Trihal cast resin dry type transformers (ENG) - Trinet

HV/LV distribution transformersTRIHAL cast resin transformersthermal protection by PTC sensorsAn optional thermal protection module is availableon request. This will monitor thetemperature of the windings and preventoverheating.the standard thermalprotection comprises : 2 PTC sensors assemblies, each onecomprising three positive temperaturecoefficient thermistors connected in series.The first one gives an alarm signal at 150°C(alarm 1), the second an alarm signal at 160°C(alarm 2).The PTC sensor abruptly changes its resistancevalue at its operating temperature threshold.This is preset during manufacture and notadjustable. The rapid increase in resistance ofthe sensors at their operating temperature isdetected by the Z electronic converter, towhich they are connected. Sensors, one foralarm 1 and one for alarm 2 per phase arelocated in tubes between the magnetic coreand the LV winding and can be withdrawn andreplaced should this ever be necessary. 1 A Z electronic converter with3 independent metering circuits.Two of these circuits respectively control thevariation in resistance between the 2 PTCsensor units. When the temperature reaches150° C (or 160° C), information from Alarm 1 (orAlarm 2) is respectively processed by the2 independent output relays equipped with achangeover switch contact; the position ofthese two relays is signalled by 2 red colouredLED’s.The third metering circuit is shunted by anexternal or enclosure mounted resistance R; itcan control a 3 rd PTC sensor unit at 140° C aslong as this resistance is eliminated. In thiscase (“Forced Air” option on request), the FANinformation is processed by a 3 rd independentoutput relay equipped with a closing contact;the position of this relay is signalled by a yellowLED.In case of the failure of one of these 3 probecircuits (breaking or short-circuit), a redcoloured LED marked SENSOR flashes,together with that of the incriminating circuit.A green coloured LED signals the presence ofvoltage to the enclosure. a terminal board with plug-in connectorsin order to connect the PTC sensors to theelectronic converter.The PTC sensors are supplied connected tothe terminal board fixed on the upper coreclamp of the transformer.Z electronic converterterminal-board with plug-in connectorsconnecting the PTC sensor and the Zelectronic converterkWresistance0normal¡CtemperaturePTC sensorscharacteristic curve diagram of a PTC sensor