TECHNICAL_EXHIBIT_A.pdf

TECHNICAL EXHIBIT A

MINIMUM PREVENTATIVE MAINTENANCE, INSPECTION, AND TESTING

PROCEDURE

138KV FUSED AIR DSCONNECT SWITCHES

• Visually inspect for loose or missing hardware, evidence of rust, deterioration, overheating, arcing, corona tracking, and chipping and cracking.

• Operate switch mechanism. Check for evidence of binding or excessive friction. Verify contact alignment and pressure. Adjust as necessary.

• Clean and vacuum the compartment, apparatus, and insulators. Clean, file, or polish contacts.

138KV SF6 CIRCUIT BREAKERS

• Isolate breakers from the system and ground.

• Inspect main brushings and studs. Clean the entire breaker and inspect for loose and missing hardware. Check and tighten all control wiring connections.

• Clean breaker mechanism. Operate to check for binding and proper latching / tripping action.

• Measure breaker contact resistance.

• Check and record breaker timing for open / close sequence.

• Measure breaker insulation resistance using a HiPot tester.

• Inspect and record all operational set points in accordance with manufacturer specification. Note any deviations and adjust depending on specific conditions.

LOAD TAP CHANGERS

• Test oil for liquid only.

• Drain and filter oil.

• Open cover and visually inspect for loose or missing hardware, metal shavings, or signs of tracking.

• Clean and flush with clean transformer oil.

• Manually operate and check contract wipe and alignment.

• Inspect gaskets and replace if necessary.

• Perform a transformer turns ratio test on five taps ( two lower, neutral, and two upper ).

• Close up LTC applying uniform pressure to gaskets and compressing 25-50 percent.

• Reinstall oil, purge with nitrogen, and check for leaks.

• Synchronize tap changer with other transformers.

( continued )

20MVA 138/13.2KV LIQUID FILLED TRANSFORMERS

• Take fluid sample for lab analysis to include dissolved gas analysis, dielectric strength, interfacial tension, acidity, color, and moisture content.

• Perform external inspection for signs of leakage or physical damage. Inspect all gauges.

• Check fluid level.

• Perform power factor test on complete unit.

• Perform power factor test on high voltage bushings and arrestors.

• Perform turns ration and megger test on all windings.

• Review prior inspection report for comparison of analytical data.

15KV VACUUM CIRCUIT BREAKERS

• Remove breakers and clean cells.

• Inspect main studs and finger clusters for uneven contact, cracked, or broken retaining rings. Clean the entire breaker and inspect for loose and missing hardware. Check and tighten all control wiring connections.

• Test breaker poles with digital low resistance ohmmeter for continuity.

• Test breaker contacts with AC HiPot for insulation breakdown.

• Test closed and latched breakers with megger for insulation resistance measured pole-to-pole and pole-to-ground.

• Rack-in breakers and operate in test position to check cell controls.

• Return breakers to service.

PROTECTIVE RELAYS

• Remove relays from cases to allow for cleaning and inspection.

• Clean and inspect for mechanical operation, broken or rusted springs, freedom of disc movement, and loose connections. Tighten connections, clean, and dress electrical contacts.

• Verify operation of targets.

• Perform megger test to verify insulation properties.

• Perform electrical test to verify proper calibration and time feature. Test at three timing points on manufacturer curve. Check instantaneous pick-up point.

• Reassemble relays, reinstall, and return to service.

13.2KV DRY TYPE TRANSFORMERS

• Vacuum clean transformer enclosure and inspect for rust and deterioration.

• Vacuum clean core and coils as necessary.

• Wipe clean all porcelain insulators and inspect for cracks and chipping.

• Inspect windings and core iron for signs of overheating, arcing, and corona tracking.

• If transformers can be electrically isolated without disconnecting cables, perform turns ration test and megger test on all windings.

LOW VOLTAGE AIR CIRCUIT BREAKERS

• Remove breakers from cells and clean.

rings. Clean the entire breaker and inspect for loose and missing hardware. Check and tighten all control wiring connections.

• Operate breaker mechanism to check for binding and proper latching / tripping action.

• Inspect breaker contacts for burning and pitting. Check for proper alignment and compression.

• Check breaker contact sequence and adjust as necessary.

• Check trip unit plungers for sufficient travel and over-travel to insure they are capable of tripping the breakers.

• Time-current test the breaker by passing current through each pole. Series trip unit one at a time while measuring the time required for the breaker to trip. Compare results to manufacturer time-current characteristic curves. Current limiting fuses, if present, will be removed prior to testing.

• Close and latch breaker to measure insulation resistance pole-to-pole and pole-to-ground using a megger.

• Reinstall breaker and return to service.

MEDIUM VOLTAGE AIR CIRCUIT BREAKERS

• Remove breakers and clean cells.

rings. Clean the entire breaker and inspect for loose and missing hardware. Check and tighten all control wiring connections.

• Test breaker poles with digital low resistance ohmmeter for continuity.

• Test breaker contacts with AC HiPot for insulation breakdown.

• Test closed and latched breakers with megger for insulation resistance measured pole-to-pole and pole-to-ground.

• Rack-in breakers and operate in test position to check cell controls.

• Return breakers to service.

MEDIUM VOLTAGE AIR DISCONNECT SWITCHES

• Visually inspect for loose or missing hardware, evidence of rust, deterioration, overheating, arcing, corona tracking, and chipping and cracking.

• Operate switch mechanism. Check for evidence of binding or excessive friction. Verify contact alignment and pressure. Adjust as necessary.

• Clean and vacuum the compartment, apparatus, and insulators. Clean, file, or polish contacts.

BUSS DUCTS

• Inspect and perform megger induction test.