Various floating contacts are provided as interfaces to other units. These can be used: − To transmit the status of the electronics to a remote control room − To send commands to a circuit breaker feeding into the arc fault − As an interlock to block the reclosing of a circuit breaker directly after tripping.
fig 3 Sequence of operation
Together with the electronic watchdog function, the functional capability of the SMGG-igniter is also continuously monitored. The electronic unit can be switched to test mode in which all the response criteria for the switchgear can be simulated and
checked by the user, and the corresponding trips displayed but not transmitted to the SMGGs.
In combination with ABB’s TVOC light detection system, up to 54 compartments in a switchgear system (three compartments per panel) can be monitored using one electronic unit. The TVOC extension modules, each of which contains nine optical inputs, can be directly connected to the five interfaces provided. Because detection of an arc fault by these modules is also monitored by the electronic unit, at least 18 panels in a switchgear system are provided with active protection. As each compartment is individually monitored, the location of the fault can be easily determined.
Rated for voltages up to 40.5 kV
The UFES system, suitable for rated voltages up to 40.5 kV and rated short-time withstand currents up to 63 kA, is an active internal arc fault protection solution for new internal arc classified medium-voltage switchgear as well as for existing older generation switchgear. It helps to avoid serious damage to the switchgear, the equipment and the direct environment. Therefore, it greatly increases both system availability and personnel safety in the event of internal arc fault. Furthermore it enables the minimization of pressure relief arrangements in switchgear installation rooms with limited access.
The UFES primary switching elements can be installed in the switchgear cable connection compartments or simply in each separate busbar section to ensure the entire system is covered. The UFES is available as a complete unit in a type-tested ABB service box for simple installation in existing switchgear systems and later as a “loose device” (ie, the electronic unit and three primary switching elements).
Table 1 - Arc fault duration in electrical systems and the associated consequences
Using a conventional protection device – Arc fault duration: 200–300 ms – Detection by standard relay – Clearing of arc fault current by the upstream circuit breaker
Possible dramatic consequences include – Fire/explosion – Serious injuries to personnel (depending on the switchgear design)
Fast-acting protection relay with supplementary equipment (eg, Is -limiter) − Arc fault duration: 50–100 ms − Fast detection by special protection relay − Clearing of arc fault current by the upstream circuit breaker
Limited damage to equipment and personnel (depending on the switchgear design) For all the most up to date news and products visit www.thepanelbuilder.co.uk
March 2012 Page 9
Ultra-fast earthing switch (UFES) − Arc fault duration: ≤4ms after detection − Ultra-fast detection by UFES electronic unit − Ultra-fast extinction of the internal arc by switching of the UFES primary-element − Final clearing of fault current by the upstream circuit-breaker
No damage expected
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