Cold Load Pickup Logic; Cold Load Pickup Logic Theory - NR Electric PCS-9611 Instruction Manual

3 Operation Theory

3.11 Cold Load Pickup Logic

3.11.1 Cold Load Pickup Logic Theory

The cold load pickup (CLP) logic which is included within this relay serves to either inhibit the
selected protective elements for an appointed duration, or to raise the settings of the selected
protective elements. Therefore, it allows the protection settings to be set closer to the load profile
by automatically increasing them following circuit energization. The CLP logic thus provides
stability, whilst maintaining protection during starting.
The CLP function acts upon the overcurrent protection and the No.1 group of zero sequence
overcurrent protection. The output signal of the CLP logic also can be used as a blocking signal
for a selected protective element through the PCS-Explorer configuration tool software.
The logic diagram of the cold load pickup function is shown in Figure 3.11-1.
The cold load pickup logic operates when the circuit breaker remains open for a time greater than
[CLP.t_Cold] and is subsequently closed. The CLP operation is applied after [CLP.t_Cold] and
remains for a time delay [CLP.t_Rst] after the circuit breaker is closed. The status of the circuit
breaker is provided either by means of the load current ([CLP.Opt_LogicMode] = 1) or by means
of the CB auxiliary contact ([CLP.Opt_LogicMode] = 2). The signal [CLP.OnLoad] can be gotten
from the signal "Prot.OnLoad" through the PCS-Explorer.
If the CLP output "CLP.St" is "1", the CLP settings are enabled for the overcurrent protection and
the No.1 group of zero sequence overcurrent protection respectively. After the delay [CLP.t_Rst]
has elapsed, the normal protection settings are applied. And if a fast resetting signal is received,
the normal protection settings are applied after the delay [CLP.t_ShortRst].
[CLP.OnLoad]
[CLP.Opt_LogicMode] = 1
[BI_52b]
[CLP.Opt_LogicMode] = 2
[CLP.ShortRst]
[CLP.St_50/51]
[CLP.Init]
[CLP.En]
[CLP.Blk]
Figure 3.11-1 Logic diagram of the cold load pickup function
Where:
[CLP.OnLoad] is the signal denotes anyone of the phase currents is greater than 0.04In;
[CLP.Opt_LogicMode] is used for selecting the cold load condition mode;
3-40
&
t
Cold
&
t 0
Rst
t 0
&
ShortRst
Date: 2014-04-08
0
S Q
R Q
&
&
[CLP.St]
PCS-9611 Feeder Relay