A chemical plant in Saudi Arabia lost a transformer to overheating. The site protected the transformer with a Schneider VIP400 microcomputer unit, which has no temperature input, so the winding and oil temperature were never part of the trip logic. The requirement was to add an eight-channel PT100 controller that alarms independently of the protection relay.
What the controller has to do
- Read several PT100 elements at once: winding hot spots, top oil, and often the ambient temperature of the vault as a reference.
- Raise a relay alarm when a channel passes a setpoint, and a separate one for a higher, trip-level value, so the plant can react before the protection relay does.
- Report the same temperatures to the plant system over RS485 rather than staying inside the cabinet.
- Keep running on the substation auxiliary supply, which may be AC or DC.
ARTM-8 series, confirmed data
Transcribed from the ARTM-8L installation manual V1.2
| Parameter | Value |
|---|---|
| Measurement channels | 8 |
| Input signal | PT100, PT1000, thermocouple (K, T and other types) or NTC |
| Range with PT100 | up to -200 C to +850 C, limited by the sensor actually fitted |
| Range with NTC | -40 C to +140 C |
| Accuracy | NTC +/-1 C; PT100 / PT1000 +/-1 C over -200 C to +200 C |
| Alarm outputs | 5 groups, normally open contact |
| Auxiliary supply | AC 85-265 V or DC 100-300 V, 2 W or less |
| Communication | RS485, Modbus-RTU; address 1-247, baud 2400 / 4800 / 9600 / 19200 |
| Typical PT100 sensor | TPS01TP100-2000, -50 to +200 C, three-wire, 2 m lead |
The original text on this page quoted -200 C to +600 C. The manual states -200 C to +850 C as the maximum supported range for PT100 input, with the usable limit set by the sensor; the figure has been corrected to the documented value.
Why a separate temperature alarm
A protection relay trips on electrical fault current. An overheating transformer draws normal current while its insulation degrades, so the relay never sees it. A temperature controller closes that gap: it starts a fan, raises an alarm to the control room, and can be wired to a shed command before the winding reaches a destructive temperature.
What to send us
Number of transformers, where the sensors must be placed (top oil, winding, room), which alarm levels the plant uses, the auxiliary supply voltage, and whether the readings must reach an existing Modbus master. We confirm channel count, sensor type and cable length, then return the ordering code and the wiring diagram.
Related products: ARTM-8 temperature controller · ATC600 wireless temperature system
Topology
Post time: Jun-21-2023
