Siemens 7SR51 - 50 GS Instantaneous Sensitive Earth Fault - Measured; Overview of Function; Structure of the Function

50GS Instantaneous Sensitive Earth Fault – Measured
Overview of Function
Instantaneous sensitive earth fault protection is used to provide:
•
Detection of low level earth current in electrical equipment
•
Earth fault protection for compensated or isolated networks. This requires directional current detection,
(see 5 Protection and Automation Functions , section 67 Directional Overcurrent/Earth Fault).
•
Backup or emergency protection in addition to other protection functions or devices
•
Coordinated operation with other devices using time graded settings
Structure of the Function
The measured instantaneous earth fault element has group dependent settings. These settings can be
different in each settings group – group numbers (Gn) 1 to 4.
This function corresponds to the logical node A50GSPTOC* in IEC 61850.
The function monitors the primary system current using the earth fault CT input e.g. CT4.
The basic instantaneous measured earth fault function (50GS) is summarized below:
•
Measurement is based on fundamental frequency current
•
Elements operate with a definite time-delayed (DTL) characteristic
•
Outputs are provided for general pickup and trip
The basic function is non-directional, it can be directionalized when the device is fitted with VT inputs.
Each 50GS element can be set to operate for forward current, reverse current or independently of current
direction. Directionalized functionality uses the decision of the 67GS element.
•
Provides information regarding flow direction of earth current for selective application of earth fault
protection
•
Ensures selective fault detection for parallel lines or transformers with infeed at one end
•
Ensures selective fault detection in cable runs with infeed at both ends or in lines connected to form ring
topologies
•
Can provide earth fault protection for compensated or isolated networks, (see 5 Protection and Automa-
tion Functions , section 67 Directional Overcurrent/Earth Fault).
Where earth fault protection is directionalized correct operation is dependent on valid information being
received from the VT inputs, operation of each directionalized element will be affected if a VT fuse fails. When
a fuse failure is detected, 60VTS function, each element can be selected to either ignore the VT failure, switch
to non-directionalized operation (which does not require VT inputs) or be inhibited.
Elements can be mapped to start 79 Automatic Recloser by selection of the element as a 79 GS
Trigger within the 79 function element menus. For autoreclose sequences that require operation of instan-
taneous or protections to be inhibited this can be selected in settings menu.
5.14
5.14.1
5.14.2
Protection and Automation Functions
5.14 50GS Instantaneous Sensitive Earth Fault – Measured
228 Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019