Three Phase Pad Mounted Transformers

Tap Changer – Used to match incoming voltage

• Location: Usually mounted on cabinet wall in High Voltage compartment.
• Layout: Rotary switch clearly marked with tap positions – usually 5 or 7 positions – for voltages, refer to nameplate.
• Function: Provides flexibility in operation by compensating for variations in line voltage, ensuring consistent service.

High Voltage Bushings – Insulated connection point for incoming high- voltage supply cables.

• Location: On the wall of the High Voltage compartment
• Layout: Porcelain or polymer insulated bushing with conductor connection hardware.
• Function: Provides a safe and insulated connection point for high-voltage conductors into the transformer’s primary winding.

Loadbreak Switch – Allows for safe de-energizing of the transformer while under load.

• Location: High-voltage compartment, positioned for operator access.
• Layout: Rotary switch with clearly marked switch positions – Operated by Hotstick
• Function: Enables switching between sources or isolation for maintenance

Bay-O-Net Fuse Assembly – Used to provide overcurrent protection

• Location: On the HV side of the cabinet
• Layout: Removable fuse holder with oil-immersed bayonet-style contacts
• Function: Interrupts the circuit under fault or overload conditions, protecting the transformer and distribution system.

Standard Gauge Package – A combined monitoring assembly integrates vital indicators for transformer health and safety.

• Location:  Positioned externally on the transformer tank, usually in the Low Voltage compartment, for easy visibility.
• Layout:  Includes a thermometer, pressure relief valve, and oil level gauge or sight gauge.
• Function:  Provides real-time visual monitoring of internal temperature, oil level, and tank pressure.

Low Voltage Bushings – Low Voltage output points

• Location: In the Low Voltage compartment.
• Layout: Insulated bushings typically marked X0, X1, X2, and X3.
• Function: Provides a secure and durable connection for delivering power to downstream loads.

Drain Valve – Designed for safe oil management during maintenance or fluid sampling.

• Location:  Installed at the bottom of the transformer tank.
• Layout:  A threaded valve assembly with an accessible outlet.
• Function:  Allows controlled draining or sampling of insulating fluid to support testing and servicing.

Cabinet Lock – The cabinet lock on a three-phase padmount transformer
secures the cabinet doors from unauthorized access.

• Location: Mounted on the Cabinet Door
• Layout: Padlockable handle mechanism, often interlocked with a Penta Head safety locking device.
• Function: Ensures tamper-resistance, controls access to internal compartments, and improves safety.