Woodward SEG HighPROTEC MRA4, Device Manual

Page: 321 / 510

ThR-Protection Module: Thermal Replica [ANSI 49]
Commissioning: Thermal Replica [ANSI 49]
Object to be tested
Protective function ThR
Necessary means
•
Three-phase current source
•
Timer
Procedure
Calculate the tripping time for the current to be constantly impressed by using the formula for the thermal image.
The parameter of the temperature rise of the component
» τ
w
«
has to be
known to guarantee an optimal protection.
Legend:
Testing the threshold values
Apply the current you have based your mathematical calculation on.
Testing the trip delay
The thermal capacity should be zero before the test is started. See
»Measuring Values«.
For testing the trip delay, a timer is to be connected to the contact of the associated trip relay.
Apply the current you have based your mathematical calculation on. The timer is started as soon as the current
is applied and it is stopped when the relay trips.
Successful test result
The calculated tripping time and the fallback ratio comply with the measured values. For permissible
deviations/tolerances, please see Technical Data.
EN MRA4 04/09 Page 321
( )
t = t -warm ln
I
2
- Ip
2
I
2
- (K*Ib)
2
t = Tripping delay
t -warm = Warming-up time constant
K =
I = measured current (x In)
Ip = previously existing load
Ib = Base current: Maximum permissible thermal continuous current.
Over load factor: The maximum admissible thermal limit is defined/
calculated by the product of overload factor and basic current k*IB.