Very good evening as maintenance activities going on just for awareness daily used technical services to avoid error in daily schedule Preventive maintenance activitie

 Dear sir,

Very good evening as maintenance activities going on just for awareness daily used technical services to avoid error in daily schedule Preventive maintenance activities.

[4/16, 11:57] Dr. Amar Nath Giri: Preventive maintenance for a Trisquare HT Panel (33KV) ensures operational reliability, prevents catastrophic failures, and extends equipment life. The following Q&A covers maintenance procedures, safety protocols, and technical aspects based on industry standards and typical operation manuals for vacuum circuit breakers (VCB). 

1. Preparatory & Safety Procedures

Q1. What is the first step before performing preventive maintenance on a 33KV panel?

A: Isolate the feeder, switch OFF the VCB, rack out the trolley to the 'Test' or 'Withdraw' position, and place "Permit to Work" (PTW) tags. 

Q2. How do you ensure the 33KV HT panel is safe for working?

A: Rack out the breaker, check mechanical indications for Earth Switch position, and use an Earth Discharge Rod to discharge stored energy in high-voltage terminals to earth. 

Q3. What PPEs are required for 33KV HT panel maintenance?

A: HT voltage gloves (tested), safety shoes, helmet, arc flash suit/apron, safety goggles, and cotton mask. 

Q4. What is the purpose of "Rack-in/Rack-out" during maintenance?

A: It connects or disconnects the VCB main contacts (jaw contacts) to the busbars, allowing maintenance on the breaker in the "Test" position while the busbar remains energized. 

2. Physical Inspection & Cleaning

Q5. What is the frequency for routine HT panel preventive maintenance?

A: Monthly for visual checks and cleaning; Annual/Half-yearly for detailed testing, tightening, and lubrication. 

Q6. What cleaning agent should be used for 33KV insulators?

A: Dry lint-free cloth or CRC-226. Avoid water. Use specialized cleaning agents to remove carbon dust and ensure insulation integrity. 

Q7. How do you check for hot spots in a 33KV panel?

A: Use thermography scanning to check for overheated joints, bushings, and cable terminations before shutting down. 

Q8. What should be done to the moving parts of the VCB?

A: Clean and apply fresh, recommended grease to sliding surfaces, shutter mechanisms, and racking rods. 

3. VCB & Protection Testing

Q9. What is the acceptable Insulation Resistance (IR) value for 33KV VCB?

A: >34 Megaohms, measured between poles and pole-to-earth. 

Q10. How do you measure the contact resistance of a VCB?

A: Use a Micro-ohm meter (CRM) to measure resistance across the main jaw contacts in the closed position. Typical value: <50-60 micro-ohms. 

Q11. What is the procedure for checking VCB closing/opening timings?

A: Use a Circuit Breaker Timing Tester (CBTT) to measure contact travel times to match manufacturer data. 

Q12. What test confirms the integrity of the vacuum interrupter? 

A: High Voltage (HV) test or Hipot test (AC or DC) on each vacuum interrupter. 

Q13. How do you test the protection relay trip circuit?

A: Perform secondary injection testing to ensure protective relays activate the master trip coil and open the breaker. 

4. Component Inspection (CT/PT/Heaters)

Q14. What are the key checks for the Current Transformer (CT)?

A: Check for insulation health (IR test), polarity, CT ratio, and magnetization curve. 

Q15. Why are space heaters important in HT panels?

A: To eliminate moisture inside the panel, preventing flashovers, tracking on insulators, and corrosion. 

Government 

Q16. What should be checked on potential transformers (PT) or fuses? 

A: Clean epoxy PT insulation, check for tightness of connections, and ensure PT fuses are intact and correct rating. 

5. Troubleshooting & Maintenance Records

Q17. What should be done if the breaker fails to close?

A: Check: 1) Spring charged switch, 2) Trip circuit health, 3) Control supply voltage (DC), 4) Mechanical interlocks, 5) Anti-pumping relay. 

Q18. What do "Master Trip & Auto Trip Check" indicate?

A: Confirms that the protection relay sends a trip signal to the VCB through the master trip relay. 

Q19. What is the purpose of checking SF6 gas pressure in VCBs?

A: Ensures the arc quenching medium is at the correct density; low pressure trips the incomer. 

Q20. What is the purpose of maintaining a maintenance checklist report?

A: It records IR values, contact resistances, and action taken, essential for future troubleshooting and compliance.

[4/16, 12:06] Dr. Amar Nath Giri: Preventive maintenance for Tri Square 33 kV HT panels (Vacuum Circuit Breaker - VCB) is crucial for ensuring the reliability of high-voltage systems, with a strong focus on EHS (Environment, Health, and Safety) protocols to prevent electrical, physical, and environmental hazards. 

Here is a 20-question and answer guide based on standard SMPs (Safe Maintenance Procedures) for 33 KV HT Panels.

EHS Protocols & Preparation

1. What is the most important EHS step before starting maintenance?

A: Obtaining a Permit to Work (PTW), Isolating, Locking Out/Tagging Out (LOTO), and confirming zero energy status (testing for voltage). 

2. Which PPE is mandatory for 33 kV VCB maintenance?

A: Helmet, Electrical Safety Shoes, 33kV Rated Rubber Gloves, Fire-resistant clothing, and Goggles. 

3. What should be done with the VCB before working on it?

A: Rack out the breaker to the "Test/Disconnected" position and ensure the spring is discharged. 

4. How is the 33 KV cable safely discharged?

A: Using a calibrated discharge rod, earthing the conducting parts before touching them. 

5. What should be checked on the panel door?

A: Check for the healthiness of door interlocks and hinges. 

Mechanical & Physical Maintenance (Tri Square Panel Specific)

6. What is the purpose of cleaning the epoxy insulators and spouts?

A: To remove dust and tracking marks that can cause flashovers, using cleaning agents like CRC-226. 

7. How should VCB contacts be treated?

A: Clean moving parts and apply a thin layer of petroleum jelly or specified grease to the high-voltage jaw contact area. 

8. What mechanical checks are done on the breaker truck?

A: Test VCB Rack-in/Rack-out alignment, shutter mechanisms, and safety interlocks for smooth operation. 

9. How do you check for hotspots during maintenance?

A: Perform a tightness check with a torque wrench on all busbar bolts and cable terminations, looking for discolored metal. 

10. What is the procedure for checking the earthing system?

A: Verify the panel body and VCB truck are securely connected to the main earthing grid, checking for corrosion. 

Electrical Testing & Protection

11. What is the recommended insulation resistance (IR) test voltage for a 33 KV panel?

A: A 5 kV Megger should be used to test Phase-to-Phase and Phase-to-Earth. 

12. What is the safe IR value for a 33 kV breaker?

A: Generally, >2000 MΩ is considered acceptable for high-tension switchgear. 

13. How do you check VCB operation?

A: Perform electrical ON/OFF, spring charging, and interlock trials in the "Test" position, followed by manual operation trials. 

14. What protection settings should be verified?

A: Inject secondary current to ensure relay functions (Overcurrent - 51, Earth Fault - 51G) trip the breaker within the set times. 

15. How do you verify the functioning of the Heater and Thermostat?

A: Energize the heater and check the current draw to ensure it prevents moisture condensation. 

Troubleshooting & Finalization

16. What is the symptom of an SF6 gas pressure issue?

A: The SF6 pressure gauge will show low pressure, potentially causing an automatic trip of the incomer. 

17. What should be checked for in the auxiliary wiring compartment?

A: Check all control wire terminations for tightness and remove dust with a blower. 

18. What action is taken if porcelain insulators are found damaged?

A: Replace the insulators immediately; do not operate if cracks exist. 

19. What should be checked before final, full re-energization?

A: Ensure all tools are removed, the area is clean, all earth leads are removed.

20. What is the final EHS step after work completion?

A: Handover the system to operations and cancel the PTW (Permit to Work).