The surge protection device's half-wave Fourier algorithm measuring the current under normal operating conditions has high requirements for measurement accuracy, but the response can be slower, and the required current effective value is an average concept, and the root mean square algorithm is generally used. The protection data and measurement data generally cannot be shared, but must be collected independently, and should be taken from the protection TA and measurement TA windings respectively. Currently, only one set of protection TA can meet the requirements for domestic 10kV vacuum switches. FTU generally should also monitor the power supply voltage and the remaining capacity of the battery.

(3) Remote control function. FTU should be able to accept remote commands to control the switch on and off on the pole, and start the energy storage process, etc.

(4) Statistics function. The FTU should also be able to monitor the number of times and operation time of the switch and the level of the accumulated cut-off current.

(5) Time synchronization function. FTU should be able to accept the time synchronization command from the main system so as to keep consistent with the system clock.

(6) Sequence of Event Recording (SOE). Record the time and sequence of changes in state quantities.