CYG PRS-7367 - Page 198

Protection Functions
190 PRS-7367
)CorAng(270arg)CorAng(90 






o
U
jRCA
e
o
I
Or,
-
90 ( CorAng) arg 270 ( CorAng)
j RCA
Ue
o
I
o

   
The RCA setting can be automatically changed by the RCA_CTL signal. The RCA_CTL is used in
the compensated networks where the compensation coil sometimes is temporarily disconnected.
When the coil is disconnected, the compensated network becomes isolated and the Characteristic
angle setting must be changed. The RCA setting should be added -90˚ when RCA_CTL=1.
The CorAng is used to improve the selectivity when there are inaccuracies due to the
measurement transformer.
The relay calculates the forward and backward operate area by directionality formula. The
directional calculation module enables the residual power calculation only if both of the zero
current and zero voltage are exceeding the minimum operation value.
 Residual power calculation
The residual power calculation module calculates the magnitude of residual power
Ires·Ures·Cos(Φ-RCA). Angle Φ is the angle between the operating quantity and polarizing
quantity, compensated with a characteristic angle RCA. The angle value is received from the
directional calculation module.
The power setting can be set as:
   
res res Cos RCA 3 3 Cos RCAI U Io Uo        
Where:
Φ=Angle between the Polarising Voltage (-Ures) and the Residual Current(Ires)
RCA=Relay Characteristic Angle Setting
Ures=Residual Voltage
Ires= Residual Current
Uo=Zero Sequence Voltage
Io= Zero Sequence Current
 Initiation logic
The initiation logic diagram of the protection is as below: