FUNCTION CHARACTERISTICS
263
NVA100X-D - Manual - 02 - 2016
Cold Load Pickup - CLP
Preface
CLP feature allows selected thresholds to be changed or blocked for an adjustable time in order to
overcome transient overcurrents.
The trigger of the CLP feature is the logical condition of circuit breaker closed, that Pro-N relay de-
tect by means of two digital inputs connected to the circuit breaker auxiliary contacts 52a and 52b.
When the circuit breaker closed condition is detected, the CLP timer set in the submenu of CLP func-
tion is initiated and, throughout the CLP set time:
The threshold is blocked if CLP is set to ON threshold block.
The threshold is changed to the value that is set if CLP is set to ON threshold change.
When CLP timer has elapsed, the threshold is unblocked if CLP is set to ON threshold block or the
threshold is revert back to the original value if CLP is set to ON threshold change.
Note that when the circuit breaker is open, the threshold is already blocked if CLP is set to ON
threshold block or the threshold is already changed to the value if CLP is set to ON threshold change:
this is useful in order to avoid unwanted tripping due to unblocked threshold or threshold with his
original value for cases where a delay of the circuit breaker closing happen, i.e. where the three
poles of the CB do not close at the same time or during long CB closing time.
Typical applications where the CLP feature may be useful are for overcurrent protections on feeders
where the circuit breaker closing starts air conditioning/heating loads after a long cooling time, mo-
tors or more generally momentary large loads.
The CLP may be also useful for instantaneous ground fault overcurrent protections on motors start-
ing, because it is likely that incorrect operation of the protection would occur on imbalance transient
secondary current due to asymmetric line CTs saturation.
Depending upon the magnitude and duration of the starting current, it may be necessary to block
operation of thresholds or raising his setting. Also a combination of both blocking some thresholds
and raising others may be adopted.
For each threshold the CLP function may be disabled (
OFF
), enabled with threshold blocking (
ON-
Element blocking
) or enabled with threshold change (
ON-Change setting
) by means the
xx-
CLPx Mode
parameter.
The operating mode and the relative activation time concerning each threshold of the 49,
50/51, 50N/51N, 67 and 67N elements are adjustable inside the
Set \ Profi le A(or B) \ xxx - xx
\ xxx Element \ Setpoints
menus.
Example: to change the fi rst threshold of the defi nite time overcurrent element 50/51 within CLP dur-
ing a 0.1 s time interval:
the
ICLP> Mode
parameter must be set as
ON-Change setting
,
the
tCLP>
parameter must be adjusted to a wanted value (0.1 s) inside the
Set \ Profi le A(or B) \
Phase overcurrent - 50/51 \
I> Element \ Setpoints
menu,
The threshold within CLP parameter
ICLP>def
must be adjusted to a wanted value inside the
Set
\ Profi le A(or B) \ Phase overcurrent - 50/51\
I> Element \ Defi nite time
menu.
CB position can be acquired by means one or two binary inputs; allocation of
52a
and
52b
func-
tions is available inside the
Set \ Board 1(2) inputs \ Binary input IN1-1...(IN1-x)
menus.
—
•
•
•
•
•
I n p u t
t
x x RES
T
0
R E S E T
t
x x
0
T
≥
1
I
xx
t
x x RES
Start Ixx
Trip Ixx
Start
I
2ndh>
CB State
(Threshold outside CLP)
G e n e r i c p r o t e c t i v e e l e m e n t
Block1, Block2
T
0
t
CLPxx
&
2nd harmonic restraint enable (ON
≡
Enable)
Ixx2ndh-REST
ICLPxxMode
I
C L P xx
t
C L P xx
TRIP
P
ING
M
ATRIX
(LED
+R
EL
AY
S
)
A
B
C
A =“1”
A =“0 or OFF”
TRANSIENT THRESHOLD
STEADY STATE THRESHOLD
t
CLPxx
CB State
CB CLOSED (52a=ON)
CB OPEN
(52a=OFF)
CB OPEN
(52a=OFF)
Output t
CLP
xx
t
0.1 s
TRANSIENT THRESHOLD/
TRANSIENT THRESHOLD/
BLOCK
STEADY STATE
THRESHOLD/UNBLOCK
BLOCK
A = ON - Change setting
B = OFF
C = ON - Element blocking
≥
1
CLP Ixx
Operate time
Cold Load Pickup logic diagram - CLP
