8.6
Thermal overload protection, one time constant,
Celsius LPTTR
GUID-446B7894-9CAC-47C6-BABC-8D3F4C7CA5F4 v1
8.6.1
Identification
M17106-1 v7
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Thermal overload protection, one time
constant, Celsius
LPTTR
θ>
26
8.6.2
Application
M15283-3 v9
Equipment in the power system is designed for a certain maximum load current
level. If the current exceeds this level the losses will be higher than expected. As a
consequence the temperature of the conductors will increase. If temperature of the
equipment reaches too high values, the equipment might be damaged:
•
The sag of overhead lines can reach unacceptable value.
•
If the temperature of conductors, for example aluminium conductors, gets too
high the material will be destroyed.
•
In cables the insulation can be damaged as a consequence of the
overtemperature. As a consequence of this phase to phase or phase to earth
faults can occur.
•
The paper insulation used inside a power transformer will deteriorate quicker
and expected life of the transformer will be shortened. Even an internal flash-
over may occur.
In stressed situations in the power system it can be required to overload lines and
transformers for a limited time. This should be done while managing the risks
safely.
The thermal overload protection provides information that makes a temporary
overloading possible. The thermal overload protection estimates the conductor
temperature continuously in Celsius. This estimation is made by using a thermal
model based on the current measurement.
If the temperature of the protected object reaches a set alarm level
AlarmTemp
, a
signal ALARM can be given to the operator. This enables actions in the power
system to be taken before dangerous temperatures are reached. If the temperature
continues to increase to the trip value
TripTemp
, the protection initiates trip of the
protected object.
Section 8
1MRK 506 375-UEN A
Current protection
184
Railway application RER670 2.2 IEC
Application manual
Summary of Contents for RELION RER670
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