TML Winding and Oil Temperature Supervisor

Treetech’s TML Temperature Supervisor is a thermal protection digital system that also controls the forced cooling of transformers and reactors immersed in oil. It is ideal for low cost small to medium- size equipment applications. For medium to large size/strategic applications or application that require equipment of Temperature Monitor class, please apply the following products: TM1, TM2, TM and SDT.

The TML monitors the temperature of the oil and one winding, and optionally can monitor the temperature of up to three windings. It provides temperature supervision and thermal protection of up to three windings.For this purpose it is equipped with:

• Two Pt100 inputs; for redundant top oil temperature if required;
• One or three inputs for load current measurement to calculate the temperatures of one or three windings;
• Twelve output relays for alarms,selective shutdown, cooling control and signalling;
• Two or four current loop outputs for remote temperature indications;
• Serial communication port to connect to supervisory or monitoring systems;
• Optional communication through GRPS cell modem function inside the equipment.

Main Features

• IED (Intelligent Electronic Device) specifically designed for the substation patio conditions and able to integrate to supervisory or monitoring systems through the standard RS485 port or optional GRPS communication.
• Operating Temperature -10 to +70 ºC or optionally -40 to +85 ºC. Expanded  operating  temperature,  provides increased  ruggedness,  reliability  and  service  life  in  extreme temperatures.
• Fulfils the strictest tests performed by the transformer manufacturers. Type tested to stringent standards by independent laboratories.
• Modbus standard RTU and optional DNP3.0 protocols, with time-stamp support, able to signal events such as: Alarms, Disconnections, Cooling on, etc., with a resolution of 1ms.
• Extended temperature measurement range, from -55 ºC to 200 ºC
• Temperature measurement inputs with self-calibration, guaranteeing high precision and stability throughout the ambient temperature range.
• Oil temperature redundant measurement, avoiding unavailability of the measurement in case of sensor Pt100 failure.
• Two optional inputs for Pt100 additional temperature sensors, for ambient, bottom oil, radiator temperatures or others.
• True-rms AC current measurement inputs for the connection of the CT secondary (0 to 10A) through an external spilt core CT clip-on, reducing the risk of accidental opening of the secondary and allowing installation without turning off the transformer.
• Alphanumeric high brightness LED displays for easy viewing;
• Calculation of the final gradient prediction of oil-winding temperature for the current load
• Local control of theAutomatic or Manual   cooling   via   front keypad   and   remote keyboard via communication port.
• Automatic interchange of the forced cooling groups, offering uniform use of the fans and pumps
• Pre-cooling function to increase the service life of the insulation under high loads.

It  expands  the  service  life  of  the  insulation  when  activating  the  cooling  groups  at  the moment when load levels that were previously selected by the user are reached. Using the great thermal inertia of the oil, forced cooling is turned on before the temperature increases too  much,  reducing  the  exposure  of  the  windings  to  high  temperatures  and  limiting insulation loss of service life. The user can program:

– Loading percentage to individually activate each step of the forced cooling.

– Hysteresis to turn off forced cooling steps when loading slows down.

• Cooling Exercise Function to prevent failure in fans and pumps

The Cooling or Fan Exercise function obviates lack of fan and/or pump activity for long periods of time, in low load transformers or during periods in which ambient temperature is low. This is done so the axles are not blocked due to build-up of dirt or dry grease. Cooling equipment is activated daily, by the internal clock as set up by the user.

– Hour and minute of the beginning of fan operation.

– Total daily fan operation time, from 0 to 999 minutes.

The  cooling  exercise  function  can  also  be  used  with  the  purpose  of  pre-cooling,  intransformers that are subject to cyclic loading, the cooling start-up can be programmed for any time before the daily load peak.

• Four programmableanalog  outputs  for  remote  indications  of  temperatures (e.g. remote indication of 4 variables),  with  selection  of  the variable and the output range in 0-1, 0-5, 0-10, 0-20 or 4-20mA
• Internal  clock  kept  for  48  hours  with  no  supply,  without  batteries,  making  the  TML  totally maintenance-free.
• Mass memory for over 10 months of measurements, alarms, disconnections and other events.Interval between recordings set by the user or the temperature variation for recording.
• Self-Diagnosis for the detection of internal failures or sensor and wiring problems.
• Total absence of mechanical parts for configuration and calibration.
• Output contacts sufficient to annunciate individual alarms as well astrips for each oil and winding temperature measured.
• Trip contacts with adjustable timing from 0 to 20 minutes, with countdown indication on the display and via serial communication ports.
• Output display showing a countdown for an activetrip.
• NC output contacts to actuate two forced cooling groups – safe cooling actuation in case of controller power failure, sensor failure or internal failure, triggered by the self-diagnostic function
• NC Output contact, to signal lack of power supply, sensor or wiring failure or internal failure detected by the self-diagnostics.
• Communication through a GPRS Cellular Modem inside the TML.

PT100Ω Temperature Sensor at 0ºC

Top oil temperature in power transformers is usually measured by a temperature sensor installed in a thermo-well on the transformer’s cover. The sensors used with the TML must be of the Pt100Ω kind at 0ºC. Pt100 sensorsare supplied to fit in thermo-wells (special sizes on demand). Contact us forenvironmental shelters for ambient temperature measurement and thermo-wells for installation.

External Clip-on CTs (Split Core)

The use of external clip-on CTs with a split core window allows the installation of the temperature monitors without directly connecting the bushing CT secondary to the TML, which eliminates the risk of accidentally opening the secondary and allows installation during transformer operation.

Outdoor cabinets

The TML Temperature Monitor must be installed in a weatherproof cubicle, usually inside the control panel of the transformer. When this is inconvenient, such as, for example, when old transformers are refurbished, the TML can be supplied in a weatherproof cabinet, for simple installation.