Substation transformers are essential components in high-voltage power systems, playing a vital role in voltage regulation and system protection. Compared to smaller pad mount transformers, substation units include more advanced features to ensure safe, reliable, and continuous operation.

This article — Part 1 of our substation transformer series — explores the most common monitoring and protection devices found in liquid-filled substation transformers. These components are critical for performance, longevity, and compliance with CSA and IEEE standards.

Key Components of a Substation Transformer

1. Liquid Level Indicator

This device monitors the level of insulating oil, which is vital for cooling and insulation. The indicator displays oil levels clearly, often with a dial or sight glass, and includes alarm contacts to alert operators of high or low oil conditions.

Substation-Transformer-Liquid-Level-Indicator

2. Pressure/Vacuum Gauge

Used to measure the internal gas pressure relative to atmospheric pressure, this gauge ensures the sealed tank maintains safe pressure levels. It protects against moisture or air entering the system during temperature or load fluctuations

substation transformer Pressure Vacuum-Gauge

3. Liquid Temperature Indicator (LTI)

Also known as the Oil Temperature Indicator, this device tracks the temperature of the insulating oil. Excessive heat can degrade insulation and shorten transformer life. LTIs often have alarm contacts that trigger cooling systems when oil temperatures exceed safe limits.

substation transformer Temperature-Indicator-LTI

4. Winding Temperature Indicator (WTI)

WTIs measure the temperature of the transformer windings, which is crucial in preventing insulation failure due to overheating. These indicators often integrate with SCADA or digital monitoring platforms for remote alarms and temperature control.

substation transformer Winding-Temperature-Indicator-WTI

5. Sudden Pressure Relay

This safety relay detects rapid increases in internal pressure—often caused by internal faults like arcs or short circuits. The relay can trigger immediate alarms or trip the transformer to prevent catastrophic damage.

substation transformer Sudden-Pressure-Relays

6. Pressure Relief Device (PRD)

Mounted on the transformer tank, the PRD relieves excess pressure safely to avoid structural damage. A deflector cap directs oil discharge away from critical components and personnel.

substation transformer Pressure-Relief-Device-PRD

7. Control Box

The control box houses protective relays, control logic, and communication devices. It allows local or remote access to alarms, monitoring data, and cooling system control. Integration with SCADA is common for real-time management.

8. Tap Changer

Tap changers adjust transformer output voltage to maintain stability under varying load conditions. ETAC offers both Off-Load Tap Changers and On-Load Tap Changers depending on customer needs and system requirements.

Why These Components Matter？

Each component supports safe transformer operation, prevents downtime, and extends equipment lifespan. In modern substation environments, smart monitoring and responsive control are not optional — they are essential.

ETAC Transformer Solutions

ETAC provides fully customizable substation transformers engineered for industrial and utility applications. Our transformers are built with CSA and IEEE-compliant components and offer options for smart monitoring and advanced protection. Whether you need a basic setup or an integrated control system, ETAC ensures your power infrastructure operates safely and efficiently.

👉 Explore our product line: Substation Transformer Products

Substation Transformer components Explained-（part1）