What components are included in the core part of a box transformer?

Core Components of a Pad-Mounted Substation (Compact Substation)

A Compact Substation consists of three primary functional modules integrated into a single enclosure:

1. High-Voltage switchgear
This section receives incoming power and includes load-break switches or circuit breakers, high-voltage fuses for short-circuit protection, and surge arresters to guard against lightning strikes. It also features current/voltage transformers for metering and protection.

2. Power Transformer
This is the heart of the substation, responsible for stepping down high voltage (e.g., 10kV) to low voltage (e.g., 400V). Its main components are the magnetic iron core, primary and secondary windings (coils), and insulating medium—either mineral oil (for oil-immersed types) or epoxy resin (for dry types). It also includes a tap changer for voltage regulation and a cooling system (radiators or fans) to dissipate heat.

3. Low-Voltage Distribution Panel
This section distributes power to end-users and contains the main low-voltage breaker, multiple feeder circuit breakers, measuring instruments, and power factor correction capacitors.

Modern Additions: Many units now include intelligent monitoring systems for remote control, temperature sensing, and fault detection, enabling unattended operation.