P(A, B, or C)
Power>1 1 Ph Watt
Power>1 1 Ph VAR
P(3 phase )
Power>1 3 Ph Watt
Power>1 3 Ph VAR
VTS Slow Block
Figure 137: Overpower logic
FORWARD OVERPOWER SETTING GUIDELINES
The relevant power threshold settings should be set greater than the full load rated power.
The operating mode should be set to Forward.
A time delay setting (Power>(n) TimeDelay) should be applied. This setting is dependant on the application, but
would typically be around 5 seconds. The delay on the reset timer (Power>(n) tRESET), would normally be set to
REVERSE POWER CONSIDERATIONS
A generator is expected to supply power to the connected system in normal operation. If the generator prime
mover fails, it will begin to motor (if the power system to which it is connected has other generating sources). The
consequences of generator motoring and the level of power drawn from the power system will be dependent on
the type of prime mover.
Typical levels of motoring power and possible motoring damage that could occur for various types of generating
plant are given in the following table.
Motoring level depends on compression ratio and cylinder bore stiffness. Rapid disconnection is required to limit power loss
and risk of damage.
5% - 25%
Chapter 12 - Power Protection Functions
Possible damage (percentage rating)
Risk of fire or explosion from unburned fuel
Power>1 3 PhStart
Power>1 3Ph Trip