PROTECTION OF POWER TRANSFORMER WITH RF

SIGNAL OR WITHOUT

WHAT IS POWER TRANSFORMER?

POWER TRANSFORMERS ARE TRANSFORMERS USED BETWEEN THE GENERATING STATIONS AND DISTRIBUTION NETWORK, AND ARE LARGER THAN 500 KVA IN SIZE.

POWER TRANSFORMERS USE A LAMINATED STEEL CORE WITH COPPER OR ALUMINUM WINDINGS.

USES OF POWER TRANSFORMER?USE AT GENERATING STATIONS FOR

STEPPING UP

USE AT SUBSTATIONS AT EACH END OF POWER TRANSMISSION LINE FOR STEPPING UP OR STEPPING DOWN THE VOLTAGE LEVEL.

PUT IN OPERATION DURING LOAD PERIODS AND DISCONNECTED DURING LIGHT PERIODS.

CAUSES OF OVERHEATING IN POWER TRANSFORMER?Overload Excessive loading can cause overheating. 

Transformers are rated in kVA.  This kVA rating is dependent on temperature. 

Excess current in the neutral of the transformer

Excess current in the neutral of the transformer is usually caused by high zero sequence harmonic components. 

Problems in the Cooling system Malfunctioning of the cooling equipment

such as blockages in the cooling oil circuit.• High Harmonic content in the power

supply High harmonic loads can also cause heating

in the transformer. • Sustained Overvoltages Overvoltages which exist for a long period of

time can overexcite the transformer and cause overheating.

CAUSES OF OVERHEATING OF POWER TRANSFORMERS?

PROTECTION METHODS FOR OVERHEATING

By using linear heat detector.Over-current relay.Differentional protection.

Overheat protection through RF signalPROTECTS COSTLY POWER TRANSFORMER USED IN

POWER DISTRIBUTION SYSTEMS FROM EXCESS HEATING DUE TO OVERLOADING AND OTHER CAUSES BY FOLLOWING

MEANS:

automatically trip/ off load.

Automatically starts cooling system.

Transmit warning signals to monitoring stations.

Maintain optimum temperature limit.

Starts warning alarms.

WORKING PRINCIPLE BASED ON THERMAL SENSOR LM 35

VOLTAGE COMPARATOR/ DIVIDER

THE LM35 SERIES ARE PRECISION INTEGRATED-CIRCUIT TEMPERATURE SENSORS, WHOSE OUTPUT VOLTAGE IS LINEARLY PROPORTIONAL TO THE CELSIUS (CENTIGRADE) TEMPERATURE.

 

FEATURES OF LM 35 Calibrated directly in ° Celsius (Centigrade) Linear + 10.0 mV/°C scale factor 0.5°C accuracy guaranteed (at +25°C) Rated for full −55° to +150°C range Suitable for remote applications Low cost due to wafer-level trimming Operates from 4 to 30 volts Less than 60 μA current drain Low self-heating, 0.08°C in still air Nonlinearity only ±1⁄4°C typical Low impedance output, 0.1 W for 1 mA load

Block Diagram

ADJUST THE TEMPERATURE MAXIMUM TOLERANCE LIMITS AT WHICH THERMAL SENSOR TRIGGER THE SYSTEM, WHICH FURTHER OPERATE VARIOUS CONTROLLING DEVICES FITTED ON POWER TRANSFORMER.

BY USING RF MODULE OF SUITABLE RANGE THE INFORMATION IS TRANSMITTED TO THE RECEIVING END AT REMOTE MONITORING STATION TO TAKE APPROPRIATE STEPS TO AVOID OVER HEATING CONDITION OF

TRANSFORMER QUICKLY TO AVOID HEAVY LOSS. IN THE GIVEN BLOCK DIAGRAM ,WHEN THE TEMPERATURE CROSSES

THE MAXIMUMTOLERANCE LIMIT, THE THERMAL SENSOR SENSE AND ANALOGUE VOLTAGE LEVELCONVERTER DETECT THE LEVEL OF TEMPERATURE, MONO STABLE MULTI VIBRATOR USED COMPRETER TO ENERISES THE RELAY WHICH GIVES SIGNALS TO ENCODER THEN RF TRANSMITTER TRANSMIT

INFORMATION WHICH IS RECEIVED BY RF RECEIVER, BY MATCHING CORRESPONDING DATA ADDRESS, IT ALSO TRIGGERS AUDIO VISUAL SIGNALS IN REMOTE MONITORING STATIONS.

COMPONENTS USED FOR DESIGNING 1) 5 V Regulated Power Supply.2) LM 35 Thermal Sensor.3) Voltage divider IC UM 3914.4) Transistor NPN, PNP.5) Capacitors : 1uf, 10uf, 100uf, 1000uf.6) Resistors : 1k, 10k, 47k, 220k.7) Diodes8) LED’s : Red, Green, Yellow.9) Relays.10) TX Module, RX Module .11) Encoder IC.12) Decoder IC.