
CHAPTER 5: SETTINGS
469 MOTOR MANAGEMENT RELAY – INSTRUCTION MANUAL
5–65
These settings program the differential element when the differential feature is in use. This
feature consists of three instantaneous overcurrent elements for phase differential
protection. Differential protection may be considered first line protection for phase to
phase or phase to ground faults. In the event of such a fault, differential protection may
limit the damage that may occur.
Note
Care must be taken when enabling this feature. If the interrupting device (contactor or
circuit breaker) is not rated to break potential faults, the feature should be disabled.
Alternately, the feature may be assigned to an auxiliary relay and connected such that it
trips an upstream device that is capable of breaking the fault current. A low level
differential fault can develop into a short circuit in an instant.
A trip occurs once the magnitude of either
I
aIN
-
I
aOUT
,
I
bIN
-
I
bOUT
, or
I
cIN
-
I
cOUT
(phase
differential) exceeds the Pickup Level
×
Differential CT Primary for a period of time specified
by the delay. Separate pickup levels and delays are provided for motor starting and
running conditions.
The Differential trip element is programmable as a fraction of the rated CT. The level may
be set more sensitive if the Differential CTs are connected in a flux balancing configuration
(3 CTs). If 6 CTs are used in a summing configuration, the values from the two CTs on each
phase during motor starting may not be equal since the CTs are not perfectly identical
(asymmetrical currents may cause the CTs on each phase to have different outputs). To
prevent nuisance tripping in this configuration, the
STARTING DIFF. TRIP PICKUP
level may
have to be set less sensitive, or the
STARTING DIFF. TRIP DELAY
may have to be extended to
ride through the problem period during start. The running differential delay can then be
fine tuned to an application such that it responds very fast to sensitive (low) differential
current levels.
MESSAGE
ASSIGN TRIP
RELAYS:
Range: Trip, Trip & Auxiliary2, Trip &
Aux2 & Aux3, Auxiliary2, Aux2
& Aux3, Auxiliary3
MESSAGE
STARTING DIFF.
TRIP PICKUP: 0.10
Range: 0.05 to 1.00 x CT in steps of
0.01
MESSAGE
STARTING DIFF.
TRIP DELAY: 0 ms
Range: 0 to 60000 ms in steps of 10
MESSAGE
RUNNING DIFF.
TRIP PICKUP: 0.10
Range: 0.05 to 1.00 x CT in steps of
0.01
MESSAGE
RUNNING DIFF.
TRIP DELAY: 0 ms
Range: 0 to 1000 ms in steps of 10
Содержание 469
Страница 62: ...2 16 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL CHAPTER 2 INTRODUCTION ...
Страница 89: ...CHAPTER 3 INSTALLATION 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL 3 27 3 2 14 2 Speed Motor Wiring ...
Страница 90: ...3 28 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL CHAPTER 3 INSTALLATION ...
Страница 292: ...6 42 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL CHAPTER 6 ACTUAL VALUES ...
Страница 294: ...7 2 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL CHAPTER 7 TESTING FIGURE 7 1 Secondary Injection Test Setup ...
Страница 313: ...A APPENDIX 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL A 7 HGF5C 808841A1 HGF8 808842A1 ...
Страница 315: ...A APPENDIX 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL A 9 808712A1 CDR ...
Страница 320: ...A 14 469 MOTOR MANAGEMENT RELAY INSTRUCTION MANUAL A APPENDIX ...