Chapter 3. Shore connection and interlocking

1. Shore connection for 440v circuit

(WHERE SUPPLY OF POWER IS MADE FROM A SOURCE ON SHORE)

1-1. PROCEDURE

A. CHECK THAT THE SHORE POWER SOURCE IS CONNECTED : "SHORE ALIVE" LAMP ON MAIN GENERATOR PANEL SHOULD BE ON.

B. CHECK THE SHORE POWER VOLTAGE ON VOLTMETER, TURNING "VOLT & FREQUENCY METER" SWITCH TO SHORE POSITION, IT SHOULD BE 440V.

C. OPEN ALL THE GENERATOR ACBS TO DE-ENERGINE THE BUS, THEN IMMEDIATELY CLOSE "SHORE" BREAKER ON MAIN GENERATOR PANEL: THE BUS IS NOW REENERGINED.

1-2. 440V SHORE INTERLOCKING

FIG-1)

Generator acb control circuitry for d/g1, d/g2 and d/g3

FIG-1.

EACH ONE OF THE NORMALLY CLOSED (NC) CONTACTS OF THE 440V SHORE INTERLOCKING RELAY 52XS IS CONNECTED IN SERIES WITH THE UNDERVOLTAGE TRIP(UVT) CIRCUIT AND WITH THE CLOSING CIRCUIT OF EACH GENERATOR ACB.

THE RELAY 52XS, AS SHOWN IN THE LOWER DIAGRAM, IS CONTROLLED BY AN AUXILIARY "A" CONTACT OF THE SHORE BREAKER AND OPERATES WHEN THIS SHORE BREAKER IS CLOSED.

WHEN THE SHORE BREAKER IS CLOSED THEREFORE, THE UVT AND CLOSING CIRCUITS ARE OPENED AND NONE OF THE GENERATOR ACBS CAN BE CLOSED.

(FIG-2)

Control and auxiliary circuits of shore breaker ("shore" breaker on main generator panel)

AUXILIARY CONTACTS

"a" - CLOSED WHEN BREAKER IS CLOSED.

"b" - CLOSED WHEN BREAKER IS OPEN.

FIG-2.

FOR THE SHORE BREAKER, AN AUXILIARY "B" CONTACT OF EACH OF THE GENERATOR ACBS ARE CONNECTED IN SERIES WITH ITS UVT CIRCUIT. THEREFORE, WHEN ANY OF THE GENERATOR ACBS ARE CLOSED THE SHORE BREAKER CANNOT BE CLOSED.

Chapter 4 miscellaneous

1. Earth lamps

- AN EARTH-FAULT IN PHASE R –

WHEN "EARTH TEST" SWITCH (ETS) ON A FEEDER PANEL IS OFF POSITION, THE NEUTRAL OF THE Y-CONNECTED PRIMARIES OF THREE LAMP TRANSFORMERS ARE DISCONNECTED FROM THE EARTH, AND THE VOLTAGE ACROSS THE PRIMARY IS THE SAME FOR EACH TRANSFORMER REGARDLESS WHETHER THE FEEDER SYSTEM CONTAINS AN EARTH-FAULT OR NOT, THERFORE, THREE INDICATOR LAMPS (TLS) CONNECTED TO THE RESPECTIVE TRANSFORMER SECONDARIES ARE ON AT THE SAME BRIGHTNESS.

TO CHECK THE STATE OF THE FEEDER SYSTEM'S INSULATION TO EARTH, PUT "EARTH TEST1 SWITCH (ETS) TO TEST (THIS EARTHS THE NEUTRAL THE Y-CONNECTED TRANSFORMER PRIMARIES).

IF THERE IS AN EARTH-FAULT IN PHASE R, FOR EXAMPLE, THE LAMP R WOULD BE LESS BRIGHT THAN THE OTHER TWO ; OR IF IT IS A COMPLETE EARTH-FAULT, THE LAMP R WOULD BE OFF.

WHERE THERE IS NO EARTH-FAULT, SWITCHING OF THE ETS FROM "OFF" TO 'TEST" GIVE NO CHANGE IN THE LAMP'S BRIGHTNESS.

2. Preference tripping system

A. PURPOSE

THIS SYSTEM IS INTENDED TO REDECE THE LOAD ON THE OPERATING GENERATOR IF IT IS OVERLOADED, BY TRIPPING THE FEEDER CIRCUIT BREAKERS FOR NON- ESSENTIAL SERVICES AND THEREBY MAINTAINING THE ESSENTIAL SERVICE. 

THERE ARE TWO CAUSES OF PREFERENCE TRIPPING : ONE ORIGINATES FROM A GENERATOR OVERCURRENT AND THE OTHER DUE TO ABNORMAL TRIPPING OF THE ACB OF ON OF THE GENERATORS OPERATING IN PARALLEL.

B. OPERATION

1. GENERATOR OVERCURRENT

IF THE CURRENT OF THE OPERATING GENERATOR EXCEEDS THE PREDETERMINED VALUE FOR MORE THAN THE PRESET LENGTH OF TIME, THE OVERCURRENT TRIP DEVICE(TYPE AOR) OF ITS ACB PROCEDURES A PREFERENTIAL ALARM SIGNAL, WHICH, IN TURN, TRIPS THE FEEDER CIRCUIT BREAKERS FOR NON-ESSENTIAL SERVICES.

PREFERENTIAL ALARM SETTING

110% x 120% OF RATED GENERATOR CURRENT, 10 SEC.

PREFERENCE TRIPPING BREAKERS

THE BREAKERS(MCCB) COVERED BY THE PREFERENCE TRIPPING SYSTEM ARE IDENTIFIED BY THE YELLOW STRIP INSERTED IN THEIR NAMEPLATE.

2. GENERATOR ACB ABNORMAL TRIP

IF THE ACB OF ONE OF TWO DIESEL GENERATORS OPERATING IN PARALLEL IS TRIPPED ABNORMALLY(SEE CHAPTER 2 PARAGRAPH 2-3.1 (A) REMARK 2), THE FEEDER CIRCUIT BREAKERS FOR NON-ESSENTIAL SERVICES ARE TRIPPED BY A ACB ABNORMAL TRIP SIGNAL.

PREFERENCE TRIPPING BREAKERS

SAME AS ABOVE, IDENTIFIED BY YELLOW STRIP INSERTED IN THE NAMEPLATE.