Scribd is the world's largest social reading and publishing site. Whether you have a new or existing facility, the single-line diagram is the vital roadmap for all future testing. As such, the single-line diagram is like a balance sheet for. Each substation. Critical equipment voltage and size (UPS, battery, generator, power distribution, transfer switch, computer room air conditioning).

IR Value for Transformer Insulation resistance tests are made to determine insulation resistance from individual windings to ground or between individual windings. Insulation resistance tests are commonly measured directly in megohms or may be calculated from measurements of applied voltage and leakage current. The recommended practice in measuring insulation resistance is to always ground the tank (and the core). Short circuit each winding of the transformer at the bushing terminals. Resistance measurements are then made between each winding and all other windings grounded.

Insulation resistance testing: HV – Earth and HV – LV are never left floating for insulation resistance measurements. Solidly grounded winding must have the ground removed in order to measure the insulation resistance of the winding grounded. If the ground cannot be removed, as in the case of some windings with solidly grounded neutrals, the insulation resistance of the winding cannot be measured. Treat it as part of the grounded section of the circuit. We need to test winding to winding and winding to ground ( E ).For three phase transformers, We need to test winding ( L1,L2,L3 ) with substitute Earthing for Delta transformer or winding ( L1,L2,L3 ) with earthing ( E ) and neutral ( N ) for wye transformers. IR Value for Transformer (Ref: A Guide to Transformer Maintenance.

S.D Myer) Transformer Formula 1 Phase Transformer IR Value (MΩ) = C X E / (√KVA) 3 Phase Transformer (Star) IR Value (MΩ) = C X E (P-n) / (√KVA) 3 Phase Transformer (Delta) IR Value (MΩ) = C X E (P-P) / (√KVA) Where C= 1.5 for Oil filled T/C with Oil Tank, 30 for Oil filled T/C without Oil Tank or Dry Type T/C. Steps for measuring the IR of Transformer: • Shut down the transformer and disconnect the jumpers and. • Discharge the winding capacitance. • Thoroughly clean all bushings • Short circuit the windings.

• Guard the terminals to eliminate surface leakage over terminal bushings. • Record the temperature. • Connect the test leads (avoid joints). • Apply the test voltage and note the reading. Value at 60 seconds after application of the test voltage is referred to as the Insulation Resistance of the transformer at the test temperature. • The transformer Neutral bushing is to be disconnected from earth during the test.

• All LV surge diverter earth connections are to be disconnected during the test. • Due to the inductive characteristics of transformers, the insulation resistance reading shall not be taken until the test current stabilizes.

• Avoid meggering when the transformer is under vacuum. Spore Torrent Pc Crackling. Test Connections of Transformer for IR Test (Not Less than 200 MΩ) Two winding transformer 1. (HV + LV) – GND 2.

HV – (LV + GND) 3. LV – (HV + GND) Three winding transformer 1. HV – (LV + TV + GND) 2. LV – (HV + TV + GND) 3. (HV + LV + TV) – GND 4. TV – (HV + LV + GND) Auto transformer (two windings) 1. (HV + LV) – GND Auto Transformer (three winding) 1.

(HV + LV) – (TV + GND) 2. (HV + LV + TV) – GND 3. TV – (HV + LV + GND) For any installation, the insulation resistance measured shall not be less than: • HV – Earth 200 M Ω • LV – Earth 100 M Ω • HV – LV 200 M Ω Factors affecting on IR value of Transformer The IR value of transformers are influenced by • Surface condition of the terminal bushing • Quality of oil • Quality of winding insulation • Temperature of oil • Duration of application and value of test voltage. IR Value for Electric motor For, we used a insulation tester to measure the resistance of motor winding with earthing (E). • For rated voltage below 1KV, measured with a 500VDC Megger. • For rated voltage above 1KV, measured with a 1000VDC Megger.

• In accordance with IEEE 43, clause 9.3, the following formula should be applied. • Min IR Value (For Rotating Machine) =(Rated voltage (v) /1000) + 1 Insulation resistance (IR) value for electric motor As per IEEE 43 Standard 1974, 2000 IR Value in MΩ IR (Min) = kV+1 For most windings made before about 1970, all field windings, and others not described below IR (Min) = 100 MΩ For most dc armature and ac windings built after about 1970 (form wound coils) IR (Min) = 5 MΩ For most machines with random -wound stator coils and form-wound coils rated below 1kV Example-1: For 11KV, Three Phase Motor. • IR Value =11+1=12 MΩ but as per IEEE43 It should be 100 MΩ • Example-2: For 415V,Three Phase Motor • IR Value =0.415+1=1. Serial Number Phone Clean Pro Torrent. 41 MΩ but as per IEEE43 It should be 5 MΩ. • As per IS 732 Min IR Value of Motor=(20XVoltage(p-p/(1000+2XKW).