ABB Relion 670 Series Product Manual page 30

Generator protection REG670
Version 2.2
Sensitive directional residual overcurrent and power
protection SDEPSDE
In isolated networks or in networks with high impedance
earthing, the earth fault current is significantly smaller
than the short circuit currents. In addition to this, the
magnitude of the fault current is almost independent on
the fault location in the network. The protection can be
selected to use either the residual current or residual
power component 3U0·3I0·cos j, for operating quantity
with maintained short circuit capacity. There is also
available one nondirectional 3I0 step and one 3U0
overvoltage tripping step.
No specific sensitive current input is needed. Sensitive
directional residual overcurrent and power protection
(SDEPSDE) can be set as low 0.25% of IBase.
Thermal overload protection, two time constants
TRPTTR
If a power transformer reaches very high temperatures
the equipment might be damaged. The insulation within
the transformer will experience forced ageing. As a
consequence of this the risk of internal phase-to-phase
or phase-to-earth faults will increase.
The thermal overload protection (TRPTTR) estimates the
internal heat content of the transformer (temperature)
continuously. This estimation is made by using a
thermal model of the transformer 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.
The estimated time to trip before operation is
presented.
Breaker failure protection CCRBRF
Breaker failure protection (CCRBRF) ensures a fast
backup tripping of the surrounding breakers in case the
own breaker fails to open. CCRBRF measurement
criterion can be current based, CB position based or an
adaptive combination of these two conditions.
A current based check with extremely short reset time is
used as check criterion to achieve high security against
inadvertent operation.
CB position check criteria can be used where the fault
current through the breaker is small.
CCRBRF provides three different options to select how
t1 and t2 timers are run:
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SEMOD171438-5 v6
M13243-3 v12
M11550-6 v19
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1. By external start signals which is internally latched
2. Follow external start signal only
3. Follow external start signal and the selected
FunctionMode
CCRBRF can be single- or three- phase initiated to allow
its use with single phase tripping applications. For the
three-phase application of the CCRBRF the current
criteria can be set to operate only if
operates out of three phases and neutral" for example;
two phases or one phase plus the residual current start.
This gives a higher security to the backup trip command.
The CCRBRF function can be programmed to give a
single- or three- phase retrip to its own breaker to avoid
unnecessary tripping of surrounding breakers at an
incorrect initiation due to mistakes during testing.
Pole discordance protection CCPDSC
An open phase can cause negative and zero sequence
currents which cause thermal stress on rotating
machines and can cause unwanted operation of zero
sequence or negative sequence current functions.
Normally the own breaker is tripped to correct such a
situation. If the situation persists the surrounding
breakers should be tripped to clear the unsymmetrical
load situation.
The Pole discordance protection function (CCPDSC)
operates based on information from auxiliary contacts
of the circuit breaker for the three phases with
additional criteria from unsymmetrical phase currents
when required.
Directional over/underpower protection GOPPDOP/
GUPPDUP
The directional over-/under-power protection
(GOPPDOP/GUPPDUP) can be used wherever a high/low
active, reactive or apparent power protection or
alarming is required. The functions can alternatively be
used to check the direction of active or reactive power
flow in the power system. There are a number of
applications where such functionality is needed. Some
of them are:
• generator reverse power protection
• generator low forward power protection
• detection of over/under excited generator
• detection of reversed active power flow
• detection of high reactive power flow
• excessive line/cable loading with active or reactive
power
• generator reverse power protection
Each function has two steps with definite time delay.
1MRK 502 074-BEN M
"2 elements
M13269-3 v15
SEMOD175421-4 v7
Hitachi Power Grids