ABB 615 Series ANSI, Technical Manual

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1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 165
Technical Manual
4.1.6.4 Operation principle
The function can be enabled and disabled with the Operation setting. The corresponding
parameter values are Enable and Disable.
The operation of directional ground-fault protection can be described by using a module
diagram. All the modules in the diagram are explained in the next sections.
Figure 72: Functional module diagram. I
0
and V
0
represent the zero sequence
current and zero sequence voltage.
Level detector
The measured ground current is compared with the set Pickup value . For directional
operation, the residual voltage (-Uo) also needs to be compared with the set Voltage pickup
value . If both limits are exceeded, the level detector sends an enable-signal to the timer
module. When the Enable voltage limit setting is set to "False", the Voltage pickup value
has no effect and the level detection is purely based on the ground current. If the
ENA_MULT
input is active, the Pickup value setting is multiplied by the Pickup value Mult
setting.
The pickup value multiplication is normally done when the inrush detection function
(INR) is connected to the
ENA_MULT
input.
Directional calculation
The directional calculation module monitors the angle between the operating current and
polarizing voltage. When the angle is in the operation sector, the module sends the enable
signal to the timer module.
Do not set the multiplier setting Pickup value Mult higher than necessary.
If the value is too high, the function may not trip at all during an inrush
followed by a fault, no matter how severe the fault is.
0
0