Basler DECS-150 - Page 40

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Protection DECS-150
EDM protection can be disabled and enabled by the user without altering the individual protection
settings.
The Exciter Diode Monitor screen is illustrated in Figure 8-8.
Figure 8-8. Exciter Diode Monitor Screen
Finding the Maximum Field Ripple Current
To set the pickup level, the maximum ripple current on the field must be known. This can be
accomplished by running the machine unloaded and at rated speed. Vary the machine voltage from
minimum to maximum while monitoring the EDM ripple level on the HMI display. Record the highest
value.
The DECS-150 has fixed EDM inhibit levels to prevent nuisance failed-diode indications while the
machine frequency is less than 40 hertz or greater than 70 hertz.
Testing the EDM Settings
Start the machine from rest and increase the speed and voltage to the rated value. Load the machine to
its rating and confirm that no failed diode annunciations occur. All of the EDM setup guidelines presented
here assume that the exciter diodes were not opened or shorted at the time of setup and testing.
Shutdown Enable
When checked, Shutdown Enable causes the DECS-150 to stop excitation when the exciter diode
monitor element trips.
Sync-Check Protection
BESTCOMSPlus Navigation Path: Settings Explorer, Protection, Sync Check (25)
When enabled, the sync-check (25) function supervises the automatic or manual synchronism of the
controlled generator with a bus/utility. During synchronizing, the 25 function compares the voltage, slip
angle, and slip frequency differences between the generator and bus. When the generator/bus
differences fall within the setting for each parameter, the 25 status logic output asserts. This logic output
can be configured (in BESTlogicPlus) to assert a DECS-150 contact output. This contact output can, in
turn, enable the closure of a breaker tying the generator to the bus.
An Angle Compensation setting is provided to offset phase shift caused by transformers in the system.
The angle compensation value is added only to the bus angle. For example, it is given that the generator
and bus are synchronized but the DECS-150 metered slip angle reads −30°. Equation 8-1, below,
illustrates the DECS-150 slip angle calculation. This means that the generator angle is lagging behind the
bus angle by 30° due to transformer phase shift. To compensate for this phase shift, the Angle
Compensation setting should contain a value of 30°. This value is added to the metered bus angle
resulting in an adjusted slip angle of zero degrees. Only the metered bus angle is affected by the angle
compensation setting, the metered generator angle is not biased by the DECS-150.
−
(
+ 
)
=  
Equation 8-1. DECS-150 Metered Slip Angle