7SR210 & 7SR220 Description of Operation
Unrestricted Page 44 of 94
©2018 Siemens Protection Devices Limited
3.7
Current Protection: Cold Load (51c)
The setting of each shaped overcurrent element (51-n) can be inhibited and alternative ‘cold load’ settings (51c-n)
can be applied for a period following circuit switch in.
The Cold Load settings are applied after the circuit breaker has been open for longer than the
Pick-Up Time
setting.
Following circuit breaker closure the ‘cold load’ overcurrent settings will revert to those defined in the Phase
Overcurrent menu (51-n) after either elapse of the
Drop-Off Time
setting or when the measured current falls
below the
Reduced Current Level
setting for a time in excess of
Reduced Current Time
setting.
During cold load settings conditions any directional settings applied in the Phase Overcurrent menu are still
applicable.
A CB ‘Don’t Believe It’ (DBI) condition is not acted on, causing the element to remain operating in accordance
with the relevant 51-n settings. Where the
Reduced Current
setting is set to
OFF
reversion to 51-n settings will
only occur at the end of the
Drop-Off Time
. If any element is picked up on expiry of
Drop-Off Time
the relay will
issue a trip (and lockout if a recloser is present).
If the circuit breaker is re-opened before expiry of the
Drop-Off Time
the drop-off timer is held but not reset.
Resetting the timer for each trip could result in damaging levels of current flowing for a prolonged period during a
rapid sequence of trips/closes.
Cold load trips use the same binary output(s) as the associated 51-n element.
Figure 3.7-1 Logic Diagram: Cold Load Settings (51c)
Summary of Contents for Argus 7SR21
Page 1: ...Energy Management 7SR21 7SR22 Argus Overcurrent Relay Reyrolle Protection Devices ...
Page 2: ......
Page 4: ...Contents 7SR11 and 7SR12 Page 2 of 2 2018 Siemens Protection Devices Limited ...
Page 185: ...7SR210 Settings Guide Unrestricted 2018 Siemens Protection Devices Limited Page 61 of 61 ...
Page 277: ...7SR220 Settings Guide Unrestricted Page 72 of 107 2013 Siemens Protection Devices Limited ...
Page 382: ...7SR220 Technical Manual Chapter 4 Page 2 of 96 2017 Siemens Protection Devices Limited ...
Page 386: ...7SR220 Technical Manual Chapter 4 Page 6 of 96 2017 Siemens Protection Devices Limited ...
Page 398: ...7SR220 Technical Manual Chapter 4 Page 18 of 96 2017 Siemens Protection Devices Limited ...
Page 414: ...7SR220 Technical Manual Chapter 4 Page 34 of 96 2017 Siemens Protection Devices Limited ...
Page 466: ...7SR220 Technical Manual Chapter 4 Page 86 of 96 2017 Siemens Protection Devices Limited ...
Page 468: ...7SR220 Technical Manual Chapter 4 Page 88 of 96 2017 Siemens Protection Devices Limited ...
Page 470: ...7SR220 Technical Manual Chapter 4 Page 90 of 96 2017 Siemens Protection Devices Limited ...
Page 472: ...7SR220 Technical Manual Chapter 4 Page 92 of 96 2017 Siemens Protection Devices Limited ...
Page 643: ...Unrestricted ...