NHP TemBreak PRO P - Thermal Self Protection

Protection Settings
Short Time Delay Protection (STD)
I
2
t function for STD
34
TemBreak PRO P_BE-UM-001-EN V1.3.0
Thermal Self Protection
Thermal self-protection is enabled automatically where STD is disabled. This is to ensure that the continuation of the LTD curve does not intersect with the
Critical Area of the MCCB, which could create overheating stresses in the MCCB and cause irreparable damage and/or undesirable operation or failure of
the trip-unit.
To achieve this, a supplementary I²t = K curve is added to the end of LTD tripping curve, starting from I
tsp
, where constant K = Max(I
i
)² x t
tsp
. Max(I
i
) is the
maximum I
i
settable on the trip unit and is not adjustable.
For the following MCCBs I
tsp
and t
tsp
values are specifications.
MCCB
I
tsp
x I
r
t
tsp
(seconds)
P160_BE I
n
= 160A
8
2
P250_BE I
n
= 250A
8
2
Notice: Thermal self-protection is applied to all phases where LTD protection is enabled.
In the case of 4P MCCBs, Thermal self-protection is also applied to the neutral pole (irrespective of the N
Coefficient parameter) provided that Neutral Protection (NP) is enabled. Refer to Neutral Protection section.
Notice: LTD thermal image value θ is only affected during a trip event where it is temporarily forced to a value
over 100%.