Instruction manual
–
AQ G3x7 Generator protection IED
138 (211
)
Parameter
Setting value, range
and step
Description
IPh Base
Sens
1
0…30, by step of
1%
Definition of minimal current enabling impedance calculation
The positive sequence current is considered to be sufficient if it is above the level set by
parameter PSLIP78_Imin_IPar_ (IPh Base Sens). At the same time the negative sequence
component should be below 1/6 of this parameter value.
3.2.22.8
The symbol of the function in the AQtivate 300 software
Figure 3-83 The function block of the pole slip function
Binary status signal
Explanation
Start
Start signal of the function
Trip
Trip command of the function
Binary status signal
Explanation
Block
Blocking of the pole slipping function
3.2.23
L
OSS OF EXCITATION
(40)
The loss of excitation protection function can be applied mainly for synchronous generators.
On loss of excitation, the flux decreases and the reactive current demand increases
relatively slowly. At the end, high reactive current flows from the power system into the
machine. To protect the stator coils from the harmful effects of the high currents and to
protect the rotor from damages caused by the induced slip-frequency current, a
disconnection is required.
The loss of excitation (loss-of-field) protection function is designed for this purpose.
When the excitation is lost, then a relatively high inductive current flows into the generator.
With the positive direction from the generator to the network, the calculated impedance
based on this current and on the phase voltage is a negative reactive value. As the internal