ABB RER620 Technical Manual page 160

Section 4
Protection functions
154
The RCA_CTL input is used in compensated networks where the compensation coil
sometimes can be disconnected. When the coil is disconnected, the compensated network
becomes isolated and the Characteristic angle setting (φRCA) must be changed. This can
be done automatically with the RCA_CTL input. Note that the RCA_CTL input only works
when the Characteristic angle setting is set to exactly -90 degrees or 0 degrees. The value
of the input affects the Characteristic angle setting in the following way:
Table 170: Characteristic angle control in phase angle operation mode
Characteristic
RCA_CTL = "False"
angle
setting
-90° φRCA = -90°
0° φRCA = 0°
I sin(φ) and I cos(φ) criteria
0 0
A more modern approach to directional protection is the active or reactive current
measurement. The operating characteristic of the directional operation depends on the
grounding principle of the network. The I
network, measuring the reactive component of the fault current caused by the ground
capacitance. The I cos(φ) characteristic is used in a compensated network, measuring the
0
active component of the fault current.
The operation criteria I sin(φ) and I
0
using the values "IoSin" or "IoCos", respectively.
In isolated networks, I sin(φ) does not differ from the phase angle criterion, since the
0
phase angle of the operating quantity is fairly close to -90 degrees. Furthermore, in
completely compensated networks the fault current is usually mostly resistive. Therefore,
the phase angle and I cos(φ) criteria are equally sensitive. However, if the fault is in the
0
background network, the fault current of a sound and healthy line is almost fully capacitive
and its phase angle is close to the operation area of the component. Therefore, the I
characteristic is recommended, since the risk of faulty operation is smaller than with the
phase angle criterion.
The angle correction setting can be used to improve selectivity. The setting decreases the
operation sector. The correction can only be used with the I
The RCA_CTL input is used to change the I
Table 171: Relay characteristic angle control in I
Operation criteria:
I sin(φ)
0
I cos(φ)
0
When the I sin(φ) or I cos(φ) criterion is used, the component indicates a forward or
0 0
reverse-type fault through the FAULT_DIR and DIRECTION outputs, in which 1 equals
a forward fault and 2 equals a reverse fault. Directional operation is not allowed (the Allow
non dir setting is "False") when the measured polarizing or operating quantities are not
valid, that is, when their magnitude is below the set minimum values. The minimum values
can be defined with the Min trip current and Min trip voltage settings. In case of low
RCA_CTL = "True"
φRCA = 0°
φRCA = -90°
sin(φ) characteristic is used in an isolated
0
cos(φ) are selected with the Operation mode setting
0
characteristic:
0
sin(φ) and I cos(φ) operation criterion
0 0
RCA_CTL = "False"
Actual operation criterion: I sin(φ)
0
Actual operation criterion:
I cos(φ)
0
1MAC309294-MB F
cos(φ)
0
sin(φ) or I cos(φ) criterion.
0 0
RCA_CTL = "True"
Actual operation criterion:
I cos(φ)
0
Actual operation criterion: I sin(φ)
0
RER620
Technical Manual