GE Multilin G650 - Loss of Mains (78 V) (for Enhanced Models)

GEK-113285A G650 Generator Protection & Control System 5-97
5 SETTINGS 5.5 CONTROL ELEMENTS
5
5.5.10 LOSS OF MAINS (78V) (FOR ENHANCED MODELS)
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.
Figure 5–22: VOLTAGE PHASE DISPLACEMENT EXAMPLE
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
• 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.
SETPOINT > CONTROL ELEMENTS > LOSS OF MAINS >
LOSS OF MAINS 1> LOSS OF MAINS 2 > LOSS OF MAINS 3
SETTING DESCRIPTION NAME DEFAULT VALUE STEP RANGE
Function Permission Function DISABLED N/A [DISABLED – ENABLED]
Any phase displacement mode to operate Loss of Mains Mode ONE PHASE N/A [ONE PHASE]
Minimum Phase shift angle value to operate Phase Shift Angle 1.00 0.01 Deg [2.00 : 22.00]
Minimum voltage threshold Minimum Voltage 70 1 V [30 : 500]
Snapshot Event generation Snapshot Events ENABLED N/A [DISABLED – ENABLED]
-150
-100
-50
0
50
100
150
0 50 100 150 200 250
Voltage w ith no fault
Voltage w ith phase displacement