The AFR 30 Smart Load is an instrument designed to protect metering voltage transformers against adverse effects of ferroresonance in high voltage power distribution systems with ungrounded or indirectly grounded neutral wire. Unlike other methods, it is targetedly enabled only when ferroresonance occurs, being passive in common operation or with nonsymmetrical loads or single-phase ground connection, which means it does not load the metering system.
Ferroresonance comes up between transformer inductance and conductor or switching element capacitance. Connecting, disconnecting, ground connection or other transitional effects may be the trigger events. Ferroresonance oscillations cause significant overvoltage and current surges as a result in very high transformer magnetic circuit saturation. This most often leads to metering transformer destruction.
AFR30 Smart Load acts as metering voltage transformer protection against such effects. Unlike other methods, it is targetedly enabled only when ferroresonance occurs, being passive in common operatin on with nonsymmetrical loads or single-phase ground connection, which means it does not load the mettering system.
|Nominal voltage||100 – 200 VAC|
|Insensitivity window||0 – 20 VAC|
|Climate class||5 / 50 / 40|
|Operating temperature||-20°C až 40°C|
|Storage temperature||-20°C až 70°C|
|Maximum humidity||95 % non-condensing|
|Dimensions||69 x 86 x 58 mm|
|Material of cover||polycarbonate|
|Instalation||on 35 mm DINstrip in compliance with DIN EN 50 022|
|Connection||terminal bar, wire cross section 0.5 to 2.5 sq mm|
AFR30 works in conjuction with a mettering voltage transformer while open delta is connected to auxiliary windings (terminals da, dn). Metering winding wiring is not changed. The open delta configured auxiliary windings may be, together with AFR30 Smart Load, used for ground connection protection relay, which is to be connected parallel to AFR30 using the protection relay manufacturer's recommendations. AFR30 parallel connection does not affect protection relay operation. AFR 30 Smart Load is usually installed in the measuring and protection control panels. The instrument is designed to be installed on a 35 mm DIN strip. 2.5 square millimeter copper wire is recommended for the circuit
Smart Load wireup diagram in metering voltage transformer auxiliary winding open delta configuration
|A, N:||Metering transformer high voltage terminals|
|a, n:||Secondary metering winding|
|da, dn:||Other secondarywinding terminals|