Chapter 6) 7SR23 DAD Commissioning & Maintenance Guide
©2013 Siemens Protection Devices Limited
Chapter 6 Page 16 of 26
2.3
Restricted Earth fault
(87REF)
Figure 2-3 Restricted Earth Fault
Current Inputs:
I
B
I
G
Disable:
50G
Map Pickup LED:
87REF-n - Self Reset
The external stabilising resistor value should be measured and compared to that specified in the settings data.
Both values should be recorded.
Element
Settings Data: R
STAB
Value
R
STAB
Measured
87REF-1
87REF-2
The relatively high value of stabilising resistance R
STAB
will often interfere with secondary current injection when
using a digital test set. It is normal practice in these cases to short circuit the resistor to allow testing, the shorting
link should be removed after testing.
The pick-up setting can be tested by gradually increasing current until element operates. The relay should be
disconnected from the current transformers for this test.
Apply 2x setting current if possible and record operating time
Is
(Amps)
DTL
(sec)
P.U. Current
Amps
Operate Time
2 x Is
NOTES
87REF-1
87REF-2
Summary of Contents for 7SR23 DAD
Page 1: ...Answers for energy 7SR23 DAD High Impedance Protection Relay Reyrolle Protection Devices ...
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