Table of Contents
6 Protection Functions
CBF function Reset options
CB Open + I<
Prot Reset + I<
CB Open
The Remove I> Start and Remove IN> Start settings are used to remove starts issued from the
overcurrent and earth elements respectively following a breaker fail time out. The start is removed
when the cell is set to
2.9
Cold Load Pickup Function
When a feeder circuit breaker is closed in order to energise a load, the current levels that flow for a
period of time following energisation may be far greater than the normal load levels. Consequently,
overcurrent settings that have been applied to provide overcurrent protection may not be suitable
during this period of energisation (cold load), as they may initiate undesired tripping of the circuit
breaker. This scenario can be prevented with Cold Load Pickup (CLP) functionality.
The Cold Load Pickup (CLP) logic works by either:
• Inhibiting one or more stages of the overcurrent protection for a set duration
• Raising the overcurrent settings of selected stages, for the cold loading period.
The CLP logic therefore provides stability, whilst maintaining protection during the start-up.
Cold Load Pickup Protection is implemented in the COLD LOAD PICKUP column of the relevant
settings group.
This function acts upon the following protection functions:
•
All overcurrent stages
•
All Earth Fault stages
The principle of operation is identical for the 3-phase overcurrent protection and Earth Fault
overcurrent protection.
CLP operation occurs when the circuit breaker remains open for a time greater than tcold and is
subsequently closed. CLP operation is applied after tcold and remains for a set time delay of tclp
following closure of the circuit breaker. The status of the circuit breaker is provided by means of the
CB auxiliary contacts. Whilst CLP operation is in force, the CLP settings are enabled. After the time
delay tclp has elapsed, the normal overcurrent settings are applied and the CLP settings are disabled.
If desired, instead of applying different current setting thresholds for the cold load time, it is also
possible to completely block the overcurrent operation during this time, for any of the overcurrent
stages.
2.9.1
Cold Load Pickup Logic
The CLP logic is in operation when CLP is enabled AND CLP is initiated from a CB open condition
after the tcold period has elapsed. The CLP logic becomes inactive when CLP is disabled or when
there is a CB closed condition. tcold and tclp are initiated using the CB status signal produced by
connecting CB NO auxiliary contact from the circuit breaker. The CLP logic gets driven from a single
breaker contact.
6-14
CBF function will reset when both conditions are satisfied:
•
•
CBF function will reset when both conditions are satisfied:
•
•
CBF function will reset when CB is open (i.e. CB(52B) status is active)
'Enabled'.
Description
CB is open (i.e. CB(52B) status is active)
The phase currents and earth current is less than set current
Protection is reset
Phase currents and earth current is less than set current
P50 Agile P153
P153/EN M/B
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