NS4PTOC can be used as main protection for unsymmetrical
fault; phase-phase short circuits, phase-phase-earth short
circuits and single phase earth faults.
NS4PTOC can also be used to provide a system backup for
example, in the case of the primary protection being out of
service due to communication or voltage transformer circuit
failure.
Directional operation can be combined together with
corresponding communication logic in permissive or blocking
teleprotection scheme. The same logic as for directional zero
sequence current can be used. Current reversal and weak-
end infeed functionality are available.
Sensitive directional residual overcurrent and power
protection SDEPSDE
SEMOD171438-5 v5
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. SDEPSDE can
be set as low 0.25% of IBase.
Thermal overload protection, two time constant TRPTTR
M13243-3 v10
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 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
M11550-6 v16
Breaker failure protection (CCRBRF) ensures a fast backup
tripping of the surrounding breakers in case the own breaker
fails to open. CCRBRF can be current-based, contact-based
or an adaptive combination of these two conditions.
A current check with extremely short reset time is used as
check criterion to achieve high security against inadvertent
operation.
Contact check criteria can be used where the fault current
through the breaker is small.
CCRBRF can be single- or three-phase initiated to allow use
with single phase tripping applications. For the three-phase
version of CCRBRF the current criteria can be set to operate
only if two out of four for example, two phases or one phase
plus the residual current start. This gives a higher security to
the back-up trip command.
CCRBRF function can be programmed to give a single- or
three-phase re-trip of its own breaker to avoid unnecessary
tripping of surrounding breakers at an incorrect initiation due
to mistakes during testing.
Pole discordance protection CCPDSC
M13269-3 v14
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
SEMOD175421-4 v6
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.
By using optional metering class CT inputs accuracy of 0,5%
can be achieved for steam turbine applications.
1MRK 502 068-BEN D
Generator protection REG670 2.1 IEC
Product version: 2.1
22
ABB
