2-
18
DGP Digital Generator Protection System
GE Power Management
2.3 PROTECTION FUNCTION SETTINGS
2 CALCULATION OF SETTINGS
2
2.3.3 CURRENT UNBALANCE ALARM 46A
This function is intended to alarm prior to a 46T trip to enable an operator to take corrective action. Setting 302:
PICKUP should be a safe margin below the generator's allowable continuous negative-sequence current.
For the sample generator system,
set 303: TL14 = 2 seconds
2.3.4 CURRENT UNBALANCE TRIP 46T
Algorithm:
where
I
2
= Negative sequence current
K2
= 46T K2 setting (Setting 404: K2)
I
FL
= Full load current of the machine (Setting 115: RATEDCUR)
1.
Time T is computed only if
I
2
> 46T PICKUP
2.
Reset time: Linear reset (227 seconds maximum)
Characteristics: Figure 2–6: TIME CURRENT CHARACTERISTIC OF 46T FUNCTION shows the curves for
selected values of Setting 404: K2. The curve for any other K2 setting can be derived with the above algorithm.
This function should be set at or below the negative-sequence current capability of the machine.
For the sample generator system,
set K2 = machine
capability = 10
set 302: PICKUP
70% of
I
2
capability of the machine
=
0.7
0.08
×
211765
×
1.732
18
×
----------------------------------------------------
=
380.4 A primary
=
0.24 A secondary
=
Operating Time
T
K2
I
2
I
FL
⁄
(
)
2
-----------------------
=
seconds
set PICKUP
I
2
capability of the machine
=
0.08
211765
1.732
18
×
1600
×
-----------------------------------------------
×
=
0.34 A secondary
=
I
2
2
T
Содержание DGP Series
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