Substations: Basic Principles | Circuit Breakers | Disconnectors | Relays | CTs & VTs | Arresters

Summary

This video explains the key components of an electrical substation, focusing on their functions and importance. It covers assets such as voltage transformers (VTs), current transformers (CTs), disconnectors, circuit breakers, and transformers, highlighting how they measure, isolate, and protect the system. The role of surge arresters, buzz bars, and the earthing grid is also discussed, as well as the importance of protection systems like relays and batteries in safeguarding the grid from faults and power outages. Overall, it provides an informative look into how substations ensure grid reliability.

Takeaways

• 🔌 Most power system assets are located inside substations, which may look similar but serve different purposes.
• ⚡ Substations use voltage transformers (VTs) and current transformers (CTs) to measure voltage and current, passing this data to relays or communication systems.
• 🔗 Disconnectors are simple mechanical switches used to isolate assets like circuit breakers but cannot break load or fault current.
• 💥 Circuit breakers handle the difficult task of breaking load and fault current and are essential for the protection system of a substation.
• 🔋 Transformers are the largest and most expensive assets in a substation, stepping up or down voltage with cooling systems like radiators and oil.
• 🔥 A Buchholz relay is used in transformers to detect failures by monitoring oil levels.
• 🏠 Relay houses contain relays, which monitor voltage and current and trigger circuit breakers if a fault is detected.
• 🔋 Substations are equipped with batteries to power critical equipment during power outages.
• ⚡ Surge arresters protect transformers and other assets from high-frequency surges such as lightning strikes and switching surges.
• 🌍 The substation uses an earthing grid to maintain safe voltages and provide a path to ground during faults, protecting personnel.

Q & A

What is the primary function of an electrical substation?

The primary function of an electrical substation is to house various assets that help manage, measure, and control the flow of electricity. It is responsible for transforming voltage levels, protecting the power grid from faults, and ensuring a stable and continuous supply of electricity.

What role do Voltage Transformers (VTs) and Current Transformers (CTs) play in a substation?

Voltage Transformers (VTs) and Current Transformers (CTs) measure voltage and current in the substation. They then send this information to relays or to the control room, where it is used to make decisions about potential faults and power management.

Why can disconnectors not break load current or fault current?

Disconnectors cannot break load current or fault current because they are not designed to handle such high currents. Attempting to do so would create a large arc, which can be dangerous. Their main purpose is to isolate sections of the circuit for maintenance.

What is the function of a circuit breaker in a substation?

The circuit breaker in a substation is designed to safely interrupt load current and fault current. It is a complex and expensive piece of equipment that protects the system by automatically cutting off the flow of electricity in the event of a fault.

Why are transformers the largest and most expensive asset in a substation?

Transformers are large and costly because they handle the crucial role of stepping up and stepping down voltage levels, which is necessary for efficient power transmission. They also require additional cooling systems, like radiators and fans, to manage the heat generated during operation.

How does the substation’s protection system operate?

The substation’s protection system is composed of VTs, CTs, disconnectors, circuit breakers, and surge arresters. These components work together to monitor electrical conditions, detect faults, and automatically disconnect faulty parts of the system to protect the grid.

What is the purpose of a surge arrester in a substation?

A surge arrester protects the transformer and other assets in the substation from high-frequency surges, such as those caused by lightning strikes or switching operations, which could damage the equipment.

What role does the earthing grid play in a substation?

The earthing grid provides a low-impedance path to ground, which ensures safe voltage levels in the substation and protects personnel from dangerous voltages. It also helps to stabilize the system in the event of a fault.

What is the function of the relay house in a substation?

The relay house contains the relays, which monitor voltage and current levels. In case of a fault, the relays send signals to the circuit breakers to trip and disconnect the affected part of the system.

Why are busbars used in substations, and where are they typically located?

Busbars are low-impedance metal bars that connect various assets within the substation. They are usually positioned high above the ground for safety and play a vital role in distributing power throughout the substation.