ABB Relion® Protection and Control REX640 Arc flash protection

Arc flash protection

The arc flash protection is available on the optional hardware

module. The module supports connection of up to four sensors.

The sensors can be of lens or loop types, or a free mixture. Both

sensor types are supervised against sensor failure. Fast tripping

increases staff safety and limits material damage, therefore it is

recommended to use static power outputs (SPO) instead of

normal power outputs (PO). This typically decreases the total

operating time with 4..6 ms compared to the normal power

outputs.

Power transformer differential protection

The relay offers low-impedance differential protection for two

winding (two restraints) and three-winding (three restraints)

power transformers. The power transformer protection

application package includes the protection for a two-winding

power transformer. If support for three-winding power

transformer is needed, the corresponding protection add-on

package can be selected. Both low-impedance differential

functions feature three-phase multi-slope stabilized stages and

an instantaneous stage to provide fast and selective protection

against short circuits, winding interturn faults and bushing

flash-overs. A second harmonic restraint with advanced

waveform-based blocking ensures stability at transformer

energization. The fifth harmonic based blocking and unblocking

limits stabilize the protection performance in moderate

overexcitation situations. In case of three-winding differential

protection, the connection group phase shift matching can be

done with 0.1 degree resolution supporting cycloconverter

applications. If the tap-changer position information is

available, it is possible to further increase the protection

sensitivity by compensating the tap-changer position error

within the measured differential current.

The power transformer protection application package also

includes high-impedance differential functions for a phase

segregated protection scheme. If this scheme is applied, the

related current transformers have to be correctly selected and

the necessary secondary circuit components, external to the

relay, defined.

Measurements

The base functionality of the REX640 relay contains a number of

basic measurement functions for current, voltage, frequency,

symmetrical components of currents and voltages, power,

power factor and energy. These measurement functions can be

freely connected to the measured secondary quantities

available in the relay. The relay can also measure various analog

signals via RTD and mA inputs. All these measurements can be

used within the relay configuration for additional logics. The

measurements are available locally on the HMI and can be

accessed remotely via communication. The information is also

accessible via Web HMI.

The relay is also provided with a load profile recorder. The load

profile feature stores the selected load measurement data

captured periodically (demand interval). The records can be

viewed on the LHMI and are available in COMTRADE format.