Why do we use a potential transformer in a substation?

Why Do Substations Use Voltage Transformers?

Substations use voltage transformers (VTs), also known as potential transformers (PTs), primarily to safely and accurately monitor and measure the voltage in high-voltage systems. Here are the specific reasons for using voltage transformers:

1. Safety Isolation

• High-Voltage Systems: Voltages in substations are typically very high, and direct measurement of these voltages poses significant risks to personnel and equipment.

• Isolation Function: Voltage transformers isolate the high-voltage system from low-voltage measuring devices, ensuring the safety of operators and measurement equipment.

2. Precise Measurement

• Proportional Transformation: Voltage transformers convert high voltages to proportional low voltages, typically from several kilovolts to a few hundred volts or even lower.

• Linearity: High-quality voltage transformers have good linearity, ensuring accurate measurement results.

3. Standardized Interface

• Unified Standard: Voltage transformers provide standardized low-voltage outputs, making various measuring devices (such as voltmeters, relays, and protection devices) compatible.

• Compatibility: Measuring devices from different manufacturers can easily connect to the output of voltage transformers, enhancing the system's compatibility and flexibility.

4. Protection and Control

• Relay Protection: The low-voltage signals provided by voltage transformers are used in relay protection devices to detect and protect against faults in the power system.

• Control Systems: Low-voltage signals are also used in the control systems of substations to monitor and regulate the operation of the power system.

5. Reduced Energy Consumption

• Low Power Consumption: The secondary side load of voltage transformers is typically very small, consuming minimal power and not placing a significant burden on the high-voltage system.

• Energy Efficiency: Compared to direct measurement of high voltages, using voltage transformers can significantly reduce energy consumption.

6. Data Acquisition and Transmission

• Remote Monitoring: Low-voltage signals can be more easily transmitted to remote monitoring systems for real-time monitoring and data analysis.

• Digitization: Modern substations use digital technology, and low-voltage signals can be conveniently converted to digital signals for further processing and storage.

Specific Application Scenarios

• Measuring Instruments: The secondary side output of voltage transformers is connected to measuring instruments such as voltmeters and power meters for real-time monitoring of voltage and power.

• Protection Devices: The secondary side output of voltage transformers is connected to relay protection devices to detect abnormal conditions such as overvoltage and undervoltage.

• Control Systems: The secondary side output of voltage transformers is connected to the control systems of substations for automatic regulation and protection.

Summary

The use of voltage transformers in substations not only ensures accurate and safe measurement and monitoring but also enhances the reliability and flexibility of the system. By isolating the high-voltage system from low-voltage equipment, voltage transformers play a crucial role in the operation and protection of power systems.