ABB Relion 670 Series Applications Manual page 198

Section 8
Current protection
ContactSel : Operation of the contact based pole discrepancy protection. Can be set: Disabled / PD
signal from CB . If PD signal from CB is chosen the logic to detect pole discrepancy is made in the
vicinity to the breaker auxiliary contacts and only one signal is connected to the pole discrepancy
function. If the
IED and the logic to detect pole discrepancy is realized within the function itself.
CurrentSel : Operation of the current based pole discrepancy protection. Can be set: Disabled / CB
oper monitor / Continuous monitor . In the alternative CB oper monitor the function is activated
only directly in connection to breaker open or close command (during 200 ms). In the alternative
Continuous monitor function is continuously activated.
CurrUnsymPU : Unsymmetrical magnitude of lowest phase current compared to the highest, set in
% of the highest phase current. Natural difference between phase currents in breaker-and-a-half
installations must be considered. For circuit breakers in breaker-and-a-half configured switch
yards there might be natural unbalance currents through the breaker. This is due to the existence
of low impedance current paths in the switch yard. This phenomenon must be considered in the
setting of the parameter.
CurrRelPU : Current magnitude for release of the function in % of IBase .
8.12 Directional underpower protection GUPPDUP (37)
8.12.1 Identification
Function description
Directional underpower protection
8.12.2 Application
The task of a generator in a power plant is to convert mechanical energy available as a torque on a
rotating shaft to electric energy.
Sometimes, the mechanical power from a prime mover may decrease so much that it does not
cover bearing losses and ventilation losses. Then, the synchronous generator becomes a
synchronous motor and starts to take electric power from the rest of the power system. This
operating state, where individual synchronous machines operate as motors, implies no risk for the
machine itself. If the generator under consideration is very large and if it consumes lots of electric
power, it may be desirable to disconnect it to ease the task for the rest of the power system.
Often, the motoring condition may imply that the turbine is in a very dangerous state. The task of
the reverse power protection is to protect the turbine and not to protect the generator itself.
Steam turbines easily become overheated if the steam flow becomes too low or if the steam
ceases to flow through the turbine. Therefore, turbo-generators should have reverse power
protection. There are several contingencies that may cause reverse power: break of a main steam
pipe, damage to one or more blades in the steam turbine or inadvertent closing of the main stop
192
Pole pos aux cont. alternative is chosen each open close signal is connected to the
IEC 61850
identification
GUPPDUP
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IEC 60617 ANSI/IEEE C37.2
identification device number
37
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SYMBOL-LL V2 EN-US
1MRK 511 401-UUS F
SEMOD156693-1 v4
SEMOD158941-2 v4
SEMOD151283-4 v5
Bay control REC670
Application manual