm will be activated to indicate thecondition. The local/remote LEDs on the front of the D400 will begin flashing aswell to indicate the presence of the condition. The alarm points are placed atdigital inputs 148 to 155 in the D25 Plant I/O DCA (actual point number may beoffset if there are DCAs placed before Plant I/O in the configuration).• While a contact is sealed closed, additional control requests on the point arerejected. If the board is placed in local mode via the local/remote switch on thefront of the D25, the contact will remain sealed.• The contact will remain sealed closed until the excessive current clears or anoverride command is sent. If the excessive current clears, the relay will openautomatically. No additional user input is required. Alternatively, an overridecommand may be sent via a digital output. These digital outputs are placed atdigital outputs 36 to 43 in the D25 Plant I/O DCA (actual point number may beoffset if there are DCAs placed before Plant I/O in the configuration). If acontrol operation is sent to the override digital point for a sealed-in digitaloutput, then the relay seal-in will be overridden and the relay opened. This maycause damage to the high-current control card if the excessive current is stillpresent. The override points remain online even if the control is placed in localmode, to ensure that the option to override a sealed-in relay is always available.• A current seal-in digital input alarm that is active due to seal-in will clear whenthe relay contact opens, whether due to clearing of the current or do to anoverride command being sent.• D25 Plant I/O DCA will reject control requests sent to the seal-in override digitaloutput for a point not under seal-in.