4-8 489 Generator Management Relay
GE Power Management
4.3 S2 SYSTEM SETUP 4 SETPOINT PROGRAMMING
4
4.3 S2 SYSTEM SETUP 4.3.1 CURRENT SENSING
As a safeguard, the
PHASE CT PRIMARY
and Generator Parameters setpoints are defaulted to "--------" (indicating not pro-
grammed) when shipped from the factory. The 489 will indicate that it was never programmed. Once these values are
entered, the 489 will be in service. The phase CT should be selected such that the maximum fault current does not exceed
20 times the primary rating. When relaying class CTs are purchased, this precaution will help prevent CT saturation under
fault conditions. The secondary value of 1 or 5 A must be specified when ordering so the proper hardware will be installed.
The
PHASE CT PRIMARY
setpoint applies to both the neutral end CTs as well as the output CTs.
For high resistance grounded systems, sensitive ground current detection is possible if the 50:0.025 ground CT is used. To
use the 50:0.025 ground CT input, select 50:0.025 for the
GROUND CT
setpoint. No additional ground CT messages will
appear. On solid or low resistance grounded systems, where fault currents may be quite large, the 489 1 A/5 A secondary
ground CT input should be used. The Ground CT primary should be selected such that potential fault current does not
exceed 20 times the primary rating. When relaying class CTs are purchased, this precaution will ensure that the Ground CT
does not saturate under fault conditions.
The 489 uses a nominal CT primary rating of 5 A for calculation of pickup levels.
4.3.2 VOLTAGE SENSING
The voltage transformer connections and turns ratio are entered here. The VT should be selected such that the secondary
phase-phase voltage of the VTs is between 70.0 and 135.0 V when the primary is at generator rated voltage.
The Neutral VT ratio must also be entered here for voltage measurement across the neutral grounding device. Note that
the neutral VT input is not intended to be used at continuous voltages greater than 240 V. If the voltage across the neutral
input is less than 240 V during fault conditions, an auxiliary voltage transformer is not required. If this is not the case, use
an auxiliary VT to drop the fault voltage below 240 V. The
NEUTRAL VT RATIO
entered must be the total effective ratio of the
grounding transformer and any auxiliary step up or step down VT.
For example, if the distribution transformer ratio is 13200:480 and the auxiliary VT ratio is 600:120, the
NEUTRAL VT RATIO
setpoint is calculated as:
Therefore, set
NEUTRAL VT RATIO
to 137.50:1
CURRENT SENSING
[ENTER] for more
PHASE CT PRIMARY:
-------------
Range: 1 to 5000 step 1, Not Programmed
MESSAGE
GROUND CT:
50:0.025
Range: None, 1A Secondary, 5A Secondary, 50:0.025
MESSAGE
GROUND CT RATIO:
100: 1
Range: 10 to 10000 step 1
Message seen only if Ground CT Type is 1A
MESSAGE
GROUND CT RATIO:
100: 5
Range: 10 to 10000 step 1
Message seen only if Ground CT Type is 1A
VOLTAGE SENSING
[ENTER] for more
VT CONNECTION TYPE:
None
Range: Open Delta, Wye, None
MESSAGE
VOLTAGE TRANSFORMER
RATIO: 5.00:1
Range: 1.00:1 to 300.00:1 step 0.01
MESSAGE
NEUTRAL VOLTAGE
TRANSFORMER: No
Range: No, Yes
MESSAGE
NEUTRAL VT
RATIO: 5.00:1
Range: 1.00:1 to 240.00:1 step 0.01. Seen only if
NEUTRAL VOLTAGE TRANSFORMER is "Yes"
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
NOTE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
MESSAGE
ESCAPE
NEUTRAL VT RATIO
Distribution Transformer Ratio Auxiliary VT Ratio× : 1=
13200
480
----------------
600
120
----------
× : 1 137.50 : 1==
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