Emergency Generator Automatic Bus Transfer.pdf

Emergency Generator Automatic Bus Transfer

1.0 System Components

The Automatic Bus Transfer (ABT) switch consists of the following generalized parts:

1. Electro-Industries Shark200 metering device: An Intelligent Electronic Device (IED) used to measure and display the Ship's Service voltage (SSV).

Additionally, this IED measures the quality of the Ship's Service voltage and is programmed to engage a set of dry-contact relays. Relay 1 is programmed to close at approximately 430VAC when SS voltage is present. This represents 95% of normal operating voltage. Relay 2 is programmed to close at 410VAC.

This represents 80% of normal operating voltage. Relay 1 is indicated on the IED as LIM1 and Relay 2 is indicated on the IED as LIM2.

2. Electro-Industries Shark200 metering device: Another IED used to measure and display the Emergency Generator voltage (EGV). Additionally, this IED measures the quality of the Emergency Generator voltage and is programmed to engage a set of dry-contact relays. Relay 1 is programmed to close at approximately 430VAC when EG voltage is present. This represents 95% of normal operating voltage. Relay 2 is programmed to close at 410VAC. This represents 80% of normal operating voltage. Relay 1 is indicated on the IED as LIM1 and Relay 2 is indicated on the IED as LIM2.

3. General Electric Versamax Programmable Logic Controller (PLC) and Operator Interface Terminal (OIT). The GE PLC co-ordinates the activities of the IED's, 52E and 52N, and manages the 24VDC supply.

The OIT is the graphics window into the ABT that allows automated and local control and displays diagnostics and alarms.

4. Emergency Generator motorized draw-out circuit breaker (52E).

5. Ships Service motorized draw-out circuit breaker (52N).

6. 120VAC supply and redundant 24VDC supply system: The SS bus and the EG bus are both equipped each with a 480VAC to 120VAC transformer. These transformers supply the 120VAC needed to operate the motor controls on 52N and 52E. As well, the 120VAC power is stepped down by the redundant 24VDC system. The redundant 24VDC supplies consist of a pair of 4 amp 120VAC to 24VDC power supplies, a 40 amp isolation diode, a 20 amp 24VDC battery charger, and a pair of lead-acid 12VDC batteries connected in series. The charger supplies the recharge capability and supervision of the 7.2 amp 24VDC battery system. The redundant system ensures that the PLC and IED's will continue to function through a complete power outage (black ship).

2.0 AUTO

2.1 Operating on Ship's Service

Normal operation consists of either Shore power or Ship's Service power being supplied to the emergency bus in the emergency generator room. The SSV IED continually monitors the voltage of the Ship's Service bus and is programmed to react to two events: >95% available voltage and <80% available voltage. At 95% voltage, relay 1 of the IED closes and the PLC is programmed to begin the Transfer to Ship Service Sequence when the SHIP SERVICE READY condition is present.

2.2 The SHIP SERVICE READY OIT indicator consists of the following items:

- NO DVA POWER alarm (CB4 tripped)

- NO RELAY POWER alarm (CB5 tripped)

- NO Ship Service alarms:

- 52N FAILED TO CLOSE or 52E FAILED TO OPEN

- NO 52N INVALID STATE: Auxiliary Contact Failure

- 52N open and close contacts either both open or both closed

- AUTO mode is ON

- MANUAL mode is OFF

- NO BOTH 52E AND 52N CLOSED alarm

- NO 52N OVERCURRENT alarm: Physical trip relay on 52N

2.3 The Transfer to Ship Service Sequence:

1. Wait the preset time for the SHIP SERVICE OK RETURN timer (SSV Relay 1 signal).

2. If 52E is closed, trip 52E.

3. Wait the preset time for the 52E TRIP FAIL timer.

4. If 52E fails to trip, abort the sequence and report 52E FAILED TO OPEN alarm.

5. If 52E is open and 52N is open, wait the preset time for the 52N CLOSE DELAY timer and then close 52N.

6. Wait the preset time for the 52N CLOSE FAIL timer.

7. If 52N is closed, indicate SHIP SERVICE POWER OK.

8. If 52N fails to close, abort the sequence and report 52N FAILED TO CLOSE alarm

2.4 The Transfer to Ship Service Sequence is immediately aborted or reset under the following conditions:

1. The sequence has completed.

2. 52E FAILED TO OPEN.

3. 52N FAILED TO CLOSE.

4. SHIP SERVICE READY condition becomes NOT present.

2.5 Operating on Emergency Generator Service

If the SSV IED engages Relay 2 (<80% voltage) because of a voltage problem with the Ship's Service, the PLC is programmed to begin the Transfer to Emergency Generator Sequence when the Generator Ready condition is present.

2.6 The Generator Ready OIT indicator consists of the following items:

- NO CB Alarm:

- DVA POWER alarm (CB4 tripped) or DMS POWER alarm (CB3 tripped) or RELAY POWER alarm (CB5 tripped)

- NO BOTH 52E AND 52N CLOSED alarm

- NO EG Run Alarm:

- 52E FAILED TO CLOSE, 52N FAILED TO OPEN, or

GENERATOR FAILED TO START

- NO 52E INVALID STATE: Auxiliary Contact Failure

- 52E open and close contacts either both open or both closed

- MANUAL mode is ON or AUTO mode is ON

- NO 52E OVERCURRENT Alarm

2.7 The Transfer to Generator Sequence:

1. Wait the preset time for the SHIP SERVICE BAD FILTER timer. This consists of either the SSV Relay 2 signal or the MANUAL pushbutton.

2. Send the start signal to the generator.

3. Wait the preset time GENERATOR OK DELAY for the GENERATOR POWER OK (SSV IED voltage > 95% Relay1) or the GENERATOR START FAIL alarm timer.

4. If the generator fails to start or (reach the 95% voltage relay LM1), abort the sequence and report GENERATOR FAILED TO START.

5. Otherwise, If 52N is closed, trip 52N.

6. Wait the preset time for the generator 52N TRIP FAIL timer.

7. If 52N fails to trip, abort the sequence and report the 52N FAIL TO OPEN alarm.

8. If 52N is open and 52E is open, wait the preset time for the 52E CLOSE DELAY timer and close 52E.

9. Wait the preset time for the 52E CLOSE FAIL timer

10. If 52E fails to close, abort the sequence, and report the 52E FAILED TO CLOSE alarm.

11. If 52N is closed, indicate the GENERATOR POWER OK.

The Transfer to Generator Sequence is immediately aborted or reset under the following conditions:

1. The sequence has completed.

2. 52E FAILED TO CLOSE

3. 52N FAILED TO OPEN.

4. GENERATOR FAILED TO START.

5. GENERATOR READY condition becomes NOT present

3.0 MANUAL

The ABT manual operation consists of forcing the Transfer To Generator Sequence. Normally, this sequence is started by the SSV IED reporting that Ship Service voltage is less than 80%. The MANUAL mode pushbutton simply overrides the SSV IED LIM1 relay. As long as the MANUAL mode pushbutton is engaged, the PLC will behave as if Ship Service voltage is faulty. Releasing the MANUAL mode pushbutton will cause the PLC to revert to analyzing the SSV IED LIM1 relay If the relay is closed (Ship Service voltage> 95%), the Transfer to Ship Service will begin.

4.0 OFF

The ABT OFF pushbutton inhibits any operation by the ABT program with the exception of the START pushbutton

5.0 START

On the Overview screen the START pushbutton immediately engages the diesel engine start output. This is a momentary engage pushbutton The START button must be continually pressed in order to start the generator. Once the generator is started using the START button ther will be no automatic transfer to the Emergency Bus. The transfer sequence is inhibited due to the fact that the Transfer to Generator Sequence was not begun. The transfer sequence can only be started by pressing the MANUAL button or by a failure of the Ship Service power while in AUTO mode.

6.0 BACKFEED

The BACKFEED pushbutton will become visible on the Overview screen when the following conditions are present:

- GENERATOR POWER OK

- SHIP SERVICE READY

- 52E is closed

- 52N is open

- AUTO is ON Engaging the BACKFEED button at this point in time brings up the BACKFEED screen with yet another BACKFEED button. This button must also be pressed in order to reclose 52N onto the generator.

7.0 POWER

The ABT continually monitors the 24VDC power. By extension this re monitoring also locates any 120VAC problems. The following alarms are explained in more detail:

7.1 POWER

1. EG 24VDC - indicates that the 24VDC power supply for the emergency generator is not available. In the event of loss of Ship Service, the ABT will initiate the Transfer to Ship Service and operate from the battery backup for as long as t e battery can maintain the correct voltage. This will be approximately 2 hours. After battery exhaustion, the EGV IED and the PLC will lose 24VDC power. At this point in time the ABT will be inoperative. The generator will however stay online.

2. SS 24VDC - indicates that the 24VDC power supply for the ship service is not available. The ABT will operate from the battery backup for as long as the battery can maintain the correct voltage. After battery exhaustion, the SSV and the PLC will lose 24VDC power. At this point in time, the ABT will be inoperative. In the event of a loss of ship service, no Transfer to Generator Sequence can be initiated.

3. DMS POWER - the SSV IED is fed from circuit breaker number 3. On the loss of this power, the ABT is inoperative. This is due to the fact that the system now does not know the condition of the generator voltage after starting the generator.

4. DVA POWER - the SSV IED is fed from circuit breaker number 4. On the loss of this power, the ABT is inoperative. This is due to the fact that the system now does not know the condition of the ship service power.

5. RELAY POWER - the relays are the 120VAC isolation relays used to engage 120VAC power to the 52E and the 52N motorized control circuits. If this power is lost, the ABT is inoperative since the breakers can no longer be controlled.

7.2 UPS .

1. DC NORMAL - indicates that the UPS battery charger and the 24VDC power to the charger are OK.

2. UPS CHARGING - normal operation whereby the UPS charger is either recharging or testing the battery.

3. ON BATTERY - indicates operation on battery power due to failure of both 24VDC power supplies or an internal UPS failure. Could be caused by a black ship. Reset the alarm and watch for reoccurrence.

4. UPS ALARM - failure of the UPS charger due to disconnected battery or other internal charger failure. Reset the alarm and watch for reoccurrence.

5. DEAD BATTERY - inability of the UPS charger to maintain the correct battery voltage. Could be due to age of the battery (requires replacement) or internal charger failure. Reset the alarm and watch for reoccurrence.

6. BATTERY PROBLEM - missing battery or completely discharged battery. Reset the alarm and watch for reoccurrence.

8.0 SETPOINTS

The Setpoints screen contains the pre-defined values for the timer functions in the PLC. These values can be changed from this screen however they will revert to the pre-defined values on the next power cycle. These values were not meant to be changed permanently. Changing the values permanently must be done via the PLC programming software. All timers are 1/10 second time base so the values are all multiples of 10.

9.0 ALARMS

The Alarms screen is a summary of all the fatal alarms that can abort either the Transfer to Generator Sequence or the Transfer to Ship Service Sequence.

These alarm conditions are only visible when they are active.