Siemens 7SR242 Duobias - Section 2: Protection Functions

7SR242 Duobias Commissioning & Maintenance Guide
©2010 Siemens Protection Devices Limited Chapter 6 Page 12 of 57
Section 2: Protection Functions
This section details the procedures for testing each protection function of the 7SR24 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
Biased Differential
Differential Highset
Phase Overcurrent
Derived E/F
Measured E/F
Restricted E/F
Open Circuit
NPS Overcurrent
Undercurrent
Thermal
U/O voltage
Neutral Overvoltage
U/O Frequency
Overfluxing
CB Fail
Trip cct Supervision
Inrush Detector
Overfluxing Detector
Biased Diff. O O OOOOOOO O
Diff. Hi
g
hset O O OOOOO O
Phase OC O O OO OOOO O
Derived E/F O O O OOOOOO O
Measured E/F O O O O OOOOO O
Restricted E/F O O O O O OOOO O
Open Circuit O O O O OO O
NPS OC O O O O O OO O
Undercurrent O O O O O O O O
Thermal O O O O O O O O
U/O volta
g
e O O O O
Neutral OV O O O
U/O Frequenc
y
O O
Overfluxin
g
OO O
CB Fail O O O O O O O O O O O O O O
74TCS/74CCS
Inrush Detecto
r
O/fluxin
g
Detecto
r
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.
Particular care should be taken when testing overcurrent functions that the thermal rating of the current inputs is
not exceeded.