Page 80 - SACE Tmax XT - Catalogue

3/46 SACE TMAX XT LOW VOLTAGE MOLDED CASE CIRCUIT-BREAKERS

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Ekip Touch/Hi-Touch

Protection functions

SC Synchrocheck
By comparing voltage, frequency and phase values of the two circuits involved, the synchronism control
function indicates that the synchronism conditions necessary to allow the circuit-breaker to be closed
have been reached. The function is available in two operating modes:
• In systems with both busbars supplied, where synchronism is determined by:
U, f,
1. the voltage of the two half-busbars above the Ulive threshold for the set time
2. the difference of the two voltages below the threshold ΔU
3. the difference of the frequency of the two voltages below the threshold Δf
4. the difference of the phase of the two voltages below the threshold Δ
5. the desirable time for synchronism condition tsyn
6. the circuit-breaker.
• In systems with an out-of-service line (dead busbar), where the synchronism condition is determined
by the concurrence of the following conditions for the set tRef time:
1. the voltage of the active half-busbar is above threshold Ulive
2. the voltage of the dead half-busbar is below threshold Udead
3. the circuit-breaker is open.
In both cases, the synchronism signal is activated when the required conditions are reached and it
remains active for at least 200ms. After this lapse of time, the consent signal is deactivated, if the
synchronism conditions fail.
The indication of the synchronism reached is available directly as an electrical indication via a contact
that is always provided with the module. This function can be activated simply by connecting the Ekip
Synchrocheck module to any Ekip Touch device provided with an Ekip Measuring module.

G ext – Ground fault on toroid
This is available only for the XT7, with a trip time which is independent of the current (t = k) or with a
2
constant specific let-through energy (t = k/l ). If the pre-alarm reaches a 90% threshold this permits the
fault to be reported to supervision systems without any interruption of continuity. The protection needs
an external toroid installed, for example, on the star center of the transformer, and is an alternative to the
G and Rc functions. This device works with an auxiliary supply.

Modified differential ground fault (MDGF)
2
With trip time independent of the current (t = k) or with constant specific let-through energy (t = k/l ).
This protection allows using of the MDGF scheme into XT7 circuit-breakers. Third party phase current
transformers and summing current transformers are needed to realize the complete scheme. XT7
needs a dedicated terminal in order to properly measure the ground fault (see the paragraph “Modified
differential ground fault terminals“ in the ordering codes chapter).