NATIONAL TRANSMISSION & DESPATCH COMPANY ...ntdc.gov.pk/ntdc/public/uploads/downloads/Publications... · Web view8.1) Commissioning of lines should start when construction forces

SOP CHECK SHEET: MAINTENANCE SCHEDULE AND CHECKS/TESTS OF TRANSMISSION LINESDescription of Inspection and Maintenance Work

Specified Time Period Remarks/Criteria/Standard/Safety PrecautionsD/W M3/6 Y1 Y5/10

1. Visual inspection (A walk around visual inspection from ground level and keeping in view the safe limits of approach to live and moving parts to check apparent condition, abnormal noise, rust on body of the equipment and component parts, etc.)

Yes - - - Wear PPE and carry basic line man tools, earth resistance test set, binocular, etc. Make entries of the observations in check sheets/note book.

2. Foot Patrolling Inspection (Mechanical Defects such as missing/loose braces, Condition of Jumper Terminal Pad, Missing Split Pins, and Other Problem Areas such as Cultivated and Jungle Growth, Effects of Polluted Areas/Deserts,)

- Yes - - Should be OK and no defects (foot patrolling should be done twice a year on all lines)

3. Climbing Inspection (General Problems, Evaluation of Condition of Line). Dead Line or Live Line

- - Yes - Should be OK and no defect (Climbing inspection should be done once a year on all towers)

4. Conductor Condition (Loose Strands, Broken Strands, Dislocated Spacers, Vibration Dampers, etc.)

Should be OK, intact and secured

5. Overhead Shield Wire/Earthing Conductor (Loose Strands, Broken Strands, Dead end/suspension clamps, OPGW Splicing Box Condition, etc.)

Should be OK, intact and secured

6. Structure Marking (Faded and Obsolete Signs: Numbering, Danger Plates, Phase Marking, etc.)

- Yes - - Should be OK intact as per design (Replace or repair as required)

7. Insulator Testing (Insulator String) (Mandatory Before Live

- Yes - - Should be OK and intact (Replace failed insulator)

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Line Work)8. Insulator Washing and Greasing (before Foggy Season

- Yes - - Should be OK and no defects (insulator washing should be done twice a year on all lines in polluted areas)

9. Thermovision Survey - - Yes - Should be OK and no hotspot/s (thermovision survey should be done twice a year on all lines)

10. Vibration Studies - - - Yes Should be OK and no defect (Vibration studies should be done twice a year on all lines)

TOWER11. Footings Soil: Eroded, Back filling, De-watering of saline/rainy area, etc.

Yes - - - Should be OK and intact and secured

12. Footings Concrete: Chipped, Cracked, Broken, etc.

Yes - - - Should be OK and intact and secured

13. Base Structure: Loose/Missing Braces and Missing Nut/Bolts, etc.

- Yes - - Should be OK and intact and secured

14. Counter Poise - Yes - - Should be OK and intact and secured

15. Steel Braces/Joint Plates: Bent, Rusted, Broken, etc.

- - Yes - Should be OK and no damage

16. Tower Members: Twisted, Broken, Rusted, Pitted

- - Yes - Should be OK and no damage and no missing hardware

17. Step Pins/Bolts: Loose, Missing, Rusted, etc.

Yes - - - Should be OK and intact, no damage and no missing hardware

18. Bolts: Loose, Missing, Rusted

- - - Yes Should be OK and intact, no damage, and no missing hardware

19. Galvanizing/Paint: Peeled, Pitted, etc.

- - - Yes Should be OK and intact

20. Danger Plates/ Phase Plates/Signs: Worn, Damaged, Missing, etc.

Yes - - - Should be OK and intact

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8. TRANSMISSION LINE TECHNICAL DIRECTIVE

Basic Maintenance Program of Transmission Lines

SCOPEThis directive provides for the basic minimum requirements to keep lines in an acceptable and reliable condition. Maintenance is discussed under the following headings:1) Foot Patrol 2) Climbing Inspection/Maintenance 3) Structure marking4) Insulator Testing5) Insulator Washing & Greasing6) Thermovision Survey7) Vibration Studies8) Commissioning9) Condition Survey

1) FOOT PATROL Foot Patrol should be done twice a year on all transmission lines. This should identify most mechanical defects and point out problem areas that require further attention.A report from the field on Form LMS- 1 & LMS-2 (copy attached) is required by TSG for evaluation.

2) CLIMBING INSPECTION/MAINTENANCE

2.1) This program is used to evaluate the condition of a line. A report from the field on Form LMS-3 & 4 is required by TSG for evaluation. It should identify general problems, if any, which would lead to a rehabilitation program if cost justified.

2.2) A ten year cycle is required for all transmission lines. 10% of each line will be inspected each year. If many serious defects are found on a line a more frequent cycle for those lines should be discussed with TSG (N5P0015).

2.3) Climbing maintenance should be scheduled as follows:

Divide the line into several sections (each section may contain 10 towers) and then arrange to inspect 10% of each section every year. This will then sample the whole line every year.

2.4) Minor defects should be repaired during the inspection. Spare Material should

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be available on the job. site for these repairs.

2.5) Climbing maintenance can be performed deadline or live line depending on circuit availability.

3) STRUCTURE MARKING

Faded and obsolete marking signs shall be replaced / repainted as required.

4) INSULATOR TESTING

4.1) It is required to test insulators on a string prior to performing live line work on or near an insulator string.*(N5P008 & N5P0013)

4.2) Testing insulators on 10 to 20% of a line will point out manufacturer defects as well as electrical in service defects. This program should be considered if a variety of insulator failures occur on a line.

5) INSULATOR WASHING/GREASING

In locations where there is a buildup of atmospheric pollutants, insulators shall be washed or greased at a frequency such that flashovers are prevented.

The frequency will be determined by experience and/or testing of samples *(Old No. TSG/TL-008)

6) THERMOVISION SURVEY

6.1) T his program identifies potential connection failures such as hot sleeves, pads and bolted connections which may burn-down the conductors.

6.2) Thermovision can be done from the air or the ground. For transmission lines a helicopter is highly desirable. At terminal towers or in built up areas a truck may he required.

6.3) Normally, the thermovision is done at the time when there is maximum load on line and each line is completed on a yearly cycle. (Thermovision check Form LMS-6)

7) VIBRATION STUDIES

7.1) Vibration studies on transmission lines should be done using the following order of preference.a) Lines having broken strands at suspension clamps.

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b) Lines with no dampers.c) Lines that have wire dampers.d) Lines that have one damper per spane) Lines that have two dampers per span.

7.2) GS0 should identify the lines that should be studied and set up a program in consultation with TSG.

8) COMMISSIONING

8.1) Commissioning of lines should start when construction forces begins to erect structures on new lines. On rehabilitation work, start the commissioning when the field work begins.

8.2) Commissioning is required to insure that the line is constructed to specifications and to acceptable standards.

8.3) For lines 100km in length one man can usually do most of the work except for tower bolt checking and verification.

8.4) Sag checks must be made separately from GSC, at the time of sagging the conductors.

8.5) Check 20% of the towers and all dead-end towers for proper bolt torque. 20% of tower bolts on these towers should be verified for tightness, using a torque wrench.

8.6) Suspension clamp, dampers and dead-end conductor hardware are to be checked on the towers identified for commissioning.

9) CONDITION SURVEY

9.1) Condition survey is done on as and when as required basis.

9.2) Normally a survey is required to verify conductor to ground clearances as well, as for allowable heights of proposed under builds such as distribution facilities. This may also be used to determine maximum loading due to sags on the transmission line.

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9. REFERENCE DATA FOR COMPARISON WITH THE TEST RESULTS

Reference data and previous record is one of the important pre-requisite for an effective operation and maintenance program. For evaluation of different test results and to take decisions on the bases of these test results one must need some reference values and the permissible limits. Such reference data may be the factory test results or commissioning test results or the accepted test results of similar make/type/model equipment or the recommendations of certain reputed standards/specification. In this section, the most commonly applicable data has been compiled as a ready reference for the user of this SOP. This data has been collected from all the possible sources, however supply of new or more data along with feedback comments will be welcomed.

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Table-9a: CHARACTERISTICS OF UNUSED UNINHIBITED MINERAL INSULATING OIL: IEC 296 (Old Specifications)

CHARACTERISTICS OF UNUSED UNINHIBITED MINERAL INSULATING OIL: IEC 296 (Old Specifications)Sr. No.

Property Permissible Values for Measured CharacteristicsClass-I Class-II Class-III

1 Appearance Clear, free from sediments and suspended matter

Clear, free from sediments and suspended matter


2 Density kg/dm3 at 20 °C (old Specific Gravity)

≤0.895 ≤0.895 ≤0.895

3 Interfacial Tension/Surface Tension at 25 °C (mN/m) or (N/m x 10-

3)

≥40 ≥40 ≥40

4a Kinematic Viscosity mm2/s at 40 °C (Centistokes)

≤ 16.5 ≤ 11 ≤ 3.5

4b Kinematic Viscosity mm2/s at 20 °C (Centistokes)

≤ 40 ≤ 25 ≤ 6

4c Kinematic Viscosity mm2/s at -15 °C (Centistokes)

≤ 800 - -

4d Kinematic Viscosity mm2/s at -30 °C (Centistokes)

- ≤ 1800 -

4e Kinematic Viscosity mm2/s at -40 °C (Centistokes)

- - ≤ 150

5 Pour Point °C ≤ -30 ≤ -45 ≤ -606 Flash Point °C ≥ 140 ≥ 130 ≥ 957 Neutralization Value/

Acidity (mg KOH/g)≤ 0.03 ≤ 0.03 ≤ 0.03

7

8 Water Content mg/kg (ppm)

Max. 30ppm (mg/kg) for bulk supply or 40ppm (mg/kg) for delivery in drums and IBC



9 Break Down DES(kV at 2.5 mm gap)

≥ 30 as delivered and ≥ 50 after treatment



3 Tan δ / Dielectric Dissipation Factor-DDF (at 40 to 60 Hz & 90 °C)

≤0.005 ≤0.005 ≤0.005

11 Oxidation Stability Neutralization Value(mg KOH/g)

≤0.40* see note

≤0.40* see note

≤0.40* see note

12 Oxidation StabilitySludge % by mass

≤0.10* see note

≤0.10* see note

≤0.10* see note

13 Corrosive Sulfur Non corrosive Non corrosive Non corrosive14 Anti-oxidant

AdditivesNot detectable Not detectable Not detectable

* Note. The determinations on the oxidized oil are limited to the neutralization value and to the sludge however, in certain countries it is usual to determine also the DDF. In this case the maximum value of DDF will be established by agreement between purchaser and supplier.

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Table-9b: CHARACTERISTICS OF UNUSED INHIBITED MINERAL INSULATING OIL: IEC 296 (Old Specifications)

CHARACTERISTICS OF UNUSED INHIBITED MINERAL INSULATING OIL: IEC 296 (Old Specifications)Sr. No.

Property Permissible Limiting Values for Measured CharacteristicsClass-IA Class-IIA Class-IIIA




2 Density kg/dm3 at 20 °C (old Specific Gravity)

≤0.895 ≤0.895 ≤0.895

3 Interfacial Tension/Surface Tension at 25 °C (mN/m) or (N/m x 10-3)

≥40 ≥40 ≥40


≤ 16.5 ≤ 11 ≤ 3.5


≤ 40 ≤ 25 ≤ 6


≤ 800 - -


- ≤ 1800 -


- - ≤ 150

5 Pour Point °C ≤ -30 ≤ -45 ≤ -606 Flash Point °C ≥ 140 ≥ 130 ≥ 95

9

7 Neutralization Value/ Acidity (mg KOH/g)

≤ 0.03 ≤ 0.03 ≤ 0.03










≤0.005 ≤0.005 ≤0.005

11 Oxidation Stability * see note * see note * see note12 Corrosive Sulfur Non corrosive Non corrosive Non corrosive13 Anti-oxidant

Additives: Contents at least 0.15% by mass, but not more than 0.40% by mass of (DBPC: 2.6-di-tert-butyl-paracresole) or (DBP: 2.6-di-tert-butyl-phenol)

As agreed between purchaser and supplier



* Note. In the case of inhibited oils only the induction period is determined however in certain countries it is usual to determine also the DDF. In this case the maximum value of DDF will be established by agreement between purchaser and supplier. No limit for oxidation stability is specified. For guidance only. Oils known to give satisfactory performance in transformers in service typically have induction period in excess of 120 hours.

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Table-9c: CHARACTERISTICS OF UNUSED MINERAL INSULATING OILS FILLED IN NEW TRANSFORMERS: IEC 60422

CHARACTERISTICS OF UNUSED MINERAL INSULATING OILS FILLED IN NEW TRANSFORMERS: IEC 60422Sr. No.

Property Highest Voltage for Equipment<72.5Kv 170kV >170Kv




2 Colour Max 20 Max 20 Max 203 Density kg/dm3 at 20 °C

(old Specific Gravity)≤0.895 ≤0.895 ≤0.895

4 Interfacial Tension/Surface Tension (mN/m at 25 °C)

≥35 ≥35 ≥35


≤ 16.5 ≤ 11 ≤ 3.5


≤ 40 ≤ 25 ≤ 6


≤ 800 - -


- ≤ 1800 -


- - ≤ 150

6 Pour Point °C ≤ -30 ≤ -45 ≤ -607 Flash Point °C ≥ 140 ≥ 130 ≥ 958 Neutralization Value/

Acidity (mg KOH/g)≤ 0.03 ≤ 0.03 ≤ 0.03


≤ 20 ≤ 15 ≤ 10

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≥ 40 ≥ 50 ≥ 60

11 Resistivity at 90 °C (GΩm)

min 60 min 60 min 60


≤0.15* see note

≤0.15* see note

≤0.010* see note

13 Oxidation Stability for Uninhibited Oil- Neutralization Value(mg KOH/g)

≤0.40 ≤0.40 ≤0.40

13a Oxidation Stability for Uninhibited Oil-Sludge % by mass

≤0.10 ≤0.10 ≤0.10

14 Oxidation Stability for Inhibited Oil- Induction period (hours)

Similar value as before filling



*Note. Higher DDF value may indicate excessive contamination or the misapplication of solid insulation used in manufacturing and should be investigated.

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Table-9d: CHARACTERISTICS OF UNSUED MINERAL INSULATING OILS FOR TRANSFORMERS AND SWITCHGEAR IEC 60296 (New specifications)

CHARACTERISTICS OF UNSUED MINERAL INSULATING OILS FOR TRANSFORMERS AND SWITCHGEAR IEC 60296Sr. No.

Property Unused Mineral Insulating OilIEC 60296

LowTemperature Switchgear Oil

Function1 Viscosity at 40 °C Max. 12mm2 /s Max. 3.5mm2 /s2 Viscosity at -30 °C *see note Max. 1800mm2 /s -3 Viscosity at -40 °C*see note - Max. 400mm2 /s4 Pour Point*see note Max. -40 °C Max. -60 °C5 Water Content Max. 30ppm

(mg/kg) for bulk supply or 40ppm (mg/kg) for delivery in drums and IBC


6 Breakdown Voltage or DES at 2.5 mm Gap

Min. 30 kV before dehydration or 70 kV after dehydration

Min. 30 kV before dehydration or 70 kV after dehydration

7 Density at 20 °C (old S.G) Max. 0.895 g/ml Max. 0.895 g/ml8 DDF at 90 °C (old Tan δ or DF) Max. 0.005 (0.5%) Max. 0.005 (0.5%)Refining/Stability1 Appearance Clear, free from

sediments and suspended matter


2 Acidity Max. 0.01mg KOH/g

Max. 0.01mg KOH/g

3 Interfacial Tension (IFT) Min. 40 mN/m Min. 40 mN/m4 Total Sulfur Content No general

requirementNo general requirement

5 Corrosive Sulfur No general requirement

No general requirement

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6 Antioxidant Additive Uninhibited oil (U): Not detectableTrace inhibited oil (T): Max. 0.08%Inhibited oil (I): 0.08 – 0.40%

Uninhibited oil (U): Not detectableTrace inhibited oil (T): Max. 0.08%Inhibited oil (I): 0.08 – 0.40%

7 Furfural Content **see note Max. 0.1 mg/kg Max. 0.1 mg/kgPerformance1 Oxidation Stability2 Total Acidity Max. 1.2mg

KOH/gMax. 1.2mg KOH/g

3 Sludge Max. 0.8% Max. 0.8%4 DDF at 90 °C (Dielectric

Dissipation Factor) (Tan δ)Max. 0.500 Max. 0.500

5 Gassing No general requirement

No general requirement

6 Electrostatic Charging Tendency (ECT) ***see note

Special requirement

-

Health, Safety and Environment (HSE)1 Flash Point Min. 135 °C Min. 100 °C2 PCA Content (Polycyclic

aromatics)Max. 3% Max. 3%

3 PCB Content (Polychlorinated biphenyls)

Not detectable Not detectable

* Note. This is the standard LCSET (Lowest Cold Start Energizing Temperature) for transformer oil and can be modified depending upon the climatic condition of each country. Pour point should be minimum 10K below LCSET.

** Note. Furfural and related compounds (2-FAL) in unused mineral insulating oils can result either from improper re-distillation after solvent extraction during refining or from contamination with used oil. Unused insulating oils should have a low level of 2-FAL and related compounds (IEC 1198).

*** Note. Electrostatic Charging Tendency (ECT) of oil is an important property for certain designs of HV and EHV transformers which have oil pumping rates that can give rise to the build-up of electrostatic charge. This charge can result in energy discharge causing transformer failure. A method to measure ECT is proposed by CIGRE SC 12.

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Table-9e: CONCENTRATION OF DISSOLVED GASES (DGA) IN OIL (IEC 60567 &60599)

CONCENTRATION OF DISSOLVED GASES (DGA) IN OIL (IEC 60567 &60599)Sr. No.

Gas Description Limiting Value (ppm v/v)

Limiting ValuesPTESU Standard (ppm)

1 Hydrogen (H2) <200 <1502 Methane (CH4) <50 <253 Ethane(C2H6) <15 <104 Acetylene (C2H2) <15 <155 Ethylene (C2H4) <60 <206 Carbon Mono oxide (CO) <1000 <5007 Carbon Dioxide (CO2) <11000 <100008 Oxygen (O2) 2000-350009 Nitrogen (N2) 10000-100000

General criteria for interpretation on the bases of flame colour of combustible gases detected in Buchholz Relay is as:

- If flame colour is Blue, it indicates decomposition of oil.

- If flame colour is Yellow, it indicates deterioration of solid insulation.

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Table-9f: TREATMENT OF INSULATING OIL IN TRANSFORMERS

TREATMENT OF INSULATING OIL IN TRANSFORMERS RECOMMENDED REMEDIAL MEASURESCharacteristic Description

Recommended Measures

Lower DES Value Dehydration and FiltrationHigh Water/Moisture Contents

Dehydration and Filtration under Vacuum

High DDF (Tan δ) Dehydration and Filtration under Vacuum OR Regeneration/Reclamation/Replacement

Neutralization Value Regeneration/Reclamation/ReplacementInterfacial Tension Regeneration/Reclamation/Replacement

Essential Functions of Oil- Dielectric Insulation- Heat Transfer

Principal Causes of adverse changes in dielectric properties of Oil

- Oxygen and Humidity: Main source is the breathing system and oil leak points. The desiccating material should be regenerated or renewed as soon as 1/3rd of its quantity has been moisturized (colour changed from blue to pink). Attend oil leakages without intentional delays.

- High Temperatures

- External pollution

- Electrical phenomena

- Partial discharges

- Corona

Table- 9g: CHARACTERISTICS OF SULPHUR HEXAFLOURIDE GAS (S) IEC 60376

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CHARACTERISTICS OF SULPHUR HEXAFLOURIDE GAS (SF6) IEC 60376Sr. No.

Description Limiting Value(New/Unused Gas)

Limiting Value(Gas in CB)

1 Purity (concentration of SF6

verses Nitrogen)> 99.9% > 95%

2 Dew Point (-°C) -50°C -10°C3 Impurities3a CF4 (Carbon Tetra-fluoride) < 0.05% (m/m)3b Oxygen + Nitrogen, air < 0.05% (m/m)3c Water < 15ppm (m/m)3d Acidity expressed as HF

(Hydrofluoric acid)< 0.03ppm (m/m)

3e Hydrolysable fluoride expressed as HF

< 1.0ppm (m/m)

3f Oil content < 10ppm (m/m)

Properties-Sulphur Hexafluoride is a compound having the formula SF6

-At normal room temperatures and pressures it is gaseous- It has density of 6.16g/l at 20 °C and 760 torr (about five times the density of air)- Its critical temperature 45.6 °C, it can be liquefied by compression and is normally transported as a liquid in cylinders- Inert- Colourless- Odourless- Nontoxic- Nonflammable- Good dielectric medium- Electro-negative (tends to attract the free electrons), good arc quenching medium)- High DES value, (about 3 times of the air at atmospheric pressure)- Heat transfer capability 2-5 times of air- Pressure increases with temperature by about 0.025 bar per °C- Leakage detection possible with halogen gases leakage detectors

Preferred sizes of cylinders

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-The standard sizes of cylinders, expressed in liters (l) for SF6 are: 3, 5, 10, 20, 40, 80, 150 and 500. 10 liter and 40 liter are the preferred size for use. The filling ratio of cylinders in temperate countries is 1.04kg/l and in tropical countries is 0.75kg/l.

Table-9h: 500KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE DATA

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500KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE VALUES (H: Hydraulic, S: Motor Spring, P: Pneumatic Operating Mechanisms)Sr. No.

Make Type Closing Time (ms)(Maximum)

Opening Time (ms)(Maximum)

Contact Resistance micro Ω per Pole(Maximum)

1 SIEMENS (H) SF6 3AT5 (4 Breaks per Pole)

90±10 18±3 240

2 SIEMENS (H) SF6 3AT4 (4 Breaks per Pole)

90±10 18±3 240

3 SIEMENS (H) SF6 3AT3E1 (2 Breaks per Pole)

80±6 18±2 75±5

4 SIEMENS (H) SF6 3AT2E1 (2 Breaks per Pole)

80±6 18±2 75±5

5 SIEMENS (H) SF6

(GIS)8DQ14 (2 Breaks per Pole)

80±6 18±2 75±5

6 MERLIN GERIN (H) SF6

FA4 (4 Breaks per Pole)

42±4 19±4 250


FA4R (4 Breaks per Pole)

42±4 19±4 250


GFA2R (4 Breaks per Pole)

42±4 19±4 250


GFA4R (4 Breaks per Pole)

42±4 19±4 250

10 TOSHIBA (H) SF6 GSR-500R2

100 18 100

11 TOSHIBA (H) SF6 GSR-500R2C

100 18 100

19

12 HITACHI (H) SF6 OFTB 500/40L

13 GEC ALSTHOM (H) SF6

FX32D

14 GEC ALSTHOM (H) SF6

FX22Z

15 MITSUBISHI (P) SF6

500 SFMT/50B

16 ABB (S) SF6 HPL 550 B2 (4 Breaks per Pole)

65 19±3 80

17 AEG (P) SF6 S4M-550P 100 25 20018 AREVA(S) SF6 GL317D

(FK3-4)19 ASEA (S) SF6 HPL 550/

4004LT20 DELLE

ALSTHOM (ABCB)

PK6C 450

Table-9i: 220KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE DATA

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220KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE VALUE (H: Hydraulic, S: Motor Spring, P: Pneumatic Operating Mechanisms)Sr. No.




1 SIEMENS (H) SF6 3AQ1E1 (1 Break per Pole)

95±5 39±3 60

2 SIEMENS (S) SF6 3AP2F1 (2 Breaks per Pole)

63±6 18±2 54±5

3 SIEMENS (S) SF6 3APF1 (1 Break per Pole)

62±6 37±4 40

4 SPRECHER ENERGIE (S) SF6

HGF-100/1A (1 Break per Pole) FKF 1-2

150 28 50


FA2 (2 Breaks per Pole)

100 30 170


FA2R (2 Breaks per Pole)

100 30 170


FA1 (1 Break per Pole)

100 30 170

8 CHINA (H) OCB SW6-245 (2 Breaks per Pole)

200 40 400

9 NMG (P) SF6 245-MHM-e-1P (1 Break per Pole)

100 30 50

10 BBC (P) SF6 ELVF-245 110 20 100

21

nc2at (2 Breaks per Pole)

11 ABB (H) SF6 ELF SP4-1 (1 Break per Pole)

55 18 60

12 ABB (S) SF6 LTB-245E1 (2 Breaks per Pole)

63±6 18±2 54±5

13 ABB (S) SF6 HPL 245/31B1 (2 Breaks per Pole)

63±6 18±2 54±5

14 ABB (S) SF6 HPL 245/3152 (2 Breaks per Pole)

63±6 18±2 54±5

15 AEG (S) SF6 S1-245/F3 (2 Breaks per Pole)

63±6 18±2 54±5

16 AEG (P) SF6 S1-245 (1 Break per Pole)

63±6 18±2 54±5

17 ALSTHOM (S) SF6

GL-314 (1 Break per Pole) FK3-1

82-102 16-26 50

18 NMG/VATECH (S) SF6

SB6m-245 (1 Break per Pole)

75±5 30±3 40±5

19 CHEM China (S) SF6

OFPI-252-50L, FAR (1 Break per Pole)

≤ 80 ≤ 30 ≤ 30

Table-9j: 132KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE DATA

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132KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE VALUE (H: Hydraulic, S: Motor Spring, P: Pneumatic Operating Mechanisms)Sr. No.




1 SIEMENS (H) SF6

3ARI (1 Break per Pole)

100±5 50±5 60

2 SIEMENS (H) SF6

3AQI (1 Break per Pole)

95±5 39±3 60

3 SIEMENS (S) SF6

3API FG (1 Break per Pole)

57±6 31±3 40

4 ENERGOINVEST (P) SF6

SFE-13 (1 Break per Pole)

130 35 60

5 S&S (S) SF6 HGF-112/1C (1 Break per Pole) FKF2-6

140 25 60

6 AEG (P) SF6 S1-145 (1 Break per Pole)

100 40 60

7 AEG (S) SF6 S1-145 F1/3131/SE (1 Break per Pole) CRR-5

100 40 60

8 AEG (S) SF6 S1-145 F1/4031/SE (1 Break per Pole) CRR-5

100 40 60

9 ASEA (S) SF6 HPL-145/25 A1 (1 Break per Pole) BLG 1002

90 21±2 50

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10 ABB (S) SF6 HPL-145/25 A1 (1 Break per Pole) BLG 1002

90 21±2 50

11 ABB (S) SF6 HPL-145/25 A1 (1 Break per Pole) BLG 1002A

90 21±2 50

12 NMG (S) SF6 1M-MHD-145 (1 Break per Pole)

80 250 60

13 MITSUBISHI (S) SF6

SFM-145 (1 Break per Pole)

130 28 100

14 BBC (H) OCB TR-145 (1 Break per Pole)

75±10 35±10 150

15 BBC (H) OCB TR-170 (1 Break per Pole)

75±10 35±10 150

16 LKNES (H) OCB MULB-150 (1 Break per Pole)

130 50 150

17 ASEA (S) OCB HLD-145/1250b (1 Break per Pole)

90 46 150

18 CHINA (H) OCB SW6-145 (2 Break per Pole)

200 40 180

20 BBC (P) SF6 ELF-145n1 (1 Break per Pole)

110 20 50

21 ABB (H) SF6 SL 2-1 (1 Break per Pole)

55 18 60

22 ABB (S) SF6 LTB-145D1/B (1 Break per

42 22±4 40

24

Pole)22 ABB (S) SF6 LTB-

145D1/B (1 Break per Pole) CAPACITOR BANK

A/B/C: 45/40/40

22±4 40

23 ALATOM (S) SF6

GL-212 (1 Break per Pole) FK-

100±5 50±5 60

24 PIN DING SHAN CHINA (S) SF6

LW 35-145 (1 Break per Pole)

100±20 28 +2 -4 45

25 TENAGA (S) SF6 LW9-145 (1 Break per Pole)

150 30 45

CHEM China (S) SF6

OFPI-145-40L, FAR3 (1 Break per Pole)

≤ 100 ≤ 30 ≤ 30

Table-9k: 66KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE DATA

66KV CIRCUIT BREAKERS TIMING AND CONTACT RESISTANCE

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VALUE (H: Hydraulic, S: Motor Spring, P: Pneumatic Operating Mechanisms)Sr. No.




1 ENERGOINVEST (P) SF6

SFE-9 (1 Break per Pole)

130 35 60

2 ABB (S) SF6 LTB-72.5 D1/B (1 Break per Pole)

42 22±4 40

3 CHINA (H) OCB SW6-72.5 (2 Break per Pole)

200 40 180

Table-9l: LEAD ACID DC BATTERIES OPERATION AND MAINTENANCE DATA

Sr. No.

Battery Make Battery Type

Rated Capacity

Float Charge

Boost Charge

Sp. Gravity

End of Discharge

Average Impedance

26

(AH) VPC (V)

VPC (V)

at 25°C Voltage at 10 hours rate (V)

Per Cell (mΩ) (Empirical Values0

1 YUASA (Japan)

CS-170 150 2.12 2.33 1.180± 0.1C/1.80 1.44

1 YUASA (Japan)

CS-400 300 2.12 2.33 1.180± 0.1C/1.80 0.640

2 ROCKET (Korea)

PS-170 150 2.15 2.40 1.180 0.1C/1.80 1.22

2 ROCKET (Korea)

PS-400 300 2.15 2.40 1.180 0.1C/1.80 0.658

3 VARTA (Germany)

OPZS 150 2.23 2.40 1.180 0.1C/1.80 1.44

3 VARTA (Germany)

OPZS 600 2.23 2.40 1.180 0.1C/1.80 0.407

4 TUDOR (Italy) 6TF 150 2.22 2.40 1.180 0.1C/1.80 1.304 TUDOR

(Sweden)GR200/3GR200

300 2.17 2.40 1.180 0.1C/1.83 0.731

5 NAMBANG (Korea)

PS 150 2.17 2.40 1.180 0.1C/1.80 0.731

6 HOPPECKE (Germany)

Gro E25 2.23 2.40 1.220 0.1C/1.80 0.731

7 CHLORIDE (England)

YCP-25/AE

150 2.21 2.35 1.203 0.1C/1.85 0.641

7 CHLORIDE (England)

YCP-13/AF

300 2.21 2.35 1.203 0.1C/1.85 0.378

8 DUROS (Denmark)

150 2.20 2.40 1.240 0.1C/1.80 0.731

9 BERGA (Germany)

Gro 475 2.23 2.40 1.220 0.1C/1.80 0.315

10 FIAMM (Italy) SM4 150 2.18 2.40 1.180 0.1C/1.80 0.47110 FIAMM (Italy) SM4 300 2.18 2.40 1.180 0.1C/1.80 0.23811 CHLORIDE

(Pakistan)1XMP 150 2.18 2.40 1.180 0.1C/1.80 0.471

12 EXIDE (Pakistan)

1XMP-19

150 2.20 2.40 1.180 0.1C/1.80 0.725

12 EXIDE (Pakistan)

1XMP-33

150 2.20 2.40 1.180 0.1C/1.80 0.352

Note-1. Correction of Specific Gravity at temperature 25 °C: S25 = St + 0.0007 (t – 25) WhereS25 = Corrected Specific Gravity at temperature 25 °CSt = Measured Specific Gravity at temperature t °C of electrolytet = Temperature of electrolyte (°C) as measured at siteNote-2. Open Circuit Voltage Per Cell = Specific Gravity + 0.84 VoltsNote-3. End of Discharge Specific Gravity = 1.415Note-4. Average Impedance of Strap/Inter-cell Connector = 0.24 mΩ

27

Table-9m: CAPACITANCE AND DISSIPATION FACTOR VALUES OF 132/11KV POWER TRANSFORMERS

Sr. No.

TR Make TR Type TR Ratings

Winding Tested

C Value (PF) (Empiric

%DF Value at 20 °C

28

al Value) (Empirical Value)

1 SHENYANG (China)

SFZ7-26000

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

2 SHENYANG (China) *

SFZ7-13000

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

2 TOSHIBA(Japan)

HC/OPTLR-D

20/26 MVA 132/11KV

H-LH-GL-G

406332978170

0.1380.1250.29

2 TOSHIBA(Japan) *

HC/OPTLR-D

10/13 MVA 132/11KV

H-LH-GL-G

406332978170

0.1380.1250.29

3 MINEL (Yugoslavia)

TPv-7105-26

20/26 MVA 132/11KV

H-LH-GL-G

411333648448

0.2951.3090.705

4 ELTA(Poland)

TNARC-26000/132 PT

20/26 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

4 ELTA(Poland) *

TNARC-13000/132 PT

10/13 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

5 HYUNDAI(Korea)

TL-068 20/26 MVA 132/11KV

H-LH-GL-G

540034809386

0.2490.230.26

6 OTE (Italy) BERGAMA

10/13 MVA 132/11KV

H-LH-GL-G

388230076456

0.3750.3240.504

7 ELECTROPUTRE (Romania) *

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

8 ELECTROPUTRE (Chec Republic)

10/13 MVA 132/11KV

H-LH-GL-G

429624777845

0.460.750.35

9 SIEMENS (Pakistan) *

40 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

29


20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578


20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

13 HEC (Pakistan) *

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

14 PEL (Pakistan) *

40 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

15 PEL (Pakistan) *

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

16 PEL (Pakistan) *

10/13 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

17 IRANTRAFO (Iran) *

20/26 MVA 132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

4 MEIDENSHA(Japan) *

20/26 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

4 MEIDENSHA(Japan) *

10/13 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

4 ELPROM(Bulgaria) *

20/26 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

4 ``` 20/26 MVA 132/11KV

` ```````````````````````

`

4 GANZ(Hungary) *

`````` 20/26 MVA 132/11KV

H-LH-GL-G

5400294913110

0.20.30.3

4 PAUWELS(Belgium) *

DRF-130/275 (3-WDG)

37.5 MVA 132/66/11KV

H-LH-GL-T

599444137078

0.4780.530.478

30

L-GH-TT-G

20414015860

0.52-0.688

Table-9n: CAPACITANCE AND DISSIPATION FACTOR VALUES OF 220/132/11KV AUTO TRANSFORMERS

Sr. No.

TR Make TR Type

TR Ratings Winding Tested

C Value (PF) (Empirica

%DF Value at 20 °C

31

l Value) (Empirical Value)

1 CEM (France)

AOTR.CV

160 MVA 220/132/11KV

HL-THL-GT-G

4732637410530

0.740.950.88

2 SHENYANG (China)

OSFPS-7-160000

160 MVA 220/132/11KV

HL-THL-GT-G

5778742814496

1.610.651.60

3 HAWKER SIDDELY (UK)

HSPT/TTT85

160 MVA 220/132/11KV

HL-THL-GT-G

143032763724973

0.3450.3580.360

4 ALSTHOM (France)

AUTO 160 MVA 220/132/11KV

H-LH-GL-G

10400780011600

0.2020.3280.38

5 AEG (Turkey)

MRSN-8254

160 MVA 220/132/11KV

H-LH-GL-G

8500670013800

0.3580.3860.775

6 BBC (Germany)

AUTO 160 MVA 220/132/11KV

H-LH-GL-G

5600570013200

0.3190.3240.312

7 TBEA (China) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

8 TBEA (China) *

250 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

9 HOUPING (China) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

10 SHENBIAN (China) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

11 ABB (Spain) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

12 HYUNDAI (Korea) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

13 SIEMENS 160 MVA H-L 4270 0.615

32

(Pakistan) * 220/132/11KV

H-GL-G

33797636

0.5280.578

14 ABB (Germany) *

160 MVA 220/132/11KV

H-LH-GL-G

427033797636

0.6150.5280.578

15 MEIDENSHA (Japan)

FBORSDL

160 MVA 220/132/11KV

HL-THL-GT-G

6832746014846

0.30.1650.66

16 ABB(Germany)MANGLA

TPFD66 000

138 MVA 220/132/11KV

HL-T (3HL-G (5T-G (4)

6289586412158

1.0850.870.98

Table-9o: CAPACITANCE AND DISSIPATION FACTOR VALUES OF 500/220/22KV AUTO TRANSFORMERS

Sr. No.

TR Make TR Type

TR Ratings Winding Tested

C Value (PF) (Empirical Value)

%DF Value at 20 °C (Empirica

33

l Value)1 TRAFOUNIO

N (Germany)NRPN-8157

600 (200x3) MVA 500/220/22KV

HL-THL-GT-G

419641739722

0.1330.1310.255

2 JEMOUNT SCHENIDER (France)

AUTO 450 (150x3) MVA 500/220/22KV

HL-THL-GT-G

7200570010800

0.320.2050.531

3 TBEA (China) *

450 (150x3) MVA 500/220/22KV

HL-THL-GT-G

427033797636

0.6150.5280.578

4 SIEMENS (Brazil) *

NRPN-8157

600 (200x3) MVA 500/220/22KV

HL-THL-GT-G

419641739722

0.1330.1310.255

5 SIEMENS (Germany) *

NRPN-8157

600 (200x3) MVA 500/220/22KV

HL-THL-GT-G

419641739722

0.1330.1310.255

6 TBEA (China) *

200 (200x3) MVA 500/220/22KV

HL-THL-GT-G

427033797636

0.6150.5280.578

7 ELIN (Austria) *

450 (150x3) MVA 500/220/22KV

HL-THL-GT-G

427033797636

0.6150.5280.578

Table-9p: CAPACITANCE AND DISSIPATION FACTOR VALUES OF CONDENSER TYPE BUSHINGS OF TRANSFORMERS

Sr. No.

Bushing Make

Type Rated Voltage

Insulation Tested



34

l Value)1 HAFELY

(Swiss)COT-245 220KV H-L

H-G40510840

0.681.94

2 HAFELY (Swiss)

COT-145 145KV H-LH-G

33511115

0.581.26

3 F&G (Germany)

OTF-1550/525

500KV H-LH-G

414.57828

0.030.36

4 F&G(Germany)

OTF-1050/245

220KV H-LH-G

4277828

0.0650.355

5 PASSONI&VILLA (Italy)

PNE-145/400A

145KV H-LH-G

235.95-

0.79-

6 PASSONI&VILLA (Italy) *

PNE-245/400A

145KV H-LH-G

235.95-

0.79-

7 ABB (Sweden)

GOM-1050 220KV H-LH-G

483.25-

0.774-

8 ABB(Sweden)

GOB-650 132KV H-LH-G

309.55-

0.687-

9 ABB(Sweden)

GOB-380 100KV H-LH-G

353.1-

0.687

10 BRUSH(UK)

OV-145-1000

132KV H-LH-G

375.8-

0.25-

11 MICAFIL (Swiss)

220KV H-LH-G

40510840

0.681.94

12 NGK (Japan) 132 KV

Table-9q: CAPACITANCE AND DISSIPATION FACTOR VALUES OF CURRENT TRANSFORMERS (C.T)

Sr. No.

CT Make Type Rated Voltage

Insulation Tested



35

l Value)1 MESSWAND

LER (Germany)

AT-145 132KV H-G 500 0.2

2 EMEK (Turkey)

AT4-145 132KV H-G 307.5 0.29 (<1)

3 * EMEK (Turkey)

AT4-245 245KV H-G 206.6 0.02 (<1)

4 SITW (China) LCWB6-145

132KV H-G 900 0.8 (<2)

5 NISSIN (Japan)

FGCH-200 220KV H-G 900 0.2 (<1)

6 GALILEO (Italy)

TAE-245/G 220KV H-G 634 0.6

7 ** ASEA (Sweden)

IMBD-145 132KV C1 (H-L)C2 (H-G)

80022000

(<1)(<1)

8 ** ASEA (Sweden)

IMBD-72 66KV C1 (H-L)C2 (H-G)

80013000

(<1)(<1)

9***

HAEFELY (Swiss)

ISOK-245 220KV H-GCA

1000170

(<1)

10 LK-NES (Denmark)

A8z61/A9z61

132KV H-G 500 0.2

11 MESSWANDLER (Germany)

JOS-72.5 66KV H-G 350 0.2

12 NIROU TRANS(Iran)

Note. *: Top and Bottom units should be tested separately.Note. **: Use capacitance tap for test.Note. ***: CA means the bushing capacitance.

Table-9r: CAPACITANCE AND DISSIPATION FACTOR VALUES OF CAPACITOR VOLTAGE TRANSFORMERS (CVT)

Sr. No.

CVT Make Type Rated Voltage

Insulation Tested


%DF Value at 20

36

°C (Empirical Value)

1 TRENCH ELECTRIC (Canada)

TEHM-500 500KV CN(H-G)C1C2

50005300133900

0.24

2 GALILEO(Italy)

TCS-245G 220KV CN(H-G)C1C2

8000 (<1)

3 NMG(Italy)

CPTa-245/4 220KV CN(H-G)C1C2

4000440044000

(<1)

4 HAEFLY(Swiss)

CVE-245 220KV CN(H-G)C1C2

4500 +10% -5%4790 +10% -5%74455+10% -5%

(<1)

5 TRENCH ELECTRIC(Canada)

TEM-L3OS 220KV CN(H-G)C1C2

3000 (<1)

6 MAGRINI GALILEO(Italy)

CPT-245/8 220KV CN(H-G) 8000 ±10% (<1)

7 PASSONI&VILLA(Italy)

500KV CN(H-G)C1C2

7000 +10% -5% (<1)

8 HAEFLY(Swiss)

CVE-550 500KV CN(H-G)C1C2

6900 +10% -5%7033 +10% -5%27176 +10% -5%

(<1)

9 EMEK(Turkey)

KGT-245 220KV CN(H-G) 4598 (<1)

10 EMEK(Turkey)

KGT-145 132KV CN(H-G) 5950 (<1)

12 NIROU TRANS(Iran) *

220KV

12 NIROU TRANS(Iran) *

132KV

37

Table-9s: LEAKAGE CURRENT MONITORING (LCM) OF SURGE ARRESTERS/LIGHTNING ARRESTERS

Sr. No.

Make Type Rated Voltage

Mfr. Rated Voltage

MCOV Total Leakage Current

Resistive Leakage Current

1 HITACHI(Japan)

ZLA-X25C

220KV 198KV 154KV < 800µA < 200µA

38

2 HITACHI(Japan)

ZLA-X15C

132KV 120KV 90KV < 350µA < 200µA

3 ASEA(Sweden)

XAA 132KV 116KV 90KV - < 200µA

4 MEIDENSHA(Japan)

ZSE-C1Z 220KV 198KV 154KV < 490µA < 200µA

5 MEIDENSHA(Japan)

ZSE-C1Z 132KV 120KV 90KV < 390µA < 200µA

6 BOWTHORP(England)

1MB-120 132KV 120KV 90KV - < 200µA

7 GE/TRANQUELL(USA)

9LXBH60 220KV 198KV 160KV - < 200µA

8 ABB(Sweden)

EXLIMQ 220KV 198KV 160KV < 1000µA < 200µA

9 WENZHOU YIKUN (China)

Y10W-120/295

132KV 120KV 90KV - < 200µA

10 WENZHOU YIKUN (China)

YHO 10W-12/38

12KV -KV -KV - < 200µA

Table-9t: CRITERIA FOR REPLACEMENT OF VACUUM INTERRUPTER IN 11KV VACUUM CIRCUIT BREAKERS (VCB)

Sr. No.

VCB Make Type No. of Operations

Description (to be checked in CB closed position)

1 MEIDENSHA (Japan)

VFT-12 (O/G) 10,000 When limit of contact wipe reaches to 1mm (normal 4mm)

2 MEIDENSHA VE-14 (I/C) 10,000 When wear standard line coincide

39

(Japan) with the flange face3 SIEMENS

(Pakistan)3AF 30,000 When white check mark becomes

invisible4 HITACHI

(Japan)V 10,000 When distance between the

reference lines exceeds 1mm5 AEG

(Pakistan)VA 30,000 When burn-off indicator becomes

invisible6 TOSHIBA

(Japan)VK 30,000 When limit of red-painted limit

of contact wipe decreases to less than 3mm

7 J&P (Japan) BK 10,000 When contact wear reaches 3mm/Gap reduces to 1mm (to be checked by measuring the snatch gap)

8 HYUNDAI (Japan)

10,000

9 PELKA/PEL (Turkey/Pak)

PDB5-25-8W (O/G)

10 PELKA/PEL(Turkey/Pak)

PDB5-25-25W(I/C)

11A vacuum interrupter (vacuum bottle) of 11kV VCB should be replaced when any one of the following criteria is met with:- The prescribed number of total operations have been completed (operation counter reading)- Failed in vacuum degree check/test (tested with proper test set VIDAR or when tested with Hipot set).- Limit of contact wipe reached (abnormal wear of contacts).

Note. Vacuum degree test / Limit of contact wipe should be checked yearly or after 1000 operations whichever comes first.

10. OPERATION

40

A view of 220/132kV Control Room of 220kv G/S NKLP Lahore

10.1 INTRODUCTIONThe grid stations in grid system of NTDCL&DISCOs are designed and constructed for operation, supervision and control by the staff round the clock, unlike the grid system of

41

many developed countries where the grid stations are remote operated, supervised and controlled at central control centers. The operation staff at control rooms of grid stations comprises shift engineers, operators, attendants, etc. and perform duty in three shifts i.e. morning shift, evening shift and night shift. The operation staff supervises and controls the grid station in accordance with the provisions made in the design and construction of the equipment and transmission lines and in compliance of the instructions of the system operator, i.e. NPCC & RCC.

The operation staff records hourly loading data (Amperes), voltage data (kV), temperature, and other parameters, etc. of the transformers and transmission line in the station log sheet and onward passes to NPCC and/or RCC. They also maintain the record of all the normal and abnormal events of the local system and record of telephonic instruction of all the stakeholders of the system for reference. They coordinate with NPCC and/or RCC and manage the scheduled and non-scheduled shut-downs on the grid station equipment and transmission lines, for maintenance and other purposes. They perform switching operations of the switchgear as desired under instructions of NPCC and/or RCC.

10.2 General ProvisionsGenerally operations mean all types and categories of work to be done by the employees of NTDCL&DISCOs assigned to them as a duty. These operations include

42

technical, administrative, finance, etc. duties with the ultimate goal to build, operate and maintain the power system for transmission and dispatch of electricity to the distribution companies and down to the consumers. Generally the operations are planned but it may include unplanned work activities as desired by NTDCL&DISCOs. All the operation in-charges should give proper attention for safety of the NTDCL&DISCOs employees during operations at NTDCL&DISCOs premises. The operations in NTDCL&DISCOs are integrated as under:

a) Operation of power system for generation, transmission and dispatch of electricity to the Distribution Companies (DISCOs) is a planned action by NTDCL. National Power Control Center (NPCC) Islamabad (including Regional Control Centers (RCC) North & South is the authorized System Operator on behalf of NTDCL.

b) NPCC/RCC shall be responsible for the safe, secure, openly-accessible, equitable, environmentally acceptable, reliable and adequate operation and development of the power system. The Operation Codes of NEPRA Grid Code and Distribution Code outlines the necessary rules for operation of the NTDCL&DISCOs power system which should be followed as and where applicable.

c) It is the primary responsibility of each employee of the NTDCL&DISCOs to keep the NTDCL&DISCOs system and its component apparatus/equipment in safe operating condition within their design parameters.

d) No employee shall operate any apparatus or equipment without having authority/permission or instructions from the competent authority.

e) In the existing set up of NTDCL&DISCOs, NPCC is the System Operator of the entire Grid System. In addition to the specific and general instruction of the NPCC whether written or oral, the guidelines given here under shall be followed by all NTDCL&DISCOs employees engaged in operation and maintenance work at different levels of GSO NTDCL&DISCOs such as;

- Dealing operation of the HV equipment,- Issuing operating orders and messages,- Dealing with authority to work, Permit-to-Work and Hold-OFF orders, - Dealing with office work and record of operations, etc. - Recording data in the grid station daily log sheets, etc.f) The employees of NTDCL&DISCOs and public should clearly understand the application and significance of operating voltage levels of different equipment or

43

apparatus as given below with regards to their own safety as well as of the apparatus/equipment.

- Control and Auxiliary Services Voltages: 24VDC, 48VDC, 110VDC and 220V DC;110VAC, 230VAC, 400VAC, 50 Hz;

- Three-phase four-wire 400VAC and 230VAC, 50 Hz are the domestic and commercial supply voltage levels in Pakistan.

- Medium Voltages (MV) for transmission and distribution:11kV, 22kV (tertiary voltage of EHV transformers) and 33kVAC, 50Hz;

- High Voltages (HV) for transmission: 66kV and132kV AC, 50 Hz;

- Extra High Voltages (EHV) for transmission: 220kV and 500kV AC, 50 Hz.

g) Switching operations: The operation in-charge is responsible to ensure safety of the employees as well of the NTDCL&DISCOs equipment during their normal as well as emergency operations. Similarly, the operation staff on duty besides to look after the normal operations of the grid station equipment have to do switching operation. To deal with switching operations of the HV equipment safely the operation in-charge or the shift in-charge will follow as under before, during and after switching operations:

- He will ensure for the approval of the desired operations of the equipment from NPCC/ RPCC.

- He will inform and discuss with the NPCC/RPCC any abnormal local condition of the equipment to be operated.

- He will identify the nature of operations and safety precautions required.

- He will identity the operations during which workers are/or can be exposed to hazards.- He will ensure for the clear operation instructions.

- He will follow the prescribed procedure and instructions given in the PTW (Permit to Work) for its issuance and cancellation.

44

- In case of maintenance work oriented operations, he will get complete information about the work to be done from the concerned supervisor and make sure that the equipment to be work upon is fully isolated from all possible sources of supply. He will issue PTW to the authorized supervisor for execution of the work in question indicating all the hazards known to him and not eliminated or covered by the PTW and also discus with the supervisor.

- During the switching operations, he will continuously keep contact with NPCC/RPCC and make sure that all the operations are carried out in the approved sequence.

- Satisfactory operations will be brought to the notice of NPCC/RCC regularly and abnormal situation if any will also be brought to the notice of NPCC/RCC immediately.

- He will make sure that no equipment in the system gets over loaded beyond their rating as a result of operations under execution.

- After satisfactory completion of the switching operations to be carried out he will inform to the NPCC/RPCC about the post operation system condition.- He will make entries of the switching operations in the substation order book for reference and record and place Caution Notice/Tag on the control switches of all equipment which may energize the point of work.

- After completion of the work and obtaining clearance from the PTW holder he will cancel the PTW following the prescribed procedure and instruction and inform the NPCC/RPCC for further instruction to normalize the system.

h) As the operations include technical, administrative, finance, etc. duties, therefore while working in NTDCL&DISCOs offices the office in-charges are responsible to manage for a neat, clean, safe and comfortable atmosphere. Do not use the broken furniture and office tools, etc. Do not hold paper pins, clips, etc. in the mouth and also do not use them as tooth-picks or for cleaning ears. While working on old damped record files take care of insects, dust/dirt, etc. Do not smoke and use open flames in the record rooms.

10.3 NPCC SOP FOR SYSTEM RELIABILITY AND SECURITY (issued by NPCC Islamabad in September 2006)

45

Following criteria must be followed by the Dispatcher/System Operators for reliability and Security of the system to avoid blackout/major collapse.

1. While allowing shutdown especially on 500kV transmission lines it must be ascertained that even after the outage, n-1 contingency criteria is not violated, either directly or through cross trip schemes.

2. While allowing shutdown on any 500kV auto transformers, n-1 contingency criteria may not be violated.

3. Before permitting shutdown, the load-shedding may be implemented so that the loading of the system remains within the safety criteria all the time.

4. The system frequency control must be with hydel stations i.e. Mangla/Tarbela in all seasons for effective control. It may be achieved even at the cost of water spillage/hydel energy.

5. Spinning must be made available at all times so the system can have some reserve to meet with eventualities. The spinning must be as per the standard rule of being equal to the largest unit on bar i.e. about 400MW is required round the clock. Spinning should be on units that have a high pick up.

6. Frequency of the system should be maintained within the specified limit i.e. ±1%

7. Cross-trip schemes must be revised and implemented according to seasonal load flow pattern.

8. Economic consideration must not supersede the reliability, safety and security standards.

9. The system voltages should not be allowed to drop below 5% allowable limit in normal circumstances and to meet the criteria, extra generation be taken on bar or load shedding implemented, if other measures to boost the voltage have exhausted.

10. In case of 500kV transformers, the loading should be kept within 100% normally, as outage of transformers at any big station cab also result in blackout on the system, however, short time overloading as per approved criteria may be allowed keeping in view oil/winding temperature.10.4 CONTINGENCY PLAN FOR BLACK START OF TARBELA POWER STATION (issued by NPCC Islamabad in October 2006)

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This plan is useful in restoration of station auxiliary supply and helps prompt restoration of the system as well.

1. Don’t panic please.

2. Open 220kV circuit breaker D7Q1, D7Q2 and D7Q3 to isolate 220kv and 500V system at Tarbela.

3. Open 220kV lines circuit breaker for all the lines, if they are in closed position.

4. Start Diesel Generation No: 1 & 2

5. Open all 11kV station supply circuit breakers EXCEPT 11kV BREAKER No. 1 & 28 on 11kV flank A & B respectively.

6. Close 11kV circuit breakers of Diesel Generator No. 1 & 2, Power Supply for Unit auxiliaries will appear on respective RPDC for Units (1-4).

7. Isolate both the 220kV bus bars.

8. Start any of the Unit 1-4 on “Manual Mode” and build up rated voltage after ensuring that NO INDICATION PERSISTS IN Control Room.

9. Close the relevant circuit breaker Q2 of the unit to connect it with 220kV Bus Bar No. 2. Now Bus Bar No. 2 is energized.

10. Open 11kV incoming circuit breaker for both the Diesel Generator sets.

11. Close 220kV circuit breaker D6Q2, SPT No. 1 will be energized. Now station normal supply is restored.

12. Close all the 11kV circuit breaker to restore the complete station Auxiliary power supply.

13. Ensure availability of power supply to compressors at Switchyard before any further operation of circuit breakers.

14. Reset 50V & 230V Battery Chargers at Switchyard and Power House and ensure that load shifted from batteries to chargers.

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15. Start 2nd Unit on 220kV side after ensuring that NO INDICATION PERSISTS in Control Room.

16. Connect the 2nd Unit to 220kV Islamabad line, if so desired by NPCC by closing D4Q3 in case Unit No. 3 has been started. Make sure that 220kV circuit breaker D4Q2 & D4Q1 are open.

17. Close 220kV circuit breaker D4Q1 220kV, Bus Bar No.1 is energized now.

18. Close 220kV circuit breaker D5Q1, SPT-2 is energized now.

19. Ensure that 11kV station supply buses flank A and flank B are energized with TIE circuit breaker open.

20. Open 220kV circuit breaker DQ2 of the first started unit. The first started unit is on SNL with voltage built up, keep it running on SNL. Station supply will be available from SPT-2.

21. Ensure that all 500kV circuit breakers are open except Bay 8.

22. Complete Bay 7 on 220kV side to energize 500kV Bus Bars 1&2. Now both 500kV Bus Bars are energized.

23. For further restoration proceed as desired by NPCC.

10.5 PARALLEL OPERATION OF TRANSFORMERS IN THREE-PHASE SYSTEMS

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Transformers are in parallel operation if they are connected in parallel on at least two sides or Parallel operation means direct terminal-to-terminal connection between transformers in the same installations. A distinction should be made between bus bar interconnection and network interconnection. Only two-winding transformers are considered. The logic is also applicable to banks of three single-phase transformers.

The following four conditions must be satisfied in order to avoid dangerous transient currents and for economical load sharing and successful parallel operation of two or more transformers:

a) The same vector group (winding connections/phase-angle relation/clock-hour number)

b) The same ratio with some tolerance and similar tapping range

c) The same percentage impedance voltage with some tolerance (± 10%) (same relative short-circuit impedanceThis also means that the variation of relative impedance across the tapping range should be similar for the two transformers. When operating transformers in parallel, their relative impedances will determine how they share the load. Transformers will divide load in inverse proportion to their impedance (the transformer having less impedance will tend to carry more load and vice versa). Note that the impedances of two transformers should not be more than 10% apart for economical load sharing.

d) The same power ratingIt is not advisable to combine transformers of widely different power rating (say, more than 1:2). The natural relative impedance for optimal designs varies with the size of the transformer. Rated power capacity ratio should be smaller than 3:1.

In practice, a mismatch of relative loading of no more than about 10 % between two transformers of non-identical designs should be regarded as reasonable.

10.6 LOADING OF TRANSFORMERS – GUIDE FOR SHORT DURATION EMERGENCY AND CYCLIC OVER-LOADING OF POWER TRANSFORMERS (REFERENCE IEC 60354 LOADING GUIDE FOR OIL-

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IMMERSED POWER TRANSFORMERS AND IEC60905 LOADING GUIDE FOR DRY-TYPE POWER TRANSFORMERS) (THE SAME GUIDELINES ARE ALSO RECOMMENDED AND ISSUED BY THE DESIGN T&G DEPARTMENT VIDE # CED/NTDC/DSR/4675-84 DATED 17.20.2001)

During normal operation of a transformer, in addition to its rated power for continuous loading, it can be temporarily over loaded within the permissible limits.The bushings, tap changers and other auxiliary equipment shall not to restrict the loading capabilities of the transformer. The power transformers in WAPDA system generally conform to IEC-60076 which can be overloaded to certain extent depending upon ambient air temperature and previous average loading condition of the transformers. In this regard details are given in IEC-60354 “Loading guide” for oil immersed transformers which may be gone through for more knowledge on the subject. However, convenience the salient points/instructions abstracted from the said IEC guide are given below for ready reference and knowledge of operational staff for implementation:

1. In normal cyclic duty (once in every 24 hours) the transformers can be overloaded up to 150% of its rated power in accordance with Table-1 to X. In these tables K1 indicates the average percentage load on transformer before over-loading. K2 indicates percentage load during the period of over loading and t indicates time in hours.

2. These tables are based on ambient air temperature of 0ºC, 10ºC, 20ºC, 30ºC and 40ºC. For operation at 50ºC ambient air temperature special consideration has to be made.

3. In emergency conditions (once in a few months) the transformer can be over loaded for short duration to the extent given in Table-1 to X below, provided that the winding hot spot temperature and top oil temperature do not exceed 140ºC and 115ºC respectively. The figure of 115ºC for top oil temperature is tentative in actual practice this value has to be limited to the temperature at which the conservator is completely full of oil.

4. The transformer is expected to work for its normal life span if operated continuously at a load such that winding hot spot temperature does not exceed 98 ºC. For each 6 ºC rise in temperature above 98 ºC the transformer’s life is reduced to 50%. It means that a transformer expected to give service for 30 years if operated at 98 ºC winding temperature would run only for 15 years if operated continuously at 104 ºC.

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5. As winding temperature and top oil temperature determine the effect of over loading on determination of the insulation and the resultant reduction of transformer’slife, utmost efforts should be made to keep the temperature gauges and the thermal protective devices in proper working order.

TABLE –I

ONAN and ONAF Transformers Ambient Air Temperature = 0ºCValues of K2 for given values on K1 and t

K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 >200 >200 >200 200 200 193t=1 200 200 194 138 181 172t=2 178 173 167 163 158 152t=4 151 148 145 143 140 136t=6 138 137 135 134 132 130t=8 132 131 130 129 128 126t=12 125 125 124 124 123 122t=24 116 116 116 116 116 116

TABLE –II


K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 >200 >200 >200 199 188 173t=1 200 192 182 176 167 154t=2 169 163 157 152 147 137t=4 142 139 136 133 130 124t=6 131 129 127 125 123 119t=8 124 123 122 121 119 115t=12 117 117 116 116 115 112t=24 108 108 108 108 108 108

TABLE –III

ONAN and ONAF Transformers Ambient Air Temperature = 20ºC

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Values of K2 for given values on K1 and t

K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 >200 >200 193 183 169 100t=1 189 180 170 162 150 100t=2 159 153 146 141 132 100t=4 134 131 127 124 118 100t=6 123 121 118 116 112 100t=8 116 115 113 112 109 100t=12 110 109 108 107 105 100t=24 100 100 100 100 100 100

TABLE –IV


K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 >200 192 178 164 126 - t=1 176 168 155 145 110 -t=2 149 142 134 126 99 -t=4 124 121 116 111 95 -t=6 114 111 108 104 93 -t=8 108 106 104 101 93 -t=12 101 100 99 97 92 -t=24 91 91 91 91 91 -

TABLE –V

ONAN and ONAF Transformers Ambient Air Temperature = 40ºC

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K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 190 177 158 118 - -t=1 164 154 137 104 - -t=2 137 130 118 95 - -t=4 115 110 103 88 - -t=6 104 101 96 86 - -t=8 98 96 92 84 - -t=12 92 91 88 83 - -t=24 82 82 82 82 - -

TABLE –VI

OFAF and ONWF Transformers Ambient Air Temperature = 0ºCValues of K2 for given values on K1 and t

K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 177 173 168 164 160 155t=1 163 161 155 152 149 145t=2 147 145 142 141 138 136t=4 133 132 131 130 129 127t=6 127 126 126 125 124 123t=8 123 123 122 122 122 121t=12 119 119 119 119 118 118t=24 114 141 114 114 114 114

TABLE –VII

OFAF and ONWF Transformers Ambient Air Temperature = 10ºC

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K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 170 165 160 156 152 145t=1 157 153 148 145 142 135t=2 141 138 136 134 131 126t=4 127 126 124 123 122 119t=6 121 120 119 119 118 115t=8 117 117 116 115 115 113t=12 113 113 112 112 112 110t=24 107 107 107 107 107 107

TABLE –VIII


K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 161 157 151 146 141 100t=1 148 144 139 136 131 100t=2 133 130 127 125 121 100t=4 119 118 116 115 113 100t=6 113 112 111 110 109 100t=8 110 109 108 108 106 100t=12 106 105 105 105 104 100t=24 100 100 100 100 100 100

TABLE –IX

OFAF and ONWF Transformers Ambient Air Temperature = 30ºC

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K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 153 149 142 136 120 -t=1 140 136 131 126 111 -t=2 125 123 119 116 104 -t=4 113 111 109 107 99 -t=6 107 106 104 103 96 -t=8 103 102 101 100 95 -t=12 99 98 98 97 94 -t=24 92 92 92 92 92 -

TABLE –X


K1=25 K1=50 K1=70 K1=80 K1=90 K1=100t=0.5 144 139 131 119 - -t=1 131 127 120 109 - -t=2 117 114 110 100 - -t=4 105 103 100 94 - -t=6 98 97 95 90 - -t=8 95 94 93 89 - -t=12 91 90 89 86 - -t=24 84 84 84 84 - -

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