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

4.3 S2 SYSTEM SETUP

4.3S2 SYSTEM SETUP
PATH: SETPOINTS S2 SYSTEM SETUP

CURRENT SENSING

[ENTER] for more
As a safeguard, the
PHASE CT PRIMARY
indicating that the 489 was never programmed. Once these values are entered, the 489 will be in service. Select the Phase
CT so that the maximum fault current does not exceed 20 times the primary rating. When relaying class CTs are pur-
chased, this precaution helps prevent CT saturation under fault conditions. The secondary value of 1 or 5 A must be spec-
ified when ordering so the proper hardware will be installed. The
4
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 CT input, set
resistance grounded systems, where fault currents may be quite large, the 489 1 A/5 A secondary Ground CT input should
be used. Select the Ground CT primary so 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.
PATH: SETPOINTS S2 SYSTEM SETUP

VOLTAGE SENSING

[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 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 aux-
iliary 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
4-12
CURRENT SENSING
ð
PHASE CT PRIMARY:
ENTER
ð
ESCAPE -------------
GROUND CT:
ESCAPE
50:0.025
MESSAGE
GROUND CT RATIO:
ESCAPE
100: 1
MESSAGE
GROUND CT RATIO:
ESCAPE
100: 5
MESSAGE
and
GENERATOR PARAMETERS
to "50:0.025". No additional ground CT messages will appear. On solid or low
GROUND CT
VOLTAGE SENSING
ð
VT CONNECTION TYPE:
ENTER
ð
ESCAPE None
VOLTAGE TRANSFORMER
ESCAPE
RATIO: 5.00:1
MESSAGE
NEUTRAL VOLTAGE
ESCAPE
TRANSFORMER: No
MESSAGE
NEUTRAL VT
ESCAPE
RATIO: 5.00:1
MESSAGE
NEUTRAL VT RATIO
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 in steps of 1
Message seen only if Ground CT Type is 1 A
Range: 10 to 10000 in steps of 1
Message seen only if Ground CT Type is 5 A
setpoints are defaulted to "--------" when shipped,
setpoint applies to both the neutral end
PHASE CT PRIMARY
Range: Open Delta, Wye, None
Range: 1.00:1 to 300.00:1 in steps of 0.01
Range: No, Yes
Range: 1.00:1 to 240.00:1 in steps of 0.01. Seen only if
NEUTRAL VOLTAGE TRANSFORMER
entered must be the total effective ratio of the
×
: 1
4 SETPOINTS
4.3.1 CURRENT SENSING
4.3.2 VOLTAGE SENSING
is "Yes"
NEUTRAL VT RATIO
(EQ 4.1)
GE Multilin