4.9 REJECTION FEATURE
A REJECTION FEATURE IS PROVIDED ON ALL BREAKERS. IT
PREVENTS ENTRY OF A BREAKER INTO A CRADLE Of THE SAME WIDTH
BUT DIFFERENT RATING. PINS ON BOTH SIDES OF THE BREAKER
FRAME MATCH SLOTS IN BRACKETS MOUNTED ON BOTH SIDES Of THE
CRADLE. IF THE CRADLE IS A DIFFERENT RATING THAN
THE BREAKER, THE BREAKER PINS WILL NOT MATCH THE SLOTS AND
ENTRY OF THE BREAKER IS PREVENTED.
FIG. 4.9 REJECTION FEATURE
1. BREAKER REJECTION PIN
2.
CRADLE REJECTION BRACKET
4.1O CLOSING SPRING DISCHARGE AND DRY RUNS
DISCHARGING THE MAIN SPRING WITHOUT CLOSING THE
MAIN CONTACTS IS REFERRED TO AS A DRY RUN. THIS TYPE OF
OPERATION CREATES MUCH MORE STRESS IN THE BREAKER
MECHANISM THAN NORMAL CLOSING OPERATIONS AND
SHOULD BE AVOIDED IF POSSIBLE.
TO LIMIT THE NUMBER Of DRY RUNS, THE FOLLOWING
METHOD Of SPRING DISCHARGE SHOULD ALWAYS BE USED
WHEN BREAKER IS IN "TEST" OR "DISCONNECTED" POSITION OR
WHEN REMOVED FROM CRADLE. IT SHOULD .ALSO BE USED
WHEN IN "OPERATING" POSITION IF POSSIBLE:
1. IF BREAKER IS ELECTRICALLY OPERATED, TURN OFF MOTOR
ISOLATING SWITCH.
2. IF BREAKER IS OPEN AND MAIN SPRING CHARGED: CLOSE - THEN
TRIP BREAKER.
3. If BREAKER IS CLOSED: TRIP BREAKER BY USING
ELECTRICAL OR MECHANICAL TRIP BUTTONS ON
FACEPLATE (DO NOT USE THE DRAWOUT MECHANISM
GATE). IF THE MAIN SPRING IS CHARGED, RECLOSE, THEN
TRIP BREAKER.
FIG. 4.1 1 OVERCURRENT PROTECTION
I . USD RELAY
2. CURRENT SENSOR
3. TRIP COIL
4. CURRENT SENSOR TAP INDICATION
4.11 FAULT PROTECTION
TYPE H-3 AND HL-3 BREAKERS ARE SUPPLIED WITH THE TYPE
USD SOLID STATE OVERCURRENT RELAY AS A STANDARD FEATURE.
THE USD RELAY PROTECTS LOW VOLTAGE POWER SYSTEMS
AGAINST DAMAGE CAUSED BY SHORT CIRCUITS, OVERLOADS AND
GROUND FAULTS. THE RELAY MAY HAVE UP TO FOUR PICK UP
ELEMENTS: INSTANTANEOUS, SHORT-TIME, LONG-TIME AND
GROUND FAULT. LOCAL AND REMOTE INDICATION ARE
AVAILABLE. IN ADDITION, ZSIP
(R)
(
ZONE SELECTIVE
INSTANTANEOUS PROTECTION
) IS AVAILABLE FOR THE SHORT-
TIME AND GROUND FAULT ELEMENTS.
TRIPPING ENERGY FOR THE OPERATION OF THE RELAY IS
OBTAINED SOLELY FROM THE CIRCUIT BEING PROTECTED.
THREE MULTIPLE-TAP CURRENT SENSORS, MOUNTED ON
THE BREAKER PROVIDE THE INPUT TO THE USD RELAY FROM THE
PROTECTED CIRCUIT. A FOURTH SENSOR, CAN ALSO BE USED WHERE
FOUR-WIRE GROUND FAULT PROTECTION IS REQUIRED. AN
ADJUSTABLE SENSOR TAP SETTING INDICATOR is PROVIDED ON THE
BREAKER FACEPLATE (SEE SECTION 8.10).
A DEDICATED DIRECT ACTING SOLENOID TYPE TRIP COIL
PROVIDES POSITIVE ACTIVATION OF THE TRIP LATCH ON THE
BREAKER, AND POSITIVE RESETTING AFTER OPERATION.
