GE Multilin 489 Instruction Manual page 151

CHAPTER 5: SETPOINTS
Note
Note
489 GENERATOR MANAGEMENT RELAY – INSTRUCTION MANUAL
Courtesy of NationalSwitchgear.com
GROUND DIR. ALARM
MESSAGE
DELAY: 3.0 sec.
GROUND DIR. ALARM
MESSAGE
EVENTS: Off
GROUND DIRECTIONAL
MESSAGE
TRIP: Off
ASSIGN TRIP
MESSAGE
RELAYS (1-4): 1---
GROUND DIR. TRIP
MESSAGE
PICKUP: 0.05 x CT
GROUND DIR. TRIP
MESSAGE
DELAY: 3.0 sec.
The
SUPERVISE WITH DIGITAL INPUTS
Ground Switch Status.
The 489 detects ground directional by using two measurement quantities: V
angle between these quantities determines if a ground fault is within the generator or not.
This function should be coordinated with the 59GN element (95% stator ground protection)
to ensure proper operation of the element. Particularly, this element should be faster. This
element must use a core balance CT to derive the I
element. The protection element is blocked for neutral voltages, V
The pickup level for the ground current elements is programmed as a multiple of ground
CT. The 50:0.025 CT is intended for measuring very small ground fault currents when
connected to a sensitive ground CT having the same ratio.
For example, a pickup to 0.2xCT translates into 0.2x0.0025A = 0.5mA secondary on the
terminals of the sensitive ground CT, with a relay measuring 0.2x5A = 1 A primary. A pickup
setting of 0.05xCT would lead to 0.05x0.0025A = 0.125mA secondary, or 0.05x5A =0. 25A
primary current.
It is strongly recommended not to exceed the CT continuous rating of 150mA for long
periods of time during tests.
Range: 0.1 to 120.0 sec. in steps of 0.1
Range: On, Off
Range: Off, Latched, Unlatched
Range: Any combination of Relays 1 to
4
Range: 0.05 to 20.00 × CT in steps of
0.01
Range: 0.1 to 120.0 sec. in steps of 0.1
setpoint is seen only if a digital input assigned to
signal. Polarity is critical in this
0
0
and I . The
0 0
, below 2.0 V secondary.
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