Loss Of Mains (78V) (For Enhanced Models) - GE Multilin G650 Manual

5 SETTINGS
5.5.10.1 INTRODUCTION
The Phase Shift or Loss of main element (78V) measures the length of each cycle of the voltage signal. When a generator
becomes disconnected, the sudden change in load causes a sudden change in cycle length. The single cycle becomes
shifted with time.Therefore the 78V element can be used to detect disconnection from the grid.
A phase displacement is defined as a sudden change in the voltage, which can be generated by a big load increase or a
sudden loss load. The loss of mains element detects a phase displacements comparing the period of the last cycle length
with the period average of last N cycles. If the difference between these two values is above setting the element picks up
and operates.
150
100
50
0
0 50
-50
-100
-150
5.5.10.2 LOSS OF MAINS SETTINGS DESCRIPTION
The settings can be selected at Setpoint > Control Elements > Loss of Mains
Table 5–94: LOSS OF MAINS ELEMENT SETTINGS
SETPOINT > CONTROL ELEMENTS > LOSS OF MAINS >
LOSS OF MAINS 1> LOSS OF MAINS 2 > LOSS OF MAINS 3
SETTING DESCRIPTION
Function Permission
Any phase displacement mode to operate
Minimum Phase shift angle value to operate
Minimum voltage threshold
Snapshot Event generation
• Function: This setting allows enabling or disabling the Loss of Mains element.
• Loss of mains Mode: ONE PHASE option: the loss of mains element gives indication when a phase displacement
occurs in any phase..
• Phase Shift Angle: This setting defines the minimum detected angle difference to operate the element.
• Minimum Voltage: If measured voltage is below this setting, the unit will be blocked
• Snapshot Events: The snapshot event setting enables or disables the snapshot event generation for this element.
GEK-113285A
Figure 5–22: VOLTAGE PHASE DISPLACEMENT EXAMPLE
100 150
NAME
Function
Loss of Mains Mode
Phase Shift Angle
Minimum Voltage
Snapshot Events
G650 Generator Protection & Control System

5.5.10 LOSS OF MAINS (78V) (FOR ENHANCED MODELS)

200 250
DEFAULT VALUE STEP
DISABLED N/A
ONE PHASE N/A
1.00 0.01 Deg [2.00 : 22.00]
70 1 V
ENABLED N/A
5.5 CONTROL ELEMENTS
Voltage w ith no fault
Voltage w ith phase displacement
RANGE
[DISABLED – ENABLED]
[ONE PHASE]
[30 : 500]
[DISABLED – ENABLED]
5-97
5