Md.Hamidul Haque ID: Prog:BSEEE SEC:E/3 International University of Business Agriculture and Technology (IUBAT )

Operation & Maintenance Of Power Transformer

AIM 1)Maintenance & Inspection of S/S Equipment's. 1)Introducing of Power Transformer Elements. 2)Maintenance of A Power Transformer. 3)Test of Insulating Oil. 4)Transformer Protection. 5)Testing of transformer.

General Equipments of S/S Isolator Earth Switch C.T./P.T. Lightening Arrester / Surge Diverter Switchgear / Breaker Power transformer Auxiliary Transformer Bus bar Battery and Battery Charger Control Relay Panel Remote Terminal Unit for SCADA

Maintenance & Inspection of S/S Equipments Maintenance of Substation Equipment Preventive and Schedule Maintenance Emergency or Break-down maintenance Inspection of Substation Equipment Daily Inspection Weekly Inspection Monthly Inspection Quarterly Inspection Half-yearly Inspection Annual Inspection

Power Transformer

Conservator Cooling fan Radiator HT Bushing Buchholz Relay Silica Gel LT Bushing Tap Changer

Operation of Power Transformer Operation of tap changer Operation of cooling control system Operation of breathing system

Maintenance of A Power Transformer Test oil sample of transformer main tank & tap changer tank Check condition of oil gauges and oil level Check for oil leakage & integrity of gasket joints Check the tightness of nuts & bolts Check the insulation resistance of bushing Check that silica gel crystals are blue Re-greasing of bearings of cooling fan Check the performance of oil temperature & winding temperature meter Change the oil of OLTC Check the control system and driving mechanism of OLTC Check insulation resistance between each winding and ground. Calculate the Dielectric Absorption Ratio-

Test of Insulating Oil Test/ParameterReference value Dielectric strength test: Minimum 30 kV at 2.5 mm gap between two gloves with minimum mm dia Acidity test: Acid value less than 0.02 mg KOH/g Measurement of moisture content in oil:50-60 ppm Gas analysis: Viscosity at 20°C : 40 cst Pour point maximum: -10°c Flash point: 140°c Dissipation factor or Power Factor/loss tan delta: at 90°c0.5% at 20°c 0.1% Volume resistivity : 5.7×10 14 Ω-cm Interfacial tension at 27°C:minimum 0.04 N/m Dielectric constant: 2 to 2.5

Protection of power system Requirement of protection: Normal operation Prevention of electrical failure Mitigation of the effects of electrical failure Protective device: Switchgear Fuse Functional characteristics of protective relaying Sensitivity, Selectivity and Speed Reliability

Transformer Protection Buchholz relay Differential relay Pressure relief relay Oil surge relay for OLTC Over fluctuation protection Directional over current High set over current Earth fault protection - Stand by earth fault - Restricted earth fault Thermal over heating protection a) Winding temperature b) Oil temperature

Transformer: Visual check Insulation resistance measurement Vector group test Measurement of winding resistance Ratio test of Bushing CT Magnetizing test of Bushing CT Polarity test of Bushing CT Dielectric test of oil Short circuit test Magnetic balance test Oil / winding temperature meter test Impedance test Testing of transformer

Summary 1)Study of the power transformer. 2)Knowledge based test of Insulating Oil. 3)We can familiar with protection of power system. 4)Basic operation of transformer.

Conclusion This topic is very need for electrical students because There have used each and every power transmission and distribution sector for maintenance or protection power system. For more information: www. power transformer And operation.

Thank you