Typical Limiting Values of Substation Equipment.

TYPICAL LIMITING VALUES OF SUBSTATION EQUIPMENTS.

TYPICAL LIMITING VALUES OF SUB STATION ELECTRICAL EQUIPMENTS.

TRANSFORMER / REACTOR:

Sr. No. Equipment / test data Permissible limits Reference A) Transformer oil a) BDV -At the time of first charging 600 kV (Gap – 2.5 mm) – Minimum IS – 1866 -During O&M 50 kV (Gap – 2.5 mm) – Minimum IS – 1867 b) Moisture content IS – 1868 -At the time of first charging 15 PPM (Max.) IS – 1869 -During O&M 25 PPM (Max.) IS – 1870 c) Resistivity at 90 degree C 0.1-1012 Ohm-CM (Min.) IS – 1871 d) Acidity 0.2 mg KOH/gm (Max.) IS – 1872 e) IFT at 27 degree C 0.018 N/M (Min.) IS – 1873 f) Tan delta at 90 degree C 0.20 (Max.) IS – 1874 g) Flash point 126 Deg. C (Min.) IS – 1875 B) Vibration level for reactors 200 Microns (Peak to Peak) IS – 1876 60 Microns (Average) IS – 1877 C) Tan delta for bushing at 20 Deg. C 0.007* IEC – 137 D) Capacitance for bushing + 5% variation IEC – 138 E) IR value for winding 1000 M-Ohm By 5.0/10.0 kV Megger IEC – 139 F) Tan delta for windings at 20 Deg. C 0.007* IEEE/C57.12.90.1980 G) Contact resistance of bushing terminal connectors 10 M. Ohm / Connector NGC.UK Recommendations H) Turret Neutral CT ratio errors 39 IS – 2705

2. CIRCUIT BREAKERS

Sr. No. Equipment / test data Permissible limits Reference A) Dew point of SF6 gas Dew point values as per Annexure – II B) Dew point of operating air -45 Deg. C at ATM. Pressure C) CB Operating timings 400 kV 220KV a) Closing time (Max.) 150 MS 200MS b) Trip time (Max.) 25 MS 35MS c) Close/trip time, Pole discrepancy – Phase to Phase (Max.) 3.33 MS 3.33MS -Break to break (Max.) of same phase 2.5 MS 2.5MS D) PIR time BHEL make 12-16 MS Manufacturers Recommendations ABB make 8-12 MS Manufacturers Recommendations NGEF make 8-12 MS Manufacturers Recommendations M&G make 8-12 MS Manufacturers Recommendations TELK make 8-12 MS Manufacturers Recommendations ABB make (HVDC) 8-12 MS Manufacturers Recommendations E) PIR opening time prior to opening of main contacts (ABB, CGL, NGEF make CBs) 5 MS (Min.) at rated pressure Manufacturers Recommendations F) Pir and main contacts overlap time [BHEL, M&G, ABB (imported) make CBs] 6 MS (Min.) at rated pressure Manufacturers Recommendations G) Tan delta of grading capacitors 0.007 at 20 Deg. C H) Capacitance of grading capacitors Within + 10% / -5% of the rated value IEC 359 I) Contact resistance of CB 150 M. Ohm J) Contact resistance of CB terminal connector 10 M. Ohm per connector NGC, UK recommendations K) IR value: 1. Phase – earth 1000 M Ohm (Min.) by 5.0 / 10.0 kV Megger 2. Across open contacts 1000 M Ohm (Min.) by 5.0/10.0 kV Megger 3. Control cables 50 M Ohm (Min.) by 0.5 kV Megger L) Pressure switch settings -SF6 gas pressure switches Within + 0.1 Bar of set value -Operating air pr. Switches Within + 0.1 Bar of set value -Operating oil pr. Switches Within + 0.1 Bar of set value M) BDV of oil used for MOCB -At the time of filling 40 kV at 2.5 mm Gap (Min.) Mfgs. Recommendation -During O&M 20 kV at 2.5 mm Gap. (Min.) Mfgs. Recommendation

3. CURRENT TRANSFORMER

Sr. No. Equipment / test data Permissible limits Reference A) IR value 1. Primary – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger 2. Secondary – earth 50 M – Ohm (Min.) by 0.5 kV Megger 3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger B) Tan delta value 0.007* at 20 Deg. C C) Terminal Connector 10 M-Ohm per connector NGC, UK Recommendations D) CT ratio errors + 3% -Protection cores IS – 2705 D) CT ratio errors + 1% -Metering cores IS – 2706

4. CAPACITIVE VOLTAGE

Sr. No. Equipment / test data Permissible limits Reference A) Tan Delta 0.007* at 20 Deg. C B) Capacitance Within +10%/-5% of the rated value IEC – 358 C Contact resistance of terminal connector 10 M-Ohm per connector NGC, UK Recommendations D) IR Value IR Value 1. Primary – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger 2. Secondary – earth 50 M – Ohm (Min.) by 0.5 kV Megger 3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger E) EMU tank oil parameters EMU tank oil parameters a) BDV (Min.) 30 kV (Gap. –2.5 mm) IS – 1866 b) Moisture content (Max.) 35 ppm -do- c) Resistivity at 90 Deg. C 0.1 – 1012 Ohm. – CM -do- d) Acidity 0.5 mg kOH /gm (Max.) -do- e) IFT at 27 Deg. C 0.018 N/M (Min.) -do- f) Tan delta at 90 Deg. C 1.0 Max. -do- g) Flash point 125 Deg. C (Min.) -do- F) CVT voltage ratio errors + 5% protection cores IEEE/C93.1.1990 F) CVT voltage ratio errors + 0.5% metering cores IEC 186

5. ISOLATORS

Sr. No. Equipment / test data Permissible limits Reference A) Contact resistance 300 M-Ohm. (Max.) B) Contact resistance of terminal connector 10 M – Ohm per connector NGC, UK Recommendations C) IR value 1. Phase – earth 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger NGC, UK Recommendations 2. Across open contacts 1000 M – Ohm (Min.) by 5.0/10.0 kV Megger NGC, UK Recommendations 3. Control cables 50 M-Ohm (Min.) by 0.5 kV Megger

6. SURGE ARR…