ABB RELION REX640 Technical Manual page 567

1MRS759142 F
network calculation results of the coil controller in resonant earthed networks. In
Petersen coil controller, this value is denoted as 'I_DAMPING' [A]. When evaluating
this numerical value, the connection status of the parallel resistor of the coil must
be considered. See the example in
coil has value 8.6 A and it is permanently connected. The total system damping is
calculated as 11.29 A. Thus the natural network losses including the losses of the coil
are 11.29 A - 8.6 A = 2.69 A.
Figure 326: Example of interpretation of network damping value, I_DAMPING,
calculated by the coil controller
For example, if the resistive current of the parallel resistor is 10 A (at primary voltage
level), then a value of 0.5 · 10 A = 5 A could be used for setting
Operating quantity is set to "Adaptive", the setting value Min operate current is
If
also applicable if the coil is disconnected and the network becomes unearthed.
In this case, the current magnitude supervision is automatically based on the
amplitude of
of the parallel resistor in order to allow operation in the faulty feeder. In case of
smaller ampere value of the parallel resistor, for example 5 A, the recommended
security factor should be higher, for example 0.7, so that sufficient margin for CT
and VT errors can be achieved.
Operating quantity is set to "Amplitude", the Min operate current setting should
If
be selected based on the capacitive earth-fault current values produced by the
background network in case of a solid earth fault with a security margin.
REX640
Technical Manual
The network damping value, I_DAMPING, calculated by the coil controller
can be used as a base for setting
1
I
). The selected setting value must never exceed the ampere value
o stab
Figure 326
. In this case, the parallel resistor of the
Min operate current .
Protection functions
Min operate current .
567