IEC07000117-2-en.vsd
jX
Operation area
Operation area
R
Operation area
No operation area
No operation area
IEC07000117 V2 EN
Figure 5.
Load encroachment influence on the offset mho Z3
characteristic
Load encroachment LEPDIS
Heavy load transfer is common in many power networks and
may make fault resistance coverage difficult to achieve. In such
a case, Load encroachment LEPDIS function can be used to
enlarge the resistive setting of the underimpedance measuring
zones without interfering with the load.
Each of the three measuring phase-to-phase loops has its own
load encroachment characteristic.
6. Current protection
Instantaneous phase overcurrent protection, 3-phase output
PHPIOC
The instantaneous three phase overcurrent function has a low
transient overreach and short tripping time to allow use as a
high set short-circuit protection function.
Four step phase overcurrent protection, 3-phase output
OC4PTOC
The four step phase overcurrent protection function OC4PTOC
has an inverse or definite time delay independent for step 1 and
4 separately. Step 2 and 3 are always definite time delayed.
All IEC and ANSI inverse time characteristics are available.
The directional function is voltage polarized with memory. The
function can be set to be directional or non-directional
independently for each of the steps.
Second harmonic blocking level can be set for the function and
can be used to block each step individually
Instantaneous residual overcurrent protection EFPIOC
The Instantaneous residual overcurrent protection EFPIOC has
a low transient overreach and short tripping times to allow use
for instantaneous earth-fault protection, with the reach limited
to less than typical eighty percent of the transformer impedance
at minimum source impedance. EFPIOC can be configured to
measure the residual current from the three-phase current
inputs or the current from a separate current input. EFPIOC can
be blocked by activating the input BLOCK.
Four step residual overcurrent protection, zero sequence and
negative sequence direction EF4PTOC
The four step residual overcurrent protection, zero or negative
sequence direction (EF4PTOC) has a settable inverse or definite
time delay independent for step 1 and 4 separately. Step 2 and
3 are always definite time delayed.
All IEC and ANSI inverse time characteristics are available.
EF4PTOC can be set directional or non-directional
independently for each of the steps.
The directional part of the function can be set to operate on
following combinations:
• Directional current (I3PDir) versus Polarizing voltage (U3PPol)
• Directional current (I3PDir) versus Polarizing current (I3PPol)
• Directional current (I3PDir) versus Dual polarizing (UPol+ZPol
x IPol) where ZPol = RPol + jXPol
IDir, UPol and IPol can be independently selected to be either
zero sequence or negative sequence.
Second harmonic blocking level can be set for the function and
can be used to block each step individually.
Thermal overload protection, two time constant TRPTTR
If a power transformer or generator reaches very high
temperatures the equipment might be damaged. The insulation
within the transformer/generator will have forced ageing. As a
consequence of this the risk of internal phase-to-phase or
phase-to-earth faults will increase. High temperature will
degrade the quality of the transformer/generator insulation.
The thermal overload protection estimates the internal heat
content of the transformer/generator (temperature)
continuously. This estimation is made by using a thermal model
of the transformer/generator with two time constants, which is
based on current measurement.
Two warning levels are available. This enables actions in the
power system to be done before dangerous temperatures are
reached. If the temperature continues to increase to the trip
value, the protection initiates a trip of the protected
transformer/generator.
Estimated time to trip before operation is presented.
Breaker failure protection CCRBRF, 3-phase activation and
output
CCRBRF can be current based, contact based, or an adaptive
combination of these two conditions.
Breaker failure protection, 3-phase activation and output
(CCRBRF) ensures fast back-up tripping of surrounding
Transformer protection RET650
1MRK 504 137-BEN B
Product version: 1.3
ABB
15
Содержание ret650
Страница 1: ...Relion 650 series Transformer protection RET650 Product guide...
Страница 69: ...69...
