S2 System Setup; Current Sensing; Voltage Sensing - GE 489 Instruction Manual

4.3 S2 SYSTEM SETUP

4.3 S2 SYSTEM SETUP
T

CURRENT SENSING

T
[ENTER] for more
As a safeguard, the
PHASE CT PRIMARY
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
4
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
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.
NOTE
T

VOLTAGE SENSING

T
[ENTER] for more
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
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
setpoint is calculated as:
NEUTRAL VT RATIO
Therefore, set
NEUTRAL VT RATIO
4-8
ð
PHASE CT PRIMARY:
ENTER
-------------
ESCAPE
GROUND CT:
ESCAPE
MESSAGE
50:0.025
MESSAGE
GROUND CT RATIO:
ESCAPE
MESSAGE
100: 1
MESSAGE
GROUND CT RATIO:
ESCAPE
MESSAGE
100: 5
MESSAGE
and Generator Parameters setpoints are defaulted to "--------" (indicating not pro-
setpoint applies to both the neutral end CTs as well as the output CTs.
ð
VT CONNECTION TYPE:
ENTER
None
ESCAPE
VOLTAGE TRANSFORMER
ESCAPE
MESSAGE
RATIO: 5.00:1
MESSAGE
NEUTRAL VOLTAGE
ESCAPE
MESSAGE
TRANSFORMER: No
MESSAGE
NEUTRAL VT
ESCAPE
MESSAGE
RATIO: 5.00:1
MESSAGE
Distribution Transformer Ratio Auxiliary VT Ratio
=
13200 600
×
= --------------- - --------- - : 1 = 137.50 : 1
480 120
to 137.50:1
489 Generator Management Relay
Range: 1 to 5000 step 1, Not Programmed
Range: None, 1A Secondary, 5A Secondary, 50:0.025
Range: 10 to 10000 step 1
Message seen only if Ground CT Type is 1A
Range: 10 to 10000 step 1
Message seen only if Ground CT Type is 1A
setpoint. No additional ground CT messages will
GROUND CT
Range: Open Delta, Wye, None
Range: 1.00:1 to 300.00:1 step 0.01
Range: No, Yes
Range: 1.00:1 to 240.00:1 step 0.01. Seen only if
NEUTRAL VOLTAGE TRANSFORMER is "Yes"
entered must be the total effective ratio of the
NEUTRAL VT RATIO
×
: 1
4 SETPOINT PROGRAMMING
4.3.1 CURRENT SENSING
4.3.2 VOLTAGE SENSING
NEUTRAL VT RATIO
GE Power Management