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Parameter Value
Off
Inhibit
Non-Dir
Parameter: 81HB2 Inhibit
•
Default setting: No
High levels of inrush currents into reactive components such as transformers when they are switched can
result in operation of overcurrent elements. The inrush current can be detected by a high percentage of
second harmonic current content by the 81HBL2 element. This can be configured to inhibit the overcur-
rent element automatically by configuration of this setting.
Parameter Value
No
Yes
Parameter: 79 Delayed Inhibit
•
Default setting: No
The autoreclose scheme sequence may require that some selected protection elements are only used for
the first trip(s) of the sequence, typically instantaneous ungraded protection elements, before reverting
to graded protection.
This setting is used to inhibit 50N operation when it is parameterized as instantaneous and only delayed
tripping is required. This should be selected to the default setting Off unless required by the autoreclose
sequence.
Parameter Value
No
Yes
Settings Example
There should be little or no current flowing to earth in a healthy system so earth fault relays can be given far
lower pickup levels than relays which detect excess current above load current in each phase conductor. Earth
fault relays are important where the fault path to earth is a high-resistance one (such as in highly arid areas) or
where the system uses high values of earthing resistor/reactance as any earth fault current that flows in the
phase conductors will be limited.
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
Protection and Automation Functions
5.15 50N Instantaneous Earth Fault – Calculated
Description
60VTS operation does not affect the element and the
forward/reverse directional decision assessed from
the applied voltage is applied regardless of the 60VTS
state. During a VT failure the device may assess the
direction incorrectly and the element may operate for
faults in the non-operate direction or not operate for
faults in the operate direction.
When 60VTS detects a VT failure the element is
immediately inhibited automatically and will not
operate. Tripping of a system fault will then rely on
other elements or devices.
When 60VTS detects a VT failure the element will
become non-directional and ignore the directional
decision. The element will operate for overcurrent
regardless of which direction the fault current is in.
Description
The earth fault element is not affected by operation
of the 81HBL2 element.
The earth fault element is inhibited by when the
81HBL2 element is operated.
Description
The earth fault element is normally active and is not
blocked by autoreclose sequence requirements.
The 50N element will be inhibited from the autore-
close logic as required by the applied sequence. Incor-
rect configuration can result in no protection being
enabled.
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