CYG PRS-7367 - Synchronous Motor Loss of Step 78 O

Protection Functions
228 PRS-7367
3.51 Synchronous Motor Loss of Step 78O
3.51.1 Overview
1.1.1.1. Function Block
Out-of-Step
U3P
Str
Op
Op2
I3P
Block
PTS
CB Open
Figure 3.51-1 Function block
1.1.1.2. Signals
Table 3.51-1 Input signal
Signal
Description
U3P
The voltage magnitude in all the three phases
I3P
The current magnitude in all the three phases
Block
This signal blocks all the binary output signals of the function
PTS
PT Inst Alarm
CB Open
CB Open
Table 3.51-2 Output signal
Signal
Description
Str
The start signal
Op
The first stage operation signal.
Op2
The second stage operation signal.
3.51.2 Principle
The out of step protection includes two stages of implementation, which can be enabled or
disabled separately. When the first stage of out of step protection is enabled, the first stage
operation will be triggered after the first stage of delay; When the second out of step protection is
enabled, after the second delay, the second stage operation is triggered.
The out of step protection adopts the power factor angle criterion and the static stable
impedance circle characteristic criterion. The protection only operates when both criteria are met,
that is, the out of step protection action zone is the intersection of the two criteria action zones.