Cold Load Pickup; Implementation; Clp Logic; Figure 52: Cold Load Pickup Logic - GE MiCOM P40 Agile Technical Manual

Chapter 6 - Current Protection Functions
9

COLD LOAD PICKUP

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 Pick-Up (CLP) logic works by either:
● Blocking 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.
9.1

IMPLEMENTATION

Cold Load Pickup Protection is configured in the COLD LOAD PICKUP column of the relevant settings group.
This function acts upon the following protection functions:
● All overcurrent stages (both non-directional and directional if applicable)
All Earth Fault 1 stages (both non-directional and directional if applicable)
●
All Earth Fault 2 stages (both non-directional and directional if applicable)
●
The principle of operation is identical for the 3-phase overcurrent protection and the first stages of Earth Fault
overcurrent protection for both EF1 and EF2.
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 either by means of the CB auxiliary contacts or by means of
an external device via logic inputs. 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 overcurrrent operation during this time, for any of the overcurrent stages.
Voltage-dependent operation can also affect the overcurrent settings. If a Voltage Dependent condition arises, this
takes precedence over the CLP function. If the CLP condition prevails and the Voltage Dependent function resets,
the device will operate using the CLP settings. Time-delayed elements are reset to zero if they are disabled during
the transitions between normal settings and CLP settings.
9.2

CLP LOGIC

CLP Initiate
CB Open 3 ph
tcold Time Delay
CB Closed 3 ph
tclp Time Delay

Cold Load Pickup

Enabled
Current threshold setting
in CLP column
Timer settings in CLP
column
V00635

Figure 52: Cold Load Pickup logic

116
1
tcold
&
1
tclp
&
1
S
Q
R
P14D
CLP Operation
Applied Current
Threshold
Applied Timer Settings
P14D-TM-EN-8