Section 2: Protection Functions - Siemens 7SR224 Technical Manual

Section 2: Protection Functions

This section details the procedures for testing each protection function of the 7SR224 relay. These tests are
carried out to verify the accuracy of the protection pick-ups and time delays at setting and to confirm correct
operation of any associated input and output functionality.
Guidance for calculating test input quantities is given in the relevant test description where required. In many
cases it may be necessary to disable some functions during the testing of other functions, this prevents any
ambiguity caused by the operation of multiple functions from one set of input quantities. The 'Function Config'
Menu provides a convenient high level point at which all elements of a particular function can be
Enabled/Disabled to suit testing. The 'Config' tab in 'Reydisp Evolution' can be used to 'Enable/Disable' individual
elements. Note that this screen disables functions by applying setting changes to the relay and that any changes
must be sent to the relay to take effect and settings must be returned to their correct value after testing.
The table below indicates functions where function conflicts may occur during testing, consideration should be
given to disabling functions to avoid interference.
Function
Under Test
Phase Overcurrent
Voltage Cont O/C O
Cold Load O
Measured E/F
Sensitive E/F
Restricted E/F
NPS Overcurrent O
Undercurrent
Thermal O
Phase U/O voltage
NPS Overvoltage
U/O Frequency
CB Fail O
VT Supervision
CT supervision
Broken Conductor
Trip cct
Inrush Detector
The General Pickup LED can be used to assess operation of functions during testing if other functions are
disabled or if the setting allocating General Pickup is temporarily modified.
Voltage inputs may not be required for testing of non-directional Overcurrent elements but it may be
advantageous to apply balanced 3 phase nominal rated voltage to the VT inputs during testing to avoid
inadvertent operation of other functions. Particular care should be taken when testing overcurrent functions that
the thermal rating of the current inputs is not exceeded.
It should be considered that where several overlapping elements are used simultaneously, the overall protection
operate time may be dependent on the operation of different individual elements at the various levels of applied
©2010 Siemens Protection Devices Limited
O O O
O O
O O
O
O
O
O O
O O
O O
O O O O O
O
7SR224 Argus Commissioning & Maintenance Guide
O O O
O O O
O O O
O O
O O O
O
O O
O O
O O
O
O O
O
O
O
O
O
O
O
O
O
Chapter 6 Page 13 of 73