Medium-voltage instrument transformers
Smart Load to Reduce VT
AFR 1xx
AFR 1xx smart load is an instrument designed to monitor and protect measuring voltage transformers (VT) against the potentially harmful effects of ferroresonance in a high voltage distribution network. Ferroresonance occurs between the inductance of the transformer and the capacitance of the lines or switching equipments. Ferroresonance can be initialized by switching, disconnection, ground connections or by other transient events. During the ferroresonance a significant overvoltage and concurrent current peaks can occur due to the saturation of the magnetic circuit of the VT. This often leads to a fatal destruction of the VT.
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Description
AFR 1xx smart load is an instrument designed to monitor and protect measuring voltage transformers (VT) against the potentially harmful effects of ferroresonance in a high voltage distribution network. Ferroresonance occurs between the inductance of the transformer and the capacitance of the lines or switching equipments. Ferroresonance can be initialized by switching, disconnection, ground connections or by other transient events. During the ferroresonance a significant overvoltage and concurrent current peaks can occur due to the saturation of the magnetic circuit of the VT. This often leads to a fatal destruction of the VT.
AFR 1xx acts as a protection of the VT against the unwanted effects of such events. In comparison with other protection methods AFR 1xx is only selectively activated during the occurrence of ferroresonance and stays inactive during the normal operation.
AFR 11x is intended for alone operated VTs, i. e. for single phase measuring, V connection measuring or for one pole power feeders.
AFR 13x is intended for connection into open delta of auxiliary secondary windings of three VTs.
Installation, adjusting and maintenance may by carried out by qualified personnel only with respect to installation instructions and safety regulations. When operated in contradiction with the technical specifications, proper functionality is not guaranteed. Before any manipulation with the instrument, disconnect voltage transformers out of the network. Don’t touch instrument terminals and don’t use the instrument without its cover.
Parameters
- Nominal voltage Un: options for:: 100, 110, 120 ,100/√3, 110/√3, 120/√3, 220, 230 VAC (other ranges on request))
- Activation voltage level, Activation delay: 145% Un to 200% Un, 0 s
- Recommended protection: B16A circuit breaker or equivalent fuse
- Overvoltage class: III
- Auxiliary supply voltage (option „L“): 15 to 265 VAC / 40 to 70 Hz or 15 to 265 VDC
- Input power of auxiliary supply: 3 VA resp. 3 W
- Overvoltage category of aux. Supply: 300V/CAT.II
- Communication line: RS 485, galvanically isolated
- Protocol: Modbus RTU, 4.8-230.4 kBd, 8bit, selectable parity (default 19.2 kBd, 8-bit, even)
- Protection class: IP20
- Climatic category: 40/060/02
- Working / storage temp.: -40 °C to 60 °C / -40 °C až 70 °C
- Max. moisture: 95% non-condensing
- Dimension: width 80mm x depth 90mm x height 126 mm
- Weight: 0,52 kg
- Enclosure material: stainless steel
- Installation: 35 mm DIN rail acc. DIN EN 50 022
- Wiring: terminal, wire cross-section 0,5–2,5 mm2
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