The document discusses a ring main unit (RMU) including its specifications, operational guidelines, functions, and failure reasons. The RMU has a rated voltage of 12kV, current rating of 630A, and can withstand short circuit and peak currents. It facilitates safe on-load operation, network flexibility, and uninterrupted power supply. Operational guidelines include checking gas pressure and indicators before earthing. Failure can occur due to gas leakage, cable issues, moisture, or short circuits.

1. RING MAIN UNIT
BY
MS. SNEHALI SABLE-SHITRE

2. CONTENT
• RMU SPECIFICATIONS
• OPERATIONAL GUIDELINES
• RMU FACILITATES
• FAILURE REASONS

3. RMU SPECIFICATIONS
• RATED VOLTAGE 12 KV
• RATED CURRENT BUSBAR SYSTEM 630 A
(BREAKING CAPACITY OR NORMAL LOAD CURRENT)
• RATED SHORT TIME WITHSTAND CURRENT 21KA/3S
(SHORT CIRCUIT WITHSTAND CAPACITY)
• RATED PEAK WITHSTAND CURRENT 53 KA
(MAKING CAPACITY)
• IMPULSE WITHSTAND VOLTAGE 75 KV
• POWER FREQUENCY WITHSTAND VOLTAGE 28 KV

4. RMU FACILITATES
• SAFE ON-LOAD OPERATION
• EASY NETWORK HANDLING
• NETWORK FLEXIBILITY
• PROMPT SUPPLY RESTORATION
• UNINTERRUPTED POWER SUPPLY

5. RMU FACILITATES
• PROVIDES CABLE STATUS INDICATION THROUGH VPIS
• INDICATES FAULTY SECTION THROUGH FPI
• REDUCES FIRE HAZARDS
• MAINTENANCE FREE
• REMOTE OPERATIONS AND STATUS MONITORING

6. OPERATIONAL GUIDELINE
• CHECK GAS PRESSURE
• SAFE TO OPERATE WHEN GAS PRESSURE INSIDE THE TANK
IS 1.4 BAR OR ABOVE
• 1 BAR= 1 ATMOSPHERIC PRESSURE
• CHECK VPIS BEFORE EARTHING
• FAULT PASSAGE INDICATOR AND
• EARTH FAULT INDICATOR DURING OUTAGE

7. FAILURE REASONS
• SF6 GAS LEAKAGE
• CORBONIZATION AT THE CABLE AND TERMINALS
• MOISTURE INGRESS
• SHORT CIRCUIT