ABB-Substation-Condition-Monitoring-Schedule

PSS T & D SUBSTATION – QUALITY MANAGEMENTABB LTD.

1) INTRODUCTION

This guideline is prepared in view of the requirements for switchyard service inspection (visual) and condition based maintenance of substation equipments, structures and other miscellaneous items in substations. These guidelines are necessarily general. It is recommended to carry out maintenance of equipment as per manual supplied by manufacturer. All inspections and test procedures should also be performed in accordance with applicable codes and standards.

The aim of this guideline is to provide in general visual inspection check points for the structures, grounding systems, LT switchboards, etc. for which as such there is no readymade guidelines available. Also to provide the visual inspection and condition based maintenance of Major equipments like Transformer, Circuit breakers, CTs, CVTs, PTs, Disconnectors and LAs etc. to verify the health of the equipments.

Service visual inspection is the necessary activity to identify any visible abnormality or failure and require to be performed at specified interval. Whereas condition based monitoring checks (on line/ off line) are necessary to identify internal defects or abnormality, so that necessary preventive action can be taken up.

2) SERVICE INSPECTION & CONDITION MONITORING GUIDELINE

The substation in total and the individual items of equipment contained therein should be periodically inspected. Binoculars should be used to view buses and other equipment located on structures.

Painting and Galvanizing (Applicable to all equipments and systems)Depending on geographical location, local environmental condition, periodic inspection of painting and galvanizing condition of structures, panels, equipments etc. is required. Inspect for paint condition, damage paint, chalking effect, rusting etc. If any damage observed, do necessary repaint or repair work.

Grounding System

Check for loose connections of all ground connections at equipments, structures, panels, other equipments etc. Check for any sparking marks at termination or joint. Observe the condition of any flexible braid type connections for damage. Tighten the connections, clean the joints and replaced if found damage. Earth pits should be kept wet so as to have low resistance. Measure overall ground grid resistance. The Value obtained should be comparable with initially measured values or designed values.Structure

Inspect all the structures for loose or missing bolts or nuts. Observe any damage paint/ galvanizing or signs of corrosion. Inspect for deterioration, bending, buckling and cracking.

Civil work-Foundation and Control Room

Inspect for sings of settlement, cracks, spalling, honeycombing, exposed reinforcing steel, and anchor bolt corrosion. Check for break/ missed cable trench cover. Inspect for any crack/ leakages in control room and water tank. Check for proper functioning of sump pump and drainage system.

Buses and Shield wire

Inspect for loose clamps or connections. Inspect for bending of Alu-tube bending. Observe the condition of flexible buses and shield wires for any damages.

Porcelain Insulators and Bushings (For Bus post / Suspension / Circuit breaker / CT / CVT / PT & Transformer bushings)

Inspect all insulators and equipment bushings for chipped petticoats and fractured or cracked porcelain. Flashover in the past may have damaged a portion of the glazing on the porcelain. Make this inspection at close range. Replaced damage bushings. Remove dust and dirt from porcelain insulators with suitable methods. Cable

Inspect exposed sections of cable for physical damage. Inspect the insulation or jacket for signs of deterioration. Check for loose connections, lugs, tightness, cracking of lugs etc. Inspect shield grounding (where applicable), cable support and termination. Check for any sparking marks at termination or joint. Clean sparking marks if any and make proper joint with proper tightening and lugging.

LT Cable & Metal clad switchgear (Control-Metering, Relay panel, Outdoor and indoor panel)

Examine meters, relays and instruments externally to check for loose connections and damage to cases and covers. Check whether the instruments are reading or registering. Check the functioning of annunciator panels. Inspect for damage to enclosures, doors, latching mechanisms, locks etc. Check out for burned-out lamps.

Battery and battery chargerCheck for any physical damage, loose connections. Check for low level or low specific gravity of the electrolyte. Record the electrolyte temperature. Verify vent cap and flame arresters are in place. Check electrolyte appearance. Check working of exhaust fan.Check for cleaning and corrosion.Observe temperature (by touch). If temperature is found high, check and attend the reason for the same. Check the charging current and voltage. Observe the ground detector lamps for an indication of an undesirable ground on the dc system. Compressor

Check for leakage of air. Check air pressure and Oil level. Substation area- General

Verify the existence of appropriate danger and informational warning signs. Verify whether they are missing or needs repainting.

Check for rusting of fasteners

Check for any hotspots at conductor/ equipment/ stringing termination.

Check for indoor and outdoor lighting systems for burned-out lamps or other component failures

Verify that there is adequate supply of sparesInspect the fire protection system

Check for bird/ animal nests or other foreign materials in the vicinity of energized equipment, buses or fans.

Observe the general condition of the substation yard, overall cleanliness

Observe the position of all circuit breakers in the auxiliary power system and verify the correctness of this position (indication on breaker).

Inspect the area for weed growth, trash and unauthorized equipment storage.

Ensure the fence fabric is intact and there is no rust.Ensure the gate latches are operable

Ensure flexible braid-type connections are intact.

_____ . _____ . _____ . ______. ______

1. TRANSFORMER

2. CIRCUIT BREAKERS (SF6 & AIR BLAST)

PSST&DSSDepartment:

GUIDELINE FOR SUBSTATIONS SERVICE INSPECTION AND CONDITION MONITORINGPrepared: Reviewed: Status: Date: Language:

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Check for any gas/ air leakage Check for proper gas/ air pressure Check for any hot spots at any terminals Checking of oil leaks from grading capacitors Checking of air compressor for oil level, oil quality, air filter, V-belt tension Check for crack in insulators

M M M M QY M

B) Maintenance Schedule Sr.No. Details 1 Check tightness of all clamps and connectors/ 2 3 4 5 6 7 8 9 terminals Check for damage paint condition and corrosion Replaced damaged bushings Checking of all interlocks Checking of pressure settings Cleaning of breaker interrupter, support insulators, PIRs and grading capacitors Checking of Close/ trip coil currents Checking of healthiness of operation counter Control cabinet (i) Checking of tightness of all cable termination in MB (ii) Checking of door sealing gaskets and replacement, if necessary (iii) Repainting of metallic surfaces (iv) Checking of space heaters Checking of tightness of foundation bolts Maintenance of air dryers in Air blast circuit breakers Functional checking of auto starting of air compressors and dryers Checking of air pressure drop during duty cycle operation Overhauling of compressors Maintenance of air dryer if provided Frequency Y Y SOS Y Y Y Y Y Y Y SOS Y Y½Y Y Y SOS½Y

10 11 12 13 14 15

PSST&DSSDepartment:

GUIDELINE FOR SUBSTATIONS SERVICE INSPECTION AND CONDITION

MONITORINGPrepared: Reviewed: Status: Date: Language:

Page 10 of 16Revision:

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Spring operated mechanism (i) Oil leakages from close and open dashpots, replace the same if leakage observed (ii) Greasing/ lubrication of gears and various latches in the operating mechanism (iii) Checking of play of gaps in catch gears (iv) Maintenance of spring charging motors, cleaning of carbon brushes and contactors (v) Replacement of oil in dashpots Checking of pole discrepancy relay Functional checks, duty cycle operation including rapid re-closing (O-0.3s-CO) Checking of air pressure drop during duty cycle operation Checking of all operational lock-outs including SF6 density monitor Checking tightness of earthing connections Cleaning of auxiliary switch contacts with CTC Checking of local ON/OFF indicating lamps in breaker, if provided Check interlocking of isolators with breaker After maintenance trip the breaker through backup

Y Y Y Y SOS Y Y U Y Y Y Y Y Y

17 18 19 20 21 22 23 24 25

C) Condition Monitoring (Condition based Maintenance) Sr.No. 1 2 3 Details CB operating timings (Main, PIR, Aux.) Static contact resistance measurement Dynamic contact resistance measurement (DCRM), contact travel, contact speed, contact wipe, arcing 4 5 contact length Capacitance and tanδ measurement of grading capacitors Dew point measurement of SF6 gas 4Y 3Y Frequency Y 2Y 2Y

3. CURRENT TRANSFORMER

schedule

4. POTENTIAL TRANSFORMERS/ CAPACITANCE VOLTAGE TRANSFORMERS/ COUPLING CAPACITORS

schedule. This test is not possible to be conducted at site if isolation of neutral of intermediate PT is not possible at site.5. DISCONNECTORS AND EARTH SWITCHES

6. SURGE ARRESTERS

7. WAVE TRAPS

M- Monthly, QY-quarterly, Y-yearly, 2Y-once in 2 years, 3Y-once in three years, 4Y- once in 4 years, SOS-as and when required.

3) CONCLUSION

The fundamental goal of inspection, maintenance and condition monitoring of substation is to preserve the function or operation of a system. Specifically, the function that has to be preserved for electric substations is the delivery of safe, reliable electric power to customers

4) BIBLIOGRAPHY

1. Manual on EHV Substation Equipment maintenance

2. EPRI- Inspection and Maintenance Guidelines for Distribution substation3. Design Guide for Rural substations-USDA

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