Stable Swing And Out Of Step; Biphase Loop; Power Swing Blocking - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-88
For instance:
If Delta R and DeltaX selected are around 1 ohm (Delta X=1ohm, Delta R=2 ohms as it is the
full loop),
From section 3.4.1.12 Power Swing Band:
∆R = 0.032 × ∆f × RLOAD (Formula for middle Power Swing point i.e. Electrical Centre)
And estimating RLoad for a 1 Amp relay as ((115 / √3)V / 1A) = 63.5 ohms,
We will be expecting frequency Swings from 0.5 to 1 Hz and an unblocking delay equal 2 or
3 seconds is adequated setting.
Power swing wave will be detected if speed is
Ohm/sec
4.1.2

Stable Swing and Out Of Step

The relay is able to distinguish 2 types of Power Swing:
• Stable Swing
• Out Of Step (OOS).
In case of a "Stable Swing" the sigh of the resistance value at the instant the impedance
enters the characteristic is the same as the sign of the resistance value at the instant the
impedance goes out from the characteristic (see Figure 59)
In case of an Out Of Step, the sign of the resistance value at the instant the impedance
enters the characteristic is opposite to the sign of the resistance value at the instant the
impedance goes out from the characteristic (see Figure 59).
An out of Step is a loss of synchronism.
In both cases the considered characteristic is the biphase loop characteristic. In other words
the phase to phase impedance is considered to perform Power Swing detection.
The Protection relay is able to count how many Stable Swings and how many Out of step
Occurs.
It is possible in MiCOM S1 Agile to set a number of out of step threshold above which a DDB
(Out Of Step Conf DDB#352) is triggered
4.1.3

Biphase loop

To decide what loop (what phases) has to be monitored 2 distinct algorithms are run:
• An exaggerated Delta current algorithm
• A Flat algorithm
4.1.4

Power Swing blocking

As soon as a power swing is detected the protection relay is blocked ("Power swing
blocking"). The Power Swing blocking algorithm prevents the protection relay from tripping
due to a power swing.
Power Swing blocking can be enabled or disabled per zone through "Blocking Zones"
setting.
If any or all of the distance zones are blocked, related trips are blocked including aided trip
logic.
For non-blocked zones, the swing indication is provided without tripping.
It is possible to limit the time for which blocking of any distance protection zones is applied.
For example, unblocking timer is used to override any blocked zone. Therefore, certain
MiCOM P40 Agile P442, P444
15 Ohm/sec < Speed < 450
Application Notes